【作者】 孙远军；

【导师】 黄廷林； 李小平；

【作者基本信息】 西安建筑科技大学 ， 市政工程， 2009， 博士

【摘要】 目前,国内多数城市河流在城市化进程中受到了严重污染,底泥中沉积了大量的耗氧性物质、氮磷营养物、有机污染物和重金属污染物,想从根本上改善河水水质,不仅要切断外部污染源,还必须解决水体底泥的内部污染问题。论文以上海市苏州河为例,为解决溶解氧含量偏低、氮磷污染物超标两个突出存在的问题,从控制沉积物污染的角度研究了苏州河底泥的污染特征、耗氧机理以及污染物释放规律,并对受污染底泥进行了原位稳定化的实验研究。得出以下结论:苏州河底泥中氨氮、凯氏氮、总有机碳和酸挥发性硫化物等污染物的纵向分布基本为驼峰状,表层底泥的污染物含量相对较低,淤泥层底泥的含量最高,黄泥层底泥的含量最低。淤泥层底泥的污染物含量从上游到下游呈逐渐升高的趋势,其它泥层的污染物含量差异不大。参照相关底泥质量标准,苏州河表层、淤泥层底泥有机污染和氨氮污染均已达到严重污染的级别,总凯氏氮的污染程度较小,重金属污染物目前还不存在生物毒性。温度、扰动和溶解氧是影响底泥污染物释放的重要环境因素。低温条件下水体和底泥中的污染物较为稳定,温度越高底泥污染物的释放速度和转化速度越快,扰动会在短时间内引起底泥颗粒态污染物和溶解态污染物的快速释放,厌氧条件下底泥中铁、锰结合态磷以正磷酸盐的形式释放,含氮污染物主要以氨氮的形式释放,有机物厌氧矿化的中间产物会引起水体COD_Cr和TOC含量的增加。通过人为方式提高水体中溶解氧的含量,可以有效地抑制底泥中氮、磷和有机污染物向上覆水的释放。苏州河底泥中的耗氧物质主要包括硫化物、氨氮、有机物和低价金属,亚铁离子和硫化物向上覆水的释放能力最强,耗氧速率最快,氨氮次之,有机碳则最差最慢。苏州河淤泥层底泥的耗氧当量最高,其中有机碳的耗氧当量最大,但由于释放和矿化速度较慢而产生的直接耗氧较小,短时间内硫化物和氨氮对底泥耗氧的贡献最大,前者的耗氧速度快于后者。SOD模拟实验的结果表明,在夏季苏州河表层底泥的耗氧量从上游到下游呈逐渐增大的趋势,淤泥层底泥的SOD值最大,表层底泥的次之,黄泥层底泥的最小。SOD受温度的影响较大,冬季苏州河不同深度底泥的耗氧量均小于1gO₂/m²·d,而夏季的SOD值则会明显上升。高锰酸钾、过氧化钙和硝酸钙都可以提高底泥的氧化还原电位,改善底泥的还原性环境,但是高锰酸钾和过氧化钙会同时增加底泥的碱度,4种稳定剂对水体溶解氧水平的提升作用并不明显。硝酸钙能够明显刺激底泥中异养微生物的活性,通过微生物的降解作用降低底泥中有机污染物的含量,对TOC的去除塞可达到18.72%。过氧化钙和硝酸钙能够将活性较高的NaOH-P转化成释放能力较低的HCl-P,从而有效地抑制底泥释磷,可将孔隙水中的PO₄^3-含量分别降低至0.003和0.094mg/L,这两种稳定剂主要通过化学沉淀作用来实现对磷元素的固定作用。4种稳定剂在早期均会不同程度地促进底泥释放氨氮,双氧水能在后期通过反硝化消减底泥的总氮含量,硝酸钙的投加会造成底泥向上覆水渗透硝酸盐氮。4种稳定剂都会降低酸挥发性硫化物的含量,对底泥的黑臭现象具有一定的改善作用,其中硝酸钙的效果最为明显,但是也会增大底泥的∑SEM/AVS比值,而使重金属的生物毒性有所升高。更多还原

