摘要:重金属与农药复合型污染成为重要的环境问题之一，然而当前关于两者共同作用对蚯蚓-土壤-植物系统的影响研究还很少。为了探讨镉-乙草胺复合污染对蚯蚓-土壤-玉米农田系统的生态毒理效应和生态过程的影响，本研究通过室内模拟试验，从镉-乙草胺复合胁迫下蚯蚓生理响应、土壤理化性质及玉米形态特征等变化，探讨两者复合污染对玉米生长的影响机制。结果表明：1）随着处理时间的延长，镉-乙草胺复合胁迫下蚯蚓体内SOD活性呈先降低再升高的趋势，而MDA含量呈先升高后降低的趋势；复合胁迫处理第2 d和50 d时，20~30 cm土层的蚯蚓数量占所有土层蚯蚓总量百分比比对照分别增加1.34倍和1.14倍，蚯蚓对镉-乙草胺复合污染作出规避效应而向深层土壤迁移。2）镉-乙草胺复合胁迫下土壤有机质和速效磷含量与处理时间、处理方式、污染物无关，随着处理时间的延长，土壤碱解氮含量呈先显著降低后升高的趋势。3）处理第50 d，30 mg·kg-1 镉、200 mg·kg-1 乙草胺及30 mg·kg-1 镉+200 mg·kg-1 乙草胺处理组玉米根数均显著低于对照，抑制率分别为23.21%、42.86%和50.00%，玉米生物量与株高呈相同趋势，即30 mg·kg-1 镉处理> 200 mg·kg-1 乙草胺处理> 30 mg·kg-1 镉+200 mg·kg-1 乙草胺处理。相关分析表明，两种污染物除对蚯蚓 SOD活性产生拮抗效应外，对蚯蚓 MDA、土壤养分与玉米生长指标均不存在交互作用。本研究得出镉-乙草胺复合污染促进蚯蚓向下迁移影响其垂直分布，并且可以通过改变土壤营养元素含量最终抑制玉米的生长。
关键词:镉-乙草胺复合污染/
蚯蚓垂直分布/
玉米生长/
土壤养分
Abstract:Heavy metal and pesticide pollution is a major environmental problem, and the combined effects on earthworm-soil-plant systems have not been thoroughly explored. This study investigated the individual and combined effects of cadmium (Cd) and acetochlor on earthworm physiological responses, soil physical and chemical properties, and maize growth and morphological characteristics. The results showed that superoxide dismutase (SOD) activity in earthworms decreased and then increased, whereas the opposite trend was observed with malondialdehyde (MDA) content. The earthworm distribution across soil layers increased in the compound pollution treatment, and the percentage of earthworms in the total soil layer increased by 1.34 times (on day 2) and 1.14 times (on day 50) compared with that in the control group. The soil organic matter and available phosphorus contents were unaffected by treatment time or contamination method, but alkali-hydrolyzable nitrogen content decreased and then increased with Cd + acetochlor pollution. On day 50, the maize root numbers in all treatment groups were significantly lower than those in the control group; the inhibition rates were 23.21% (30 mg·kg-1 Cd), 42.86% (200 mg·kg-1 acetochlor), and 50.00% (30 mg·kg-1 Cd + 200 mg·kg-1 acetochlor). The maize biomasses and plant heights were largest in the 30 mg·kg-1 Cd group, followed by the 200 mg·kg-1 acetochlor group, and were smallest in the 30 mg·kg-1 Cd + 200 mg·kg-1 acetochlor group. Correlation analysis showed that the interaction between Cd and acetochlor did not affect earthworm MDA content, soil nutrients, or the maize growth index, but antagonistically affected earthworm SOD activity. This study concluded that combined Cd and acetochlor pollution promoted earthworm distribution in the topsoil and inhibited maize growth by altering the soil's physical and chemical properties.
Key words:Compound pollution of Cd and acetochlor/
Vertical distribution of earthworm/
Growth of maize/
Soil nutrients
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