A simplified 137Cs transport model for estimating erosion rates in undisturbed soil

(137)Cs is an artificial radionuclide with a half-life of 30.12 years which released into the environment as a result of atmospheric testing of thermo-nuclear weapons primarily during the period of 1950s-1970s with the maximum rate of (137)Cs fallout from atmosphere in 1963. (137)Cs fallout is strongly and rapidly adsorbed by fine particles in the surface horizons of the soil, when it falls down on the ground mostly with precipitation. Its subsequent redistribution is associated with movements of the soil or sediment particles. The (137)Cs nuclide tracing technique has been used for assessment of soil losses for both undisturbed and cultivated soils. For undisturbed soils, a simple profile-shape model was developed in 1990 to describe the (137)Cs depth distribution in profile, where the maximum (137)Cs occurs in the surface horizon and it exponentially decreases with depth. The model implied that the total (137)Cs fallout amount deposited on the earth surface in 1963 and the (137)Cs profile shape has not changed with time. The model has been widely used for assessment of soil losses on undisturbed land. However, temporal variations of (137)Cs depth distribution in undisturbed soils after its deposition on the ground due to downward transport processes are not considered in the previous simple profile-shape model. Thus, the soil losses are overestimated by the model. On the base of the erosion assessment model developed by Walling, D.E., He, Q. [1999. Improved models for estimating soil erosion rates from cesium-137 measurements. Journal of Environmental Quality 28, 611-622], we discuss the (137)Cs transport process in the eroded soil profile and make some simplification to the model, develop a method to estimate the soil erosion rate more expediently. To compare the soil erosion rates calculated by the simple profile-shape model and the simple transport model, the soil losses related to different (137)Cs loss proportions of the reference inventory at the Kaixian site of the Three Gorge Region, China are estimated by the two models. The over-estimation of the soil loss by using the previous simple profile-shape model obviously increases with the time period from the sampling year to the year of 1963 and (137)Cs loss proportion of the reference inventory. As to 20-80% of (137)Cs loss proportions of the reference inventory at the Kaixian site in 2004, the annual soil loss depths estimated by the new simplified transport process model are only 57.90-56.24% of the values estimated by the previous model.     

城中村改造与生态城市建设

城市化的加速,促进了经济社会的快速发展,但同时也带来了城市发展模式的思考和城中村改造的问题。对于目前中国多数的大中城市来说,建设生态城市和改造城中村是当前城市建设工作的两项重要内容。从这两项工作的理论研究入手,阐述了城中村改造与生态城市建设的关系,论证了城中村改造遵循生态城市建设要求的重要性,论述了城中村改造中的生态保护措施,力求促使城中村改造与生态城市建设有机衔接,加速生态城市建设进程。     

预处理方式对氧化-还原联合技术修复硝基苯污染地下水的影响

为了探究氧化与还原预处理对氧化-还原联合技术修复硝基苯污染地下水的影响,选取2,4-DNT（2,4-二硝基甲苯）为研究对象,构建过硫酸盐/铁炭修复技术体系,分别设置2个试验槽,一个试验槽以过硫酸盐作为氧化预处理联合以铁炭作为还原后处理,另一个试验槽以铁炭作为还原预处理联合以过硫酸盐作为氧化后处理,对比研究构建的氧化-还原联合系统中不同氧化与还原预处理方式对2,4-DNT去除机制的影响.结果表明:①过硫酸盐氧化材料填充位置显著影响试验槽pH和ORP（氧化还原电位）的变化,在运行周期5 PV（PV为孔隙体积,1 PV时间约为4 h）内,pH可显著增至11左右,ORP值达到最高.②在运行周期5 PV内,氧化填充层S₂O₈2-浓度和还原填充层Fe2+浓度均显著降低.③在运行周期5 PV内,随运行周期的增加,以过硫酸盐作为氧化预处理联合以铁炭作为还原后处理的协同技术体系对2,4-DNT的去除效果显著降低,以铁炭作为还原预处理联合以过硫酸盐作为氧化后处理的协同技术体系对2,4-DNT的去除率维持在100%.④通过液相-质谱联用技术,识别构建的氧化-还原联合技术体系内2,4-DNT降解的主要中间产物,同时结合铁炭微电解还原机制和过硫酸盐氧化机制提出了2,4-DNT协同处理机制及其可能的降解路径.研究显示,还原预处理更有利于氧化-还原联合技术对地下水中2,4-DNT的去除,可为有效处理硝基苯化合物污染地下水提供理论支撑.      

