城市污水处理厂的大气污染治理技术

城市污水处理厂在污水处理的过程中会产生一些大气污染。我们应弄清这些污染的成分和来源并加以控制以免形成二次污染,防止给周边环境尤其是居民的居住、工作环境造成影响。介绍近年来国内外学者就城市污水处理厂的大气污染问题的最新研究成果,并调查了青岛市两个典型污水处理厂的大气污染情况,展现了当前城市污水处理厂的大气污染的研究现状。     

电子废物不当处置的重金属污染及其环境风险评价 Ⅳ. 电子废物不当回收地区流域水体沉积物的重金属污染

为了解电子废物不当处置活动对小流域内水体沉积物金属污染的影响,采集了位于广东省清远市龙塘镇和石角镇的电子废物焚烧和酸解活动核心区内水塘和水库的0～40cm沉积物以及附近河流大燕河表层(0～5cm)沉积物样本,分析了样本中的金属(水塘、水库:Zn、Cu、Pb、Cd、Cr;大燕河:Zn、Cu、Pb、Cd、Cr、Ni、Mg、Mn)含量.作为对照,对珠江口伶仃洋沉积物中的5种重金属(Zn、Cu、Pb、Cd、Cr)含量也进行了分析.结果表明,1)在核心区内,5种重金属的平均含量在接近酸解作坊的水塘沉积物中呈Cu(766.16mg·kg-1)>Zn(181.12mg·kg-1)>Pb(129.56mg·kg-1)>Cr(1.89mg·kg-1)≈Cd(1.12mg·kg-1),在其下游的水库沉积物中呈现相同的规律,但水塘沉积物的Cu、Zn、Pb含量均高于水库.水塘、水库沉积物重金属含量分布规律明显不同于伶仃洋沉积物,与伶仃洋沉积物相比,核心区水体沉积物Cu含量特别高,是伶仃洋沉积物的7～17倍,Pb和Cd则分别是伶仃洋的2.3～3.0倍和1.9～2.4倍,Zn、Cr含量与伶仃洋沉积物相近.2)Zn含量在核心区水体沉积物中均呈现出在20.0～30.0cm深度最高的趋势,Cu、Pb含量在水库沉积物中也有类似的表现,说明该深度的沉积物可能是电子废物回收处置活动最频繁的时期形成的,近年来随着政府取缔工作的加强,电子废物非法处置活动的减少,Zn、Cu、Pb含量有明显的下降.3)大燕河沉积物中6种重金属(Zn、Cu、Pb、Cr、Cd、Ni)的总含量表现为中游下段(1261.3mg·kg-1)>中游中段(1049.2mg·kg-1)>中游上段(401.8mg·kg-1)>上游(364.6mg·kg-1)>下游(215.4mg·kg-1).Cu、Zn、Pb和Cr含量均在中游下段的沉积物中出现最大值,次大值出现在中游中段,Ni、Cd在中游中段出现最大值,次大值出现在中游下段.中游中、下段沉积物中金属含量最大值和其上游(或中游上段)河段含量最低值的比值呈现Cu(10.1)>Cr(7.8)>Zn(3.8)>Cd(2.0)>Pb(1.9)>Ni(1.8),显示这些重金属主要从中游中、下段进入大燕河沉积物,其中Cu污染最为严重,而Cr污染可能与水土流失或当地其他活动释放的Cr有关.4)比较流域内土壤和各种沉积物以及伶仃洋沉积物中重金属的构成比例发现,核心区土壤和沉积物以及大燕河沉积物中的重金属具有明显的同源性.随着离源区距离的增加,重金属的构成比例中最明显的变化是Cu的比例下降以及Zn的比例上升。     

Changes in chromium distribution during the electrodialytic remediation of a Cr (VI)-contaminated soil

A laboratory study has been carried out to determine the feasibility of in situ remediation of chromium (VI)-contaminated soil using electrodialysis in relation to its speciation in soil. This technique is best suited for low-permeability soils or sediments, which may be difficult to remediate by other means and implies the application of a low-intensity direct current to the soil, which is separated from the electrode compartments by ion-exchange membranes. A clayey soil was prepared for use in the experiments and was characterized before being mixed with a solution of potassium dichromate for several days to produce a final Cr content of 4,056 mg/kg of soil dry wt. Remediation tests were carried out under constant-voltage conditions for periods of 7–14 days and the evolution of applied current to the cell, pH, and conductivity of the electrolytes were recorded periodically. Fractionation of chromium was determined for soil samples before and after remediation using a standardized four-step sequential extraction procedure (SEP) with acetic acid, hydroxylamine, hydrogen peroxide, and aqua regia solutions. Results show that chromium is mobilized from the most labile phases (soluble/exchangeable/carbonate). In a 15 V test, SEP results show that the amount of chromium extracted in the first step drops from 80% to 9%, but also that changes in the total chromium distribution occur during the treatment with some transferred to other soil phases that are more difficult to mobilize.     

