中文关键词
河流氮污染氧化亚氮(N2O)通量排放系数 | 英文关键词riverN pollutionN2Ofluxemission factor |
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| 中文摘要 |
| 以铁岭市22条河流为研究对象，分析了河流N2O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，N2O溶存浓度介于17.03~9028.60 nmol·L-1，均值为546.75 nmol·L-1，饱和度均值为6256%；河流水-气界面N2O释放通量介于17.21~15655.3 μg·（m2·h）-1，均值为949.36 μg·（m2·h）-1.铵态氮污染河流断面N2O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N2O排放系数（EF5r），结果表明3种类型河流EF5r呈现极为明显的差异，EF5r变异系数达到445%.硝态氮污染河流EF5r均值为0.0005，显著低于IPCC建议值（0.0025）；但铵态氮污染河流硝态氮浓度较低，导致EF5r计算均值高达0.4456，为IPCC建议值的180倍；氮限制河流EF5r均值为0.0050，为IPCC建议值的2倍.因此，在计算EF5r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N2O产生机制，对EF5r进行了分类计算，探讨了EF5r的修正计算方法.建议针对氨氮污染和氮限制河流采用[N2O]/[NH4+]方法计算EF5r；如不考虑河流氮污染特征，建议采用[N2O]/[DIN]方法计算EF5r. |
| 英文摘要 |
| 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 9028.60 nmol·L-1, with a mean value of 546.75 nmol·L-1 (mean saturation=6256%). The emission fluxes across the water-air interface range from 17.21 to 15655.3 μg·(m2·h)-1, with a mean value of 949.36 μg·(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, EF5r varies greatly among the three types of rivers and the coefficient of variation of EF5r is 445%. The EF5r for NO3--polluted rivers is on average 0.0005, which is lower than the recommended value of 0.0025. However, the EF5r for NH4+-polluted rivers is on average 0.4456, which is 180 times the recommended value and may be caused by the lower NO3- concentration of those rivers. The EF5r of N-limited rivers averages 0.0050 and is two times the recommended value. Thus, it is necessary to assess the pollution status of N before calculating the EF5r for the riverine system. We suggest that the EF5r for NH4+-polluted and N-limited rivers should be calculated using[N2O]/[NH4+] and[N2O]/[DIN], respectively, without assessing the composition and concentration of N. |
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