Multiresidue determination and potential risks of emerging pesticides in aquatic products from Northeast China by LC–MS/MS

A simple method for determining 33 pesticides with a wide polarity range(log Kow0.6-4.5) in aquatic products was developed based on LC–MS/MS. The target analytes included three types of widely used pesticides: insecticides, fungicides and herbicides. Based on the optimization of ultrasonic assisted extraction and GPC clean-up procedures, the matrix effect, extraction recoveries and LOD were improved distinctively. LOQ of this method was below 0.5 ng/g for all pesticides, which is superior to values in the literature, and the matrix effect was reduced effectively(-14.7% to 7.5%). The method was successfully applied to investigate the pesticide residue levels of twenty-five samples including seven common kinds of fishes from Northeast China. The results showed that all targeted pesticides were present in the fish samples; however, their levels were low, except for atrazine, linuron,ethoprophos, tetrachlorvinphos, acetochlor and fenthion. Atrazine and linuron caught our attention because the concentrations of atrazine in fish samples from Liaoning province were in the range of 0.5-8 ng/g(w/w) with mean concentration of 2.3 ng/g, which were far above those of other pesticides. The levels of linuron were in the range of 0.6-6 ng/g(mean concentration 2.8 ng/g), which were the highest among all targeted pesticides in the Inner Mongolia. This is the first systematic investigation on the characteristics and levels of these pesticides in aquatic products from northeast China. Considering their toxicity and bioaccumulation, the potential risk of atrazine and linuron from consuming aquatic products should be paid more attention.     

Observations of atmospheric pollutants at Lhasa during 2014–2015: Pollution status and the influence of meteorological factors

Atmospheric pollutants including SO₂, NO₂, CO, O₃ and inhalable particulate matter (PM_2.5 and PM₁₀) were monitored continuously from March 2014 to February 2015 to investigate characteristics of air pollution at Lhasa, Tibetan Plateau. Species exhibited similar seasonal variations except O₃, with the peaks in winter but low valleys in summer. The maximum O₃ concentration was observed in spring, followed by summer, autumn, and winter. The positive correlation between O₃ and PM₁₀ in spring indicated similar sources of them, and was assumed to be turbulent transport. Temperature was the dominant meteorological factor for most species in spring. High temperature accelerates O₃ photochemistry, and favors air disturbance which is conductive to dust resuspension in spring. Relative humidity (RH) and atmospheric pressure were the main meteorological factors in summer. RH showed negative correlations with species, while atmospheric pressure posed opposite situation. Wind speed (WS) was the dominant meteorological factor in autumn, the negative correlations between WS and species indicated diffusion by wind. Most species showed non-significant correlations with meteorological factors in winter, indicating the dependence of pollution on source emission rather than restriction by meteorology. Pollution weather character indicated that emissions were from biomass burning and dust suspension, and meteorological factors also played an important role. Air stream injection from the stratosphere was observed during O₃ pollution period. Air parcels from Southwest Asia were observed during air pollution period in winter. An enhancement in air pollutants such as O₃ would be expected in the future, more attention should be given to countermeasures for prevention of air pollution in the future.     

Inhibition of thrombin by functionalized C60 nanoparticles revealed via in vitro assays and in silico studies

The studies on the human toxicity of nanoparticles (NPs) are far behind the rapid development of engineered functionalized NPs. Fullerene has been widely used as drug carrier skeleton due to its reported low risk. However, different from other kinds of NPs, fullerene-based NPs (C₆₀ NPs) have been found to have an anticoagulation effect, although the potential target is still unknown. In the study, both experimental and computational methods were adopted to gain mechanistic insight into the modulation of thrombin activity by nine kinds of C₆₀ NPs with diverse surface chemistry properties. In vitro enzyme activity assays showed that all tested surface-modified C₆₀ NPs exhibited thrombin inhibition ability. Kinetic studies coupled with competitive testing using 3 known inhibitors indicated that six of the C₆₀ NPs, of greater hydrophobicity and hydrogen bond (HB) donor acidity or acceptor basicity, acted as competitive inhibitors of thrombin by directly interacting with the active site of thrombin. A simple quantitative nanostructure-activity relationship model relating the surface substituent properties to the inhibition potential was then established for the six competitive inhibitors. Molecular docking analysis revealed that the intermolecular HB interactions were important for the specific binding of C₆₀ NPs to the active site canyon, while the additional stability provided by the surface groups through van der Waals interaction also play a key role in the thrombin binding affinity of the NPs. Our results suggest that thrombin is a possible target of the surface-functionalized C₆₀ NPs relevant to their anticoagulation effect.     