Soil lead (Pb) in residential transects through Lubbock,Texas: a preliminary assessment

Residential lead (Pb) contamination, resulting from decades-long use of leaded gasoline and lead-based paint, is likely to be present in soils in most urban areas. A screening level sampling effort demonstrated that Lubbock, Texas, USA, like other cities of its age and size, has areas of elevated soil Pb. This effort was based on soil sampling performed on residential, commercial and thoroughfare properties. The focus of this study was to investigate that component of soil contamination due to combustion of leaded gasoline. Soils were collected from the 1–2 cm surface layer from street-side property borders, well away from buildings that might lead to soil contamination from leaded paint chips. All samples were analyzed for Pb after a 1 M HNO₃ mild extraction to determine the amount of bioavailable Pb. Two of three transects through the city demonstrated significant trends of decreasing Pb concentrations with distance from the city center, paralleling a decrease in developed property age. Peak soil Pb concentrations outside city development was 4.9 ± 0.6 mg/kg while the median concentration for the city was 35.4 mg/kg. Peak soil Pb concentrations in the city center ranged from 90.0 to 174.0 mg/kg and decreased exponentially to 6.0–9.0 mg/kg at the furthest terminus of the residential transects.     

广州某黑臭河涌沉积物中的挥发物质组分

在广州市城区内的猎德涌采集了3个采样点中0~10cm深的表层沉积物,通过DVB/CAR/PDMS固相微萃取(SPME)纤维顶空富集,使用气相色谱/质谱联用仪(GC/MS)对其挥发物进行检测分析。在猎德涌的沉积物中共检测出54种挥发物质,包括36种烷烃、2种环烷烃、1种烯烃、2种硫单体、13种带有发香基团的有机物。在3个采样点分别鉴定出19、49、52种挥发物。在下游河段沉积物中检测出的挥发物种类和峰面积都超过上游。由挥发物质的组成可以判断出其主要污染是来源于交通污染和居民的日常生活污染,其中有3种毒性较大的成分:万山麝香、邻苯二甲酸二异丁酯(DIBP)和2,4-二叔丁基苯酚。     

Major and trace elements in paddy soil contaminated by Pb–Zn mining: a case study of Kočani Field,Macedonia

The objective of this study was to assess the bulk chemical composition as well as the extent and severity of heavy metal contamination in the paddy soil of Kočani Field (eastern Macedonia). The results revealed that the paddy soil of the western part of Kočani Field is severely contaminated with Pb, Zn, As and Cd in the vicinity of the Zletovska River due to irrigation with riverine water that is severely affected by acid mine and tailing effluents from the Pb–Zn mine in Zletovo. The detected total concentrations of these metals are far above the threshold values considered to be phytotoxically excessive for surface soil. The paddy soil in the vicinity of the Zletovska River was also found to exhibit elevated levels of Ba, Th, U, V, W, Mo, Cu, Sb, Bi, Ag, Au, Hg and Tl, with concentrations above their generally accepted median concentration values obtained during this study. A correlation matrix revealed that the Mn and Fe oxides/hydroxides are the most important carrier phase for several trace elements, with the exception of rare earth elements (REEs). These also represent a major sink for the observed heavy metal pollution of the soil. REEs are mostly associated with two phases: light (L)REEs are bound to K-Al, while heavy (H)REEs are bound to Mg-bearing minerals. Although there is no direct evidence of a health risk, the paddy soil in the vicinity of Zletovska River needs further investigation and an assessment should be made of its suitability for agricultural use, particularly in view of the highly elevated concentrations of Pb, Zn, As and Cd.     

