Concentration and characterization of plutonium in soils of Hubei in central China

To study the Pu concentration and isotope ratio distributions present in China, the ^239+240Pu total activities and ²⁴⁰Pu/²³⁹Pu atom ratios in core soil samples from Hubei Province in central China were investigated using Accelerator Mass Spectrometry (AMS). The activities ranged from 0.019 to 0.502 mBq g⁻¹ and the ^239+240Pu inventories of 45 and ∼55 Bq m⁻² agree well with that expected from global fallout. The ²⁴⁰Pu/²³⁹Pu atom ratios in the soil ranged from 0.172 to 0.220. The ratios are similar to typical global fallout values. Hence, any close-in fallout contribution from the Chinese nuclear weapons tests, mainly conducted in the 1970s, must have either been negligible or had a similar ²⁴⁰Pu/²³⁹Pu ratio to that of global fallout. The top 10 cm layer of the soil contributes ∼90% of the total inventory and the maximum concentrations appeared in the 2-4 cm or 4-6 cm layers. It is suggested that climatic conditions and organic content are the two main factors that affect the vertical migration of plutonium in soil.     

Radon, helium and CO2 measurements in soils overlying a former exploited oilfield, Pechelbronn district, Bas-Rhin, France

The Pechelbronn oilfield (Rhine Graben, France), where mining activity ended in the 1960s, has been used for waste disposal for twenty years. Since the wastes are varied, work is underway to identify the discharged materials and their derivatives, as well as to locate and quantify potential discharge sites. Two major goals were assigned to the present work. The first was to identify or refine the location of hidden structures that could facilitate gas emanation up to the surface, by studying soil gas concentrations (mainly ²²²Rn, CO₂, CH₄ and helium) and carbon isotope ratios in the CO₂ phase. The second was devoted to examining, from a health and safety viewpoint, if the use of the oilfield as a waste disposal site might have led to enhanced or modified gas emanation throughout the area.It appeared that CO₂ and ²²²Rn evolution in the whole area were similar, except near some of the faults and fractures that are known through surface mapping and underground observations. These ²²²Rn and CO₂ anomalies made it possible to highlight more emissive zones that are either related to main faults or to secondary fractures acting as migration pathways. In that sense, the CO₂ phase can be used to evaluate ²²²Rn activities distant from tectonic structures but can lead to erroneous evaluations near to gas migration pathways. Dumping of wastes, as well as oil residues, did not appear to have a strong influence on soil gaseous species and emanation. Similarly, enhanced gas migration due to underground galleries and exploitation wells has not been established. Carbon isotope ratios suggested a balance of biological phenomena, despite the high CO₂ contents reached. Other monitored gaseous species (N₂, Ar, H₂ and alkanes), when detected, always showed amounts close to those found subsurface and/or in atmospheric gases.     

Variation of radiation level and radionuclide enrichment in high background area

Significantly high radiation level and radionuclide concentration along Quilon beach area of coastal Kerala have been reported by several investigators. Detailed gamma radiation level survey was carried out using a portable scintillometer. Detailed studies on radionuclides concentration in different environmental matrices of high background areas were undertaken in the coastal areas of Karunagapalli, Kayankulam, Chavara, Neendakara and Kollam to study the distribution and enrichment of the radionuclides in the region. The absorbed gamma dose rates in air in high background area are in the range 43-17,400 nGyh⁻¹. Gamma radiation level is found to be maximum at a distance of 20 m from the sea waterline in all beaches. The soil samples collected from different locations were analysed for primordial radionuclides by gamma spectrometry. The activity of primordial radionuclides was determined for the different size fractions of soil to study the enrichment pattern. The highest activity of ²³²Th and ²²⁶Ra was found to be enriched in 125-63 μ size fraction. The preferential accumulation of ⁴⁰K was found in <63 μ fraction. The minimum ²³²Th activity was 30.2 Bq kg⁻¹, found in 1000-500 μ particle size fraction at Kollam and maximum activity of 3250.4 Bq kg⁻¹ was observed in grains of size 125-63 μ at Neendakara. The lowest ²²⁶Ra activity observed was 33.9 Bq kg⁻¹ at Neendakara in grains of size 1000-500 μ and the highest activity observed was 482.6 Bq kg⁻¹ in grains of size 125-63 μ in Neendakara. The highest ⁴⁰K activity found was 1923 Bq kg⁻¹ in grains of size <63 μ for a sample collected from Neendakara. A good correlation was observed between computed dose and measured dose in air. The correlation between ²³²Th and ²²⁶Ra was also moderately high. The results of these investigations are presented and discussed in this paper.     

Effects of landforms on the erosion rate in a small watershed by the Cs tracing method

It's very important to analyze and evaluate quantitatively the effects of landforms on soil erosion for the prevention and treatment of soil loss in a small watershed. The objective of this study was to evaluate the effects of landform factors on erosion rate by the ¹³⁷Cs tracing method in a small watershed in the Purple Hilly Area of China. The erosion rates under different slope lengths, slope gradients and slope aspects were estimated in Xiangshuitan watershed in the Purple Hilly Area in Sichuan Basin by the ¹³⁷Cs tracing method. The results showed that the erosion rate decreased exponentially with downslope distance, and it increased with increasing slope gradient during the scope of 5°-16°. The slope aspect had great impact on the erosion rate, and the hillside on the sunny slope had larger erosion rate than that on the shady slope, particularly for the farmland.     

