铬渣污染土壤PM10和PM2.5组分中六价铬的生物可给性及健康风险评估

为获取土壤细颗粒组分中污染物的浓度及其生物可给性,分析了某铬渣污染场地土壤PM_(10)和PM_(2.5)组分中六价铬的浓度分布特征,并采用统一生物可给性测试方法(Unified Bioaccessibility Method,UBM)和呼吸吸入生物可给性测试方法(Inhalation Bioaccessibility Method,IBM) 2种体外模拟法测试了六价铬在胃、肠及肺中的生物可给性。结果显示:(1)六价铬和总铬在PM_(10)和PM_(2.5)组分中的含量大多明显低于PM_(250)组分,PM_(10)组分中六价铬和总铬的累积因子(accumulation factors,AF)分别为0.080#12.297和0.008#0.261,PM_(2.5)组分中六价铬和总铬的AF分别为0.019#5.721和0.005#0.342,相比于总铬而言,六价铬在细颗粒中的累积程度更高。较低的有机质(organic matter,OM)含量可能导致了六价铬AF的明显增加。不同组分中六价铬占总铬的比例分别为2%#17%(<250μm)、21%#98%(<10μm)和22%#82%(<2.5μm),表明在土壤细颗粒中,铬更多地以六价铬的形式存在;(2)通过UBM获取的PM_(250)组分中六价铬在胃提取阶段的生物可给性因子为0.0301%#0.9483%,平均值为0.4821%;肠阶段可给性因子为0.0018%#0.3934%,平均值为0.1578%,约为胃提取阶段的0.33倍;(3)通过IBM获取的PM_(10)组分中六价铬在肺阶段的生物可给性因子为2.52%#41.50%,平均值14.47%; PM_(2.5)组分中六价铬的生物可给性因子为2.40%#88.12%,平均值为48.86%,约为PM_(10)组分的3.38倍;(4)在考虑生物可给性条件下,六价铬产生的人体总致癌风险水平从2 430.04×10~(-6)下降至125.83×10~(-6),而且,六价铬呼吸途径产生的致癌风险水平极高,是经口摄入的5.04#176.38倍(胃)、10.92#10 198.00倍(肠),表明呼吸吸入是六价铬致癌风险最为关键的暴露途径。因此,通过测定土壤细颗粒组分中六价铬的生物可给性,能够显著提高铬渣污染土壤健康风险评估的可靠性。     

我国六价铬淡水水生生物安全基准推导研究

参照美国国家环境保护局(USEPA)"推导保护水生生物及其用途的国家水质基准的技术指南"的程序和规范,筛选了我国广泛存在的淡水水生生物物种,收集现有的急性和慢性毒性数据,结合课题组实验得到的部分本土生物毒性数据,分别采用物种敏感度排序法(SSR)、物种敏感度分布法(SSD)以及澳大利亚的水质基准技术方法对我国六价铬的淡水水生生物安全基准进行了推导。获得了我国淡水水生生物的六价铬的双值基准,3种方法得到的基准最大浓度(CMC)分别为23.97、22.84、29.06μg·L-1,基准连续浓度(CCC)分别为14.63、10.35、9.00μg·L-1,在同一个数量级上,但与美国的基准值有一些差异,建议使用SSD法推导CMC值和CCC值。研究结果可为我国水质基准的制定提供一些有用的基础资料。     

Effects of phosphorus concentration on Cr（VI） sorption onto phosphorus-rich sludge biochar

