应用概率稀释模型计算允许纳污量

进一步剖析了引进的概率稀释模型,考虑了上游来水浓度CS,在理论上完整地体现了物质平衡基本原理,提高了模型的科学性和正确性,使设计条件更加接近于我国的实际情况(CS≠0),使应用性和可操作性大大提高。      

动态稀释法在汽车涂装行业固定污染源挥发性有机物测定中的应用

介绍了固定污染源中挥发性有机物(VOCs)的主要采样方法,并重点介绍了动态稀释法在固定污染源中采样的应用。采用动态稀释法取样,对某汽车企业涂装车间的排放废气进行了定性分析,并对其中主要的10种VOCs进行了定量分析。研究了方法测定的稳定性,10种化合物相对标准偏差为9%~32%,符合工况变动范围。将不同采样时间及不同吸附材料的测定结果与在线监控数据进行比较,结果显示动态稀释法的测定结果均在实际工况波动范围内,说明该方法能够较好地满足汽车涂装行业VOCs的采样要求。     

鸡、猪粪便源大肠杆菌对4种抗生素耐药性的比较

以琼脂稀释法对67株鸡源大肠杆菌及61株猪源大肠杆菌进行最低抑菌浓度(MIC)测定,并以SPSS分别进行卡方检验和Probit模型估算,分析不同来源大肠杆菌耐药差异显著性及不同抗生素的半数抑菌浓度(MIC50),以期对不同畜禽粪便来源的大肠杆菌耐药差异进行详细准确的探讨。结果显示,鸡源大肠杆菌对头孢噻肟、诺氟沙星、环丙沙星和四环素耐药率分别为98.51%、68.66%、56.72%和100%,猪源大肠杆菌对头孢噻肟耐药率为88.52%,对诺氟沙星、环丙沙星和四环素则100%耐药。除四环素,鸡源、猪源大肠杆菌对诺氟沙星、环丙沙星、头孢噻肟的耐受差异显著(P0.05),51%的鸡源大肠杆菌和89%的猪源大肠杆菌均呈4重耐药。SPSS分析结果表明,Probit模型估算结果优于当前MIC50常规计算方法,头孢噻肟、诺氟沙星、环丙沙星和四环素对鸡源大肠杆菌MIC50分别为40.031μg·m L~(-1)、40.020μg·m L~(-1)、2.683μg·m L~(-1)和101.418μg·m L~(-1),对猪源大肠杆菌MIC50分别为8.724μg·m L~(-1)、56.044μg·m L~(-1)、31.214μg·m L~(-1)和130.915μg·m L~(-1)。回归方程显示环丙沙星对鸡源大肠杆菌抑制作用最强;高于40.031μg·m L~(-1)时,诺氟沙星抗菌作用弱于头孢噻肟,低于120.23μg·m L~(-1)时,诺氟沙星抗菌作用强于四环素;头孢噻肟、环丙沙星、诺氟沙星和四环素对猪源大肠杆菌的抑菌作用则呈递减趋势。同时验证了诺氟沙星和环丙沙星属同种作用机制,基于Probit模型计算更简单、快速、直观。研究结果可为畜禽养殖中大肠杆菌的耐药差异监控提供一定的数据基础。     

Estimating chemical biotransformation rates from food web concentrations

Biotransformation is widely recognized as the most important and most uncertain determinant of bioaccumulation. A step-wise method for estimating organism-specific biotransformation half-lives from field observations and using established food web modeling is developed. As a proof of concept, the method is applied to the case of nine polycyclic aromatic hydrocarbons (PAHs) in a well-studied food web in Bohai Bay, China. The estimated half-lives are in good agreement with the existing literature. The proposed biotransformation estimation method, through data mining, for sufficiently defined ecosystems, may greatly reduce the necessary animal testing involved in chemical assessments by providing useful guidance to experimentalists and regulators.     

Hexavalent chromium reduction kinetics in rodent stomach contents

Reduction of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) in the stomach prior to absorption is a well-recognized detoxification process thought to limit the toxicity of ingested Cr(VI). However, administration of high concentrations of Cr(VI) in drinking water cause mouse small intestinal tumors, and quantitative measures of Cr(VI) reduction rate and capacity for rodent stomach contents are needed for interspecies extrapolation using physiologically-based toxicokinetic (PBTK) models. Ex vivo studies using stomach contents of rats and mice were conducted to quantify Cr(VI) reduction rate and capacity for loading rates (1-400 mg Cr(VI) L⁻¹ stomach contents) in the range of recent bioassays. Cr(VI) reduction was measured with speciated isotope dilution mass spectrometry to quantify dynamic Cr(VI) and Cr(III) concentrations in stomach contents at select time points over 1 h. Cr(VI) reduction followed mixed second-order kinetics, dependent upon concentrations of both Cr(VI) and the native reducing agents. Approximately 16 mg Cr(VI)-equivalents of reducing capacity per L of fed stomach contents (containing gastric secretions, saliva, water and food) was found for both species. The second-order rate constants were 0.2 and 0.3 L mg⁻¹ h⁻¹ for mice and rats, respectively. These findings support that, at the doses that caused cancer in the mouse small intestine (?20 mg Cr(VI) L⁻¹ in drinking water), the reducing capacity of stomach contents was likely exceeded. Thus, for extrapolation of target tissue dose in risk assessment, PBTK models are necessary to account for competing kinetic rates including second order capacity-limited reduction of Cr(VI) to Cr(III).     

