基于实时控制的电絮凝-气浮处理重金属清淤尾水

针对重金属清淤尾水具有污染物浓度高、水质波动大、沉淀性能差等特点,选取pH值和浊度作为实时监测因子,并借助沉淀模拟和数据拟合等手段,建立了比电流与镉残留量之间的实时控制响应模型.结果表明:铝-电絮凝-气浮兼有中和pH值和改善泥水分离的优点,实现了重金属铅、镉和锌的达标排放;此外实时控制策略节省了35.8%的材料消耗和43.4%的电能消耗以及降低了47.9%的产泥量.     

巢湖南淝河河口底泥污染特征及疏浚决策

为了解巢湖南淝河河口区域底泥污染特征,为底泥疏浚提供决策依据,对该区域底泥中营养物、重金属含量及释放特征进行分析,并采用有机指数法、污染指数法及潜在生态风险评价对底泥的污染状况进行评估.结果表明,调查区域总氮（TN）、总磷（TP）以及有机质（OM）的均值为1461 mg·kg^-1、438 mg·kg^-1和1.77%,在表层（0~10cm）富集明显,随着底泥深度增加有逐渐降低的趋势.有机污染指数和污染指数结果表明,表层底泥（0~10 cm）总氮、有机质处于中度污染状态,而总磷处于重度污染状态,且随着底泥深度的增加,污染风险逐渐降低,并在30 cm以下处于低风险.静态释放结果发现底泥氨氮（NH₄⁺-N）和TP的平均释放通量分别为8.04 mg·（m²·d）^-1和0.19 mg·（m²·d）^-1,释放潜力较大,且与底泥营养物污染区域一致.对于底泥重金属而言,除Cr和Ni外的其它6种重金属含量均高于安徽省土壤背景值,其中Hg和Cd的含量超标最为严重,且重金属潜在生态风险结果表明,表层（0~20 cm）底泥均处于重污染风险等级,而30 cm以下底泥重金属降为低风险等级.底泥重金属浸出毒性实验结果表明,该区域底泥疏浚后重金属释放风险较低,不属于危险废物.根据以上结果,综合确定了南淝河口区域的重点疏浚面积（3.93 km²）和深度（30 cm）,为底泥疏浚提供了重要依据.     

LAKE RESTORATION BY SEDIMENT REMOVAL1

ABSTRACT: Fresh water lake sediment removal is usually undertaken to deepen a lake and increase its volume to enhance fish production, to remove nutrient rich sediment, to remove toxic or hazardous material, or to reduce the abundance of rooted aquatic plants. Review of more than 60 projects and five case histories reveals that the first three objectives are usually met through sediment removal. Dredging to control aquatic plants has not been well documented. Disadvantages of dredging include cost, temporary phosphorus release from sediment, increased phytoplankton productivity, noise, lake drawdown, temporary reduction in benthic fish food organisms, the potential for toxic material release to the overlying water and potential for environmental degradation at the dredged material disposal site. The technique is recommended for deepening and for long range reduction of phosphorus release from sediment. Sediment removal to control toxic materials is possible with minimal environmental impact when proper equipment is used, but it may more than double the cost. Lack of definitive information about rooted plant regrowth rates in dredged areas prohibits explicit recommendations on sediment removal to control plant growth.     

Environmental Monitoring Of Remedial Dredging At The New Bedford Harbor, Ma, Superfund Site

New Bedford Harbor (NBH), MA, is a Superfund site because of high polychlorinated biphenyl (PCB) concentrations in the sediment. From April 1994 to September 1995, a remedial dredging operation (termed the “Hot Spot”) removed the most contaminated sediments (PCB concentrations greater than 4000μg/g) from the upper harbor. During remediation, a monitoring program assessed the potential environmental impacts to NBH and adjacent Buzzards Bay. The monitoring program was developed with input from federal, state, and local authorities. Site-specific decision criteria were established to assess net PCB transport, water column toxicity, and PCB bioaccumulation in blue and ribbed mussels (Mytilus edulis and Geukensia demissa, respectively). The remediation was completed without exceeding PCB net transport or acute toxicity effects specified in the decision criteria. In addition, PCB bioaccumulation in mussels during this time period was not significantly greater than pre- or post-operational measurements. The results indicated that approximately 14000 cubic yards of highly PCB contaminated sediment were permanently removed with minimal environmental effects. The lessons learned during this operation, as well as previous pilot studies at the site, will be used to make full-scale remedial efforts in NBH more efficient and environmentally protective.     

