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Review for the effects of urban topsoil on the ecological health
XU Guoliang1,2, WEN Ya3, CAI Shaoyan4, LUO Xiaofeng11. 2.
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收稿日期:2019-04-8修回日期:2019-05-13网络出版日期:2019-12-20
| 基金资助: |
Received:2019-04-8Revised:2019-05-13Online:2019-12-20
作者简介 About authors
徐国良（1975-）,男,江苏泰州人,博士,教授,硕士生导师,研究方向为土壤地理与环境变化E-mail:xugl@gzhu.edu.cn。
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徐国良, 文雅, 蔡少燕, 罗小凤. 城市表层土壤对生态健康影响研究述评. 地理研究[J], 2019, 38(12): 2941-2956 doi:10.11821/dlyj020190240
XU Guoliang.
1 引言
地球表层系统人地关系是地理学的主要研究内容[1],而快速发展的城市化促使人地矛盾日益凸显。联合国研究报告表明,2007年底全球城市人口比例已经超过50%,至2050 年全球96亿人中,约有50%~68%的人口将居住在城市[2]。城市化趋势在中国表现得尤为明显,因为中国正在大力实施城镇化战略,以适应经济和社会的快速发展。早在2011年左右,中国城市人口比例已经超过50%,标示中国全面进入城市化时代[2]。大量人口聚集在城市区域,密集、剧烈的人为活动将导致显著的城市环境变化,这种变化又会反馈到城市居民生活,因此城市人地关系、城市生态健康愈来愈成为自然科学和社会科学研究关注的问题。土壤圈是地球关键带中最活跃的圈层[3],而城市土壤与城市大气、水体密切互作,积极作用于城市地球化学循环,成为城市人-地关系最活跃的生态环节。城市土壤在生物多样性维持、大气沉降、水文过程、环境要素地化循环、环境污染缓冲与清洁等过程中都起着重要作用。尤其是城市土壤表层成为城市人-地联系的关键生态界面,因为城市区域内人类生命活动与自然的互作过程无不经历城市土壤表层的正负反馈作用。首先,城市化人类聚居对土壤的影响体现在污染物的大量产生和转移上,这些污染物大多沉降、汇集在城市土壤表层[4,5,6],尤其在大城市,土壤表层往往暴露于严重的人为活动影响中[7,8,9]。其次,城市土壤表层也可以通过土-气、土-水交换,以及土壤生物作用,对城市大气和水体持续产生积极的反馈作用[9,10,11]。由于这些密切的土-气、土-水联系,以及丰富的土壤生物群落及其功能作用,城市土壤表层成为影响城市生态环境结构、功能和可持续发展的重要因子。因此,本文从城市表层土壤的界面意义着手,通过系统梳理城市表层土壤的生物、理化性质,及其在城市化影响下与大气、水体、人类活动之间的正负反馈作用,对城市表层土壤的生态健康意义进行了述评,彰显城市生态系统中各要素的综合作用及人地关系现状。
2 城市表层土壤的界面意义
来自于人为排放和大气沉降而蕴积在城市土壤中的重金属,如Cu、Zn、Pb、Cr、Cd等在土壤中的迁移距离都比较小,使得重金属在土壤表层明显聚集。Ruan等利用高密度取样法,以2 cm的间隔对土壤重金属的垂直分布进行细致的研究,表明0~2 cm的表层土壤中Cu、Zn、Pb、Cd含量最高,其后至8 cm时Zn、Pb、Cd的含量迅速降低;Cu的主要变动范围为0~13 cm,证明城市土壤重金属含量主要分布在0~10 cm以内[12];即使在严重污染下土壤表层铜含量达到背景值的5~50倍,但在10 cm以下土层铜含量迅速回归背景值水平[13]。同时,作为土壤食物网物质、能量重要来源的有机质主要分布在土壤表层,而且土壤表层疏松多孔的结构提供了充分的生物栖息地、空气和热量来源,使得土壤生物也具有显著的表聚性,尤其是在有机质层较薄的城市土壤,绝大多数土壤生物都分布在土壤表层。据报道,上海徐汇区绿地中60%~80%土壤动物个体分布在0~5 cm土壤层[14];王焕华等研究表明0~5 cm城市土壤层的微生物量、微生物碳/氮都显著高于5~20 cm土层[4]。土壤表层生物群落很容易受地上环境变化的影响。例如,在历史悠久的莫斯科城和华沙城,环境稳定的自然林土壤动物群落表现出很大的相似性,但环境多变的路域绿地土壤动物群落却表现出很大的变异性[15]。
地球表层是地球系统科学的关键界面层[1],而土壤表层是区域小尺度水平人-地联系的关键生态界面。具体而言,城市土壤表层与外界环境存在密集的物质交换过程：环境污染物在大气沉降和降雨的作用下大多沉积、蕴积于土壤表层,然后在外力的作用下可以重新进入大气层和河湖地表水甚至地下水系统;土壤表层聚居的生物群落也会随地表环境变化产生结构和功能过程的变化,这些变化将进一步通过影响凋落物分解、有机质的产生积累和土壤物理化学性质等,最终改变环境元素的地化循环过程。事实上,0~2 cm城市土壤表层中,大量以可交换、或水溶态等形式存在的一些重金属（如Cu、Pb、Mn等）含量与城市大气中多年平均重金属含量之间存在可靠的相关关系[10]。姚晶晶对兰州市不同主干道路域空气（距地面1.5 m）和土壤0~5 cm的微生物群落进行调查,结果显示表层土壤与其上空大气微生物群落存在密切关系：大气中三大类微生物的数量线和土壤中相应微生物的数量线整体趋势相似;路域空气中微生物密度与表层土壤的微生物密度成正比。这种规律与土壤生物及重金属等污染物沉降的表聚性直接相关[16]。
3 城市表层土壤的理化特征
处于人为活动频密的城市,土壤不可避免受到不同程度的人为影响。关于城市表层土壤的研究表明,在城市构筑物和绿地建设中,土壤翻动、压实及封闭等现象普遍存在,这些活动都能明显改变表层土壤的物理性状,使土壤孔隙度减小、容重增大、碱性加强、水分和养分含量降低等,尤其对土壤生物的多样性、群落结构及时空分布有明显影响,最终使得城市表层土壤性质显著偏离同地带（区域）背景土壤的特征[9,17]。pH对土壤性质起着综合性作用。虽然城市土壤pH同时受到成土母质、自然沉降和人为输入物的作用,但短期、强烈的人为影响明显远超自然作用,并使得城市土壤pH可能的变动范围相当大。朱纯等在华南中心城市广州建立了一条长100 km、宽10 km的绿地土壤样带,发现土壤pH 复杂多样,变幅在2.21~7.82之间,其均值5.44相对赤红壤4.5~5.5的自然背景值,体现了部分碱化的趋势[18]。实际上,城市土壤整体上偏碱化是普遍规律。何兰等对全国由南至北一些大城市绿地土壤pH做了统计分析,发现相对于背景值,城市土壤pH明显变大[19]。这个规律在从酸性土为主的东部往碱性土为主的西部尺度上也有同样的体现,例如上海[20]、重庆[19]、兰州[16]、乌鲁木齐[21]等。城市表层土壤偏碱化的原因主要来自水泥、砖块等建筑废弃物和其他碱性混合物、大气降尘,以及偏碱性的灌溉用水等。另外,城市化也使得土壤表层中有机碳含量增加,但变异性大。来自北京、上海、南京、杭州、乌鲁木齐、开封、长春、沈阳等城市的研究都发现,城市化有利于土壤有机质的积累,结果使得城区土壤有机质含量大于郊区。例如,新疆最大城市乌鲁木齐土壤表层（1~10 cm）有机质的平均含量超出自治区土壤有机质背景值3倍[21];开封城区土壤有机质高出郊区122%[22]。造成城市表层土壤中有机质含量显著增高的主要原因可能是城市绿地不以生产为目的,所以消耗的有机质少,凋落物累积较多,同时人类直接或间接也会输入部分营养物质,例如生活垃圾等,使得土壤中有机质含量增高。在构筑物建设和人类踩踏作用下,城市土壤表层压实严重。土壤压实造成土壤密度增大,阻碍物质循环过程[23]。土壤压实也大大减少了土壤孔隙度,使得许多土壤生物赖以生存的生态位消失,直接影响了多样化土壤生物的存在和发展。Devigne等在法国Capinghem城的一个生活小区范围,对不同压实度区域的土壤跳虫生物多样性进行调查,发现最丰富的跳虫群落大多数分布在压实度最低的区域;相反,压实度最高的区域具有最贫乏的跳虫群落[24]。但相关的研究还很缺乏。
随着城市化的发展和城市建设不断加强,城市中心区域气温上升趋势日益明显。据统计,城-郊最高气温差在纽约可达到8.0 ℃,在上海最高达7.4 ℃;北京在1961—2000年间城-郊日均温差为3.3 ℃[25]。这就是著名的城市“热岛效应”。城市气温上升必然也导致土壤温度的上升。在纽约市Central Park和Latorite Park年均土温比邻近的林地高3.1~11.2 ℃[25]。土壤温度升高的后果是土壤物理、化学、生物性质以及物质、能量循环过程的改变,如CO2排放、N素硝化和反硝化、有机质分解、重金属效态变化等。当前关于城市土壤温度上升对区域物质循环和功能过程的量化影响还缺乏研究。但是,已有研究发现,热岛效应对城市生物多样性产生了显著影响。因为城市环境中仍广泛存在变温性无脊椎动物,其生命活动受到环境温度变化强烈而直接的影响[26]。例如,城市热岛效应改变了美国城市Phoenix节肢动物群落的数量和丰富度[27]。Arianta arbustorum是中、西欧地区的常见蜗牛,但经过长达18年的跟踪研究,发现瑞士Basel城市附近这种蜗牛原有的29处分布地消失了16处,在排除了坡度、植被高度、离水源距离等因素后,最终认为城市热岛效应是导致蜗牛消失的最主要原因[28]。
4 城市表层土壤的生物多样性
生物多样性是维持生态系统稳定和可持续发展的重要基石,然而有很多研究证实,城市化是生物多样性下降最显著的因子之一[27,29]。因为城市是由居民区、工业区、交通区、商业区、绿化区等不同功能区在相对狭小区域内高度镶嵌形成的复合系统,所以城市生境严重破碎化和岛屿化;同时,城市绿地大多经历人工改造,引种单一,也减少了自然生态系统的复杂性。因此,一般来说,城市化和人居环境影响不利于生物多样性的发展,尤其对于需要较大活动空间而依赖于物种-面积分布的地上动物和植物来说,城市生境导致它们难以生存甚至消亡[30]。然而,对于土壤中生活的部分低等无脊椎动物和微生物,城市却可能成为更好的拓展空间。4.1 土壤动物多样性
城市土壤表层动物多样性是城市生物多样性的重要组成部分。城市土壤动物在改善土壤理化性质、提升城市雨水吸蕴能力、有机质形成、环境化学元素的固定以及城市土壤健康状况评估等方面都具有重要意义。很多研究表明,城市土壤动物多样性丰富。即使在某些有机或无机物严重污染区域,看似生物难以存活的生境,甚至在人工技术土中,仍然活跃着丰富的土壤动物群落[8,31-33],而且,由于缺乏天敌控制和生态位竞争,某些城市土壤动物种群可以发展到相当高的密度水平[15]。21世纪初,国内外一些****开始对城市土壤动物多样性进行研究,如McIntyre等利用节肢动物研究城市生态系统对周边环境的影响[27]。近些年来城市土壤动物研究逐渐增多,尤其是很多****调查了不同城市土地利用方式对土壤动物生物多样性的影响,以及城市生境梯度、交通污染的影响等[34,35,36,37]。由于城市生境的特殊性,城市生物群落的存在发展形成了许多不同于自然状态的空间分布特征。其中历史悠久、仅有适度利用的城市公园由于保持了较为稳定的生境,是城市生物多样性的聚居地,形成较为稳定的土壤动物群落,成为城市生物多样性热点区域。然而街道绿化带等生境,由于人为反复干扰,生物群落变异很大。研究发现,在莫斯科和华沙两个大城市中,所有城市森林土壤跳虫群落都非常相似,然而街道绿地土壤跳虫组成特征的变异性却非常大[15]。不过,在稳定维护的前提下,城市无脊椎动物生物多样性也能够随着城市绿地年龄的增加而增长[8]。另外,城市土壤压实会造成土壤动物群落组成结构的变化。例如,在压实较严重的城市草地,活动能力强的跳虫Lepidocyrtus cyaneus成为群落的优势种,而压实较小的城市草地,活动能力较弱的跳虫Brachystomella parvula或Isotoma viridis成为优势种[24]。
