上海市郊中小河流氮磷污染特征

Characteristics of Nitrogen and Phosphorus Pollution in the Middle and Small Creeks, Suburban Shanghai

①上海市郊中小河流有很高的氮磷和有机负荷 ,其表层水凯氏氮、总磷和CODCr指标均数倍于V类水的最大允许值 .②由于受纳污染物类型和总量上的差异 ,中小河流氮磷污染存在明显的空间分异 :居民区附近的小河流氨氮和磷的污染很重 ;主要受农田径流影响的小河流 ,氨氮和磷的污染较轻 ,但受硝氮污染的风险加大 ;养殖场附近的小河流 ,氨氮和磷有突发性暴增的现象 .③中小河流氮磷污染 ,还受河流季节性生态环境演变的影响 .随着气温升高和河流表层生物量的增大 ,表层水NH+ 4 、NO- 3 因大量消耗而降低 ;有机N和颗粒态P含量因生物量的增加而上升 ;NO- 2 也会因硝化细菌活动的加剧而增加 .水溶态磷和总磷也有随着气温和生物活动的增加而增高的趋势 ,但还要受到水体 pH、DO等条件的影响 .④在盛夏高温季节 ,水流滞缓的小河流表层水和底层水的氮磷指标存在明显分异 :底层水NH+ 4 、水溶态磷和总反应态磷含量高于表层水 ;而表层水NO- 3 和NO- 2 含量高于底层水 .这种富营养化水质分层现象的产生是夏季河流表层生物量暴增和底泥氮磷释放加剧的必然结果 .至秋季 ,随着气温的回落 。

The middle and small creeks in suburban Shanghai were under heavy eutropic condition, with high loadings of nitrogen, phosphorus and organic pollutants. KN, TP and COD Cr of the surface water of them were several times greater than the critical values of Types V, the worst level of water. ② Spatial variations of N and P pollution were observed, as the creeks in different places accepted different types and amounts of pollutants. Affected by domestic sewage, the creeks nearby residential areas were often heavily polluted by NH + 4 and P. The creeks in agricultural fields were more easily polluted by NO - 3 than by NH + 4 and phosphorus. The creeks nearby livestock farms often witnessed sudden soaring of NH + 4 and P. ③ N and P loadings of the creeks were also affected by the seasonal evolvement of ecological environment. With the increase of temperature and biomass, NH + 4 and NO - 3 in the surface water were largely consumed and decreased as a result; while organic N and particle P increased as the enhancement of suspending biological particles. NO - 2 in the surface water increased with temperature as nitrifying bacteria became active. Total P and water soluble P also showed the trend of enhancement with the intensification of biological activities, however, they were also controlled by the condition of pH and DO in the water. ④ At the height of the summer, the surface and bottom water of the creeks differed in N and P loadings. NH + 4, soluble P and total reactive P in the bottom water were higher than those in the surface; while NO - 3 and NO - 2 in the surface were higher than those in the bottom. Such water quality stratification inevitably resulted from the enhancement of phytoplankton in the surface water and intensified release of NH + 4 and P from the sediments. In the autumn, as the temperature decrease, such phenomenon declined gradually.