To investigate effects of phosphorus content on Cr（VI） sorption onto phosphorus-rich biochar, sewage sludge of different phosphorus concentrations from 4 to 60 mg.g-1 by dry weight were prepared and carbonized to make biochar for batch sorption experiments. Test results revealed that different phosphorous concentration of raw sludge had respective impacts on surface area, pore surface area, average pore diameter and pH value of derived biochar. The adsorption kinetics of phosphorus-rich biochar could be described by the pseudo-second-order model. The sorption isotherm data followed Langmiur model better than Freundlich model. Biochar produced from sludge with phosphorus concentration of 20 mg. gl gave the largest chromium sorption capacity, which could be attributed to its largest surface area and pores surface area comparing with those of＇biochars from sludge with other phosphorus concentrations. The chromium loaded biochar was analyzed using Fourier Transform Infrared Spectroscopy and X-ray Diffraction measurement. The results indicated that chemical functional groups hydroxyl and methyl on surface of biochar were involved in Cr（VI） binding and its reducing to Cr（III）. Then, a portion of Cr （III） in form of various phosphate precipitates was bound onto biochar surface and the rest was released into the solution. The experimental results suggested that phos- phorus played an important role in pore and surface area development of sludge biochar during pyrolytic process. It also could react with Cr（III） on the biochar surface that impacted on capacity of Cr（VI） removal from solution by sludge biochar. Therefore, phosphorus concentration in sludge should be considered when sludge pyrolytic residue would be reused for heavy metals sorbing.     

土壤铬(Ⅵ)对赤子爱胜蚓的生态毒性效应

为研究土壤中Cr(Ⅵ)对赤子爱胜蚓(Eisenia fetida)的毒性效应,以人工土壤为测试介质,按照OECD指南中的方法,测定了Cr(Ⅵ)对赤子爱胜蚓的LC₅₀(半数致死浓度),并考察了w〔Cr(Ⅵ)〕为10~160mg/kg(以干质量计,下同)时Cr(Ⅵ)对赤子爱胜蚓的生长和生殖的影响. 结果表明:①Cr(Ⅵ)在人工土壤中14d的LC₅₀为245.06mg/kg,95%置信限为208.31~288.29mg/kg;②与对照组相比,暴露28d时,w〔Cr(Ⅵ)〕为10~20mg/kg试验组的赤子爱胜蚓体质量显著增加(P<0.01);w〔Cr(Ⅵ)〕为80~160mg/kg试验组的赤子爱胜蚓体质量则受到显著抑制(P<0.01);③赤子爱胜蚓的产茧量和幼蚓孵化量均随着w〔Cr(Ⅵ)〕的升高而降低,其中,Cr(Ⅵ)抑制赤子爱胜蚓产茧量和幼蚓孵化量的EC₅₀(半数有效浓度)分别为62.32和49.92mg/kg. 赤子爱胜蚓的体质量、产茧量和幼蚓孵化量均对土壤中w〔Cr(Ⅵ)〕比较敏感,尤其幼蚓孵化量是赤子爱胜蚓毒性效应的几项测试终点中最为敏感的一种,可以作为生态风险评估的指标.      

Kinetic and equilibrium models for the biosorption of Cr(III) on Streptomyces rimosus

This study focused on the biosorption of trivalent chromium onto mycelial bacterium (Streptomyces rimosus) biomass from effluent of tannery. The biomass was prepared by treatment with alkali. Fourier transforms-infra red analysis of the mycelial bacterial revealed the presence of carboxyl groups as possible binding sites. Experimental parameters affecting biosorption processes such as pH contact time were studied. Langmuir, Freundlich, and Temkin models were applied to describe the biosorption isotherms. The Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The biosorption capacity of S. rimosus biomass for trivalent chromium was found to be 83 mg g^?1 at pH 4.8 and 3 g L^?1 biomass dosage, 300 min equilibrium time and 20°C. Kinetic evaluation of experimental data showed that the biosorption processes of trivalent chromium followed pseudo-second-order kinetics well.     

Adverse effects of chromium on amino acid levels in freshwater fish Clarias batrachus (Linn.)

