为了更好地对太子河上游区域河流硝酸盐污染进行防治,联合硝酸盐氮氧同位素(δ15 N-NO-3和δ18 O-NO-3)、水的氧同位素(δ18 O-H2O)、氯离子(Cl-)、硝酸盐(NO-3)、氨氮(NH+4-N),对不同水文期太子河上游区域河流硝酸盐来源进行了识别。结果 表明:枯水期ρ(Cl-),ρ(NO-3),ρ(NH+4-N)和δ18 O-NO-3显著高于丰水期,δ15 N-NO-3无显著时间差异。空间上,枯水期,太子河北支ρ(NO-3)显著高于南支。丰水期,太子河南支ρ(Cl-)显著高于北支。太子河北支ρ(Cl-)和ρ(NO-3)在丰水期和枯水期的空间变化呈相反趋势。丰水期太子河南支ρ(Cl-)和ρ(NO-3)的空间变化趋势与枯水期一致。枯水期太子河上游地区NO-3主要来源于土壤有机氮。可见,丰水期的主要来源是土壤有机氮、复合肥料。另外,丰水期上游区域土壤中的大气沉降可能也是河流硝酸盐的一个主要来源。丰水期硝酸盐从土壤冲刷进入河流过程中发生了硝化作用。枯水期太子河北支河流内硝化过程影响着硝酸盐浓度变化。
In order to better control the nitrate pollution in the upstream areas of Taizi River Basin, the nitrate(NO-3), chloride(Cl-), ammonium(NH+4-N), δ15 N-NO3-, δ18O-NO-3 and δ18O-H2O were analyzed. The sources of nitrate in upstream areas of Taizi River Basin in different hydrological periods were identified. The results show that: Cl-, NO-3, NH+4-N concentrations and the δ18O-NO-3 in the dry season are significantly higher than those in the wet season, and the δ15 N-NO-3 does not show significant seasonal variations; spatially, the nitrate concentrations in the north branch of Taizi River Basin(NTR)are significantly higher than those in the south branch of Taizi River Basin(STR)in the dry season; the Cl- concentrations in STR were significantly higher than those in NTR in the wet season; the trends of Cl- and NO-3 concentrations from the upper reach to the lower reach of NTR in the dry season are opposite with those in the wet season; the trends of Cl- and NO-3 concentrations from the upper reach to the lower reach of STR in the dry season are consistent with those in the wet season. It can be concluded that the nitrate is derived mainly from the soil nitrogen in dry season, whereas it is from synthetic fertilizer and soil N in the wet season; moreover, the atmospheric nitrate deposition in the upper reaches of the soil may also be a source of the nitrate in the wet season. Nitrification occurs in the process of transport of nitrate from the soil to the river in the wet season. The nitrification process affects the nitrate concentration in NTR during the dry period.