Applications of isotope differentiation for metabolic studies with di‐(2‐ethylhexyl) phthalate

Abstract

The pervasiveness of the plasticizer di‐(2‐ethylhexyl) phthalate (DEHP) in the environment and especially in the laboratory results in a background that may cause severe interference with analytical studies. Animal‐to‐animal variability in the distribution of DEHP metabolites in excreta normally makes it necessary to use large groups of animals when different treatments are compared. Finally, radioactive tracers are usually considered undesirable for metabolic studies involving human subjects. All of these problems can be overcome through the use of muliple isotopic labels, especially ¹²C/¹³C/¹⁴C. Examples are given involving rats and monkeys, and applicability to humans is discussed. The principles involved are not limited to any particular class of test compounds. In rats, the competing pathways for metabolism of phthalate esters produce a different distribution of metabolites from a small intravenous dose of DEHP than from a large oral dose.     

Hydrogeological and biogeochemical constrains of arsenic mobilization in shallow aquifers from the Hetao basin, Inner Mongolia

Little is known about the importance of drainage/irrigation channels and biogeochemical processes in arsenic distribution of shallow groundwaters from the Hetao basin. This investigation shows that although As concentrations are primarily dependent on reducing conditions, evaporation increases As concentration in the centre of palaeo-lake sedimentation. Near drainage channels, groundwater As concentrations are the lowest in suboxic-weakly reducing conditions. Results demonstrate that both drainage and irrigation channels produce oxygen-rich water that recharges shallow groundwaters and therefore immobilize As. Groundwater As concentration increases with a progressive decrease in redox potential along the flow path in an alluvial fan. A negative correlation between SO₄²⁻ concentrations and δ³⁴S values indicates that bacterial reduction of SO₄²⁻ occurs in reducing aquifers. Due to high concentrations of Fe (>0.5 mg L⁻¹), reductive dissolution of Fe oxides is believed to cause As release from aquifer sediments. Target aquifers for safe drinking water resources are available in alluvial fans and near irrigation channels.     

固含率和稀释率对餐厨垃圾水解酸化过程的影响研究

研究了餐厨垃圾分批厌氧消解过程中不同起始固含率（10％,12％和14％）和稀释率（0.25 d^－1和0.33 d^－1）对水解酸化过程pH值、垃圾消解、水解酸化液生产效率、脂肪酸组成和浓度等的影响。实验结果发现：以总固体去除率、单位质量垃圾累积COD溶出量（ACODm）和单位体积反应器累积COD溶出量（ACODv）等指标作为评价标准,起始固含率12％的体系具有较高的垃圾处理效率和反应器运行效率。与稀释率0.25 d^－1的体系相比,稀释率0.33 d^－1的体系在pH稳定性、总固体去除率和水解酸化液生产效率等方面具有明显的优势。所有体系中水解酸化产生的脂肪酸和醇均以乙酸、乙醇和丁酸为主,丙酸占总脂肪酸和醇的百分数在14.6％到17.1％之间,这种脂肪酸组成不会发生丙酸抑制,有利于后续产甲烷发酵的进行。     

同位素技术在环境科学研究中的应用进展

综述了近年来同位素技术在国内外环境科学研究中的应用状况,简要介绍了同位素技术的应用原理与分析方法。总结了放射性同位素技术和稳定同位素技术在环境史重建、污染物示踪及源解析等方面的应用,重点介绍了稳定同位素技术在水、大气和土壤污染物源解析中的应用进展。对未来同位素技术在环境科学研究中的应用进行了展望,提出了多种同位素联合解析、建立和完善定量源解析模型等建议。     

改进污径比计算方法及应用

为了使现行污径比更加科学合理,提出底标比、排标比和危害系数并用来对原污径比进行改进完善.以东辽河为例,对新污径比进行检验.结果表明,新污径比不仅能作为生态水质评价的指标,还能量化反映河流环境容量盈亏度.新污径比还可以更广泛地应用到水资源水质评价、水资源承载力计算和区域可持续发展等研究领域.