在城市环境胁迫显著的区域,土壤动物形成明显的逆垂直分布现象。例如,在开封市工业区,较深的10~15 cm层土壤动物类群数反而多于较浅的5~10 cm层,而前气门亚目螨类在0~10 cm层完全消失,在10~15 cm层才开始出现,与自然状态下土壤动物的表聚性显著区别[35]。另外,城市的道路、桥梁和建筑群将城市区域分割成斑块状,使得城市土壤生境显著“岛屿化”。据报道,500 m的间隔就会对节肢动物造成显著的隔离效应[38]。这无疑暗示城市土壤动物的区系发展和演化将会产生明显有别于自然生态系统的格局特征。
虽然已有不少研究者开始关注城市化背景下的土壤动物生物多样性,但现有研究存在一些明显的不足。首先,现有研究主要集中在点、线尺度,缺乏面上尺度的研究,不能对城市化的整体影响提供评价依据;其次,由于大多数研究者缺乏土壤动物分类技能,多以科级以上分类单元为基础进行定性分析,不能建立有价值的城市土壤动物物种信息数据库,难以在种群、个体、乃至分子水平上对环境影响做较细致的量化研究;第三,缺乏有效的指示种群生物效应研究,不能对城市环境变化的健康风险进行准确评估。
4.2 土壤微生物多样性
土壤微生物量及其极为多样化的代谢活动是调控土壤矿质养分动态和有机质分解转化的重要因子,对土壤生态系统的物质能量循环、污染代谢及生态健康都有重要意义。一般认为,城市化使土壤中微生物总数减少[39]。符方艳等通过设置城区-近郊-远郊梯度样地,对广州城市存留南亚热带常绿阔叶林土壤生物进行研究,发现远郊区土壤微生物量最高,而城区土壤微生物量无论在干季和湿季都显著低于远郊,据此认为城市化会降低南亚热带常绿阔叶林土壤微生物量[40]。城市环境下土壤微生物的减少可能与城市重金属污染有关,因为重金属对微生物有直接毒害作用,导致了微生物数量和活性的降低[41]。杨元根等选择英国Aberdeen市区主要交通要道两旁及市内主要公园作为对象,研究城市重金属污染对土壤微生物的影响,结果表明农业土壤、公园土壤和城市路边土壤中的微生物量依次显著减少,认为城市重金属污染的胁迫对Aberdeen城市土壤微生物特征产生了显著影响[42]。不过,也有研究认为,城市化并没有严重影响土壤微生物量。南京市土壤微生物的调查研究表明,与自然土壤相比,城市土壤微生物量碳和氮并没有明显降低,反而稍微有所增加[4]。Madejón发现在城市一些区域,由于土壤有机碳成分的增加,可以抵消重金属影响,激发土壤微生物和酶的活性,最终使土壤微生物量增大[43]。虽然城市化对土壤微生物量的影响具有一定的不确定性,但对土壤微生物群落结构的影响却得到广泛共识。与自然土壤相比,城市土壤由于受到重金属污染等影响,微生物空间变异性增大。在Aberdeen市区和邻近农村土壤微生物群落的比较研究中,根据对碳源利用种类和利用程度产生的明显分异,证实两个区域微生物群落结构发生了改变[42]。一般来说,在城市建成区,土壤中细菌和真菌所占微生物总数的比例会高于郊区和农村,而放线菌占比在农村要高于城市建成区和郊区[39]。土壤微生物结构的变化必然造成功能过程的变化。例如,在Aberdeen市,虽然母质来源和土类一致,但在不同的环境背景下,农村、城市公园、城市路边土壤微生物群落功能产生分异：农村土壤微生物群落优先利用碳水化合物,公园土则以不饱和长链脂肪酸为主,而路边土则以氨基酸和苯酸为其主要能源;同时结果显示,城市土壤虽然对能源碳的消耗量和速度显著升高,但利用效率却明显降低,使得微生物量下降[42]。相对生物量的变化,城市化背景下土壤微生物群落结构和功能的变化更应该引起重视,因为它直接与物质能量的代谢水平相关,影响生态系统的可持续性及城市污染物负荷等。
5 城市表层土壤的“源-汇”效应
在城市化区域,相对于传统的生产功能,土壤的环境和生态功能更为重要。城市表层土壤是城市环境元素地化循环的关键界面层,与地下水、地表水、大气之间一直进行密切的物质交换;同时,城市表层土壤也是一个疏松多孔体系,可以集聚城市生活、生产的各类代谢物。这使得城市表层土壤既可以成为各样污染物重要的汇,又是污染物向上、向下或水平扩散的重要源。5.1 “汇”效应-环境污染物累积
城市表层土壤的重要特征之一就是重金属和有机污染物等的累积,明显高于周边环境背景值[9]。早在20世纪60年代,工业化历史悠久的英国就对伦敦等大城市土壤和灰尘中Pb、Cu、Zn、Cr等重金属元素开展研究,发现城市表层土壤和道路灰尘中的重金属与工业、交通密切相关,并可以作为城市大气污染指标[44,45]。Pouyat等在美国纽约市东南方向建立了一条长140 km、宽20 km的“城-郊-乡”样带,采集0~10 cm土壤样品,对其中的重金属分布格局进行研究,发现从市中心到效外,Cu、Ni、Pb 的含量逐渐降低,其中Cu、Pb含量的变化尤其明显,城区土壤含量分别达到农区的213%和410%[46]。虽然,重金属元素可以通过金属加工与机械制造、电镀、电子设备与仪表、冶金和金属腐蚀等多种方式进入土壤[47],但交通行业和含重金属的生活废料无疑是城市土壤重金属的主要来源,尤其是Pb、Zn、Cu 和Cd等[11]。研究表明,纽约市土壤表层Pb含量与城市的交通流量和人口密度（对数）呈正相关关系[48]。陈畅等定量分析了武汉土壤Pb含量与道路网密度的关系,也发现二者存在高度相关性[7]。虽然近二十年来,国家已经开始控制和禁止含Pb汽油的使用,但早期各种汽油含Pb量都较高,在燃烧过程中75%的Pb以颗粒态随汽车尾气进入环境,经过数十年显著的沉积,即使再经数十年,城市道路两侧土壤Pb污染仍然会十分严重[49,50]。城市环境中的Hg可能与生活中大量使用含汞化妆品与含汞用品（例如日光灯、电池、血压计、体温计等）有关[51],从这些废弃物逸散出来的汞也大多沉积于城市土壤中。尹伟等以广州中心城区为对象,对城市土壤表层（0~10 cm）土壤汞的含量及分布特征进行研究时发现,建成历史最悠久、人类活动时期最长的越秀区和荔湾区土壤汞污染最严重,50%以上土壤污染指数≥3,区内部分公园,如越秀公园、荔湾湖公园、青年公园和流花湖公园等土壤汞含量都超过背景值数倍[52]。
与此同时,近100多年来城市大量人口聚居生活、生产制造了大量有机废弃物及中间产物,使得环境中多环芳烃（PAHs）、多氯联苯（PCBs）、多氯联萘（PCNs）等持久性或难降解有机污染物的浓度不断增加,例如低环的PAHs（2~3环）主要来源于自然界和没有经过燃烧的石油类产品,而高环的PAHs（4环及以上）主要来自各类燃烧[53,54,55]。这些有机污染物大多具有挥发性和半挥发性,很容易通过挥发、淋溶和扩散作用等在城市生态系统中迁移,或逸入空气,最终通过降雨、降雪和降尘等方式进入土壤,且多集中在工业区和居住区花园绿地附近[55,56]。由于PAHs（特别是高环PAHs）的低水溶性和易于吸附在土壤颗粒物上的特性,使得它们很难淋失或者向下运动扩散至深层土壤[55]。最终,城市表层土壤各种有机污染物的浓度不断增加,成为有机污染物重要的汇。
5.2 “源”效应-人居健康风险
土壤的健康状况可以作为城市居民生活质量的衡量指标[16]。因为各种污染物随尘、水、雪等沉降在地表,然而土壤的物质转化能力是有限的,尤其是重金属进入土壤后不能被生物降解。同时,各污染物在土壤中的迁移能力也有限。因此,大量汇聚在城市土壤表层的污染物,通过动植物吸收、风力驱动、水分携播等途径,将再次进入水、气、生物环境,对城市居民健康造成威胁。近年来,有研究者利用一些现代技术,例如核探针技术,对土壤与大气之间的交互作用进行论证,发现上海市大约有31%的大气颗粒物来自土壤扬尘[57]。城市人群暴露于土壤来源的环境污染物主要有两条途径：① 间接食物链途径：即通过食物链传递途径到达人体并在体内积累,比如城郊农业产品;② 直接吸收途径：即城市人群通过直接接触污染的土壤、呼吸携带污染物的空气等途径摄入环境污染物;例如,空气中高环的PAHs主要吸附在小于2.5 μm的颗粒物上,比较容易通过呼吸作用进入肺部或者吸附在皮肤上[55]。一些研究已表明,城市土壤重金属是城市人群体内重金属的重要来源。李有文等调查了白银市不同功能区土壤表层8种重金属含量,并研究了其与人体健康风险的关系,结果表明,土壤As和Cr是各功能区致癌风险最主要的2个贡献因子[11]。住宅区附近土壤Pb可以通过灰尘形式或通过土-手-嘴接触进入人体,对于6岁以下的儿童这种影响尤其明显;进一步的研究表明,居住区土壤和灰尘中的Pb含量与儿童血液中Pb浓度显著正相关[58]。因此,即使全球很多国家早已开始限制含Pb汽油的使用,但由于Pb在土壤中长期的积累,仍然可以成为城市人群重要的Pb摄入源。据统计,中国部分城市0~6岁儿童血Pb浓度几何平均值依然达到5.94 μg·dL-1。而且,部分地区依然有儿童Pb中毒的事件发生。例如,2008年报道了陕西凤翔22.7%的儿童血Pb浓度超过20 μg·dL-1,84.13%的儿童血Pb浓度超过10 μg·dL-1 [59]。
6 城市表层土壤与城市生态健康
自从Rapport在1989年提出生态健康的概念和原则,并论述了生态系统健康的内涵之后[60],众多专家、****纷起响应,并在不同类型生态系统中开展了相关研究,其中也包括城市生态系统。1997年Colin在“人类健康的生态系统研究方法”研究报告中,较早对城市生态系统健康的内涵、标准、评价指标,以及城市生态系统管理的目标、管理方式等作了比较深入的阐述[61];其后,在过去的二十年期间,围绕城市生态系统健康的概念、评价指标的选择和建立、评价模型的构建、以及城市生态健康评价实例等,都已有了不少的研究[62,63]。虽然,现有研究对于城市生态系统健康的概念、评价标准等仍未形成明确一致的理论和方法,但越来越多的****认识到,城市生态系统包括自然、社会、经济等多个子系统,城市生态健康评价需要考虑自然环境、人工构筑环境,以及社会、经济、文化、政治环境等诸多要素。因此,城市生态系统健康评价具有明显的多维度、多尺度特征[61,64,65]。然而,从自然科学维度,城市生态健康包括两方面：一是城市生态系统自身的健康,能够保持一定的结构、功能和生物多样性,实现可持续发展;二是城市环境对居民健康的影响,因为从生态学角度,人类无疑是城市生态系统的核心,健康的城市生态应该有益于人类的身心发展,且不会产生直接健康危害。但现有城市化的发展在这两个方面都已经发生并将持续产生负面影响,“城市皮肤”——土壤表层的诸般响应就是城市生态系统机体“病征”的明显表现。城市化对表层土壤负面影响的极端情形是不透水硬底化地面的扩展。据报道,美国城市内部不透水地表面积比例平均约为40%~50%,而中国城市不透水地表面积平均约为66%,且仍不断增长[66]。1990—2000年期间,广州市不透水地面积年均增长率为6.18%,2000—2010年期间为7.19%,2010—2016年期间为2.81%,老城区中心的不透水面率竟然达到85%,接近饱和状态[67]。城市不透水地面切断了地上-地下联系,使得土壤生态功能几乎完全丧失,雨水不能下渗,城市地下水位下降,城市内涝频发;污染物不能自然吸附降解,排放至江河造成水域的富营养化等。在未硬底化区域,土壤表层的生物多样性、物理化学性质以及元素循环、环境污染物降解、代谢等功能也受到严重胁迫。城市土壤因压实和板结减少了总孔隙度,降低了大孔隙的比例,影响了土壤通气、排水功能,同时由于富钙水浇灌及含钙、镁粉尘等影响,城市土壤偏离同地带（区域）背景土壤特征,普遍向碱性方向演变,导致城市土壤营养元素有效性降低,本土生物发展受到威胁[68]。更值得关注的是,城市生产和生活区附近风险污染物集聚,其中多环芳烃、多氯联苯、多氯联萘等持久性或难降解有机污染物的含量是远郊农田土壤的数倍[16]。土壤污染能够明显降低土壤动物多样性。例如,随着Cu污染程度的增加,土壤动物的数量急剧减少,土壤动物种类和个体数量也与Cd浓度呈明显负相关[69];土壤跳虫的物种丰富度随污染程度的加重而降低,但不同的种类对重金属污染的反应有差异[70]。土壤生物多样性的降低,将产生一个明显的后果,即削弱土壤表层对环境污染物的积蓄、转化和分解能力,因为土壤动物的生命活动有助改善土壤结构及有机质的团聚体结构,它们可以对环境污染物产生更好的络合和吸附作用,从而降低污染物生物毒性。
因此,在生物多样性汇聚的土壤表层,同时也是土-水-气交互作用显著的城市生态系统关键界面层,随着环境风险物的积聚和土壤生物、物理、化学性状的恶化,必将削弱城市土壤作为生物多样性栖息地、陆上生态系统供给维持、以及城市环境污染物吸附、降解、转化等生态功能,严重影响城市生态系统自身的可持续发展。
