摘要
摘要:大气活性氮（N_r）是导致霾污染和过量氮沉降的主要前体物。随着近年来大气污染防治行动的深入，消减农业源N_r排放逐渐被提上议事日程。目前，针对农田和畜禽养殖场内外环境大气中N_r的实地测量资料较为缺乏，且以往研究多以氨气（NH₃）为主，很少关注其他N_r成分。为了阐明农业活动对大气N_r的潜在影响，本研究基于扩散管主动采样系统，对华北平原典型农田（河北香河和栾城农田）、养猪场和蛋鸡养殖场环境大气中的4种N_r成分，即NH₃、硝酸气体（HNO₃）、颗粒态铵盐（p-NH₄⁺）和颗粒态硝酸盐（p-NO₃^-）开展了现场同步观测。结果显示：观测期间猪舍内NH₃和p-NH₄⁺平均浓度（1 250.9 μg·m^-3和76.6 μg·m^-3）显著高于舍外（378.5 μg·m^-3和4.2 μg·m^-3）；而猪舍内HNO₃和p-NO₃^-平均浓度（10.3 μg·m^-3和20.8 μg·m^-3）与舍外接近（9.8 μg·m^-3和22.1 μg·m^-3）；鸡舍内仅NH₃平均浓度（197.7 μg·m^-3）显著高于舍外（77.3 μg·m^-3），而p-NH₄⁺、HNO₃和p-NO₃^-平均浓度（7.3 μg·m^-3、9.0 μg·m^-3和6.2 μg·m^-3）均与舍外接近（10.7 μg·m^-3、9.9 μg·m^-3和7.2 μg·m^-3）。总体上看，养猪场环境大气中N_r浓度显著高于养鸡场（P < 0.05）。香河和栾城农田大气NH₃、p-NH₄⁺、HNO₃和p-NH₄⁺的平均浓度分别为21.4 μg·m^-3、1.9 μg·m^-3、4.4 μg·m^-3和5.5 μg·m^-3，显著低于养殖场外N_r浓度（P < 0.05）。从形态组成上看，养殖场和农田大气N_r主要以NH₃-N（占比>80%）的形态存在，说明华北农业活动产生的N_r主要通过NH₃的形式向外扩散传输，并没有在当地快速转化为颗粒物。未来需要进一步研究N_r在大气中的传输路径和转化机制，为制定有效的减排措施提供科学支持。
关键词:华北平原/
农田/
养殖场/
养殖圈舍/
活性氮/
大气污染
Abstract:Reactive nitrogen (N_r) is the main precursor of atmospheric haze pollution, which leads to excessive nitrogen deposition. With prevention and control measured for air pollution in recent years, reducing N_r from agricultural sources has recently been suggested. Currently, field measurements focusing on atmospheric N_r in farmland and animal farms are still limited and are mainly focused on ammonia (NH₃), with little attention being paid to other N_r components. In order to characterize the potential impact of agricultural activities on atmospheric N_r concentrations, this study carried out simultaneous field measurements of major N_r species, including gaseous NH₃, nitric acid (HNO₃), particle ammonium (p-NH₄⁺) and nitrate (p-NO₃^-), in two farmlands (Xianghe farmland and Luancheng farmland in Hebei Province), a pig farm and a poultry farm in the North China Plain using the active denuder sampling system. The results showed that the average concentrations of NH₃ and p-NH₄⁺ inside the pig house (1 250.9 and 76.6 μg·m^-3, respectively) were significantly higher (P < 0.05) than those outside the pig house (378.5 and 4.2 μg·m^-3, respectively). However, the average concentrations of HNO₃ and p-NO₃^- inside the pig house (10.3 and 20.8 μg·m^-3, respectively) were comparable to those outside the pig house (9.8 and 22.1 μg·m^-3, respectively). In contrast, the measured N_r concentrations were similar both inside and outside the poultry house for all N_r species (overall ranged from 6.2 to 10.7 μg·m^-3) except for NH₃, which was significantly higher (P < 0.05) inside (197.7 μg·m^-3) compared to outside (77.3 μg·m^-3). In general, atmospheric N_r concentrations in the pig farm were significantly higher than those in the poultry farm (P < 0.05). The average air concentrations of NH₃, p-NH₄⁺, HNO₃ and p-NO₃^- in the farmland were 21.4, 1.9, 4.4 and 5.5 μg·m^-3, respectively, which were significantly lower than those outside the pig and poultry farms (P < 0.05). From the perspective of chemical composition, N_r mainly existed in the form of NH₃-N (accounting for more than 80%) in pig, poultry and farmland environments, which indicated that the N_r produced by agricultural activities in the North China Plain mainly diffused outward in the form of NH₃ instead of transforming into particles locally. Detailed investigations on the transmission mechanisms and transport pathways of N_r in the atmosphere are urgently needed to provide scientific support for the implementation of effective emission mitigation measures.
Key words:North China Plain/
Farm land/
Intensive pig and poultry farms/
Breeding house/
Reactive nitrogen/
Air pollution



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