Mercury in soil, vegetable and human hair in a typical mining area in China: Implication for human exposure

Concentrations of total mercury(T-Hg) and methylmercury(MeHg) in soil, vegetables, and human hair were measured in a mercury mining area in central China. T-Hg and MeHg concentrations in soil ranged from 1.53 to 1054.97 mg/kg and 0.88 to 46.52 μg/kg, respectively.T-Hg concentrations was correlated with total organic carbon(TOC) content(R~2= 0.50, p0.01)and pH values(R~2= 0.21, p0.05). A significant linear relationship was observed between MeHg concentrations and the abundance of sulfate-reducing bacteria(SRB)(R~2= 0.39, p0.05) in soil.Soil incubation experiments amended with specific microbial stimulants and inhibitors showed that Hg methylation was derived from SRB activity. T-Hg and MeHg concentrations in vegetables were 24.79 – 781.02 μg/kg and 0.01 – 0.18 μg/kg, respectively; levels in the edible parts were significantly higher than in the roots(T-Hg: p0.05; MeHg: p0.01). Hg species concentrations in rhizosphere soil were positively correlated to those in vegetables(p0.01), indicating that soil was an important source of Hg in vegetables. Risk assessment indicated that the consumption of vegetables could result in higher probable daily intake(PDI) of T-Hg than the provisional tolerable daily intake(PTDI) for both adults and children. In contrast, the PDI of MeHg was lower than the reference dose. T-Hg and MeHg concentrations in hair samples ranged from 1.57 to 12.61 mg/kg and 0.04 to 0.94 mg/kg, respectively, and MeHg concentration in hair positively related to PDI of MeHg via vegetable consumption(R~2= 0.39, p0.05), suggesting that vegetable may pose health risk to local residents.     

Allowance and allocation of industrial volatile organic compounds emission in China for year 2020 and 2030

As an effective pollution control method, emission allowance and allocation just implemented in volatile organic compounds(VOCs) control strategy of China in 2016. This article presents a possible way to set the emission allowance targets and establishes an allowance allocation model for the object year, 2020 and 2030, using 2010 as the reference year. On the basis of regression and scenario analysis method, the emission allowance targets were designed,which were 17.902 Tg and 18.224 Tg for 2020 and 2030, with an increasing rate of 28.75% and31.06% compared to 2010. From the perspective of industries, processes using VOCscontaining products, like machinery and equipment manufacturing, would continue to be the most significant industrial VOCs emission sources in the future of China. Four allocation indicators were selected, which are per capita GDP of each province, per capita industrial VOCs emission of each province, the economic contribution of industrial sector to regional economy of each province, and the emission intensity per land area of each province, respectively.Based on information entropy, the weights of the indicators were calculated and an emission allocation model was established, and the results showed that provinces like Shandong,Jiangsu, Guangdong, Zhejiang and Fujian were calculated to obtain more emission allowance while burden more reduction responsibility. Meanwhile, provinces like Guizhou, Ningxia,Hainan, Qinghai and Xizang were on the contrary. This paper suggests governments to enhance or ease to industrial VOCs reduction burden of each province in order to stimulate its economy or change its way of economy development.     

Characterization and acid-mobilization study for typical iron-bearing clay mineral

In this study, iron speciation in five standard clay samples was characterized. Iron mobilization from these clays was then measured in acidic media. For comparison, a commercially available Arizona test dust (ATD) was also observed. The results showed that the free-Fe contents of clays were commonly lower than that of dust aerosols. The components of clays were dominant by the structural Fe held in the aluminosilicate lattice. The iron solubility of the clays were in the order of KGa-2?>?SWy-2?>?CCa-2?>?IMt-2?>?NAu-2. Based upon the Mössbauer spectrum and transmission electron microscopy (TEM) analysis, the Fe(II) fraction and the Fe/Si ratio of clay particles changed after dissolution, suggesting the total Fe solubility depended on the Fe atom states existing within the aluminosilicate lattice. The Fe in KGa-2 and SWy-2 was most likely substituted for alkaline elements as the interlayer ions held by ionic bonds in the aluminosilicate, which are more liable to dissolution. However, the Fe in NAu-2 was more likely to be bound by strong covalent bonds in aluminosilicate mineral, which is less soluble. The much highly soluble Fe in ATD was not only linked to the dissolution of an appreciable fraction of Fe(II), but also could be attributed to the fact that the Fe bonds in the clay fraction of ATD were mainly present as ionic bonds. The TEM images showed that reacted clay particles displayed less aggregate particles, with nanoparticle aggregates and the Fe/S-rich tiny particles attached to the remains.