Variations in Environmental Tritium Dose Estimates Due to Meteorological Data Averaging and Uncertainties in Pathway Model Parameters

The large amounts of tritium produced at the Savannah River Site (SRS) coupled with the current dose reconstruction study at the facility emphasize the importance of ensuring accurate and efficient prediction of tritium doses to the public. Presently, dose estimates to the general population in the site vicinity are calculated annually using a five year meteorological database. Determining whether detailed monthly dose estimates are necessary or whether annual averaged data is sufficient offers the potential for more efficient dose prediction. In this study, off site collective committed doses and maximum individual doses due to atmospheric tritium releases were calculated according to the methods outlined in the U.S. Nuclear Regulatory Commission's Regulatory Guide 1.109 and compared using monthly versus five-year meteorological data and source terms. Site-specific variables not currently utilized at SRS for annual dose estimates also have been included. In addition, the range of predicted doses, based on the distribution in model parameters given in the literature, were estimated. Finally, a sensitivity analysis was performed in order to determine the influence of model inputs on dose estimates. Results corroborate previous studies by indicating that the primary contributor to infant tritium dose is the ingestion of milk, while for all other age groups, the most important pathway is the ingestion of vegetation. These relative pathway contributions remain constant throughout the year for infants; for children, teenagers, and adults, however, inhalation and absorption of tritium through the skin increases in relative importance in the months of June to September. It was found that the model utilized was most sensitive to dose factors, the ratio of the specific activity of tritium oxide in vegetation to the specific activity of atmospheric tritium oxide, and breathing rates. Most importantly, it was found that over a five-year period, the use of averaged meteorological data results in total individual doses that are only 2 to 6% higher than doses determined monthly, depending on the pathway of interest.     

中国能源安全及其资源开发与利用的策略研究

通过采用“霍夫曼系数”的分析方法,提出能源危机是国家在工业化过程中的必经阶段,并从资源经济理论角度认识我国经济增长对资源消耗的关系,剖析国际能源危机背景与经济格局的成因。中国目前和今后主要受制于国内资源不足,要应对能源危机,只有实现多元化的策略,才能保障能源的供应,实现我国经济社会和谐、稳定、可持续发展。因此,能源资源开发与利用策略的研究具有极其重要的现实意义。     

Identifying Potential Conflict Associated with Oil and Gas Exploration in Texas State Coastal Waters: A Multicriteria Spatial Analysis

Recent interest in expanding offshore oil production within waters of the United States has been met with opposition by groups concerned with recreational, environmental, and aesthetic values associated with the coastal zone. Although the proposition of new oil platforms off the coast has generated conflict over how coastal resources should be utilized, little research has been conducted on where these user conflicts might be most intense and which sites might be most suitable for locating oil production facilities in light of the multiple, and often times, competing interests. In this article, we develop a multiple-criteria spatial decision support tool that identifies the potential degree of conflict associated with oil and gas production activities for existing lease tracts in the coastal margin of Texas. We use geographic information systems to measure and map a range of potentially competing representative values impacted by establishing energy extraction infrastructure and then spatially identify which leased tracts are the least contentious sites for oil and gas production in Texas state waters. Visual and statistical results indicate that oil and gas lease blocks within the study area vary in their potential to generate conflict among multiple stakeholders.     

快速测定地面水中阴离子表面活性剂

通过比对实验来探讨用孔雀绿试剂法测定地面水中阴离子表面活性剂的可行性。实验结果证明,该方法精密度与准确性均达到现行监测规范要求,与国标亚甲基蓝分光光度法相比具有操作简单,不用萃取剂,分析时间短的优点,可适用于地面水的监测。     

以沙湖为例探究宁夏内陆封闭型湖泊水体污染原因

为研究西北地区封闭式湖泊水质恶化原因及水体污染物迁移转化规律,以宁夏沙湖为研究对象,对沙湖2012—2017年水体污染物总量变化趋势及沙湖周边地表水环境质量进行分析。研究结果表明:沙湖水环境质量变化主要由内源性污染和外源性输入造成,其中内源性污染源主要为沙湖沉积物污染物释放,沙湖水体沉积物通过孔隙水向沙湖水体转移的CODMn、CODCr、TP、TN、氟化物分别占水体总污染物的6.4%、6.6%、16.6%、14.2%、31.4%;沙湖外源性污染源主要为黄河补水和农垦集团稻田等面源污染,其中黄河补水向沙湖 转移的 CODMn、CODCr、TP、TN、氟化物分别占沙湖水体污染物总量的49%、30%、279%、99%、13%,沙湖周边面源性污染通过渗透作用向沙湖水体输入的CODMn、CODCr、TP、TN、氟化物分别占沙湖水体污染物总量的23%、18%、52%、34%、19%,外源性污染物输入占沙湖水体污染物总量CODMn、CODCr、TP、TN、氟化物分别为72%、48%、331%、133%、32%,但由于水体自身净化作用, TP和TN已大幅度降解。     

