太湖流域农村黑臭河流表层沉积物营养盐的污染特征

目的]分析农村黑臭河道沉积物中营养盐的空间分布情况和形态构成特征并给予分析与评价,为认识河流污染现状、黑臭河流治理和太湖富营养化防治提供基础数据。方法]以江苏省宜兴市周铁镇掌下浜(北段)为例,沿河流从上游到入河河口共采集了13个沉积物表层样,分析其总氮(TN)、总磷(TP)、氨氮(NH_4~+-N)、硝氮(NO_3~--N)、有机氮(Org-N)、有机碳(TOC)的空间分布特征,并对表层沉积物中碳(C)、氮(N)、磷(P)的组分分布进行耦合分析以及污染状况评价。结果]Org-N是河流表层沉积物中氮素的主要成分,平均值为2 193.69mg/kg,占TN质量分数的90.86%;各采样点处TN,Org-N,TP和TOC含量从上游到下游总体呈现波动中上升趋势,最高值分别是最低值的2.98,3.46,6.29和1.59倍;NH_4~+-N含量的变化趋势是缓慢上升而后急速下降,而NO_3~--N含量呈现出缓慢下降而后急速上升;各采样点C/N均值为12.07,有机物以外源输入为主,TOC与TN含量具有极显著正相关(p0.01,n=13);C/P均值为2.04,TOC与TP具有显著正相关(p0.05,n=13);N/P均值为2.04,TN与TP具有极显著正相关(p0.01,n=13),N,P污染具有同源性。结论]太湖流域农村黑臭河流沉积物环境状况属有机污染,其中氮污染程度属有机氮污染状态。

Nutritional Pollution Characteristics of Surface Sediments from a Rural Malodorous Black River in Taihu Lake Area

Objective] In order to provide fundamental data for a better understanding of the current pollution status and management for the malodorous black rivers, especially to prevent and control the eutrophication of Taihu lake, the spatial distribution and morphological characteristics of sediment nutrient in a rural malodorous black river were analyzed and evaluated.Methods] Thirteen surface sediment samples along the Northern Branch of Zhangxia Stream in Zhoutie Town of Yixing City, Jiangsu Province were collected from the upstream to the downstream. The spatial distribution of total nitrogen concentration(TN), total phosphorus(TP), ammonia nitrogen(NH₄⁺-N), nitrate nitrogen(NO₃^--N), organic nitrogen(Org-N) and total organic carbon(TOC) were investigated. The component distribution of carbon(C), nitrogen(N), phosphorus(P) in surface sediments were studied by coupling analysis for pollution assessment.Results] Org-N was the main component of nitrogen in surface sediments with an average concentration of 2 193.69 mg/kg, accounted for 90.86% of TN. Concentrations of TN, Org-N, TP and TOC presented a fluctuant increasing trend from upstream to downstream, and the highest values were 2.98, 3.46, 6.29 and 1.59 folds of the minimum values, respectively. The concentration of NH₄⁺-N increased slowly at the initial stage and then decreased rapidly, while the concentration of NO₃^--N showed an opposite trend. Mean ratio of C/N for the entire stream was 12.07, and the organic matter were mainly sourced from exogenous input. In addition, concentrations of TOC and TN showed an extremely significant positive correlation (p<0.01, n=13). Mean ratio of C/P was 2.04, and concentrations of TOC and TP showed a significant positive correlation (p<0.05, n=13). Mean ratio of N/P was 2.04, and concentrations of TN and TP showed an extremely significant positive correlation (p<0.01, n=13). As a result, the pollution of nitrogen and phosphorus was homogenous.Conclusion] Organic pollution is the main pollution for rural malodorous black river in the Taihu lake watershed, where the nitrogen pollution is mainly Org-N pollution.