【作者】 朱广伟；

【导师】 陈英旭；

【作者基本信息】 浙江大学 ， 环境工程， 2001， 博士

【摘要】 本文通过对柱状沉积物样品的污染特征分析、沉积物中污染物释放模拟试验、沉积物土地投放的盆栽试验以及原状土柱淋洗试验等方法，研究了运河（杭州段）沉积物的污染特征、潜在生态风险、污染物释放规律、土地投放中对蔬菜和花草生长影响以及土地投放后N、P、Cu、Zn等在土层中的下移规律。得到以下结论： 运河（杭州段）沉积物中Zn、Cu、Cd、有机质、有效态磷的积累比较明显，高于沉积物背景值4.5倍以上。与15年前的调查结果相比，运河（杭州段）沉积物中有机质的含量显著增高，说明15年来的污染控制措施并未有效消除运河的有机污染源。运河（杭州段）沉积物中Zn的含量峰值及平均含量都显著下降，其余金属元素尽管在峰值上有所下降，但平均值与15年前无显著差异。淤泥层有机质的污染已经明显影响到沉积物的下伏基底层，Hg由淤泥层向基底层的迁移也比较明显。 运河（杭州段）的运河—钱塘江沟通段、生活商贸市区河段、工业区河段及余杭农村河段的四个河段中沉积物的污染特征显著不同。从沉积物的潜在生态风险因子看，运河（杭州段）沉积物中Cd的生态风险最高，其次是Hg、Cu。四个河段中，工业区河段沉积物的综合生态风险指数最高，运河—钱塘江沟通段最低。运河（杭州段）沉积物中Cu主要残渣态存在，其次是还原提取态，Zn则主要以乙酸提取态为主，占沉积物中Zn总量的50％以上，具有较强的化学活性。 运河（杭州段）沉积物Cu的释放速率很快，在上覆水受到间歇性扰动的情况下，1～2天就达到释放最大值。不同河段的沉积物Cu的释放潜力相差很大。提高上覆水的pH值、投加Fe³⁺类盐或提高上覆水的含氧量都显著降低上覆水中Cu的释放平衡浓度。沉积物释放到上覆水体中的Cu可以通过换水清洗措施而有效地降低。沉积物释放平衡后上覆水Cu浓度不超过二类地表水的浓度限定值。沉积物Zn的释放较缓慢，在21天的模拟试验中，上覆水Zn浓度因沉积物释放而持续增加，但增加幅度越来越小。不同河段的沉积物Zn的释放潜力相差也很大，工业污染为主的东谢村河段沉积物释放到上覆水中的Zn浓度比有机污染为主的大关桥河段沉积物高40％左右。提高上覆水的pH值、投加Fe³⁺类盐或提高上覆水的含氧量也都显著降低了上覆水中Zn的平衡浓度。换水清洗降低了上覆水Zn浓度，但当Zn浓度降至100μg l^-1以下后，换水清洗的效果已不明显。沉积物释放平衡后上覆水Zn浓度也不超过二类地表水的浓度限定值，但沉积物释放导致上覆水Cu、Zn的浓度均高出渔业水质标准数倍。 在间歇性扰动情况下，沉积物耗氧物质释放的波动性较大。有机污染为主的大关桥河段沉积物比工业污染为主的东谢村河段的沉积物对上覆水COD的影响更大。提高上覆水pH值，表观上提高了上覆水透明度，但同时沉积物耗氧物质的释放量也显著增加。Fe³⁺类盐则既增加了水体透明度，又显著降低了上覆水COD。水体曝气由于增加了对沉积物的扰动，因此对上 覆水＊OD无显X降低作川。换水消洗对沉积物一上进水体系中＿．Lffi水＊OD有一定的M氏仆 川，但当上覆水 COD R到 30mg“’左心时，换水消洗己经基本没有效贝。 沉积物磷的释放在试验初］山最人，在间歇件扰动的试验条什卜，上覆水总磷浓度逐渐下 降。沉积物释磷能力与沉积物的总磷含敢无大，有机污染相对较重的人大桥河段沉积物释磷 能力显著高于总磷含量较高的东谢村河段沉积物。提高上覆水州最终导致沉积物释磷量的增 加，投加 Fe’”类盐则显著降低了上覆水总磷浓度，水体曝气也最终降低上覆水的平衡磷浓度， 换水消洗对上覆水磷浓度的降低效贝十分有限。上述卅施均术能将上阻水总磷浓度控制在万 且 类水的浓度限定值以下。在间歇性扰动的试验条仆卜，沉积物氮的释放引起的上覆水总氮浓 度也是在前一、两天就达到最人，而后逐渐卜降到 10mgl”’左右。生活污水污染较重的人关桥 河段沉积物样品的释放曲线与工业污染较重的东谢村河段沉积物样品的释放曲线之间无显著 差异。提高上召水pH值可以显著降低上覆水TN含量，Feh盐在试验初朋也能降低上覆水TN 浓度，后期则反而增加了上覆水TN浓度。水体曝气对上覆水总氮浓度无显群影响。换水清洗 可以很快降低上覆水总氮含量，而当上覆水总氮下降到 10mgi”’左右以后，换水清洗的效果变 得很低。 运河（杭州段）沉积物投放到红壤、水稻十两种典仰杭州十壤时，可以叨显提高宵菜的 发芽率，然而青菜的产量随沉积物用量的增加允升后降，存在一个最佳川量。在 270t hd’的沉 积物用量下，红壤、水稻士上青菜的生长都受到了明显的促进，青菜中重金属含量、土壤中 重金属含量均未超过食品卫生和环境质量标准。运河（杭州段）沉积物用量的人小对红更多还原