石油开采行业土壤污染防治对策与建议

在文献和实地调研的基础上,分析了石油开采行业生产工艺及产排污情况,识别了油井、注水井、输油管道、联合站等主要工艺节点的土壤污染风险,总结了目前行业处理废水和危险废物的主要方法,指出了行业在废弃钻井液处理、地下输油管道泄漏后期处置及突发环境事件应急预案中土壤污染防治等方面存在的问题,并提出了相应的对策和建议。     

建设项目竣工环境保护验收监测现场勘察

从资料收集、工程概况了解和现场察看3方面阐述了建设项目竣工环境保护验收监测现场勘察的具体步骤和内容。     

Choice set formation for outdoor destinations: The role of motivations and preference discrimination in site selection for the management of public expenditures on protected areas

Effective public expenditure currently dominates the management focus of many protected areas. This calls for explicit modeling of constraints and motivations that, respectively, obstruct and stimulate visits to selected outdoor destinations. Choice set formation is the result of screening and/or inclusion of specific sites (alternatives) to form the set of sites considered in real choices. Evidence shows that the omission of a structural representation of choice set formation is harmful to econometric inference. Yet, the literature has largely ignored the underlying behavioral phenomenon. We show, using a discrete choice experiment involving selection among seven recreational sites in an Italian national park, that choice set formation is behaviorally relevant, even after controlling for preference discrimination. Motivations (why visit?) are important determinants of preliminary site screening for choice set inclusion, as well as site selection, justifying the additional value of such modeling extension.     

页岩气勘探开发过程中的环境影响

当前,我国正积极推进页岩气资源的勘探和开发工作,但其对环境的影响尚缺乏科学评价和规范管理。在系统分析页岩气勘探开发主要流程:井场选址与建设、水平井钻井、水力压裂和投产等的基础上,辨识了其造成生态破坏和环境污染的主要因素以及可借鉴的技术和经验。结合我国页岩气资源的分布和勘探开发现状,从法规政策、企业责任以及技术创新三个层面,提出我国页岩气开发过程中环境保护和管理应努力的方向。     

Diffusive partitioning tracer test for the quantification of nonaqueous phase liquid (NAPL) in the vadose zone: Performance evaluation for heterogeneous NAPL distribution

A partitioning tracer test based on gas-phase diffusion in the vadose zone yields estimates of the residual nonaqueous phase liquid (NAPL) saturation. The present paper investigates this technique further by studying diffusive tracer breakthrough curves in the vadose zone for a heterogeneous NAPL distribution. Tracer experiments were performed in a lysimeter with a horizontal layer of artificial kerosene embedded in unsaturated sand. Tracer disappearance curves at the injection point and tracer breakthrough curves at some distance from the injection point were measured inside and outside of the NAPL layer. A numerical code was used to generate independent model predictions based on the physicochemical sand, NAPL, and tracer properties. The measured and modeled tracer breakthrough curves were in good agreement confirming the validity of important modeling assumptions such as negligible sorption of chlorofluorocarbon (CFC) tracers to the uncontaminated sand and their fast reversible partitioning between the soil air and the NAPL phase. Subsequently, the model was used to investigate different configurations of NAPL contamination. The experimental and model results show that the tracer disappearance curves of a single-well diffusive partitioning tracer test (DPTT) are dominated by the near-field presence of NAPL around the tip of the soil gas probe. In contrast, breakthrough curves of inter-well tracer tests reflect the NAPL saturation in between the probes, although there is no unique interpretation of the tracer signals if the NAPL distribution is heterogeneous. Numerical modeling is useful for the planning of a DPTT application. Simulations suggest that several cubic meters of soil can be investigated with a single inter-well partitioning tracer test of 24-hour duration by placing the injection point in the center of the investigated soil volume and probes at up to 1 m distance for the monitoring of gaseous tracers.