摘要
通过太湖原状沉积物柱室内模拟试验,研究了有机质(腐殖酸)和硝态氮随下行水流进入潜流带对氮素转化和硝态氮还原途径的影响。结果表明,仅输入硝态氮时,潜流带中硝态氮出现持续累积现象,硝态氮还原速率为0.087-0.186μg/(cm^(3)·d)(平均0.162μg/(cm^(3)·d));而同时输入腐殖酸和硝态氮时,潜流带还原性环境逐渐增强,在21 d内Eh值降至-200 mV以下,硝态氮还原速率为0.092-0.251μg/(cm^(3)·d)(平均0.220μg/(cm^(3)·d)),腐殖酸有效促进了硝酸盐的还原。反硝化作用是潜流带中硝酸盐还原的主要途径,特别是潜流带上部(0-22.5 cm),其贡献达到90%以上;而潜流带的深部(22.5-45.0 cm)硝酸盐还原量总体较小,反硝化作用贡献也仅占39.5%。随着腐殖酸的消耗(6.92 mg/L降为3.32 mg/L),硝酸盐异化还原成铵过程对硝酸盐还原的贡献由14.0%降为2.7%。综合来看,补充有机质有利于潜流带特别是浅层潜流带的硝酸盐还原,且以反硝化过程为主,对湖泊水体碳氮循环和去除具有重要作用。
Laboratory experiments using an undisturbed sediment core were conducted to explore the effect of organic matter(humic acid)on the nitrogen transformation and the nitrate reduction pathway in the hyporheic zone of Lake Taihu.Results show that,when only the nitrate was input along with the downwelling flow,nitrate reduction rates were 0.087-0.186μg/(cm^(3)·d)with an average of 0.162μg/(cm^(3)·d),and the nitrate apparently accumulated in the hyporheic zone.Both the humic acid and the nitrate input along with hyporheic flow gradually promoted a reduction environment in the hyporheic zone within 21 days with Eh of below-200 mV.Nitrate reduction was greatly enhanced under this condition with an average reduction rate of about 0.220μg/(cm^(3)·d)from 0.092 to 0.251μg/(cm^(3)·d).These indicated that added humic acid substantially promoted the nitrate reduction process.At a shallow depth of the hyporheic zone(0-22.5 cm),the contribution of denitrification to the nitrate reduction reached more than 90%,indicating that the denitrification was the main pathway of nitrate reduction.At the deep depth of the hyporheic zone(22.5-45.0 cm),due to the deficient nitrate source,the contribution of nitrate reduction to the whole hyporheic zone accounted for less than 10%,and the denitrification accounted for about 39.5%.Dissimilatory nitrate reduction to ammonium,as a secondary pathway of nitrate reduction,was obviously influenced by organic matter content,and its contribution to nitrate reduction decreased from 14.0%to 2.7%when organic matter concentrations decreased from 6.92 mg/L to 3.32 mg/L.Overall,supplementary organic matter was helpful for the nitrate reduction mainly by denitrification particularly at the shallow depth of hyporheic zone,playing a great role on the cycling and removing of carbon and nitrogen in a lake aquatic system.
作者
李勇
单雅洁
李娜
钱佳宁
冯家成
徐鸿
LI Yong;SHAN Yajie;LI Na;QIAN Jianing;FENG Jiacheng;XU Hong(Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes of Ministry of Education,Hohai University,Nanjing 210098,China;College of Environment,Hohai University,Nanjing 210098,China;National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety,Nanjing 210098,China)
出处
《河海大学学报（自然科学版）》
CAS
CSCD
北大核心
2022年第1期44-51,共8页
Journal of Hohai University(Natural Sciences)
基金
国家自然科学基金(51879081,51579074)。
关键词
腐殖酸
反硝化
硝酸盐异化还原成铵
下行流
潜流带
太湖
humic acid
denitrification
dissimilatory nitrate reduction to ammonium
downwelling hyporheic flow
hyporheic zone
Lake Taihu
