Methodology for setting risk-based concentrations of contaminants in soil and groundwater and application to a model contaminated site

In Japan, environmental standards for contaminants in groundwater and in leachate from soil are set with the assumption that they are used for drinking water over a human lifetime. Where there is neither a well nor groundwater used for drinking, the standard is thus too severe. Therefore, remediation based on these standards incurs excessive effort and cost. In contrast, the environmental-assessment procedure used in the United States and the Netherlands considers the site conditions (land use, existing wells, etc.); however, a risk assessment is required for each site. Therefore, this study proposes a new framework for judging contamination in Japan by considering the merits of the environmental standards used and a method for risk assessment. The framework involves setting risk-based concentrations that are attainable remediation goals for contaminants in soil and groundwater. The framework was then applied to a model contaminated site for risk management, and the results are discussed regarding the effectiveness and applicability of the new methodology.     

Hierarchical Bayesian models to assess between- and within-batch variability of pathogen contamination in food

Assessing within-batch and between-batch variability is of major interest for risk assessors and risk managers in the context of microbiological contamination of food. For example, the ratio between the within-batch variability and the between-batch variability has a large impact on the results of a sampling plan. Here, we designed hierarchical Bayesian models to represent such variability. Compatible priors were built mathematically to obtain sound model comparisons. A numeric criterion is proposed to assess the contamination structure comparing the ability of the models to replicate grouped data at the batch level using a posterior predictive loss approach. Models were applied to two case studies: contamination by Listeria monocytogenes of pork breast used to produce diced bacon and contamination by the same microorganism on cold smoked salmon at the end of the process. In the first case study, a contamination structure clearly exists and is located at the batch level, that is, between batches variability is relatively strong, whereas in the second a structure also exists but is less marked.     

合法性、合理性与后续问题——反卫星实验的法律问题

近年来反卫星试验问题引起国际上诸多关注。文章从现行法和应有法的角度,根据外层空间法的有关规定,论证了中国反卫星试验在现行空间法律体系中的合法性和合理性,指出目前并不引起国际责任,并对空间碎片的未来规范问题提出了设想,国家可以通过由法律意义的相应行为来确立新规则。文章还指出,国际社会有必要进一步明确外空条约中的“有害污染”一词的具体含义。     

Measuring the Dynamic Efficiency Costs of Regulators' Preferences: Municipal Water Utilities in the Arid West

Evidence suggests that municipal water utility administrators in the western US price water significantly below its marginal cost and, in so doing, inefficiently exploit aquifer stocks and induce social surplus losses. This paper empirically identifies the objective function of those managers, measures the deadweight losses resulting from their price‐discounting decisions, and recovers the efficient water pricing policy function from counterfactual experiments. In doing so, the estimation uses a “continuous‐but‐constrained‐ control” version of a nested fixed‐point algorithm in order to measure the important intertemporal consequences of groundwater pricing decisions.     

An outlier-resistant test for heteroscedasticity in linear models

The presence of contamination often called outlier is a very common attribute in data. Among other causes, outliers in a homoscedastic model make the model heteroscedastic. Moreover, outliers distort diagnostic tools for heteroscedasticity such that it may not be correctly identified. In this article, we show how outliers affect heteroscedasticity diagnostics. We then proposed a robust procedure for detecting heteroscedasticity in the presence of outliers by robustifying the non-robust component of the Goldfeld–Quandt (GQ) test. The performance of the proposed procedure is examined using simulation experiment and real data sets. The proposed procedure offers great improvement where the conventional GQ and other procedures fail.     

Robust cusum: a robustness study for cusum quality control schemes

A standard CUSUM control scheme and four modified CUSUM control schemes are evaluated for robustness. The average run length (ARL) for each scheme is evaluated using a contaminated normal distribution, a distribution that has longer tails than the normal. A CUSUM control scheme that ignores the first suspected outlier, but gives an out-of-control signal for two successive outliers is found to perform well.     

The Immediate Impact of the Fukushima Daiichi Accident on Local Property Values

The Fukushima Daiichi accident released huge amounts of radioactive material over a wide area. We can appreciate the geographical extent of radioactive contamination from the information published online by the Japanese government. Historically, this is an unprecedented situation, which allows “natural experimentation” to estimate the causal effects of radioactive contamination on our society. This study focused on property value losses caused by the accident and analyzed changes in land appraisals around the Fukushima Daiichi plant from July 2010 to July 2011 within the framework of hedonic approach. Thus, we estimated the short‐run impact of the contamination or the change in marginal value of proximity to the plant. The results suggest that the appraisals significantly and monotonically depreciated with increasing contamination levels. However, there was no evidence to suggest changes in the marginal value of proximity to the plant. A comparison between the appraisals and transaction prices indicates that this result could be interpreted as an underestimate of actual property value losses.     

Maximum likelihood estimation in the presence of outiliers

This paper deals with the maximum likelihood estimation of parameters when the sample (x₁…x_n ) may heve k spuriously generated observations from another distribution, say G≠F, where F is the distribution of the target population. If G is stochastically larger than F, then these k observations may give rise to k extreme observations or ‘outliers’. This situation is often described by a so-called ‘k-outlier model’ in which in addition to the parameters involved in F and G, the set ν={ν₁,…,ν_k} of indices, for which x_νj , j=1,…,k, come from G, is also unknow.     

Information and Risk Perception: A Dynamic Adjustment Process

It is common in catastrophic food-contamination events that consumers fail to adjust instantaneously to a normal consumption level. One explanation is that consumers only gradually accept new positive information as being trustworthy. The gradual establishment of the trustworthiness of the released information depends on both positive and negative media coverage over time. We examine the individual "trust" effects by extending the prospective reference theory (Viscusi, 1989) to include a dynamic adjustment process of risk perception. Conditions that allow aggregation of changes in risk perceptions across individuals are described. The proposed model describes a general updating process of risk perceptions to media coverage and can be applied to explain the temporal impact of media coverage on consumption of a broad range of goods (food or nonfood). A case study of milk contamination is conducted to demonstrate consumer demand adjustment process to a temporarily unfavorable shock. The results suggest that effects of positive and negative information to adjustment of consumption and risk perception are asymmetric over time.     

灵山岛地下水资源储存特征与利用研究

探讨了灵山岛地下水资源储存特点、时空分布变化规律，计算出该区地下水资源的储量，并讨论了水资源利用现状及其合理开发途径