外秦淮河疏浚后底泥中多环芳烃分布特征及其变化

利用GC-MS对外秦淮河疏浚后3个月及6个月采集的13个底泥样品中16种优控多环芳烃(PAHs)进行了分析.结果表明,疏浚后3个月底泥中PAHs含量较低,疏浚后6个月PAHs含量明显上升,说明疏浚对减少水体底泥污染确实有效果,但保持时间不长,经过一段时间的沉积和富集后污染物含量会发生回复现象,外源输入和河道沉积物内源释放对疏浚后新生表层底泥PAHs含量有较大的贡献. 草场门和集庆门河段处底泥中PAHs含量较高. 底泥中的PAHs以4～6环高分子量的PAHs为主,低环PAHs所占比例春季比冬季高. 根据PAHs中特殊组分(菲/蒽和荧蒽/芘)比例(w(Phe)/w(An), w(Flu)/w(Pyr))判断外秦淮河表层底泥中的多环芳烃主要来源为石油产品燃烧.      

湖泊内源污染的环保疏浚及其效果--以长春南湖清淤工程为例

通过介绍长春南湖底泥清淤工程及其治理效果,论述了底泥环保疏浚的实施原则和方法,并从湖泊水质的改善等方面证明了该方法在治理湖泊的富营养化污染中不可替代的作用和环境效应。      

香港海域翡翠贻贝(Perna viridis L.)中多氯联苯的研究

用气相色谱 毛细管双柱 电子捕获检测器研究了香港海域翡翠贻贝中多氯联苯(PCBs)的含量及其分布特征 ,结果表明 ,翡翠贻贝体内PCBs的污染现状与香港周边污染状况相符 ,在香港某些海域中翡翠贻贝体内PCBs有较高的含量 ,特别是靠近香港陆地的海域 ,PCBs总浓度最高达 3 0 3ng·g- 1 (干样 ) .PCBs同系物的分布亦有明显的不同特征 .运用二恶英毒性当量 (TEQ)表征翡翠贻贝中PCBs的毒性 ,TEQ最高值达 4 96ng·kg- 1 ,低于美国FDA允许值     

Effects of mussel shell addition on the chemical and biological properties of a Cambisol

The use of a by-product of the fisheries industry (mussel shell) combined with cattle slurry was evaluated as soil amendment, with special attention to the biological component of soil. A wide number of properties related to soil quality were measured: microbial biomass, soil respiration, net N mineralization, dissolved organic carbon, dissolved organic nitrogen, dissolved inorganic nitrogen, dehydrogenase, β-glucosidase, urease and phosphomonoesterase activities. The amendments showed an enhancement of soil biological activity and a decrease of aluminium held in the cation exchange complex. No adverse effects were observed on soil properties. Given that mussel shells are produced in coastal areas as a by-product and have to be managed as a waste and the fertility constraints in the local soils due to their low pH, our research suggest that there is an opportunity for disposing a residue into the soil and improving soil fertility.     

微生物絮凝剂用于河道疏浚底泥快速脱水的研究

河道疏浚底泥含水率高、体积庞大,不便于储存、运输和资源化利用。首先需要对其进行减量化,使其快速脱水。通过筛选获得一株高效的微生物絮凝剂产生菌F22,通过试验获得其最佳培养条件:葡萄糖为碳源,酵母膏和尿素为氮源,培养时间为60h,培养温度为32℃。将F22菌株所产絮凝剂应用于底泥脱水,试验结果表明,当底泥泥浆(含水率为93%)体积为100mL时,絮凝体系最佳pH为8～10,助凝剂CaCl2最佳投加量为4～5mL,F22菌株发酵液最佳投加量为3mL;絮体在1min左右大部分沉降至底部,F22菌株所产絮凝剂能够使底泥快速脱水。F22菌株所产絮凝剂在絮凝过程中起作用的是糖类物质,其通过氢键结合力产生絮凝作用。     

Small farm ponds: overlooked features with important impacts on watershed sediment transport

Despite their size, small farm ponds are important features in many landscapes. Yet hydrographical databases often fail to capture these ponds, and their impacts on watershed processes remain unclear. For a 230‐km² portion of central Texas, United States (U.S.), we created a historical inventory of ponds and quantified the accuracy of automated detection methods under varying drought conditions. In addition, we documented pond dredging/enlargement events and identified sites that had been abandoned. We also analyzed sediment cores from downstream reservoirs to track changes in watershed sediment transport. Over 75 years, pond densities increased more than 350% — to among the highest documented in the U.S. — and the ability of automated methods to detect these ponds was highly dependent on drought severity (R² = 0.96). Approximately 5% of ponds present in the 1950s were no longer present in 2012, while 33% were dredged between 1937 and 2012. Downstream reservoir sedimentation has decreased by an average of 55% as ponds have increased in number. These findings suggest that small ponds and the maintenance of trapping efficiency have large‐scale impacts on sediment dynamics. Accurately accounting for these storage effects is vital to water resource planning efforts.