【Abstract】 In this paper, pollution characteristics of the sediment of the Hangzhou section of the Grand Canal was investigated, the ecological risk of the sediment was evaluated with potential ecological index, and the releasing mechanism of pollutants from the sediment was studied with modeling experiments. Moreover, the ecological toxicology of the land application of the sediment from the Hangzhou section of the Grand Canal and the downward movement of the pollutants in soil system were studied by pot experiments and soil column leaching experiments. Investigation of the pollution of the sediment showed that, the sediment had been polluted by heavy metals, mean values of Cd, Zn, Cu, Pb, Hg, As and Cr were 6.50, 6.46, 4.60, 2.81, 2.32, 1.29, and 1.17 times higher than the background values, respectively. The sediment also contained plenty of nutrients. Concentrations of organic carbon (0.0.), available phosphorus, available potassium and total nitrogen were 11.3, 5.4, 3.3 and 1.4 times higher than the paddy soil near the canal, respectively. Owing to the complex pollution sources, accumulating extents of the pollutants in the sediment varied drastically in different section of the canal. Although the connecting section between the canal and Qiantang River was newly dug section, its sediment also been polluted owing to the back-flux of the polluted water from the downstream. Concentration of 0.0. in the sediment of the downtown section of the canal was significantly high, and the concentration of Zn in industrial section of the canal was also remarkably high. Concentration of 0.0. was significantly higher than that investigated at 15 years ago, showed that the pollution abatement engineering which taken on in the last fifteen year hadn抰 effectively decreased the organic pollution sources. However, compared with the investigation of 15 years ago, the concentration of Zn in the sediment significantly decreased. Organic pollution in the top layer sediment had seriously affected the bottom layer, and the downward movement of Hg in the sediment was also remarkable. Ecological risk evaluation with potential ecological risk index showed that, the most dangerous ecological risk factor of the sediment was Cd, followed with Hg and Cu. Ecological risk of different section of the canal was also drastically varied. The most ecologically dangerous sediment was that from the industrial section of the canal. Fractionation of the Cu and Zn in the sediment showed that, Cu in the sediment mainly presented in residual fraction, more than 50 percent of the total Cu in the sediment presented in residual fraction. Reducible fraction was another major fraction of Cu. More than 60 percent of Zn in the sediment was presented in acid extractable fraction. Principal factor analysis of the pollutants showed that, most of the pollutants in connecting section between the canal and Qiantang River and in the countryside section of the canal were homologous, while those in the urban section sediment were complex, reflecting the complex pollution sources. In the releasing experiment, releasing-adsorption balance of Cu was arrived in 2 days, which was significantly quicker than that of Zn. Equilibrating concentrations of Cu in overlying water (OW) releasing from the sediment sampled from different section of the canal were quite different. Concentration of Cu in OW releasing from the sediment of industrial section of the canal was significantly higher than that releasing from the sediment of downtown section, so did the Zn. Owing to the rel更多还原