The continuous increase of nitrate(NO_(3)^(-))level in rivers is a hot issue in the world.However,the driving mechanism of high NO_(3)^(-)level in large rivers is still lacking,which has limited the use of river water...The continuous increase of nitrate(NO_(3)^(-))level in rivers is a hot issue in the world.However,the driving mechanism of high NO_(3)^(-)level in large rivers is still lacking,which has limited the use of river water and increased the cost of water treatment.In this study,multiple isotopes and source resolution models are applied to identify the driving mechanism of high NO_(3)^(-)level and key processes of nitrogen cycling in the lower reaches of the Yellow River(LRYR).The major sources of NO_(3)^(-)were sewage and manure(SAM)in the low-flow season and soil nitrogen(SN)and chemical fertilizer(CF)in the high-flow season.Nitrification was the most key process of nitrogen cycling in the LRYR.However,in the biological removal processes,denitrification may not occur significantly.The temporal variation of contributions of NO_(3)^(-)sources were estimated by a source resolution model in the LRYR.The proportional contributions of SAM and CF to NO_(3)^(-)in the low-flow and high-flow season were 32.5%-52.3%,44.2%-46.2%and 36.0%-40.8%,54.9%-56.9%,respectively.The driving mechanisms of high NO_(3)^(-)level were unreasonable sewage discharge,intensity rainfall runoff,nitrification and lack of nitrate removal capacity.To control the NO_(3)^(-)concentration,targeted measures should be implemented to improve the capacity of sewage and wastewater treatment,increase the utilization efficiency of nitrogen fertilizer and construct ecological engineering.This study deepens the understanding of the driving mechanism of high nitrate level and provides a vital reference for nitrogen pollution control in rivers to other area of the world.展开更多
通过室内模拟试验(2013年7月23日~8月15日),研究不同含水量(20%,35%,60%)条件对东北黑土区土壤氮素转化及土壤酶活性的影响,初步探讨了其作用机制。结果表明:随着培养时间的增加,不同含水量的铵态氮含量呈波动性变化,最后呈下降趋势;硝...通过室内模拟试验(2013年7月23日~8月15日),研究不同含水量(20%,35%,60%)条件对东北黑土区土壤氮素转化及土壤酶活性的影响,初步探讨了其作用机制。结果表明:随着培养时间的增加,不同含水量的铵态氮含量呈波动性变化,最后呈下降趋势;硝态氮含量随着时间的增加一直呈下降趋势,35%及60%含水量的黑土铵态氮和硝态氮含量在相同培养时间高于20%含水量的黑土。各含水量处理组氨化速率、矿化速率、硝化速率随着培养时间的增加均逐渐下降,说明土壤中可被转化的有机氮含量逐渐降低,60%含水量的黑土净矿化速率和净硝化速率变化幅度最大,分别从1.518 g kg-1d-1、1.376 g kg-1d-1下降到0.009 g kg-1d-1,0.007 g kg-1d-1;除了35%含水量处理组在24 h内的氨化速率高于其他两组含水量氨化速率外,整个培养期间的氮素转化速率均表现为60%含水量】35%含水量】20%含水量。对土壤酶活性的研究表明:在培养初期(前2 d),20%含水量土壤脲酶活性逐渐增加,35%和60%含水量土壤脲酶活性先增加后下降,随后脲酶活性趋于稳定,直到第13 d开始略有下降,总体来看,2 d后不同含水量对脲酶活性的影响变化不显著;而转化酶活性呈波动性变化,整个培养周期,35%含水量的转化酶活性始终高于60%含水量处理组,而20%含水量的转化酶活性在其他两组含水量的转化酶活性上下波动。研究表明含水量对黑土氮素转化影响显著,硝化、矿化、反硝化作用及土壤中微生物活性的变化是氮素转化及酶活性变化的主要原因。展开更多
基金supported by the open Funds of laboratory of water environmental science of Hebei Province,China(No.HBSHJ202103)the Natural Science Foundation of Hebei Province of China(Nos.D2022504015,D2020504001 and D2021504003)+2 种基金the High-level talent Funding project of Hebei Province,China(No.A202101003)the Fundamental Research Funds for the Institute of Hydrogeology and Environmental Geology,Chinese Academy of Geological Sciences(Nos.SK202117 and SK202209)China Geological Survey,China(No.DD20221773)。
文摘The continuous increase of nitrate(NO_(3)^(-))level in rivers is a hot issue in the world.However,the driving mechanism of high NO_(3)^(-)level in large rivers is still lacking,which has limited the use of river water and increased the cost of water treatment.In this study,multiple isotopes and source resolution models are applied to identify the driving mechanism of high NO_(3)^(-)level and key processes of nitrogen cycling in the lower reaches of the Yellow River(LRYR).The major sources of NO_(3)^(-)were sewage and manure(SAM)in the low-flow season and soil nitrogen(SN)and chemical fertilizer(CF)in the high-flow season.Nitrification was the most key process of nitrogen cycling in the LRYR.However,in the biological removal processes,denitrification may not occur significantly.The temporal variation of contributions of NO_(3)^(-)sources were estimated by a source resolution model in the LRYR.The proportional contributions of SAM and CF to NO_(3)^(-)in the low-flow and high-flow season were 32.5%-52.3%,44.2%-46.2%and 36.0%-40.8%,54.9%-56.9%,respectively.The driving mechanisms of high NO_(3)^(-)level were unreasonable sewage discharge,intensity rainfall runoff,nitrification and lack of nitrate removal capacity.To control the NO_(3)^(-)concentration,targeted measures should be implemented to improve the capacity of sewage and wastewater treatment,increase the utilization efficiency of nitrogen fertilizer and construct ecological engineering.This study deepens the understanding of the driving mechanism of high nitrate level and provides a vital reference for nitrogen pollution control in rivers to other area of the world.
文摘通过室内模拟试验(2013年7月23日~8月15日),研究不同含水量(20%,35%,60%)条件对东北黑土区土壤氮素转化及土壤酶活性的影响,初步探讨了其作用机制。结果表明:随着培养时间的增加,不同含水量的铵态氮含量呈波动性变化,最后呈下降趋势;硝态氮含量随着时间的增加一直呈下降趋势,35%及60%含水量的黑土铵态氮和硝态氮含量在相同培养时间高于20%含水量的黑土。各含水量处理组氨化速率、矿化速率、硝化速率随着培养时间的增加均逐渐下降,说明土壤中可被转化的有机氮含量逐渐降低,60%含水量的黑土净矿化速率和净硝化速率变化幅度最大,分别从1.518 g kg-1d-1、1.376 g kg-1d-1下降到0.009 g kg-1d-1,0.007 g kg-1d-1;除了35%含水量处理组在24 h内的氨化速率高于其他两组含水量氨化速率外,整个培养期间的氮素转化速率均表现为60%含水量】35%含水量】20%含水量。对土壤酶活性的研究表明:在培养初期(前2 d),20%含水量土壤脲酶活性逐渐增加,35%和60%含水量土壤脲酶活性先增加后下降,随后脲酶活性趋于稳定,直到第13 d开始略有下降,总体来看,2 d后不同含水量对脲酶活性的影响变化不显著;而转化酶活性呈波动性变化,整个培养周期,35%含水量的转化酶活性始终高于60%含水量处理组,而20%含水量的转化酶活性在其他两组含水量的转化酶活性上下波动。研究表明含水量对黑土氮素转化影响显著,硝化、矿化、反硝化作用及土壤中微生物活性的变化是氮素转化及酶活性变化的主要原因。
