Uncertainty analysis using a fugacity-based multimedia mass-balance model: Application of the updated EQC model to decamethylcyclopentasiloxane (D5)

The EQuilibrium Criterion (EQC) model developed and published in 1996 was recently revised to include improved treatment of input partitioning and reactivity data, temperature dependence and an easier sensitivity and uncertainty analysis. This New EQC model was used to evaluate the multimedia, fugacity-based fate of decamethylcyclopentasiloxane (D5; CAS No. 541-02-6) in the environment over a temperature range of 1–25 °C. In addition, Monte Carlo uncertainty analysis was used to quantitatively determine the influence of temperature and input partitioning and reactivity data on the behavior of D5 under various emission scenarios. Results indicated that emission mode was the most influential factor determining the fate and distribution of D5 in the model environment. When emitted to air and soil, D5 partitioned to and remained in the air compartment where rates of removal from degradation and advection processes were relatively rapid. In contrast, D5 emitted to water resulted in a substantial mass fraction of D5 being accumulated in the sediment compartment, where rates of removal from degradation and advection processes were slow. The mass distributions and fate of D5 in the model environment were strongly influenced by multiple input parameters, including temperature, the mode of emission (especially emission rate to water), K_OC and half-life in air. As temperature decreased from 25 °C to 1 °C, K_OC and half-life in air became increasingly more influential such that the mass distribution of D5 increased in air and decreased in sediment, resulting in decreased overall persistence.     

重金属由水相到沉积物相的标准迁移自由能

采用电位法测定了淀山湖水体中,Cu、Zn、Pb、Cd等重金属的氯化物由水相到沉积物相的标准迁移自由能(△Gt0)。结果表明,重金属离子的△Gt0随沉积物-水悬浮液中的沉积物含量增加而减小;△Gt0的大小次序为:Cd2+>Pb2+>Cu2+>Zn2+,即Zn2+最易迁入沉积物中,而Cu2+、Pb2+、Cd2+依次减弱,这同重金属离子在沉积物/水两相间的分配系数大小相一致。     

4种农药流失性质的研究

对４种农药的流失性质，进行了实验室和田间的试验研究，结果表明，水溶性农药乐果和杀虫单，有较低的土壤水分配比，较强的渗滤性和淋洗性，较易流失并污染水环境。脂溶性农药氰戊菊酯易被土壤强烈吸附，较难渗及被淋洗，不易流失，对水环境污染较轻。丁草胺的流失性质介于水溶性农药与脂溶性农药之间。     

可吸入颗粒物研究现状及发展综述

可吸入颗粒物严重影响空气质量和人体健康。人类对可吸入颗粒物的研究已经取得了相当多的成果,对其来源、组分及形成等都有了一定的认识。本文详细的综述了这部分内容,并对可吸入颗粒物的采样、分离和分析方法都做了介绍。更深层的认识可吸入颗粒物的生成机理和脱除手段是以后努力研究的方向。     

阴-阳离子有机膨润土吸附水中苊的性能及机理研究

用溴化十二烷基三甲铵（DTMAB）、十二烷基硫酸钠（SDS）、十二烷基苯磺酸钠（SDBS）按不同配比制得一系列阴一阳离子有机膨润土,研究了有机膨润土吸附水中苊的性能及机理。结果表明,阴一阳离子有机膨润土对水中苊的吸附去除能力大于单阳离子有机膨润土,且与改性时所用阴离子表面活性剂的种类、浓度有关;阴一阳离子有机膨润土对苊的吸附等温线呈线性,吸附机理主要是分配作用。     

Investigation of partitioning mechanism for volatile organic compounds in a multiphase system

