蔬菜常用农药在地下水中残留风险评估

为明确蔬菜常用农药在地下水中的环境风险,运用China-Pearl和SCI-GROW模型开展地下水环境暴露评估,并根据我国成人和儿童暴露参数推导25种农药预测无效应浓度(PNEC)。研究发现,25种农药PECgw为0~18.340μg·L-1,成年人PNECgw为0.003~19.654 mg·L-1,儿童PNECgw为0.001~23.253 mg·L-1。成年人和儿童的RQgw值均小于1,表明25种农药按照登记用量使用,我国成人和各年龄阶段儿童直接饮用施用农药区域地下水的环境风险可接受。     

System Dynamics to Sustainable Water Resources Management in the Eastern Snake Plain Aquifer Under Water Supply Uncertainty1

Abstract: Water supply uncertainty continues to threaten the reliability of regional water resources in the western United States. Climate variability and water dispute potentials induce water managers to develop proactive adaptive management strategies to mitigate future hydroclimate impacts. The Eastern Snake Plain Aquifer in the state of Idaho is also facing these challenges in the sense that population growth and economic development strongly depend on reliable water resources from underground storage. Drought and subsequent water conflict often drive scientific research and political agendas because water resources availability and aquifer management for a sustainable rural economy are of great interest. In this study, a system dynamics approach is applied to address dynamically complex problems with management of the aquifer and associated surface‐water and groundwater interactions. Recharge and discharge dynamics within the aquifer system are coded in an environmental modeling framework to identify long‐term behavior of aquifer responses to uncertain future hydrological variability. The research shows that the system dynamics approach is a promising modeling tool to develop sustainable water resources planning and management in a collaborative decision‐making framework and also to provide useful insights and alternative opportunities for operational management, policy support, and participatory strategic planning to mitigate future hydroclimate impacts in human dimensions.     

Recycling of EDTA solution after soil washing of Pb, Zn, Cd and As contaminated soil

Soil washing with EDTA is known to be an effective means of removing toxic metals from contaminated soil. A practical way of recycling of used soil washing solution remains, however, an unsolved technical problem. We demonstrate here, in a laboratory scale experiment, the feasibility of using acid precipitation to recover up to 50% of EDTA from used soil washing solution obtained after extraction of Pb (5330 mg kg⁻¹), Zn (3400 mg kg⁻¹), Cd (35 mg kg⁻¹) and As (279 mg kg⁻¹) contaminated soil. Up to 100% of EDTA residual in the washing solution and 100%, 97%, 98% and 100% of initial Pb, Zn, Cd and As concentration in the solution, respectively, were removed in an electrolytic cell using a graphite anode. We employed the recovered EDTA and treated washing solution to prepare recycled soil washing solution with the same potential for extracting toxic metals from soil as the original. The efficiency of soil washing depends on the EDTA concentration. Using twice recycled 30 mmol EDTA kg⁻¹ soil, we removed 44%, 20%, 53% and 61% of Pb, Zn, Cd and As, respectively, from contaminated soil.     

Ex situ remediation of contaminated sediments using mineral additives: assessment of pollutant bioavailability with the Microtox solid phase test

The aim of this work is to assess the potential ecotoxicological effects of contaminated sediments treated with mineral additives. The Microtox solid phase test was used to evaluate the effect of mineral additives on the toxicity of sediment suspensions. Four Mediterranean port sediments were studied after dredging and bioremediation: Sample A from navy harbor, sample B from commercial port and samples C and D from pleasure ports. Sediment samples were stabilized with three mineral additives: hematite, zero-valent iron and zeolite. Results show that all studied mineral additives can act as stabilizer agent in highly contaminated sediments (A and C) by decreasing dissolved metal concentrations and sediment toxicity level. On the contrary, for the less contaminated samples (B and D) hematite and zeolite can provoke toxic effect towards Vibrio fischeri since additive particles can favor bacteria retention and decrease bioluminescence emission.     

Genotoxicity of sediment extracts of the Berre lagoon (France)

To evaluate the genotoxic risk that contaminated sediment could constitute for benthic organisms, three contaminated (VA, VC and VN) and one uncontaminated (RN) sediment samples were collected in the Berre lagoon (France). Potentially bioavailable contaminants in sediments were obtained using sediment extraction with synthetic seawater adjusted to pH 4 or pH 6, simulating the range of pH prevailing in the digestive tract of benthic organisms. The genotoxic activities of these extracts were evaluated by three short-term bioassays: the Salmonella mutagenicity test using the Salmonella typhimurium strain TA102, the alkaline comet assay and the micronucleus assay on the Chinese Hamster Ovary cells CHO-K1. Results of the Salmonella mutagenicity assay detected a mutagenic response for RN extract at pH 6, and for VA extract at pH 4. Results of the comet and micronucleus assays detected low genotoxic/clastogenic activities for VA and VC extracts at pH 6 and higher activities for RN, VA and VC extracts at pH 4. To identify if metals (Al, Fe, Mn, As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn) were involved in these genotoxic activities, their concentrations were determined in the extracts, and their speciation was assessed by thermodynamic calculations. Results showed that extracts from sites VA, VC and VN generally presented the highest trace metal contents for both extractants, while the site RN presented lower trace metal contents but the highest Fe and Mn contents. Thermodynamic calculations indicated that Fe, Mn, As and in a lower extend Co, Ni and Zn were mainly present under free forms in extracts, and were consequently, more likely able to induce a genotoxic effect. Results globally showed no correspondence between free metal contents and genotoxic activities. They suggested that these positive results could be due to uncharacterized compounds, acting as direct genotoxic agents or enhancing the genotoxic properties of analyzed metals.     

