生物沥滤去除污泥重金属:污泥固体浓度和类型影响

研究了污泥固体浓度和污泥类型对Cu、Pb和Zn生物沥滤的影响。结果表明,污泥固体浓度越高,重金属沥出效果越差;高固体浓度污泥pH值降低缓慢,其SO42-产生量明显高于低污泥浓度。低固体浓度污泥下,氮磷钾营养物质流失量比高固体浓度污泥明显增多。厌氧消化污泥和生污泥中重金属的生物沥滤效果差异不大,但厌氧消化污泥的肥效流失明显高于生污泥。     

动电技术去除城市污泥中重金属的可行性探讨

本文简要介绍了我国城市污泥的处理处置和利用现状及动电技术去除重金属的基本原理,分析动电技术处理土壤中重金属的国内外的试验研究和应用情况,对动电技术处理城市污泥中重金属的可行性进行探讨,认为动电技术去除城市污泥中的重金属具有可行性,并提出了今后研究的方向.     

Heavy metal concentrations in plants and soils at roadside locations and parks of urban Guangzhou

Introduction In 2003, 48 per cent of the world's population is estimated to live in urban areas with the proportion that is urban projected to rise to 61 per cent by 2030 (United Nations, 2004). Moreover, during 2000— 2030 the world's urban population is…     

Leaching behavior of Pb and Zn in air pollution control residues and their modeling prediction

Increasing attention has been paid to air pollution control （APC） residues in China recently due to the rising proportion of waste incineration and the hazardous characteristics of the residues, among which heavy metal leaching toxicity plays an important role. Leaching behavior and potential risk of Pb and Zn in the APC residues from a Shanghai municipal solid waste （MSW） incinerator was studied, based on the leaching tests under different conditions and theoretical calculation using a geochemical thermodynamic equilibrium model MINTEQA2. Results showed that, extractant species and liquid to solid （L/S） ratio predominantly controlled the leaching toxicity of Pb and Zn, while ionic strength, vibration method and leaching time had less effect on the metals release. Leachate/final pH determined the metal leaching behavior, which changed the speciation of heavy metals in the extraction system. The equilibrium aqueous speciation, precipitation-dissolution of Pb and Zn was investigated according to the model computation, which was well in agreement with the experimental results.     

The Effects of Small Dam Removal on the Distribution of Sedimentary Contaminants

With increasing concern over degradation of aquatic resources, issues of liability, and maintenance costs, removal of small dams has become increasing popular. Although the benefits of removal seem to outweigh the drawbacks, there is a relative paucity of studies documenting the extent and magnitude of biological and chemical changes associated with dam removal, especially those evaluating potential changes in contaminant inventories. In August and November of 2000, a run-of-the-river dam on Manatawny Creek (southeast Pennsylvania) was removed in a two-stage process. To assess the effects of dam removal on the contaminant redistribution within the creek, sedimentary concentrations of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and trace metals (Cd, Cr, Cu, Ni, Pb, Zn) were evaluated prior to and several months after removal. Pre- and post-removal analyses revealed elevated and spatially variable concentrations of total PAHs (ranging from approximately 200 to 81,000 ng(g dry weight) and low to moderate concentrations of trace metals and PCBs. The concentrations of these sedimentary contaminants pre- versus post-removal were not significantly different. Additionally, though the impoundment received storm water run-off and associated contaminants from the adjacent city of Pottstown, the total inventory of fine-grain sediments in the impoundment prior to removal was very low. The removal of the low-level Manatawny Creek dam did not significantly redistribute contaminants downstream. However, each dam removal should be assessed on a case by case basis where the potential of sedimentary contaminant redistribution upon dam removal exists.     

Characterization, Source Identification and Apportionment of Selected Metals in TSP in an Urban Atmosphere

To understand the metal distribution characteristics in the atmosphere of urban Islamabad, total suspended particulate (TSP) samples were collected on daily 12 h basis, at Quaid-i-Azam University campus, using high volume sampler. The TSP samples were treated with HNO₃/HClO₄ based wet digestion method for the quantification of eight selected metals; Fe, Zn, Pb, Mn, Cr, Co, Ni and Cd by FAAS method. The monitoring period ran from June 2001 to January 2002, with a total of 194 samples collected on cellulose filters. Effects of different meteorological conditions such as temperature, relative humidity, wind speed and wind direction on selected metal levels were interpreted by means of multivariate statistical approach. Enhanced metal levels for Fe (930 ng/m³), Zn (542 ng/m³) and Pb (210 ng/m³) were found on the mean scale while Mn, Cr, Co and Ni emerged as minor contributors. Statistical correlation study was also conducted and a strong correlation was observed between Pb-Cr (r=0.611). The relative humidity showed some significant influence on atmospheric metal distribution while other meteorological parameters showed weak relationship with TSP metal levels. Regarding the origin of sources of heavy metals in TSP, the statistical procedure identified three source profiles; automobile emissions, industrial/metallurgical units, and natural soil dust. The metal levels were also compared with those reported for other parts of the world which showed that the metal levels in urban atmosphere of Islamabad are in exceedence than those of European industrial and urban sites while comparable with some Asian sites.     