其次,城市居民作为城市生态系统的核心,城市生态健康必然要探讨城市环境变化对人居健康的影响。现有研究结果表明,城市土壤与人居健康之间存在密切联系,其相互作用过程与机理成为越来越重要的科学议题[71]。城市土壤对人群的作用包括直接和间接两种途径。首先,城市表层土壤与大气污染之间存在密切关系。以往研究已经揭示城市空气中多年平均的重金属含量与城市土壤表层中大量、可交换态重金属（如Cu、Pb、Mn等）含量之间可靠的相互依赖关系[10],这种关系早在20世纪60年代英国伦敦就有报道[72]。这是因为,土壤扬尘是城市大气颗粒物的最重要来源之一,其比例可以高达36.7%[73],其暗示了城市表层土壤接触人体的一种途径[47]。因此,城市生活区周边土壤的污染物将对当地长期居住和活动的人群,尤其是儿童产生较大的危害,有报道认为城市儿童血Pb与城市土壤Pb含量呈显著的指数关系[74]。李有文等调查了白银市5个城市功能区表层土壤中重金属含量,发现土壤As、Cr和Pb是各功能区人群非致癌风险最主要的3个贡献因子;土壤As和Cr是各功能区致癌风险最主要的2个贡献因子[11]。因此,城市居民的健康状态与当地土壤的污染水平之间存在密切关系。城市表层土壤污染状况与大气污染（气溶胶、尘埃和降尘）、城市居民健康风险的关系值得持续关注和研究。
同时,作为土壤的固有禀性,城市土壤仍然发挥着重要的生产功能。例如都市农业已然成为城市经济生活的一部分。北京拥有农业龙头企业一百余家,每年发展蔬菜基地2666.67 hm2;上海市蔬菜自给率已达到55%,绿叶菜自给率90%;武汉市主要菜篮子产品自给率也达到68%[75]。因此,城市人类活动产生的环境污染物也可以通过土壤-作物系统以食物链的形式积累与传递,最终进入人体。近30年来,国内外已有大量蔬菜重金属富集污染的研究报道,其中重金属超标率最低为12%,最高可达90%以上[76]。例如,在广州市12个区（市）对8种常见蔬菜进行调查,发现Cr的超标率高达91.67%,Pb在莴苣、丝瓜、番茄和胡萝卜中的超标率高达35.71%,Cd在番茄上的超标率达31.25%[77]。尤其是对于一些生物富集效率高的污染元素来说,土壤污染造成人体健康风险来自于食物消耗的比例可达87.5%[76]。
综上所述,当环境负荷超过城市土壤承载力,城市土壤表层将通过与大气、水体和生物圈的交流作用,致使环境风险物直接或间接进入人体,结果影响城市居民健康和引发诸多的“城市病”。现已知土壤中PAHs的污染水平与当地居民患乳腺癌、胃癌、皮炎和肺炎等疾病之间存在较高的相关性[78],还有通过水污染造成的急性腹泻、恶性肿瘤,通过大气污染物造成上呼吸道感染、哮喘、肺炎等[61]。
7 城市土壤健康生物指示
从20世纪60年代,人们就利用土壤无脊椎动物作为环境变化的指示[8],因为大多数土壤动物终生栖息于土壤中,是土壤环境质量和健康状态的重要指示,特别是土壤动物如线虫、跳虫、螨类、蚯蚓等能够敏感地反映土壤污染的存在和程度（表1）。作为优良的土壤质量指示生物,土壤动物具备以下特征：① 个体数量庞大,例如土壤跳虫密度可以达到每平方米数百万只[79];② 物种及其生态位组成极为丰富,土壤动物生物多样性极显著,包含8个门类,几乎涵盖所有陆生无脊椎动物类群;因此在不同生态环境、不同土壤空间内都能发现丰富的土壤动物群落;充足的个体数量和丰富的物种组成使得土壤动物群落绝大多数情况下都可以为数理统计提供充足的分析样本;③ 世代周期短,例如跳虫20多天就可以完成一个世代,能够对一些快速城市化过程中的环境胁迫因子产生即时的可观察反应[15];④ 活动和迁移能力弱,与区域环境变化具有可靠的相关关系,形成可溯源反应;⑤ 最后,土壤动物取样相对简便,只需要简单的工具即可完成。Tab. 1
表1
表1土壤动物与城市环境变化指示研究
Tab. 1
| 动物类别 | 指标特征 | 环境变化 | 文献来源 |
|---|---|---|---|
| 土壤动物群落 | 群落结构,营养类型结构 | 土地利用变化,城市化 | McIntyre等[27] |
| 土壤动物群落 | 密度-类群指数、多样性指数、均匀度、优势度和丰富度 | 生境复杂度,人类干扰程度 | 王金凤等[93] |
| 土壤动物群落 | 群落结构,个体数,多样性 | 城市路桥重金属污染 | 白义等[70] |
| 土壤动物群落 | A/C值,优势度,多样性指数,生境分布系数, | 城市环境干扰 | 叶水送等[94] |
| 土壤动物群落 | 类群丰度,个体数量 | 重金属污染 | 王存龙等[69] |
| 土壤动物群落 | 群落结构,多样性,丰富度 | 土地利用变化影响 | 宋英石等[36] |
| 土壤螨类 | 种类和数量、性比、功能、类群、群落结构、生物多样性 | 土壤环境质量 | 刘漫萍等[95] |
| 土壤甲螨,中气门螨 | 物种组成,多样性 | 土地利用类型 | Minor等[96] |
| 土壤跳虫 | 群落结构,优势类群 | 城市化影响 | Sterzyńska等[15] |
| 土壤跳虫 | 群落结构,敏感类群 | 城市环境污染 | Fiera[97] |
| 土壤跳虫 | 功能群和物种结构 | 土壤理化性质,土地利用变化 | Santorufo等[98] |
| 土壤跳虫 | 群落结构,类群丰富度,个体数量 | 土壤压实度 | Devigne等[24] |
| 土壤跳虫 | 群落结构,个体数,类群丰度,多样性 | 土地利用变化及历史,城市化影响,土壤理化性质 | Milano等[8] |
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McIntyre是较早对城市土壤动物开展研究的****,认为可以利用节肢动物来研究城市生态系统的环境影响[27]。宋博等在开封市研究了城市生态系统土壤动物对土壤污染的响应,认为可以利用土壤动物多样性指数指示土壤综合污染程度,它们之间具有显著的负相关关系[35]。宋英石等在北京特定区域土壤动物多样性与土壤环境参数的相关性研究中,发现土壤动物优势度指数与土壤温度及速效钾,均匀度指数与土壤pH均表现出显著负相关,而速效钾与土壤动物多样性、均匀度指数均呈正相关[36]。实际上,大量的研究证实,土壤动物群落组成与特定环境具有一定的对应关系。因为某些类群和种群对人类干扰和生境变化非常敏感,特定的土壤物理、化学因子变化成为这些物种显著的限制因素,可以在存活率和繁殖率等方面产生明显作用,因此能够为特定环境变化提供最早的信号[69,80-82]。例如,r-策略生物土壤跳虫是土壤环境质量优良的指示者,可以高效地同化环境元素,并对环境变化产生迅速反应[83,84]。McIntyre等发现,14种跳虫可以作为四种城市化生境的指示因子[27],而利用土壤跳虫群落结构特征可以区分不同程度土壤压实土地利用类型[24]。Milano等认为嗜氮及趋人为活动的Desoria tigrina具有很好的指示土壤重金属污染的潜力[8]。土壤跳虫的群落结构和种群特征被作为土壤质量评估的指标,多年来已经在欧美发达国家被广泛应用[85,86]。还有很多研究利用蚯蚓作为土壤重金属污染的生态毒理诊断指标[87]。有报道显示蚯蚓体中镉的浓度与土壤中Cd的浓度明显相关,蚯蚓对土壤中的Pb也有较高的敏感性,各项病理变化指标均能定性地反映土壤的重金属污染状况[57]。此外,土壤动物线虫[88]、原生动物[69]、甲螨[89]、线蚓[90,91]等也被认为是优良的土壤质量指示生物。
除了群落和种群等宏观水平的反应外,城市环境变化也会在微观水平上对土壤动物形态、生理乃至基因特征产生作用,这为探讨城市环境变化的生物生理影响机制及生物适应机制提供了依据。首先,较严重的污染会引起土壤动物组织形态的病理学变化。例如,在农药污染环境下状伟环毛蚓（Pheretima robusta）胃肠道粘膜上皮细胞出现线粒体凝缩,基质中电子密度显著增加、高尔基复合体增生、肿胀扩张等病症[28];长期的土壤污染也会对土壤动物基因表达发生影响,刺激土壤动物组织产生应激反应,诱导产生一些应激蛋白,影响土壤动物同工酶、氨基酸等生理生化指标;例如,跳虫能够在Cd含量极高的土壤中生存,是因为在重金属刺激下,它们能够产生一些防御性应激蛋白,例如金属硫蛋白,尤其是白符跳的金属硫蛋白具有更多的金属离子络合结构[92]。因此,即使在高浓度Cd土中,跳虫通过启动金属硫蛋白编码基因,制造大量的金属硫蛋白,与重金属Cd结合,再将其排出体外;同时跳虫的抗生素合成、伤口愈合、止血等基因也会大量表达,有助于跳虫在高Cd环境中生存[92]。土壤动物在城市环境变化下产生的生理学及分子生物学反应可以为宏观水平土壤污染的影响提供机理解释,也为环境健康风险提供了很好的依据,但相关研究还有待进一步开展。
8 研究展望
城市化进程中产生的各种环境胁迫问题已经引起众多****,以及政府和公众的关注。城市化及其区域生态安全,包括城市土壤研究方兴未艾。但是,现有的研究尚未将城市表层土壤作为城市生态系统的一个重要界面,并对城市环境要素以其为介质发生的功能过程及生态效应展开研究,这是今后城市土壤学应当加强的一个研究领域。另外,城市居民健康是城市生态系统健康的核心,但是在区域尺度,作为人为排放物汇聚地的城市土壤表层如何通过其源-汇效应,以及食物链传递,造成城市人居健康风险,以及如何对区域环境质量进行综合、有效的生物健康评估,都有待进一步系统的研究。关于城市土壤表层与城市生态健康,今后应重点开展以下几方面的研究：8.1 加强城市土壤表层生态界面效应研究
界面生态学是研究在界面两端各种生态因子通过介质相互交流、作用规律的科学。传统的土壤学大多致力于将土壤作为一个独立的自然体而研究其形成、特性及其内部相互作用,较少重视土壤在地球表层中的巨大作用,也就是它与大气圈、水圈和岩石圈复杂的相互作用。目前己经广泛认识到土壤构成了陆地环境的主要循环和清洁体系,对于区域化学元素循环和水资源状况起着决定性作用。城市土壤表层存在密切的土-气、土-水交换,也是多样性显著的土壤生物群落的聚居地,加强其中的源-运移-扩散模式及其动力学过程研究,对于建立科学的城市土壤污染风险评估体系、控制城市土壤污染、实现城市人居环境的可持续发展都具有重要的意义。8.2 建立长期、多尺度的城市土壤研究计划
首先,在空间尺度上,需要在城市不同功能区或不同城市化水平的梯度区域内建立城市土壤定位研究站点,掌握城市土壤空间尺度上的格局特征;同时在这些站点开展城市环境效应的长期监测,了解城市环境变化过程及其在时间尺度上的累积效应。在实验开展尺度上,不仅需要大尺度的野外观测调查研究,也需要小尺度的模拟控制实验,通过对特定因子或多因子的控制技术,量化分析城市环境变化的影响。在微观尺度上对典型土壤生物开展环境毒理学研究,在生理学、病理学、分子生物学上进行测试分析,以揭示城市化干扰对生命体造成威胁的生理生化和遗传机制,深入揭示城市环境变化健康风险的本质。8.3 重视土壤动物在城市土壤健康诊断和改良中的作用
现有城市土壤环境研究侧重于土壤污染物的调查分析,而对土壤健康诊断认识不足,尤其是土壤健康状态与人类健康风险直接相关,发展城市土壤的健康诊断研究,可以为城市可持续发展和人居环境保障提供依据。土壤生物群落组成、种群发展及生理状况就是反映城市土壤健康状况的良好指示器。土壤动物不同尺度水平的生物学特征,比如,个体尺度上的细胞或亚细胞生化效应,种群尺度上的关键物种、特有物种、环境敏感物种及其种群数量、出生率、死亡率等,群落尺度上不同物种的结构组成、生物量及功能过程等,都可以从生物风险和生命健康的角度指示城市生态健康状况[97,98]。同时,因为动物的积极活动及旺盛的取食和代谢功能,不仅可以提高土壤肥力,还可以提高城市绿地雨水下渗和污染物分解转化效率等。国外已经有城市尝试利用蚯蚓分解城市垃圾,可以大大提高有机质的熟化效率,也有研究证实蚯蚓可以加速PCB降解率[17]。因此,城市土壤动物在土壤健康诊断、城市环境可持续发展研究中都有重要潜力。致谢：
感谢广州大学地理科学学院吴志峰教授、杨现坤副教授、广东省生态环境技术研究所肖辉林研究员在论文写作过程中提供的帮助。参考文献 原文顺序
文献年度倒序
文中引用次数倒序
被引期刊影响因子
DOI:10.11821/dlxb201901014URL [本文引用: 2]
国家自然科学基金的学科申请代码是形成合理基础研究资助格局、促进学科均衡发展、鼓励学科交叉和发展新兴方向的指南。本文系统梳理了自1986年国家自然科学基金委员会创建至今,地理学科申请代码体系的历史沿革,重点对新时期地理学科申请代码体系在水、土、生态系服务、环境和人地关系演变等方向的布设特点,以及对未来学科基础研究资助格局的影响进行了分析和展望。
