西苕溪干流水体、悬浮物和表层沉积物中营养盐分布特征与水质评价

了解不同介质的营养盐分布可以全面掌握河流的环境现状。为了调查西苕溪干流的营养盐分布特征和水质现状,沿着干流采集了11个点位的水体、悬浮物和表层沉积物样品,并对水体、悬浮物和表层沉积物中的营养盐特征进行了分析,拟为苕溪流域的水污染防治提供基础数据。研究表明:整个西苕溪干流,水体和沉积物中总氮(TN)和总磷(TP)浓度均存在丰水期明显高于枯水期的季节变化特征,水体中总氮的浓度均超出地表水环境质量Ⅴ类的标准,显示氮污染是西苕溪流域的特点。相关性分析结果表明,悬浮物中的TN和有机质(OM)呈极显著性正相关(r=0.974,p0.01);水体中的TN和悬浮物的各营养盐指标之间的相关性均达到了极显著水平,但沉积物营养盐指标与水体的TN和TP相关性不明显,显示沉积物并不能很好反映流域水质的现状。

DISTRIBUTION AND EVALUATION OF NUTRIENTS FROM WATER,SUSPENDED SEDIMENT AND SURFACE SEDIMENT IN THE MAIN STREAM OF THE XITIAOXI RIVER

Understanding the distributions of nutrients in different medium can help to fully grasp the current situation of river environments. To investigate the distribution characteristics, pollution degree and relationships of nutrients in the main stream of the Xitiaoxi River, water, suspended sediment and surface sediment samples were recently taken from 11 sites along this River. These data can help us to recognize the nutritional levels of diverse sections in the mainstream. The results showed that, the concentrations of TN and TP in the waters were higher in the wet season than in the dry season from upper reaches to lower reaches of the Xitiaoxi River. The contents of TP showed they were worse than Grade Ⅲ level of National Environment Quality Standard for Surface Water in half of total sites. In contrast, the concentrations of TN showed that they were worse than Grade V of the surface-water standard (GB3838-2002). NH₃-N in the wet and dry seasons all reached level Ⅱ and Ⅲ, respectively, in the middle and lower reaches. The overall NH₃-N pollution showed the pattern of lower reaches> middle reaches> upper reaches. Therefore, compared to phosphorus pollution, nitrogen pollution of water was more serious in the Xitiaoxi River. The contents of TN in suspended matter basically increased with an order of the upper reaches, lower reaches, and middle reaches from high to low, and the contents of TP showed an order of the upper reaches, middle reaches, and lower reaches. The contents of organic matter of upper reaches were higher than those of lower reaches and middle reaches. The maximum of both TN and organic matter appeared in XTX1 of upper reaches, which indicated a high organic matter and nitrogen values in forested lands. Inorganic phosphorus took up a higher proportion than organic phosphorus in sediment TP, which indicated that inorganic phosphorus was the main form of phosphorus forms. Although inorganic nitrogen accounted for a small proportion of TN, they can indicate a good water quality. Results from statistical correlation analyses showed that TN content in suspended sediment was obviously positively correlated with OM (r =0.974, p<0.01). TN of all sites in waters were correlated with the nutrients in suspended sediment. No significant relationship was found between nutrient in sediment and TN, TP in water, which indicated that sediment could not reflect the status of water quality in basin well. Therefore, control and treatment of water pollution in Xitiaoxi River should focus on abatement of suspended matter in water.