Distribution and Statistical Analysis of Leachable and Total Heavy Metals in the Sediments of the Suez Gulf

The concentrations of nine heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pd and Zn) in the labile and total fractions of muddy and sandy sediment samples collected from twelve sites in Suez Gulf during April 1999 were studied to evaluate the pollution status of the Suez Gulf. The enrichment factors (EF) for each element were calculated. There are extremely high concentrations of Cd, Ni, Pb and slightly concentration of Cr and Cu in both muddy and sandy sediments. The concentration of Zn was moderately high and can be considered as seriously contaminate Metal pollution index (MPI) shows high values ranged between 46 to 156 and 40 to 232 for both sandy and muddy sediments, respectively. Concentrations of heavy metals were normalized against iron for total fraction in both of sandy and muddy sediments. Principal component analysis (PCA) was studied on the data matrix obtained and represented three-factor model explaining 92.22% for labile and 88.82% for total fractions of muddy sediment. The main source of contamination is the offshore oil fields and industrial wastes. This is largely a result of ineffective and inefficient operation equipment, illegal discharge of dirty ballast water from tankers and lack of supervision and prosecution of offenders.     

Contaminant Exposure of Barn Swallows Nesting on Bayou D'Inde, Calcasieu Estuary, Louisiana, USA

Current and historical point source discharges, storm water runoff, and accidental spills have contaminated the water, sediment, and biota within the Calcasieu Estuary in southwestern Louisiana. In 2003, barn swallow (Hirundo rustica) eggs and nestlings were collected beneath two bridges that cross Bayou d′Inde, the most contaminated waterway within the Calcasieu Estuary. Samples were also collected from a bridge over Bayou Teche, a reference site in south central Louisiana. Polychlorinated biphenyl (PCB) concentrations in barn swallow eggs and nestlings were significantly higher at the downstream site on Bayou d′Inde (2.8 μ g/g PCBs in eggs and 1.5 μ g/g PCBs in nestlings) than at the other two sites (< 0.2 μ g/g PCBs in eggs and nestlings at both sites). Ethoxyresorufin-O-dealkylase activity in nestling livers was significantly higher at the downstream site on Bayou d′Inde (50 pmol/min/mg) compared to the other two locations (24 pmol/min/mg, each), probably because of exposure to PCBs. Polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran concentrations in eggs and polycyclic aromatic hydrocarbons in nestlings were at background concentrations at all sites. Trace element concentrations in barn swallow eggs and nestling livers were at background levels and did not differ among the three sites. A biomarker of DNA damage did not differ among sites.     

Potential Use of the Plant Antioxidant Network For Environmental Exposure Assessment of Heavy Metals in Soils

In recent years, awareness has risen that the total soil content of pollutants by itself does not suffice to fully assess the potential ecotoxicological risks involved. Chemical analysis will require to be complemented with biological assays in a multidisciplinary approach towards site specific ecological risk assessment (SS-ERA). This paper evaluates the potential use of the plants' antioxidant response to metal-induced oxidative stress to provide a sensitive biological assay in SS-ERA. To this end, plants of Phaseolus vulgaris were grown for two weeks on 15 soils varying in contamination level. Morphological parameters and enzymatic plant responses were measured upon harvest. Foliar concentrations of the (heavy) metals Al, Cu, Cd, Cr, Fe, Mn, Ni, Pb, Zn were also determined. Metal mobility in the soil was further assessed by determining soil solution and NH₄OAc extractable levels. In general more significant correlations were observed between plant responses and foliar metal concentrations or exchangeable/soluble levels than between plant responses and the total soil content. The study demonstrates the potential use of the plants' antioxidant defence mechanisms to assess substrate phytotoxicity for application in SS-ERA protocols. However, the system, based on calculation of a soil Phytotoxicity Index (PI), will require adaptation and fine-tuning to meet the specific needs for this type of environmental monitoring. Large variation was observed in phytotoxicity classification based on the various test parameters. The thresholds for classification of the various morphological and enzymatic response parameters may require adaptation according to parameter stress sensitivity in order to decrease the observed variation. The use of partial PI's (leaves and roots separately) may in addition increase the sensitivity of the system since some metals show specific effects in one of both organs only. Loss of biological functionality of enzymes, as was observed for ICDH in one of the more strongly contaminated soils, may also be recognized as an additional stress symptom when assigning phytotoxicity classification, whereas the current system only considers increasing enzymatic capacities. Other easily distinguishable parameters, which could be added to the current indexation are: failure to germinate and the incapacity to develop roots in the toxic substrate.Additional research will be required to determine the possible application range of soil properties for this biological assay and to further improve its performance in SS-ERA.