DOI:10.11821/dlxb201901014URL [本文引用: 2]
国家自然科学基金的学科申请代码是形成合理基础研究资助格局、促进学科均衡发展、鼓励学科交叉和发展新兴方向的指南。本文系统梳理了自1986年国家自然科学基金委员会创建至今,地理学科申请代码体系的历史沿革,重点对新时期地理学科申请代码体系在水、土、生态系服务、环境和人地关系演变等方向的布设特点,以及对未来学科基础研究资助格局的影响进行了分析和展望。
DOI:10.5846/stxb201801310263URL [本文引用: 2]
土壤作为地球表层系统物质和能量迁移转化的关键节点，其生态功能受到城市化快速发展的严重影响，土壤安全面临严峻的挑战。城郊生态系统受到城市和乡村的双重影响，具有复杂的景观结构和剧烈的动态变化，土壤安全问题更为突出和复杂。基于文献计量学方法，对1990-2017年发表的相关文献进行了统计，梳理和总结了城郊生态系统土壤安全研究的趋势和热点问题，对城郊生态系统中土壤安全面临的问题，及其特殊性、复杂性进行了重点论述，明确了当前快速城市化发展过程中城郊土壤安全研究面临的问题和挑战。建议今后的城郊生态系统土壤安全研究应加强区域尺度上的综合和不同城市发展模式下地区之间的比较，明确城市扩张对城郊生态系统土壤安全的影响机制；建立和完善基于"土壤安全"的城郊生态系统服务评价框架，深入研究城郊生态系统格局-过程-服务之间的关系；明确解析城郊土壤主要污染物来源及其复合污染状况，并结合区域特征，因地制宜开展科学的生态规划，优化城郊景观格局，提升城郊地区土壤安全与生态系统服务功能；明确土壤安全在城郊生态系统可持续发展目标中的重要性，建立科学合理的管理政策。
DOI:10.5846/stxb201801310263URL [本文引用: 2]
土壤作为地球表层系统物质和能量迁移转化的关键节点，其生态功能受到城市化快速发展的严重影响，土壤安全面临严峻的挑战。城郊生态系统受到城市和乡村的双重影响，具有复杂的景观结构和剧烈的动态变化，土壤安全问题更为突出和复杂。基于文献计量学方法，对1990-2017年发表的相关文献进行了统计，梳理和总结了城郊生态系统土壤安全研究的趋势和热点问题，对城郊生态系统中土壤安全面临的问题，及其特殊性、复杂性进行了重点论述，明确了当前快速城市化发展过程中城郊土壤安全研究面临的问题和挑战。建议今后的城郊生态系统土壤安全研究应加强区域尺度上的综合和不同城市发展模式下地区之间的比较，明确城市扩张对城郊生态系统土壤安全的影响机制；建立和完善基于"土壤安全"的城郊生态系统服务评价框架，深入研究城郊生态系统格局-过程-服务之间的关系；明确解析城郊土壤主要污染物来源及其复合污染状况，并结合区域特征，因地制宜开展科学的生态规划，优化城郊景观格局，提升城郊地区土壤安全与生态系统服务功能；明确土壤安全在城郊生态系统可持续发展目标中的重要性，建立科学合理的管理政策。
DOI:10.11821/dlxb201512001URL [本文引用: 1]
土壤是人类赖以生存和文明建设的重要基础资源。作为地球关键带的核心要素,土壤圈是地球表层系统最为活跃的圈层,而且土壤过程是控制地球关键带中物质、能量和信息流动与转化的重要节点。由于土壤的多重功能不断得到重视,传统的土壤概念已经无法全面反应土壤的功能和作用,为此本文提出了土壤安全的概念。土壤安全是一种基于土壤可持续发展目标而提出一种系统战略框架,为土壤资源的可持续利用和保护提供了理论基础。本文重点论述了地球关键带和土壤安全的内涵以及两者之间的差异和紧密关系。此外,还对土壤安全框架下的生态系统服务进行了梳理和总结,最后对面向生态系统服务的土壤安全需求进行了展望。
DOI:10.11821/dlxb201512001URL [本文引用: 1]
土壤是人类赖以生存和文明建设的重要基础资源。作为地球关键带的核心要素,土壤圈是地球表层系统最为活跃的圈层,而且土壤过程是控制地球关键带中物质、能量和信息流动与转化的重要节点。由于土壤的多重功能不断得到重视,传统的土壤概念已经无法全面反应土壤的功能和作用,为此本文提出了土壤安全的概念。土壤安全是一种基于土壤可持续发展目标而提出一种系统战略框架,为土壤资源的可持续利用和保护提供了理论基础。本文重点论述了地球关键带和土壤安全的内涵以及两者之间的差异和紧密关系。此外,还对土壤安全框架下的生态系统服务进行了梳理和总结,最后对面向生态系统服务的土壤安全需求进行了展望。
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DOI:10.1016/j.envpol.2009.02.026URLPMID:19303182 [本文引用: 1]
The response of specific groups of organisms, like Collembola to atmospheric nitrogen (N) deposition is still scarcely known. We investigated the Collembola community in a subalpine forest (Alptal, Switzerland) as subjected for 12 years to an experimentally increased N deposition (+25 on top of ambient 12 kg N ha(-1) year(-1)). In the 0-5 cm soil layer, there was a tendency of total Collembola densities to be lower in N-treated than in control plots. The density of Isotomiella minor, the most abundant species, was significantly reduced by the N addition. A tendency of lower Collembola group richness was observed in N-treated plots. The Density-Group index (dDG) showed a significant reduction of community diversity, but the Shannon-Wiener index (H') was not significantly affected by the N addition. The Collembola community can be considered as a bioindicator of N inputs exceeding the biological needs, namely, soil N saturation.
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DOI:10.1016/j.apsoil.2017.03.022URL [本文引用: 6]
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城市化是人类活动影响下自然生态系统向人工生态系统的急剧变化形式 ,它引起一系列生态环境条件的改变。城市化对土壤资源的数量和质量产生深刻的影响 ,包括土壤地表封闭引起的土壤生态功能彻底消失 ,土壤物理性质恶化 ,土壤形态学特征和演变过程深受人为作用的影响 ,短程变异增加而总体多样性降低 ,土壤污染加剧 ,土壤养分富集等多方面。城市化过程中土地利用变化对土壤产生一系列生态环境效应 ,如养分径流输出增加 ,热缓冲能力下降 ,污染转移危险性上升等。有必要迅速开展城市化过程中土壤质量演变及其生态环境效应的系统研究 ,为我国城市可持续发展提供理论依据。
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城市化是人类活动影响下自然生态系统向人工生态系统的急剧变化形式 ,它引起一系列生态环境条件的改变。城市化对土壤资源的数量和质量产生深刻的影响 ,包括土壤地表封闭引起的土壤生态功能彻底消失 ,土壤物理性质恶化 ,土壤形态学特征和演变过程深受人为作用的影响 ,短程变异增加而总体多样性降低 ,土壤污染加剧 ,土壤养分富集等多方面。城市化过程中土地利用变化对土壤产生一系列生态环境效应 ,如养分径流输出增加 ,热缓冲能力下降 ,污染转移危险性上升等。有必要迅速开展城市化过程中土壤质量演变及其生态环境效应的系统研究 ,为我国城市可持续发展提供理论依据。
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DOI:10.1016/S1002-0160(08)60029-6URL [本文引用: 1]
Abstract
The vertical distribution and migration of Cu, Zn, Pb, and Cd in two forest soil proflles near an industrial emission source were investigated using a high resolution sampling method together with reference element Ti. One-meter soil proflle was sectioned horizontally at 2 cm intervals in the flrst 40 cm, 5 cm intervals in the next 40 cm, and 10 cm intervals in the last 20 cm. The migration distance and rate of heavy metals in the soil proflles were calculated according to their relative concentrations in the proflles, as calibrated by the reference element Ti. The enrichment of heavy metals appeared in the uppermost layer of the forest soil, and the soil heavy metal concentrations decreased down the proflle until reaching their background values. The calculated average migration rates of Cd, Cu, Pb, and Zn were 0.70, 0.33, 0.37, and 0.76 cm year−1, respectively, which were comparable to other methods. A simulation model was proposed, which could well describe the distribution of Cu, Zn, Pb, and Cd in natural forest soils.DOI:10.7326/0003-4819-122-2-199501150-00014URLPMID:7992992 [本文引用: 1]
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DOI:10.3161/00159301FF1997.40.1-9URL [本文引用: 5]
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通过对乌鲁木齐城市土壤基本理化性质、营养盐特征、重金属污染的研究,结果表明:乌鲁木齐市城市土壤较自然土壤碱性更强、有机质丰富;氮素缺乏,磷有明显的累积特征;Cr,Cu,Pb,Zn含量很高,Mn,Fe含量不高;除Mn和Fe以外,其他重金属及有机质、总氮、总磷在不同功能区的空间分布差异都很大;重金属形态均以残渣态为主,但各重金属形态分布规律并不完全相同,Pb的活性最大,Fe的活性最小.