原位热处理技术修复重质非水相液体污染场地研究进展

重质非水相液体(DNAPLs)是土壤及地下水中广泛存在的有机污染物,原位热处理技术是目前修复受DNAPLs污染土壤及地下水的最具潜力的技术之一。综述了国内外常用原位热处理技术的基本原理及其影响因素,介绍了相关现场应用实例,并展望了该技术未来的应用前景和发展趋势,以期为中国污染土壤及地下水的原位修复提供有益借鉴。     

强化土著微生物处理硝基苯和苯胺污染地下水

以硝基苯、苯胺为主要污染物的污染地下水为研究对象,加入激活剂(乳糖、Na2HPO4、乳糖+Na2HPO4、乙醇、牛肉膏、蛋白胨)激活土著微生物,并考察其对土著微生物生长及硝基苯、苯胺降解效果的影响。加入激活剂3d后测各个水样的脱氢酶活性,对培养9d后的水样进行气相色谱/质谱(GC/MS)分析。结果表明,加入乳糖的水样中,其微生物相对增长率达157.2%,硝基苯、苯胺的相对去除率分别为14.90%和0.79%;加入Na2HPO4和乙醇的水样中,其微生物增长和硝基苯、苯胺降解情况均没有明显变化;加入乳糖+Na2HPO4的水样中,微生物相对增长率达180.3%,硝基苯、苯胺的相对去除率分别为24.20%和1.21%;加入牛肉膏的水样中,微生物的相对增长率为830.7%,硝基苯、苯胺的相对去除率分别为99.99%和99.67%;加入蛋白胨的水样中,其微生物相对增长率为686.0%,硝基苯、苯胺的相对去除率分别为99.33%和58.94%。GC/MS分析结果表明,加入激活剂后对氯苯胺、1-甲基-4-硝基苯等其他有机物的降解率均有提高。由此可见,通过激活土著微生物修复有机物污染地下水是可行的。     

零价铁与厌氧微生物协同还原地下水中的硝基苯

通过间歇式实验,考察了零价铁与厌氧微生物协同还原地下水中硝基苯的效果。实验结果表明,由零价铁腐蚀为厌氧微生物提供H2电子供体还原硝基苯的效果明显优于零价铁和微生物单独作用,硝基苯去除率分别提高21.8%和57.0%。弱酸性条件有利于协同反应进行,当初始pH为5.0和6.0时,4 d后硝基苯去除率比初始pH为7.0时的提高74.4%和35.2%。增加零价铁投加量可提高协同还原的效果,零价铁最佳投加量为250 mg/L。零价铁腐蚀产生的Fe2+无法作为电子供体被微生物利用,但可作为无机营养元素促进协同过程。由于零价铁产H2速率受表面覆盖物影响不明显,在地下水修复过程中可保证协同效果并延长零价铁的使用寿命。     

高硬度富锶地下水的软化沉淀-超滤膜联用工艺

针对一种高硬度富锶地下水,分别采用石灰和石灰-碳酸钠两种方法,利用药剂软化/超滤膜工艺对其进行软化处理,同时考察了药剂投量对出水锶含量的影响。结果表明,采用石灰软化/超滤膜法,Ca(OH)2最佳投加量为270 mg/L时,出水总硬度(以CaCO3计)由287.12 mg/L降低到96.44 mg/L,硬度去除率为66.41%,出水锶含量也由原水中的0.37 mg/L下降为0.21 mg/L;而采用石灰-碳酸钠软化/超滤膜法,Ca(OH)2和Na2CO3最佳投加量分别为270 mg/L、160mg/L时,出水总硬度降低到60.34 mg/L,硬度去除率达78.98%,锶含量仅为0.02 mg/L。2种处理方法出水总硬度均达到预期目标,石灰软化/超滤膜法可使出水锶含量满足富锶水的要求,而石灰-碳酸钠软化/超滤膜法则造成了对人体有益微量元素锶的大量损失。     

地下水PRB原位生物修复中一种释氧材料的改进技术及效果分析

释氧材料经济有效的释氧是地下水原位生物修复的关键因素。实验通过在释氧材料中加入膨润土、磷酸二氢钾和硫酸铵等,改进释氧材料的性能。柱实验结果显示,该释氧材料释氧速率缓慢,释氧时间长,可以使溶液中DO长期保持在5 mg/L以上;另外,释氧材料中添加的缓冲剂及天然含水层介质对pH值有较好的缓冲作用,可以使pH值达到后续生物修复的要求。