Multidisciplinary work on barium contamination of the karstic upper Kupa River drainage basin (Croatia and Slovenia); calling for watershed management

The present work was designed as an extension of a previous study of a barium anomaly observed in stream sediments of the Kupa River. In its upper part the Kupa River drains a region underlain by a trans-boundary aquifer. The river is a significant water resource in a region of tourism, sport, and fishing in both Croatia and Slovenia. The contamination source is situated in Homer (Lokve), Croatia, where barite was mined until 10 years ago. The barium processing waste material (<3-mm fraction) was carelessly deposited in gardens, forests, and into a sinkhole, which has an underground link with the Kupica River, a tributary of the Kupa River. Barium waste and stream sediments were analyzed using comparative techniques: X-ray diffraction (XRD), X-ray fluorescence (XRF), Mössbauer spectroscopy, and grain size analysis. XRD of the waste material identified the major minerals quartz, barite, and dolomite and the Fe-containing minor minerals muscovite and goethite. Barite was identified as a minor or trace mineral in the Kupica River sediments. XRF analysis of the waste material has shown Ba and Fe to be the predominant elements, Ca and K to be minor elements, and Mn, Zn, Sr, Pb, Co, Cu, As, Zr, Rb, Y, and Mo to be trace elements. Mössbauer spectroscopy performed at room temperature (RT) was used to study iron minerals, particularly to obtain information on the valence status of Fe ions. Grain size analysis of the waste material (<63-μm fraction) has shown that it contains 23.5% clay-size material in comparison with 7–8% clay-size material in stream sediments. It is our aim to combine geochemical and medical methods to investigate the possible impact of waste disposal on human health in Lokve. At this stage of the work, concentrations of Ba and other toxic elements in the water compartment of the Kupica River (a source of drinking water) have not been monitored by Croatian Waters (name of the Croatian water authorities). The necessity of such measurements in future studies has been highlighted. A preliminary study of diseases diagnosed in Lokve shows that about 18% of the total inhabitants have serious medical problems. Diseases of the circulatory system, endocrine, nutritional, and metabolic diseases, neoplasms, and respiratory diseases predominate. This paper calls for further multidisciplinary research on the health effects of barium and trace elements, as well as for bioremediation of contaminated gardens and for watershed management of vulnerable karstic aquifers.     

氯代芳香化合物生物降解性能与其化学结构的相关性

应用结构－活性定量关系研究方法,对氯代芳香化合物的好氧生物降解性能与其化学结构间的关系进行了研究,并建立了受试物的好物降解速率常数与４个高阶分子连接性指标及取代基电子效应数为结构参数的定量关系,分析表明,有机物取代基的电性能数和空间构型是影响受试物好氧生物降解性能的２个重要因素。     

新型铝硅复合絮凝剂的制备及其絮凝性能研究

以高稳定性的有机硅(TEOS)代替聚硅酸(HS)加入到聚合铝(PAC)中,初步制备了一种新型铝硅复合絮凝剂(TEOS—PAC)。研究了制备过程中的滴碱速度、Si与Al摩尔比和碱化度等因素对该复合絮凝剂絮凝性能的影响,对比了TEOS—PAC与HS—PAC的絮凝效果。研究结果表明,制备TEOS—PAC时滴碱速度要控制适当(流量刻度定位40);随着Si与A1摩尔比的提高,TEOS—PAC复合絮凝剂的絮凝性能明显增强,最佳Si与A1摩尔比为0．2,最佳碱化度为2．5;在相同条件下,TEOS—PAC的最佳投药量低于HS—PAC,且TEOS—PAC在絮凝过程中形成的絮体沉降性能优于HS—PAC形成的絮体。     

丛枝菌根真菌对紫羊茅镉吸收与分配的影响

采用盆栽方法模拟土壤Cd污染状况,研究接种丛枝菌根真菌对紫羊茅生长及对Cd吸收、分配的影响.结果表明,土壤加Cd15～50mg·kg-1对菌根侵染率无显著影响;在不加Cd的土壤中,接种菌根真菌有助于Cd的吸收和向地上部的运输;在Cd污染土壤中,接种菌根真菌并未明显改善紫羊茅的磷营养状况,并且也没有明显增加紫羊茅的生物量,但是地上部的Cd浓度和吸收量均显著低于不接种的处理,其原因是菌根真菌强化了Cd在紫羊茅根系的固持作用,减少Cd在地上部的分配比例,从而降低了紫羊茅地上部对Cd的积累.试验还观察到,不同菌根真菌对紫羊茅吸Cd量的影响具有一定差异,Glomusintraradices在Cd污染的土壤中对Cd吸收的抑制效应大于Glomousmosseae.这些结果一方面说明菌根真菌侵染是紫羊茅地上部Cd含量减少的直接原因,同时也反映出在自然生态系统中,作为污染物由土壤环境进入食物链系统的门户之一的丛枝菌根真菌在调节生态系统中重金属Cd的生物循环、减轻重金属Cd对食物链的污染风险方面发挥着重要作用.