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通过对乌鲁木齐城市土壤基本理化性质、营养盐特征、重金属污染的研究,结果表明:乌鲁木齐市城市土壤较自然土壤碱性更强、有机质丰富;氮素缺乏,磷有明显的累积特征;Cr,Cu,Pb,Zn含量很高,Mn,Fe含量不高;除Mn和Fe以外,其他重金属及有机质、总氮、总磷在不同功能区的空间分布差异都很大;重金属形态均以残渣态为主,但各重金属形态分布规律并不完全相同,Pb的活性最大,Fe的活性最小.
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DOI:10.1007/s10653-019-00326-2URLPMID:31134395 [本文引用: 1]
Heavy metals are of environmental significance due to their effect on human health and the ecosystem. One of the major exposure pathways of Heavy metals for humans is through food crops. It is postulated in the literature that when crops are grown in soils which have excessive concentrations of heavy metals, they may absorb elevated levels of these elements thereby endangering consumers. However, due to land scarcity, especially in urban areas of Africa, potentially contaminated land around industrial dumps such as tailings is cultivated with food crops. The lack of regulation for land-usage on or near to mine tailings has not helped this situation. Moreover, most countries in tropical Africa have not defined guideline values for heavy metals in soils for various land uses, and even where such limits exist, they are based on total soil concentrations. However, the risk of uptake of heavy metals by crops or any soil organisms is determined by the bioavailable portion and not the total soil concentration. Therefore, defining bioavailable levels of heavy metals becomes very important in HM risk assessment, but methods used must be specific for particular soil types depending on the dominant sorption phases. Geochemical speciation modelling has proved to be a valuable tool in risk assessment of heavy metal-contaminated soils. Among the notable ones is WHAM (Windermere Humic Aqueous Model). But just like most other geochemical models, it was developed and adapted on temperate soils, and because major controlling variables in soils such as SOM, temperature, redox potential and mineralogy differ between temperate and tropical soils, its predictions on tropical soils may be poor. Validation and adaptation of such models for tropical soils are thus imperative before such they can be used. The latest versions (VI and VII) of WHAM are among the few that consider binding to all major binding phases. WHAM VI and VII are assemblages of three sub-models which describe binding to organic matter, (hydr)oxides of Fe, Al and Mn and clays. They predict free ion concentration, total dissolved ion concentration and organic and inorganic metal ion complexes, in soils, which are all important components for bioavailability and leaching to groundwater ways. Both WHAM VI and VII have been applied in a good number of soils studies with reported promising results. However, all these studies have been on temperate soils and have not been tried on any typical tropical soils. Nonetheless, since WHAM VII considers binding to all major binding phases, including those which are dominant in tropical soils, it would be a valuable tool in risk assessment of heavy metals in tropical soils. A discussion of the contamination of soils with heavy metals, their subsequent bioavailability to crops that are grown in these soils and the methods used to determine various bioavailable phases of heavy metals are presented in this review, with an emphasis on prospective modelling techniques for tropical soils.
DOI:10.1007/s11252-016-0547-zURL [本文引用: 4]
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城市热岛效应(Urbanheatislandeffect,简称UHI)是一种由于城市建筑及人类活动导致热量在城区空间范围内聚集的现象,是城市气候最显著的特征之一。热岛引起地表温度的提高,必将强烈地影响着城市生态系统的物流、能流,改变城市生态系统结构和功能,产生一系列生态环境效应,影响着城市气候、城市水文、城市土壤理化性质、城市大气环境、城市生物习性、城市物质循环、城市能量代谢以及城市居民健康等。提高能量利用效率、优化城市格局、建设绿色屋顶、采用高反射率地表材料以及增加城市绿地均可有效地控制城市热岛效应。利用遥感手段和数值模型技术,开展多尺度的城市热岛生态环境效应研究,为改善城市生态环境、实现城市可持续发展提供理论依据。
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城市热岛效应(Urbanheatislandeffect,简称UHI)是一种由于城市建筑及人类活动导致热量在城区空间范围内聚集的现象,是城市气候最显著的特征之一。热岛引起地表温度的提高,必将强烈地影响着城市生态系统的物流、能流,改变城市生态系统结构和功能,产生一系列生态环境效应,影响着城市气候、城市水文、城市土壤理化性质、城市大气环境、城市生物习性、城市物质循环、城市能量代谢以及城市居民健康等。提高能量利用效率、优化城市格局、建设绿色屋顶、采用高反射率地表材料以及增加城市绿地均可有效地控制城市热岛效应。利用遥感手段和数值模型技术,开展多尺度的城市热岛生态环境效应研究,为改善城市生态环境、实现城市可持续发展提供理论依据。
DOI:10.1016/j.scitotenv.2019.136068URLPMID:31869706 [本文引用: 1]
The urban heat island is a vastly documented climatological phenomenon, but when it comes to coastal cities, close to desert areas, its analysis becomes extremely challenging, given the high temporal variability and spatial heterogeneity. The strong dependency on the synoptic weather conditions, rather than on city-specific, constant features, hinders the identification of recurrent patterns, leading conventional predicting algorithms to fail. In this paper, an advanced artificial intelligence technique based on long short-term memory (LSTM) model is applied to gain insight and predict the highly fluctuating heat island intensity (UHII) in the city of Sydney, Australia, governed by the dualistic system of cool sea breeze from the ocean and hot western winds from the vast desert biome inlands. Hourly measurements of temperature, collected for a period of 18?years (1999-2017) from 8 different sites in a 50?km radius from the coastline, were used to train (80%) and test (20%) the model. Other inputs included date, time, and previously computed UHII, feedbacked to the model with an optimized time step of six hours. A second set of models integrated wind speed at the reference station to account for the sea breeze effect. The R2 ranged between 0.770 and 0.932 for the training dataset and between 0.841 and 0.924 for the testing dataset, with the best performance attained right in correspondence of the city hot spots. Unexpectedly, very little benefit (0.06-0.43%) was achieved by including the sea breeze among the input variables. Overall, this study is insightful of a rather rare climatological case at the watershed between maritime and desertic typicality. We proved that accurate UHII predictions can be achieved by learning from long-term air temperature records, provided that an appropriate predicting architecture is utilized.
DOI:10.1016/j.scitotenv.2019.136031URLPMID:31869604 [本文引用: 6]
Remediation of mercury (Hg) contaminated sites has long relied on traditional approaches, such as removal and containment/capping. Here we review contemporary practices in the assessment and remediation of industrial-scale Hg contaminated sites and discuss recent advances. Significant improvements have been made in site assessment, including the use of XRF to rapidly identify the spatial extent of contamination, Hg stable isotope fractionation to identify sources and transformation processes, and solid-phase characterization (XAFS) to evaluate Hg forms. The understanding of Hg bioavailability for methylation has been improved by methods such as sequential chemical extractions and porewater measurements, including the use of diffuse gradient in thin-film (DGT) samplers. These approaches have shown varying success in identifying bioavailable Hg fractions and further study and field applications are needed. The downstream accumulation of methylmercury (MeHg) in biota is a concern at many contaminated sites. Identifying the variables limiting/controlling MeHg production-such as bioavailable inorganic Hg, organic carbon, and/or terminal electron acceptors (e.g. sulfate, iron) is critical. Mercury can be released from contaminated sites to the air and water, both of which are influenced by meteorological and hydrological conditions. Mercury mobilized from contaminated sites is predominantly bound to particles, highly correlated with total sediment solids (TSS), and elevated during stormflow. Remediation techniques to address Hg contamination can include the removal or containment of Hg contaminated materials, the application of amendments to reduce mobility and bioavailability, landscape/waterbody manipulations to reduce MeHg production, and food web manipulations through stocking or extirpation to reduce MeHg accumulated in desired species. These approaches often rely on knowledge of the Hg forms/speciation at the site, and utilize physical, chemical, thermal and biological methods to achieve remediation goals. Overall, the complexity of Hg cycling allows many different opportunities to reduce/mitigate impacts, which creates flexibility in determining suitable and logistically feasible remedies.
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DOI:10.1038/s41598-019-56189-1URLPMID:31863081 [本文引用: 1]
Invasive ants are major agricultural and urban pests and a significant concern in conservation areas. Despite long history of control and eradication efforts, invasive ants continue to spread around the globe driven by a multitude of synergistic factors. Lack of effective management tools is one of the biggest challenges in controlling invasive ants. The goal of the current study was to improve the efficacy and safety of ant management and to develop effective control strategies for sensitive conservation areas. We utilized the Argentine ant (Linepithema humile) as a model system to evaluate a target-specific pesticide delivery system that exploits the interconnected nature of social insect colonies to distribute a toxicant effectively within the colony. The approach, based entirely on horizontal transfer, takes advantage of various levels of social interactions in ant colonies to disseminate a toxicant throughout the colony. Results of laboratory studies coupled with LC/MS/MS analysis demonstrate that fipronil is toxic to Argentine ants in extremely small (nanogram) quantities and is efficiently transferred from a single treated donor to multiple recipients, causing significant secondary mortality. A field study was conducted in native fynbos plots invaded by Argentine ants. The study consisted of collecting na?ve workers, treating them with fipronil, and releasing them within invaded plots. Results show that the release of fipronil-treated ants reduced Argentine ant abundance by >90% within 24?h. The horizontal transfer approach offers environmental benefits with regard to pesticide use in ecologically sensitive environments and appears ideally suited for ant management in conservation areas.
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DOI:10.1016/j.ecoenv.2019.110095URLPMID:31869714 [本文引用: 1]
The wide use of nanoparticles (NPs), gives concern about their possible negative implications in the environment and living organisms. In particular, titanium dioxide (TiO2) NPs are accumulated in biosolids (Bs) coming from wastewater treatment plants, which in turn are used as farm soil amendments and are becoming an important way of NPs entrance in the terrestrial ecosystems. In this study, to simulate a low and cumulative load of TiO2 NPs, 80 and 800?mg TiO2per Kg of soil were spiked in the Bs prior to its addition to soil. The effects of different crystal phases of TiO2 NPs (pure anatase and pure rutile or their mixture) and their non-coated bulk counterparts (larger particles) on the availability of mineral nutrients and on the status of the bacterial communities together with the nutritional status of Pisum sativum L. plants were evaluated. Results showed the reduction, to different extents, on the availability of important soil mineral nutrients (e.g. Mn 65%, Fe 20%, P 27%, averagely), in some cases size- (e.g. P) and dose-dependent. Bacterial biodiversity was also affected by the presence of high TiO2 dose in soil. The mineral nutrition of pea plants was also altered, showing the main reduction in Mn (80% in the roots and 50% in the shoots), K, Zn, P (respectively, 80, 40, and 35% in the roots), and an increase of N in the shoots, with possible consequences on the quality of the crop. The present study gives new integrated data on the effects of TiO2 NPs in the soil-plant system, on the soil health and on the nutritional quality of crops, rising new implications for future policies and human health.
