不同氮污染特征河流N_2O浓度、释放通量与排放系数  

Concentration,Flux,and Emission Factor of N_2O in Rivers with Different Nitrogen Pollution Features

作　　者：王淼 李亚峰[1] 雷坤[2] 杨丽标[2] WANG Miao;LI Ya-feng;LEI Kun;YANG Li-biao(School of Municipal and Environmental Engineering,Shenyang Construction University,Shenyang 110168,China;Institute of Water Environmental Research,Chinese Research Academy of Environmental Science,Beijing 100012,China)

机构地区：[1]沈阳建筑大学市政与环境工程学院,沈阳110168 [2]中国环境科学研究院水环境研究所,北京100012

出　　处：《环境科学》2018年第12期5400-5409,共10页Environmental Science

基　　金：国家自然科学基金项目(41203080);国家水体污染控制与治理科技重大专项(2013ZX07501-005)

摘　　要：以铁岭市22条河流为研究对象,分析了河流N_2O溶存浓度、释放通量及排放系数.根据氮素的主要赋存形态及氮素浓度,22条河流可分为铵态氮污染(铵态氮平均浓度5.86 mg·L^(-1))、硝态氮污染(硝态氮平均浓度3.05 mg·L^(-1))和氮限制(溶解性无机氮平均浓度1.04 mg·L^(-1))河流这3种.总体上,N_2O溶存浓度介于17.03~9 028.60 nmol·L^(-1),均值为546.75nmol·L^(-1),饱和度均值为6 256%;河流水-气界面N_2O释放通量介于17.21~15 655.3μg·(m^2·h)^(-1),均值为949.36μg·(m^2·h)^(-1).铵态氮污染河流断面N_2O浓度和释放通量显著高于硝态氮污染和氮限制断面(LSD,P<0.05).根据IPCC方法计算了河流N_2O排放系数(EF_(5r)),结果表明3种类型河流EF_(5r)呈现极为明显的差异,EF_(5r)变异系数达到445%.硝态氮污染河流EF_(5r)均值为0.000 5,显著低于IPCC建议值(0.002 5);但铵态氮污染河流硝态氮浓度较低,导致EF_(5r)计算均值高达0.445 6,为IPCC建议值的180倍;氮限制河流EF_(5r)均值为0.005 0,为IPCC建议值的2倍.因此,在计算EF_(5r)时应充分评估河流的氮污染状况.本文根据河流氮污染特征,结合不同类型河流N_2O产生机制,对EF_(5r)进行了分类计算,探讨了EF_(5r)的修正计算方法.建议针对氨氮污染和氮限制河流采用[N_2O]/[NH_4^+]方法计算EF_(5r);如不考虑河流氮污染特征,建议采用[N_2O]/[DIN]方法计算EF_(5r).In this study,22 rivers in Tieling City were selected to study the concentration,flux,and emission factor(EF5r)of N2O.Based on the concentrations and components of nitrogen（N）,the 22 rivers can be divided into ammonia nitrogen（NH4+）-polluted rivers(mean NH4+=5.86 mg·L-1),nitrate nitrogen（NO3-）-polluted rivers(mean NO3-=3.05 mg·L-1),and N-limited rivers[mean DIN（NH4++NO3-）=1.04 mg·L-1].Overall,the concentration of N2O ranges from 17.03 to 9 028.60 nmol·L-1,with a mean value of 546.75 nmol·L-1（mean saturation=6 256%）.The emission fluxes across the water-air interface range from 17.21 to15 655.3μg·（m2·h）-1,with a mean value of 949.36μg·（m2·h）-1,indicating that those rivers are net sources of atmospheric N2O.The concentration and flux of N2O observed in NH4+-polluted rivers are significantly higher than that in the NO3--polluted and N-limited rivers.According to the method proposed by the IPCC,EF5rvaries greatly among the three types of rivers and the coefficient of variation of EF5ris 445%.The EF5rfor NO3--polluted rivers is on average 0.0005,which is lower than the recommended value of0.002 5.However,the EF5rfor NH4+-polluted rivers is on average 0.445 6,which is 180 times the recommended value and may be caused by the lower NO3-concentration of those rivers.The EF5rof N-limited rivers averages 0.005 0 and is two times the recommended value.Thus,it is necessary to assess the pollution status of N before calculating the EF5rfor the riverine system.We suggest that the EF5rfor NH4+-polluted and N-limited rivers should be calculated using[N2O]/[NH4+]and[N2O]/[DIN],respectively,without assessing the composition and concentration of N.

关 键 词：河流 氮污染 氧化亚氮(N2O) 通量 排放系数 

分 类 号：X144[环境科学与工程—环境科学] X16