中国环境污染与经济增长的实证研究

本文基于我国1981-2007年环境污染与经济增长的相关数据,利用时间序列研究方法对我国EKC进行实证研究,说明建立EKC模型可能存在的问题。为弥补EKC模型中环境不影响经济的假设与变量难以量化的不足,运用VAR模型研究二者的动态关系。EKC研究结果表明:EKC是一种客观现象,而不是一般规律;与人们生产生活关系密切的污染物更有可能出现EKC特征。VAR脉冲响应和方差分解的动态分析结果与二者相互作用机理相符:一方面我国经济增长通过规模效应、结构效应、技术效应等因素影响环境;一方面随着人们环境质量需求弹性的增加,政府对环境质量的重视,环境对企业生产行为的约束机制正逐步形成,但可能由于人们通过自身消费影响产出的作用有限和环境政策实施存在滞后性等原因,这种机制的形成存在一定滞后。     

农业化学品投入状况及其对环境的影响

农业生产中,农业化学品的大量使用产生了明显的负外部性影响,尤其是农业的面源污染问题随化肥、农药投入的增加而不断加剧。通过统计分析方法,对农业化学品投入数量及区域分布特征、农业化学品投入存在的问题及其所造成的面源污染问题进行分析。结果表明:化肥和农药总投入不断增加,其中河南、山东、江苏、安徽、湖北和湖南6省投入总额接近全国的一半;农业化学品使用存在过量投入、投入结构失衡和施肥施药技术落后等问题;农业化学投入品的过量使用造成的环境污染问题正不断加剧,农业面源污染排放对污染总量的贡献率不断上升。最后提出了相关政策建议,包括加强农业面源污染控制的政策框架和配套制度建设、推广成熟的化肥农药施用技术和加强农业环保教育。     

区域经济重心及 COD、SO_2、TSP排放重心演变路径分析——以江苏省为例

运用重心模型,采用1996~2006年江苏省经济和环境数据,计算出各年份GDP、工业产值、COD、SO ₂和TSP排放重心坐标,揭示江苏省经济重心和环境污染排放重心变化轨迹及演变规律,以期为江苏省环境宏观战略决策及生态省建设提供理论参考。研究表明,经济重心总体上向东南方向偏移,GDP重心偏移距离为14.81 km,工业产值重心偏移距离为12.84 km;经济重心在南北方向上的偏移程度大于东西方向的偏移程度。环境污染排放重心也向东南方向偏移,COD和TSP排放重心轨迹呈现较大变化,SO2排放重心轨迹变动较小;COD排放重心偏移距离为79.26 km,SO₂排放重心偏移距离为15.73 km,TSP排放重心偏移距离为42.24 km;各污染排放重心轨迹在不同时段表现出不同特点。COD、SO₂和TSP排放重心相对于经济重心偏向于西北方向,且COD排放重心近年来明显趋向于工业产值重心;COD排放重心和TSP排放重心与经济重心存在着强正相关.     

基于事故树的三峡库区水体污染公共安全事件诱因分析

三峡库区蓄水后对长江水体自净能力的极大削弱,沿江聚集的各类生产、生活活动对长江水质的多渠道污染极易引发库区各类水体污染公共安全事件。结合对库区水体污染公共安全事件多维度诱发因素的调研结果,运用事故树的分析方法对三峡库区水体污染公共安全事件的逐级诱发过程进行分析。研究表明：存在13条诱发库区水体污染公共安全事件的路径以及3条防治水体污染公共安全事件的路径;在不考虑诱因发生概率的情况下,排污因素是诱发库区水体污染公共安全事件最重要、最根本的因素,促成库区水体自净能力下降的回水区变长,水流紊动减弱和水位抬升三方面因素是次重要的诱发因素。只有对不同的诱因施行不同的监测和控制策略,才能对库区水体污染公共安全事件开展有效预警、预控.     

Use of Composted Animal Manures to Reduce 1,3-Dichloropropene Emissions

Atmospheric emission of the soil fumigant 1,3-dichloropropene (1,3-D) has been associated with the deterioration of air quality in certain fumigation areas. To minimize the environmental impacts of 1,3-D, feasible and cost-effective control strategies are in need of investigation. One approach to reduce emissions is to enhance the surface layer of a soil to degrade 1,3-D. A field study was conducted to determine the effectiveness of composted steer manure (SM) and composted chicken manure (CKM) to reduce 1,3-D emissions. SM or CKM were applied to the top 5-cm soil layer at a rate of 3.3 or 6.5 kg m^?2. An emulsified formulation of 1,3-D was applied through drip tape at 130.6 kg ha^?1 into raised beds. The drip tape was placed in the center of each bed (102 cm wide) and 15 cm below the surface. Passive flux chambers were used to measure the loss of 1,3-D for 170 h after fumigant application. Results indicated that the cumulative loss of 1,3-D was about 48% and 28% lower in SM- and CKM-amended beds, respectively, than in the unamended beds. Overall, both isomers of 1,3-D behaved similarly in all treatments. The cumulative loss of 1,3-D, however, was not significantly different between the two manure application rates for either SM or CKM. The results of this study demonstrate the feasibility of using composted animal manures to control 1,3-D emissions.     

EFFECT OF SOIL STERILIZATION BY MERCURIC CHLORIDE ON HERBICIDE SORPTION BY SOIL

Microbial inhibitors such as mercuric chloride are frequently used to sterilize soil or soil–water slurries in experimental studies on the fate of xenobiotics in the environment. This study examined the influence of mercuric chloride additions to soil–water slurries on the sorptive behaviour of a phenoxy herbicide (2,4-D) in soil. The results demonstrated that mercuric chloride strongly decreased the capacity of the soil to retain herbicides, and that the interference of mercuric chloride with herbicide sorption increased with increasing soil organic carbon contents. Because of the competitive sorption between mercuric chloride and the phenoxy herbicide, we conclude that mercuric chloride may not be a good soil sterilization procedure for use in xenobiotic fate studies.