DOI:10.1016/j.scitotenv.2015.07.112URLPMID:26282755
Soil pollution has adverse effects on the performance and life history traits of microorganisms, plants, and animals, yet evidence indicates that even the most polluted sites can support structurally-complex and dynamic ecosystems. The present study aims at determining whether and how litter decomposition, one of the most important soil ecological processes leaf, is affected in a highly trace-metal polluted site. We postulated that past steel mill activities resulting in soil pollution and associated changes in soil characteristics would influence the rate of litter decomposition through two non-exclusive pathways: altered litter chemistry and responses of decomposers to lethal and sub-lethal toxic stress. We carried out a litter-bag experiment using Populus tremula L. leaf litter collected at, and allowed to decompose in, a trace metal polluted site and in three unpolluted sites used as controls. We designed a fully-factorial transplant experimental design to assess effects of litter origin and exposure site on the rate of litter decomposition. We further determined initial litter chemistry, fungal biomass, mesofauna abundance in litter bags, and the soil macrofauna community. Irrespective of the site of litter exposure, litter originating from the polluted site had a two-fold faster decomposition than litter from the unpolluted sites. Litter chemistry, notably the lignin content, seemed most important in explaining the degradation rate of the leaf litter. Abundance of meso and macro-detritivores was higher at the polluted site than at the unpolluted sites. However, litter decomposition proceeded at similar rates in polluted and unpolluted sites. Our results show that trace metal pollution and associated soil and litter changes do not necessarily weaken consumer control on litter decomposition through lethal and sub-lethal toxic stress.
DOI:10.1016/j.geoderma.2015.08.008URL [本文引用: 1]
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城市化对城市土壤动物有重要影响，为了探究城市中不同的地表覆盖类型对土壤动物多样性和群落结构的胁迫作用，以北京市奥林匹克公园为例，于2013年秋季通过Baermann法和Tullgren法研究了4种不同地表类型(裸地、完全硬化地表、部分硬化地表、草坪)下的0～5、5～10、10～15 cm 3个土层深度下土壤动物群落结构和多样性的变化.结果表明： 4种地表类型下,单位体积(100 cm3)内土壤动物的个体总数表现为：草坪(210只)>部分硬化(193只)>完全硬化(183只)>裸地(90只).线虫占总捕获量的72.0%～92.8%，为共有优势类群.类群数上，草坪下土壤动物类群数显著高于裸地.在垂直方向上，除了完全硬化外，其他3种地表类型下的土壤动物具有明显的表聚现象.裸地的Shannon多样性指数和Pielou均匀度指数显著低于其他类型，但Simpson优势度指数显著高于其他类型.草坪的Shannon多样性指数和Margalef丰富度指数最高.硬化类型下土壤动物的多样性介于草坪和裸地之间.从群落相似性来看，除完全硬化和草坪表现为中度相似外，其他地表类型间土壤动物群落相似性指数均表现出中等不相似的特征.动物的多样性指标与土壤温度、pH、速效钾均有显著相关性.
URL [本文引用: 3]
城市化对城市土壤动物有重要影响，为了探究城市中不同的地表覆盖类型对土壤动物多样性和群落结构的胁迫作用，以北京市奥林匹克公园为例，于2013年秋季通过Baermann法和Tullgren法研究了4种不同地表类型(裸地、完全硬化地表、部分硬化地表、草坪)下的0～5、5～10、10～15 cm 3个土层深度下土壤动物群落结构和多样性的变化.结果表明： 4种地表类型下,单位体积(100 cm3)内土壤动物的个体总数表现为：草坪(210只)>部分硬化(193只)>完全硬化(183只)>裸地(90只).线虫占总捕获量的72.0%～92.8%，为共有优势类群.类群数上，草坪下土壤动物类群数显著高于裸地.在垂直方向上，除了完全硬化外，其他3种地表类型下的土壤动物具有明显的表聚现象.裸地的Shannon多样性指数和Pielou均匀度指数显著低于其他类型，但Simpson优势度指数显著高于其他类型.草坪的Shannon多样性指数和Margalef丰富度指数最高.硬化类型下土壤动物的多样性介于草坪和裸地之间.从群落相似性来看，除完全硬化和草坪表现为中度相似外，其他地表类型间土壤动物群落相似性指数均表现出中等不相似的特征.动物的多样性指标与土壤温度、pH、速效钾均有显著相关性.
URL [本文引用: 1]
于2014年4月(春季)、7月(夏季)、10月(秋季)和2015年1月(冬季)对上海市4种城市森林中小型土壤动物群落进行调查，共捕获土壤动物2190只，隶属于6门15纲22个类群，优势类群为线虫纲和蜱螨亚纲，分别占总密度的56.0%和21.8%，常见类群为线蚓科、轮虫纲、弹尾纲和膜翅目，共占总密度的18.7%.不同类型城市森林中小型土壤动物密度存在显著差异(P<0.05)，其中，水杉林密度最高，香樟林最低；类群数以近自然林最高，水杉林最低.各林地中小型土壤动物群落结构具有明显的季节动态，整体表现为秋、冬季密度值较高，夏、秋季类群数较高.在垂直分布上，香樟林表聚程度最为突出，近自然林各层分布相对均匀.密度类群指数(DG)大小顺序为近自然林(6.953)>香樟林(6.351)>悬铃木林(6.313)>水杉林(5.910)，该指数可以较好地表征各林地的群落多样性.冗余分析(RDA)显示，土壤容重、土壤有机质、土壤总氮等是影响城市森林中小型土壤动物群落结构的主要环境因子，其中蜱螨亚纲和线蚓科与土壤有机质和总氮呈正相关，双翅目幼虫和轮虫纲与土壤含水量呈正相关.
URL [本文引用: 1]
于2014年4月(春季)、7月(夏季)、10月(秋季)和2015年1月(冬季)对上海市4种城市森林中小型土壤动物群落进行调查，共捕获土壤动物2190只，隶属于6门15纲22个类群，优势类群为线虫纲和蜱螨亚纲，分别占总密度的56.0%和21.8%，常见类群为线蚓科、轮虫纲、弹尾纲和膜翅目，共占总密度的18.7%.不同类型城市森林中小型土壤动物密度存在显著差异(P<0.05)，其中，水杉林密度最高，香樟林最低；类群数以近自然林最高，水杉林最低.各林地中小型土壤动物群落结构具有明显的季节动态，整体表现为秋、冬季密度值较高，夏、秋季类群数较高.在垂直分布上，香樟林表聚程度最为突出，近自然林各层分布相对均匀.密度类群指数(DG)大小顺序为近自然林(6.953)>香樟林(6.351)>悬铃木林(6.313)>水杉林(5.910)，该指数可以较好地表征各林地的群落多样性.冗余分析(RDA)显示，土壤容重、土壤有机质、土壤总氮等是影响城市森林中小型土壤动物群落结构的主要环境因子，其中蜱螨亚纲和线蚓科与土壤有机质和总氮呈正相关，双翅目幼虫和轮虫纲与土壤含水量呈正相关.
DOI:10.1126/science.264.5165.1581URLPMID:17769603 [本文引用: 1]
Fragmentation of habitats in the agricultural landscape is a major threat to biological diversity, which is greatly determined by insects. Isolation of habitat fragments resulted in decreased numbers of species as well as reduced effects of natural enemies. Manually established islands of red clover were colonized by most available herbivore species but few parasitoid species. Thus, herbivores were greatly released from parasitism, experiencing only 19 to 60 percent of the parasitism of nonisolated populations. Species failing to successfully colonize isolated islands were characterized by small and highly variable populations. Accordingly, lack of habitat connectivity released insects from predator control.
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文章对哺乳动物、土壤动物和微生物遭受重金属污染后的生理变化及生长反应进行了论述;并对今后相关研究工作提出了建议.
URL [本文引用: 1]
文章对哺乳动物、土壤动物和微生物遭受重金属污染后的生理变化及生长反应进行了论述;并对今后相关研究工作提出了建议.
URL [本文引用: 3]
在重金属的胁迫下,阿伯丁市城市土壤中微生物特征发生了显著的变化,与农村土相比,微生物基底呼吸作用明显增强,但微生物生物量却显著降低,微生物生理参数Cmic/Corg、qCO2值明显升高,Biolog数据显示城市土壤对能源碳的消耗量和速度显著升高,而且对能源碳的利用方式发生了改变,但利用效率却明显降低,反映出微生物特性可作为城市土壤环境质量变异的有效指标.
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在重金属的胁迫下,阿伯丁市城市土壤中微生物特征发生了显著的变化,与农村土相比,微生物基底呼吸作用明显增强,但微生物生物量却显著降低,微生物生理参数Cmic/Corg、qCO2值明显升高,Biolog数据显示城市土壤对能源碳的消耗量和速度显著升高,而且对能源碳的利用方式发生了改变,但利用效率却明显降低,反映出微生物特性可作为城市土壤环境质量变异的有效指标.
DOI:10.1007/s003740100379URL [本文引用: 1]
DOI:10.1111/1750-3841.14985URLPMID:31869860 [本文引用: 1]
The quality perception of gluten-free beer was explored using conjoint analysis with a panel of Polish millennials (n = 200; aged 20 to 35), who were given 64 gluten-free beer concepts to evaluate and score on a 9-point scale of interest (1 = not interested at all; 9 = extremely interested). The constituent factors of the beer concepts were alcohol content, color, type of malt, price, drinking location and occasion, bottle size, label claims, type of farming, type of brewer, and bottle closure. Consumers judged price (38.4%) and alcohol (28.8%) five times more important than the other factors. Bottle size (5.3%), claims (4.8%), type of brewer (4.8%), malt type (4.6%), bottle closure (4.0%), beer color (3.6%), drinking location (2.3%), drinking occasion (2.0%), and type of farming (1.3%) were considered of little importance. The interest of Polish Millennials in gluten-free beer resulted moderate and not linked to medical needs. Males were more interested in gluten-free beers and gave more importance to alcohol content and less importance to price, compared to females. However, for both genders, interest and price were inversely correlated, while interest and alcohol content were directly correlated. PRACTICAL APPLICATION: The identification of the product factors that are preferred by consumers is paramount to translate consumers' needs and expectations into a beer designed to produce the best possible product in a relatively short period. Including information directly obtained from consumers before final design decisions are taken on the final beer output, helps ensuring development directions are on target and constitutes a cost-competitive approach to product development.
DOI:10.1016/j.scitotenv.2014.03.026URLPMID:24686142 [本文引用: 1]
The concentrations of As, Ba, Co, Cr, Cu, Mn, Ni, Pb, V and Zn in campus dust from kindergartens, elementary schools, middle schools and universities of Xi'an, China were determined by X-ray fluorescence spectrometry. Correlation coefficient analysis, principal component analysis (PCA) and cluster analysis (CA) were used to analyze the data and to identify possible sources of these metals in the dust. The spatial distributions of metals in urban dust of Xi'an were analyzed based on the metal concentrations in campus dusts using the geostatistics method. The results indicate that dust samples from campuses have elevated metal concentrations, especially for Pb, Zn, Co, Cu, Cr and Ba, with the mean values of 7.1, 5.6, 3.7, 2.9, 2.5 and 1.9 times the background values for Shaanxi soil, respectively. The enrichment factor results indicate that Mn, Ni, V, As and Ba in the campus dust were deficiently to minimally enriched, mainly affected by nature and partly by anthropogenic sources, while Co, Cr, Cu, Pb and Zn in the campus dust and especially Pb and Zn were mostly affected by human activities. As and Cu, Mn and Ni, Ba and V, and Pb and Zn had similar distribution patterns. The southwest high-tech industrial area and south commercial and residential areas have relatively high levels of most metals. Three main sources were identified based on correlation coefficient analysis, PCA, CA, as well as spatial distribution characteristics. As, Ni, Cu, Mn, Pb, Zn and Cr have mixed sources - nature, traffic, as well as fossil fuel combustion and weathering of materials. Ba and V are mainly derived from nature, but partly also from industrial emissions, as well as construction sources, while Co principally originates from construction.