【Abstract】 Nowadays,most of urban rivers in China had been seriously polluted during the urbanization process.There are a large number of oxygen-consuming substances, nitrogen and phosphorus pollutants,organic pollutants and heavy metals pollutants in sediments,to radically improve the water quality,we should not only cut off external sources of pollution,but also address the internal pollution sources of sediments.In this paper,Suzhou creek was studied as an example.For resolving the two prominent problems of low dissolved oxygen and high nutrient content,the pollution characteristic of Suzhou creek sediments was investigated,the degree of pollution was assessed consulting some relevant sediment quality standards.Aiming at Suzhou Creek sediment characteristics,the release rule of pollutants from sediments and sediment oxygen-consuming mechanism were studied.To actively seek a solution,an in-situ stabilization experiment of Suzhou Creek contaminated sediments was conducted based on the previous experimental findings.The vertical distributions of ammonia nitrogen,Kjeldahl nitrogen,total organic carbon and acid volatile sulfide in Suzhou Creek sediments are basicly hump-shaped, the concentrations of pollutants in surface sediments are relatively low,the concentrations in Silt layer are the highest,the concentrations in original soil layer are the lowest.Pollutants contained in Silt layer are gradually increased from the upstream section to the downstream section along Suzhou Creek,the change trend of pollutants in other layer has little difference.According to the relevant sediment quality standards, organic pollution and ammonia nitrogen pollution in surface layer and silt layer all reach a serious pollution level,the total Kjeldahl nitrogen pollution degree is lower,the heavy metal toxicity do not exist.Temperature,disturbance and dissolved oxygen content of water body are important environmental factors,which effects the pollutants releasing from sediments. The pollutants in water and sediments will be more stable under low temperature condition,the higher temperature is,the releasing and transforming velocity of pollutants is faster.Disturbance can cause the rapid release of particulate pollutants and dissolved pollutants from sediments in a short time.Under anaerobic conditions,the iron/manganese-bound phosphorus will release in the form of orthophosphate,the nitrogen pollutants will release in the form of ammonia.The product of organic anaerobic mineralization will cause the increase of COD_Cr and TOC content in water body.Improving dissolved oxygen in water can effectively inhibit the the release of nitrogen,phosphorus and organic pollutants from sediments.The oxygen-consuming material in Suzhou Creek mainly consist of sulfide, ammonia,organic matter and low valence metal ion,the release capacity of ferrous ion and sulfide to overlying water is the strongest,the oxygen consumption rate is the fastest,ammonia follows by,organic carbon is the slowest worst.The oxygen equivalent of pollutants in Suzhou Creek silt layer sediment is maximum,in which oxygen consumption equivalent caused by organic carbon is the highest,but it can only consume less oxygen because of the slow release and mineralization.The oxygen consumption by sulfide and ammonia has the greatest contribution to sediments oxygen demanding,the oxygen consuming rate of sulfide is faster.The simulated Experiment results show that the SOD value of Suzhou Creek gradually increases from upstream to downstream,the SOD value in silt layer is the highest,the value in surface layer follows by,the value in original soil layer is the lowest.Temperature can remarkably influence the SOD value,the SOD values of Suzhou Creek are all less than 1gO₂/m²·d in winter, but will obviously increase in summer.Potassium permanganate,calcium peroxide and calcium nitrate could increase the ORP in sediments,calcium peroxide and potassium permanganate would significantly increase the alkalinity of sediments.calcium nitrate could effectively reduced the organic pollutants content in sediment,the removal rate of TOC reached up to 18.72%. Calcium peroxide and calcium nitrate could effectively inhibit phosphorus release from sediments,the PO₄^3- content in interstitial water respectively reduced 0.003 and 0.094mg/L,and the inhibitory effect was quietly stable.Four kinds of stabilizer could not significantly improve dissolved oxygen content in water body,the stabilization effect of the four stabilizer on nitrogen pollutants in sediments was not ideal,in the early stage they would promote ammonia release from sediments at different degree, calcium nitrate could result in the nitrate infiltration upward to overlying water.Four kinds of stabilizer would reduce the content of acid-volatile sulfide in sediment, increase theΣSEM/AVS ratio,and enhance the biological toxicity of heavy metals.更多还原