Laboratory experiments were performed to investigate the partitioning behavior of a set of diverse volatile organic compounds (VOCs). After equilibration at a temperature of 25 °C, the VOC concentrations were measured by headspace method in combination with gas chromatography/mass spectrometry (GC/MS). The obtained data were used to determine the partition coefficients (K_P) of VOCs in a gas-liguid-solid system. The results have shown that the presence and nature of solid materials in the working solution control the air-water partitioning of dissolved VOCs. The air/solution partitioning of BTEX and C₉-C₁₀ aldehydes was most affected in the presence of diesel soot. K_P values decreased by a factor ranging from 1.5 for toluene to 3.0 for ethylbenzene. The addition of mineral dust in the working solution exhibited greater influence on the partitioning of short aldehydes. K_P values decreased by a factor of 1.8. The experimental partition coefficients were used to develop a predictive model for partitioning of BTEX and n-aldehydes between air, water and solid phases.     

Linear and non-linear relationships between soil sorption and hydrophobicity: model, validation and influencing factors

The hydrophobic parameter represented by the octanol/water partition coefficient (log P) is commonly used to predict the soil sorption coefficient (K_oc). However, a simple non-linear relationship between log K_oc and log P has not been reported in the literature. In the present paper, soil sorption data for 701 compounds was investigated. The results show that log K_oc is linearly related to log P for compounds with log P in the range of 0.5-7.5 and non-linearly related to log P for the compounds in a wide range of log P. A non-linear model has been developed between log K_oc and log P for a wide range of compounds in the training set. This model was validated in terms of average error (AE), average absolute error (AAE) and root-mean squared error (RMSE) by using an external test set with 107 compounds. Nearly the same predictive capacity was observed in comparison with existing models. However, this non-linear model is simple, and uses only one parameter. The best model developed in this paper is a non-linear model with six correction factors for six specific classes of compounds. This model can well predict log K_oc for 701 diverse compounds with AAE = 0.37. The reasons for systemic deviations in these groups may be attributed to the difference of sorption mechanism for hydrophilic/polar compounds, low solubility for highly hydrophobic compounds, hydrolysis of esters in solution, volatilization for volatile compounds and highly experimental errors for compounds with extremely high or low sorption coefficients.     

Migration and leaching risk of extraneous antimony in three representative soils of China: Lysimeter and batch experiments

Antimony (Sb) distribution, solubility and mobility onto natural soils of China were studied in lysimeter and batch experiments as a function of physicochemical properties of the soil. An outdoor lysimeter experiment investigated the leaching and migration of Sb in the soils with Sb-polluted topsoil and unpolluted subsoil over a 5 month period. Soil solutions were collected by suction cups installed at different depth of lysimeters, and leachates were regularly collected and analyzed for Sb concentrations. The majority of the added Sb was retained in the topsoil layers, but small portions were moved to the sub-layers. Sb concentrations in the soil solutions and leachates ranged from 0–755.5 (6.38 ± 54 on average) μg l⁻¹ and 0–0.45 (smaller than the detection limit) μg l⁻¹ respectively, indicating the low solubility of Sb in the soils. Batch experiments were performed in order to determine the sorption capacity and the partition coefficient (K_d). Freundlich isotherm described properly the equilibrium experimental data and results show that the K_d values for Primosol, Isohumosol, Ferrosol equal to 22.5, 87.8, 704 L kg⁻¹, respectively. These results showed the strong capacity of the soils to retain Sb, and prevent it being leached down the profile. The mobilizable Sb was in the order: Primosol > Isohumosol > Ferrosol. Sb migration in the soils was mainly associated with the exchangeable, carbonate-bound, and metal–organic complex-bound fractions. Health risk assessment indicates that Sb leaching from Ferrosol will not harm to human health through groundwater under the test conditions, while it has certain health risks from the Isohumosol and Primosol.     

农药分配系数及其在环境研究中的应用

简述了农药分配系数的直接摇瓶测定法和其它间接估算方法，讨论了分配系数与农药其他理化性质和环境行为之间的关系。分配系数是估测农药水溶性，生物富集性及底泥沉积物吸附系数等参数的较好方法。