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DOI:10.1016/j.envint.2006.06.022URL [本文引用: 1]
Abstract
This review article focused on the current status of mercury (Hg) contamination in different ecological compartments in China, and their possible environmental and health impacts, focusing on some major cities. Mercury emission from non-ferrous metals smelting (especially zinc smelting), coal combustion and miscellaneous activities (of which battery and fluorescent lamp production and cement production are the largest), contributed about 45%, 38% and 17%, respectively, to the total Hg emission based on the data of 1999. Mercury contamination is widespread in different ecological compartments such as atmosphere, soil and water. There is evidence showing bioaccumulation and biomagnification of Hg in aquatic food chains, with higher concentrations detected in carnivorous fish. In terms of human exposure to Hg, fish consumption is the major exposure pathway for residents living in coastal cities such as Hong Kong, but inhalation may be another major source, affecting human health in areas with severe atmospheric Hg, such as Guiyang City (Guizhou Province). The first case study indicated that after closure of the acetic acid plant 20years at Songyuan City (Jilin Province), 16.7% of residents' hair still contained Hg concentration in excess of 1mg/kg (the reference dosage value, RfD set by USEPA). The second case study indicated that the male residents of Hong Kong who consumed more than four or more meals of fish per week tended to contain higher Hg in their hair, which was linked to their subfertility. There is also increasing evidence showing that skin disorders and autism in Hong Kong children are related to their high Hg body loadings (hair, blood and urine), through prenatal methyl Hg exposure. There seems to be an urgent need to identify the sources of Hg, speciation and concentrations in different ecological compartments, which may lead to high body loadings in human beings. Adverse health effects of residents living in places with a higher background level of Hg, due to long-term exposure to chronic levels of Hg through oral intake should not be overlooked.[本文引用: 1]
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DOI:10.1016/0269-7491(94)90079-5URLPMID:15091669 [本文引用: 1]
This paper estimates the present UK environmental loading of polychlorinated biphenyls (PCBs). Of the estimated approximately 40,000 t SigmaPCB sold in the UK since 1954, only an estimated 1% (400 t) are now present in the UK environment. Comparisons of estimated production and current environmental loadings of congeners 28, 52, 101, 138, 153 and 180 suggest that PCB persistence broadly increases with increasing chlorination. Those PCBs that are not now present in the UK environment are considered to have been destroyed--by natural or anthropogenic mechanisms, to be still in use, to reside in landfills or to have undergone atmospheric and/or pelagic transport from the UK. The dramatic fall in PCB levels in archived UK soils and vegetation between the mid-1960s and the present is evidence that the latter mechanism is the most important and that a significant proportion of PCBs released into the UK environment in the 1960s have subsequently undergone environmental transport away from the UK. The bulk (93.1%) of the estimated contemporary UK environmental burden of SigmaPCBs is associated with soils, with the rest found in seawater (3.5%) and marine sediments (2.1%). Freshwater sediments, vegetation, humans and sewage sludge combined account for 1.4% of the present burden, whilst PCB loadings in air and freshwater are insignificant. Although consideration of individual congeners does not reveal any major deviations from the relative partitioning of Sigma PCBs, the importance of sinks other than soils is enhanced for individual congeners, particularly 138 and 180. In particular, around 2% of the total UK burden of congener 180 is present in humans, implying that biodata as a whole may constitute an important sink for the higher chlorinated congeners. The contemporary flux of SigmaPCBs to the UK surface is estimated at 19 t yr(-1), compared with an estimated annual flux to the atmosphere of 44-46 t. This implies that the major sources of PCBs to the UK atmosphere have been identified and that there is currently a net loss of these compounds from the UK. These sources are: volatilisation from soils (88.1%), leaks from large capacitors (8.5%), the production of refuse-derived fuel (RDF) (2.2%), leaks from transformers (0.6%), the recovery of contaminated scrap metal (0.5%) and volatilisation from sewage sludge-amended land (0.2%). Interestingly, whilst large excesses of estimated annual fluxes to the atmosphere over deposition fluxes for individual congeners exist for congeners 28, 52 and 101, estimates of fluxes in both directions across the soil-atmosphere interface agree closely for congeners 138, 153 and 180. This suggests that lower chlorinated congeners are more susceptible to both long-range environmental transport beyond the UK and to atmospheric degradation. Retrospective analysis of dated sediment cores, vegetation and soils indicates that environmental transport from North America and continental Europe introduced PCBs into the British environment well before the onset of their commercial production in the UK in 1954. Since that time, the input of PCBs to the UK environment has essentially reflected temporal trends in UK use. After peaking in the 1960s they declined rapidly through the 1970s following restrictions on PCB use. Recent evidence, however, is that the rate of decrease has diminished and that further significant reductions in fresh environmental input will take some time to occur. Such reductions will be especially slow for humans and other biota with long life-spans. This stems partly from cross-generational transfer from parents to offspring and also because the persistence of PCBs in biota means that present body burdens will reflect past as well as current exposure.
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随着城市化进程的加快，城市土壤中的多环芳烃（PAHs）污染日趋严重.本文从城市土壤中多环芳烃的分布和来源等方面综述了国内外取得的最新研究成果,对影响城市土壤多环芳烃分布的人为因素、自然因素，常见的多环芳烃源解析方法，以及城市土壤多环芳烃污染的风险评价进行了全面的阐述，尤其对地统计学在多环芳烃空间分析及风险评价上的应用进行了总结.最后，对未来城市土壤中多环芳烃研究的重点与发展趋势进行了展望.
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随着城市化进程的加快，城市土壤中的多环芳烃（PAHs）污染日趋严重.本文从城市土壤中多环芳烃的分布和来源等方面综述了国内外取得的最新研究成果,对影响城市土壤多环芳烃分布的人为因素、自然因素，常见的多环芳烃源解析方法，以及城市土壤多环芳烃污染的风险评价进行了全面的阐述，尤其对地统计学在多环芳烃空间分析及风险评价上的应用进行了总结.最后，对未来城市土壤中多环芳烃研究的重点与发展趋势进行了展望.
DOI:10.1016/s0269-7491(02)00285-3URLPMID:12535597 [本文引用: 1]
We determined the concentrations of 35 PCNs, 12 PCBs, and 20 PAHs in 49 urban topsoils under different land use (house garden, roadside grassland, alluvial grassland, park areas, industrial sites, agricultural sites) and in nine rural topsoils. The sums of concentrations of 35 PCNs (sigma35 PCNs) were &lt;0.1-15.4 microg kg(-1) in urban soils and &lt;0.1 to 0.82 microg kg(-1) in rural soils. The PCN, PCB, and PAH concentrations were highest at industrial sites and in house gardens. While rural soils receive PCNs, PCBs, and PAHs by common atmospheric deposition, there are site-specific sources of PCNs, PCBs, and PAHs for urban soils such as deposition of contaminated technogenic materials. The PCN, PCB, and PAH concentrations decreased from the central urban to the rural area. In the same order the contribution of lower chlorinated PCNs and PCBs increased because they are more volatile and subject to increased atmospheric transport. The PCNs 52+60, and 73 were more abundant in soil samples than in Halowax mixtures, indicating that combustion contributed to the PCN contamination of the soils.
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DOI:10.1016/j.scitotenv.2019.136044URLPMID:31855652 [本文引用: 1]
There has been an increasing interest in enhancing freshwater aquaculture processes without hindering the progress of the Water Framework Directive. This constitutes the first study to describe a new concept in integrated multitrophic aquaculture (IMTA) that uses cutaway peatlands (bogs) to farm rainbow trout and Eurasian perch with associated organic status that is powered by wind energy and utilizes algae and duckweed to treat rearing water. Approximately 5% of Ireland comprises bogs that support natural ecosystems where there is a pressing need to develop alternative innovation to that of burning peat in order to reduce Ireland's carbon emissions. Specifically, this study evaluates water quality from this new IMTA where intake and terminal holding tank samples were evaluated from May to August 2019. Physicochemical parameters (temperature, pH, nitrogen, phosphorus, oxygen, suspended solids, hardness and alkalinity), and ecotoxicological bioassays (Pseudokirchneriella subcapitata and Daphnia pulex), were used to investigate the potential effects that introducing aquaculture processes may have on peatlands. Nitrite (P?&lt;?0.001), nitrate (P?=?0.016), and chemical oxygen demand (P?=?0.011), were the only physicochemical parameters that differed significantly between the intake and holding tank water indicating that water quality for the most part remained unchanged. Low levels of toxicity were observed between the bioassays suggested the introduction of the processes into the bog were unlikely to cause adverse effects on the ecosystem and the organisms therein. Observations were similar to or lower than those reported previously by other researchers for intensive flow-through aquaculture processes that discharge to receiving water. Findings from this study support the use of peatlands as future locations for integrated aquaculture processes.