Various heavy metals released into the rivers and lakes affect aquatic fauna including Clarias batrachus. Elevated levels of chromium (Cr) in aquatic organisms, especially fish, represent an ecological and human concern. Amino acid levels were estimated in five tissues (gills, liver, kidneys, muscle, and brain) of C. batrachus after 28 days of exposure to Cr. This study showed that Cr elevated levels of free amino acids in organs of fish C. batrachus, indicating a compensatory mechanism to counter sublethal metallic stress. Data suggest that the measurement of amino acids may serve as a biomarker for Cr toxicity in fish.     

Carbon paste electrode modified with chromium thiopental for the potentiometric flow injection analysis of chromium (III)

A chemically modified carbon paste electrode for chromium (III) based on the formation of ion-association complex of chromium with 5-ethyl-6-oxo-5-pentan-2-yl-sulfanyl-pyrimidin-4-olate (thiopental, THP) as electroactive ion-exchanger (Cr-THP) was prepared and investigated. The electrode has a linear dynamic range of 1.7?×?10^?6–1.3?×?10^?2?mol?L^?1, with a Nernstian slope of 19.6?±?0.5?mV per decade and a detection limit of 9.0?×?10^?7?mol?L^?1. It has a fast response time of <15?s and can be used for at least 7 weeks without any considerable divergence in potential. The proposed sensor revealed good selectivity for Cr(III) over a wide variety of mono-, di-, and trivalent cations and could be used in the pH range of 2.3–6.5. The proposed electrode was used in batch measurements and in flow injection analysis. The Cr-CMCPE was successfully applied for the determination of Cr(III) in real samples (wastewater of hot dip galvanizing unit and alloys). The present electrode was also used as an indicator electrode in potentiometric titration of Cr(III). The results were highly satisfactory.     

Chromium recovery from solid leather waste by chemical treatment and optimisation by response surface methodology

The leather industry uses conventional tanning methods which cause environmental pollution due mainly to the presence of chromium. This study suggests a treatment for solid leather waste containing chromium as an ecological alternative to the pollution generated by tanneries. The study uses an original approach to the optimisation of chromium recovery by mathematical and statistical treatment of the experimental data. Several factors that influence recovery, such as temperature, concentration, time and solid/liquid ratio through acid and basic hydrolysis were analysed with the aid of experimental design. Tanning liquor was obtained by adjusting pH, alkalinity and concentration when hydrolysis finished. An appropriate response surface model was constructed using alkaline hydrolysis experiments with sodium hydroxide, leading to conditions for maximum recovery of Cr₂O₃. The optimal NaOH concentration (1.58%), temperature (63.7 °C), time (3 h) and solid/liquid ratio (1/70 g·mL^?1) were established. The results indicate that sodium hydroxide as an hydrolysis agent is a highly efficient means of recovering chromium from solid leather waste in order to produce tanning liquor.     

Comparative diversity and heavy metal biosorption of myxomycetes from forest patches on ultramafic and volcanic soils

Ultramafic and volcanic soils are exploited for industrial activities such as mining due to their high metal content, thus it is important that species in these areas are documented before irreversible environmental damage sets in. In this study, aerial and ground leaf litter, dead vines and twigs from six forest patches on volcanic and ultramafic soils in the provinces of Bataan, Pangasinan and Zambales in the Philippines were cultured in moist chambers (MC) and assessed for myxomycete diversity. From the 77% positive MC for myxomycetes, a total of 40 species from 14 genera were identified. Despite the higher heavy metal content, forest patches on ultramafic soils had greater species diversity as compared to volcanic soils. In this study, 10 species were abundant in both forest patches, namely Arcyria cinerea, Diachea leucopodia, Diderma effusum, D. hemisphaericum, Didymium ochroideum, Perichaena chrysosperma, P. corticalis, P. depressa, P. dictyonema and Physarum melleum. Selected myxomycetes tested for Cr and Mn content had equal or higher heavy metal levels than that of their leaf substrate. The study hypothesised that the presence of Mn⁷⁺ in fruiting bodies of myxomycetes was due to the phagocytosis of food bacteria inhabiting the substrates on the forest soil laden with heavy metal.