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DOI:10.1016/j.cities.2016.01.010URL [本文引用: 1]
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DOI:10.13249/j.cnki.sgs.2018.10.006URL [本文引用: 1]
新型城镇化和乡村振兴战略的深入实施,推动城乡关系进入了一个融合发展的新阶段。采用Citespace1.0软件分析及文献归纳方法,识别了城乡关系研究热点,梳理了城乡关系研究在理论探索、影响因素、测度与评价、空间组织及推进策略等方面的研究进展。在此基础上,重点对面向城乡融合发展的新型城乡关系研究进行了总结,从理论基础与总体思路、多源数据与方法集成等方面提出了基于要素流动的城乡融合分析框架,指出了城乡融合研究的重点是基于多源数据的城乡关系测度与评价,城乡要素流动的特征、格局与效应,城乡要素融合发展的流动机制,城乡融合发展调控策略等。
DOI:10.13249/j.cnki.sgs.2018.10.006URL [本文引用: 1]
新型城镇化和乡村振兴战略的深入实施,推动城乡关系进入了一个融合发展的新阶段。采用Citespace1.0软件分析及文献归纳方法,识别了城乡关系研究热点,梳理了城乡关系研究在理论探索、影响因素、测度与评价、空间组织及推进策略等方面的研究进展。在此基础上,重点对面向城乡融合发展的新型城乡关系研究进行了总结,从理论基础与总体思路、多源数据与方法集成等方面提出了基于要素流动的城乡融合分析框架,指出了城乡融合研究的重点是基于多源数据的城乡关系测度与评价,城乡要素流动的特征、格局与效应,城乡要素融合发展的流动机制,城乡融合发展调控策略等。
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通过对台州市路桥区峰江再生园区及周围的8个样地采样调查,分析了重金属污染对土壤动物多样性的影响。对研究区域进行大量取样调查并测定土样中Cu、Zn、Pb、Cd 的含量。计算出重金属综合污染指数,运用地理信息系统(GIS)技术中的插值法根据重金属综合污染指数制作重金属综合污染趋势图。结合重金属综合污染趋势图与实地勘察,共设置8个采样地。研究方法为大型土壤动物采用野外分层手捡计数,中小型土壤动物用取土器分层取土,带回室内分别用干湿漏斗分离并镜检。结果表明:(1)8个样地共获得土壤动物844只,分属于4门9纲20个类群,其中优势类群为蜱螨目、弹尾目和线虫纲,其他为常见类群和稀有类群。(2)8个样地中土壤动物的个体数量存在极显著性差异(P<0.01),类群数存在极显著性差异(P<0.01)。在严重污染区,土壤动物的数量和类群数稀少,而轻度污染区土壤动物的密度大、群落多样性高,稀有类群大量出现。表明重金属污染能对土壤动物多样性构成严重影响,土壤动物群落的类群和个体数量随污染程度的加重而减少(3)用群落多样性指标DG衡量重金属污染对土壤动物多样性的影响,结果为随着综合污染指数的减小,DG指数逐渐增大。(4)用简单相关性分析表明土壤动物数量变化与综合污染指数具有极显著负相关性(相关系数-0.86),与有机质含量有一定相关性(相关系数0.42)。在轻度污染的样地中,土壤动物的数量随有机质含量的升高而上升,表明在严重的污染区,重金属的毒性对土壤动物的影响是主要的,而在轻度污染区,有机质含量可能成为影响土壤动物多样性的主要因素。(5)从弹尾目的等节跳科和球角跳科在8个样地中的分布特点可知,本地区的等节跳科对重金属污染的耐受力最强。球角跳科数量大、密度高,对重金属污染较敏感,可作为重金属污染的指示生物。
URL [本文引用: 2]
通过对台州市路桥区峰江再生园区及周围的8个样地采样调查,分析了重金属污染对土壤动物多样性的影响。对研究区域进行大量取样调查并测定土样中Cu、Zn、Pb、Cd 的含量。计算出重金属综合污染指数,运用地理信息系统(GIS)技术中的插值法根据重金属综合污染指数制作重金属综合污染趋势图。结合重金属综合污染趋势图与实地勘察,共设置8个采样地。研究方法为大型土壤动物采用野外分层手捡计数,中小型土壤动物用取土器分层取土,带回室内分别用干湿漏斗分离并镜检。结果表明:(1)8个样地共获得土壤动物844只,分属于4门9纲20个类群,其中优势类群为蜱螨目、弹尾目和线虫纲,其他为常见类群和稀有类群。(2)8个样地中土壤动物的个体数量存在极显著性差异(P<0.01),类群数存在极显著性差异(P<0.01)。在严重污染区,土壤动物的数量和类群数稀少,而轻度污染区土壤动物的密度大、群落多样性高,稀有类群大量出现。表明重金属污染能对土壤动物多样性构成严重影响,土壤动物群落的类群和个体数量随污染程度的加重而减少(3)用群落多样性指标DG衡量重金属污染对土壤动物多样性的影响,结果为随着综合污染指数的减小,DG指数逐渐增大。(4)用简单相关性分析表明土壤动物数量变化与综合污染指数具有极显著负相关性(相关系数-0.86),与有机质含量有一定相关性(相关系数0.42)。在轻度污染的样地中,土壤动物的数量随有机质含量的升高而上升,表明在严重的污染区,重金属的毒性对土壤动物的影响是主要的,而在轻度污染区,有机质含量可能成为影响土壤动物多样性的主要因素。(5)从弹尾目的等节跳科和球角跳科在8个样地中的分布特点可知,本地区的等节跳科对重金属污染的耐受力最强。球角跳科数量大、密度高,对重金属污染较敏感,可作为重金属污染的指示生物。
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DOI:10.1016/0013-9351(81)90047-5URLPMID:7274204 [本文引用: 1]
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DOI:10.1016/s1001-0742(10)60554-2URLPMID:22128544 [本文引用: 1]
Soil is an important environmental medium that is closely associated with humans and their health. Despite this, very few studies have measured toxicants in soils, and associated them with health risks in humans. An assessment of health effects from exposure to contaminants in soils surrounding industrial areas of chemical production and storage is important. This article aims at determining pollution characteristics of persistent toxic substances (PTS) in an industrial area in China to unravel the relationship between soil pollution by PTS and human health. One hundred and five soil samples were collected and 742 questionnaires were handed out to residents living in and around an industrial area around Bohai Bay, Tianjin in Northern China. Concentrations of organochlorine pesticides and polycyclic aromatic hydrocarbons (PAHs) were determined in soil. Mann-Whitney U and binary multivariate non-conditional logistic regression models were employed to analyze the relationship between health indicators of local residents and contaminant levels. Odds ratio (OR) and a 95% confidence interval (CI) for health incidences were also calculated. The average concentrations of DDT (73.9 ng/g), HCH (654 ng/g) and PAHs (1225 ng/g) were relatively high in the industrial area. Residents living in the chemical industry parks were exposed to a higher levels of PTS than those living outside the chemical industry parks. This exposure was associated with a higher risk of breast cancer (OR 1.87, 95% CI 0.12-30.06), stomach cancer (OR 1.87, 95% CI 0.26-13.41), dermatitis (OR 1.72, 95% CI 1.05-2.80), gastroenteritis (OR 1.59, 95% CI 0.94-2.68), and pneumonia (OR 1.05, 95% CI 0.58-1.89).
DOI:10.1016/j.ecoenv.2019.110095URLPMID:31869714 [本文引用: 1]
The wide use of nanoparticles (NPs), gives concern about their possible negative implications in the environment and living organisms. In particular, titanium dioxide (TiO2) NPs are accumulated in biosolids (Bs) coming from wastewater treatment plants, which in turn are used as farm soil amendments and are becoming an important way of NPs entrance in the terrestrial ecosystems. In this study, to simulate a low and cumulative load of TiO2 NPs, 80 and 800?mg TiO2per Kg of soil were spiked in the Bs prior to its addition to soil. The effects of different crystal phases of TiO2 NPs (pure anatase and pure rutile or their mixture) and their non-coated bulk counterparts (larger particles) on the availability of mineral nutrients and on the status of the bacterial communities together with the nutritional status of Pisum sativum L. plants were evaluated. Results showed the reduction, to different extents, on the availability of important soil mineral nutrients (e.g. Mn 65%, Fe 20%, P 27%, averagely), in some cases size- (e.g. P) and dose-dependent. Bacterial biodiversity was also affected by the presence of high TiO2 dose in soil. The mineral nutrition of pea plants was also altered, showing the main reduction in Mn (80% in the roots and 50% in the shoots), K, Zn, P (respectively, 80, 40, and 35% in the roots), and an increase of N in the shoots, with possible consequences on the quality of the crop. The present study gives new integrated data on the effects of TiO2 NPs in the soil-plant system, on the soil health and on the nutritional quality of crops, rising new implications for future policies and human health.
DOI:10.1007/s003740050382URL [本文引用: 1]
DOI:10.1016/S0038-0717(00)00153-XURL
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DOI:10.1007/s00442-003-1310-8URL [本文引用: 1]
Dynamic approaches to forest ecosystems are surprisingly rare. Here we report about successional changes in collembolan community structure and microbial performances during forest rotation. The study was carried out in a chronosequence of four spruce forest stands (5-, 25-, 45-, and 95 years old; Tharandter forest, Germany). CO2 release significantly increased after clear-cutting and the amount of C stored in the organic layer subsequently declined. The early phase of forest rotation was characterized by a very active decomposer microflora, stimulation of both fungi and bacteria as well as by a high abundance of surface-oriented Collembola. In addition, collembolan species turnover was accelerated. While the biomass of fungi further increased at intermediate stages of forest rotation, the metabolic activity of the microflora was low, the functional diversity of bacteria declined and the collembolan community became impoverished. Euedaphic species dominated during this stage of forest development. These changes can be explained by both reduction in microhabitat diversity and depletion of food sources associated with an accumulation of recalcitrant soil organic matter. Results of the General Regression Model procedure indicate a shift from specific associations between collembolan functional groups and microbiota at the early stage of forest rotation to a more diffuse pattern at intermediate stages. Though the hypothesis that Collembola are relatively responsive to changes in environmental conditions is confirmed, consistently high community similarity suggests a remarkable persistence of some components of microarthropod assemblages. Our study provides evidence for substantial ecosystem-level implications of changes in the soil food web during forest rotation. Moreover, correlations between bacterial parameters and Collembola point to the overarching impact of differences in the composition of the microbial community on microarthropods.
DOI:10.1007/s00374-017-1200-6URL [本文引用: 1]
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DOI:10.1016/s0269-7491(99)00130-xURLPMID:15093010 [本文引用: 1]
Laboratory studies were carried out to cast light on differences in density responses among collembolan species to copper (Cu)-polluted environments. In a recolonisation experiment, mesofauna originating from a copper (Cupolluted arable field were allowed to colonise defaunated Cu-contaminated and uncontaminated soil cores for 3 months. The abundances of Pseudosinella alba and gamasid mites were higher in the uncontaminated soil, whereas the majority of other collembolans tended to be more abundant in the Cu-enriched soil. Behavioural experiments were conducted to test the ability of single Collembola species to distinguish between filter paper and food soaked in water, Cu, and calcium (Ca) solutions. Onychiurus armatus avoided both Cu and Ca, whereas Folsomia quadrioculata and Folsomia manolachei showed a significant preference for Cu. Isotomurus palustris was not able to distinguish between Cu and water. The results are compared and discussed with regard to other studies on the occurrence and behaviour of Collembola in Cu-contaminated environments. We suggest that microsite selection according to preference or avoidance of high salinity of pore water may partly explain the community structure of Collembola in Cu-polluted soils which are characterised by an increase of euedaphic species. More studies have to be carried out to generalise this concept and to explore to what extent reduced predation by gamasid mites contribute to the success of certain Collembola in Cu-contaminated sites.
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对清水塘重金属污染区土壤生态系统重金属的富集及毒性效应的研究结果表明，土壤中
主要富集的重金属元素为生物毒性较强的Cd、Hg、As以及具有一定毒性的Zn、Pb、Cu，平均综
合污染指数为640.大型土壤动物重金属含量的分析结果表明，重金属富集量随污染程度的
增加而增加，尤其某些巨蚓科种类对Cd表现高富集，富集系数为1196.通过染毒试验进一
步证明，土壤动物种类和数量随Cd浓度的增加而减少.同工酶分析表明，Cd对蚯蚓同工酶活性
有明显的毒性效应.污染区主要种植蔬菜作物，而重金属在蔬菜体内的富集量也随污染
程度的增加而增加，其中蔬菜对Cd的富集有明显的品种间差异.
URL [本文引用: 1]
对清水塘重金属污染区土壤生态系统重金属的富集及毒性效应的研究结果表明，土壤中
主要富集的重金属元素为生物毒性较强的Cd、Hg、As以及具有一定毒性的Zn、Pb、Cu，平均综
合污染指数为640.大型土壤动物重金属含量的分析结果表明，重金属富集量随污染程度的
增加而增加，尤其某些巨蚓科种类对Cd表现高富集，富集系数为1196.通过染毒试验进一
步证明，土壤动物种类和数量随Cd浓度的增加而减少.同工酶分析表明，Cd对蚯蚓同工酶活性
有明显的毒性效应.污染区主要种植蔬菜作物，而重金属在蔬菜体内的富集量也随污染
程度的增加而增加，其中蔬菜对Cd的富集有明显的品种间差异.
DOI:10.1007/BF00324627URLPMID:28313236 [本文引用: 1]
Nematode assemblages constitute a potential instrument for assessing the quality of submersed, temporarily submersed, and terrestrial soils and for the development of an ecological typology and biomonitoring system. Interpretation of physical or pollution-induced disturbances has hitherto mainly been based on changes in diversity, dominance patterns or percentage of dorylaimids (Adenophorea). The maturity index, based on the nematode fauna, is proposed as a gauge of the condition of the soil ecosystem. Values on a coloniser/persister scale are given for nematodes that occur in The Netherlands. The possibilities of the use of this index are demonstrated by a retrospective interpretation of some literature data. The use of nematodes in environmental studies is discussed.
DOI:10.1016/S0167-8809(99)00046-8URL [本文引用: 1]
DOI:10.1007/s0021663540672URLPMID:15067469 [本文引用: 1]
Responses of soil decomposer animals to heavy metal contamination and to concomitant changes in organic matter quality and quantity and in soil microbial biomasses have been studied along a pollution gradient from a Cu-Ni smelter. Samples have been taken separately for nematodes, enchytraeids and microarthropods 0.5, 2 and 8 km from the smelter. Special attention has been paid to the changes in the collembolan fauna. The sampling sites have been located in homogeneous Scots pine ( Pinus sylvestris) forests with podsolic soil profiles. In addition, an experiment has been carried out in which intact soil cores have been transferred in mesh baskets between the sites 2 and 8 km from the smelter (control samples have been transferred within the sites). Although most soil animals seemed to be quite resistant to direct and indirect effects of heavy metals, results indicate that certain soil animals like enchytraeids can be useful and easy to monitor when the effects of heavy metals on soil decomposition systems are assessed.
DOI:10.1016/S0269-7491(98)00198-5URL [本文引用: 1]
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DOI:10.1016/j.apsoil.2006.05.004URL [本文引用: 1]
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DOI:10.1016/j.ejsobi.2015.07.003URL [本文引用: 2]
