应用铅锶同位素示踪研究泉州某林地垂直剖面土壤中重金属污染及来源解析

分别用原子吸收光谱仪(AAS)和电感耦合等离子体质谱仪(ICP-MS)分析了泉州市某林地垂直剖面土壤中8种重金属元素(Sr、Ni、Fe、Cr、Cu、Mn、Pb、Zn)的含量及垂直剖面土壤的铅锶同位素组成,并采用BCR四步提取法对重金属形态进行了分析.重金属总量及形态分析结果表明,泉州市林地土壤重金属污染较轻,主要污染因子为Sr.Pb的非残渣态含量最高,活性最大.内梅罗综合污染指数的评价结果表明,Sr在0~60 cm深度处达到重度污染.次生相与原生相比值法评价结果表明,Pb活性最强,对土壤的潜在危害最大;富集因子计算结果表明,Pb、Sr、Mn、Zn受到外源的影响;因子分析结果表明,重金属主要受到交通源、自然源和农业生产的影响.根据垂直剖面土壤样品与泉州市潜在污染源在~(206)Pb/~(207)Pb-~(207)Pb/~(204)Pb图中的分布特征,Pb主要来源于汽车尾气尘和土壤母质层,利用铅同位素二元混合模型计算出土壤母质层对垂直剖面土壤中铅的贡献率为85.14%(62.53%~98.36%),汽车尾气尘的贡献率平均值为14.86%(1.640%~37.47%).锶同位素示踪结果表明,锶主要来源于汽车尾气尘和土壤母质.铅锶同位素联合示踪结果与前述研究一致.     

基于Monte Carlo模拟法对水源水体中微囊藻毒素的健康风险评估

调查水源水体中微囊藻毒素MCs(MC-RR、MC-LR和MC-YR)的污染情况,结合调查情况应用蒙特卡洛法(Monte Carlo)模拟量化人群通过饮水途径摄入微囊藻毒素的风险.在珠江西航道沿线设置5个采样点,在2016年1~6月期间共采集90份水样,根据国标(GB/T 20466-2006)推荐的HPLC方法检测水体中的微囊藻毒素,运用专业风险评估软件@Risk7.0,构建非参数概率评估模型,对通过饮水途径摄入微囊藻毒素(暴露)风险进行概率评估.对随机采集90份水源水体中微囊藻毒素MCs质量浓度检测值进行分布拟合,并运用Chi-Squared、Anderson-Darling、Kolmogorov-Smirnov这3种统计方法进行拟合度检验,根据3种评估拟合结果,确定最佳拟合分布模型.结果表明,在检测的90个水样品中,MC-RR的检出率最高,达到51.11%,质量浓度范围为0.001 7~0.386 3μg·L~(-1);其次为MC-LR和MC-YR,检出率分别是47.78%和21.11%,质量浓度范围分别是0.028 5~0.279 6μg·L~(-1)和0.003 0~0.136 2μg·L~(-1),水源水体中3种微囊藻毒素以MC-RR为主,最大检出质量浓度为0.386 3μg·L~(-1),MC-YR的含量最低.采用软件@Risk7.0分布拟合结果显示,MC-LR质量浓度最适的拟合分布为Ext Value Min模型(0.113 91,0.098 462),MC-RR质量浓度最适的拟合分布为Logistic(0.058 064,0.053 044).健康风险评估表明,MC-LR对人体健康危害的风险高于MC-RR的风险,儿童比成人更易于受到MCs污染的威胁.MC-LR对儿童健康危害的致癌年风险数值大于美国环保署(USEPA)推荐的最大可接受风险水平1×10-4;MC-LR对成人的致癌暴露年风险数值大于国际辐射防护委员会(ICRP)推荐的最大可接受风险水平5×10-5,表明水源水体中的MCs对人体健康存在潜在的危害,有必要加强饮用水源水体的保护与监控,为有效控制水源地水质污染和更好地保障人民健康奠定基础.     

基于地形分区的射线跟踪法加速方法的研究

通过分析影响射线跟踪法计算效率的因素,提出一种基于多线程的用于开放地理环境中的射线跟踪加速方法,以提高射线跟踪法在计算机仿真中的计算效率。该方法应用于特定复杂战场电磁环境,根据电磁波射线传播特性,采用对地形分区的途径减少射线与规则三角面地形面的求交次数,同时使用多线程追踪单个辐射源的射线路径。经过对方法进行仿真计算,验证该方法的有效性。     

Assessing and testing prediction uncertainty for single tree-based models: A case study applied to northern hardwood stands in southern Québec, Canada

Estimating prediction uncertainty for a single tree-based model is hindered by the complex structure of these models. In this paper, we addressed this issue with a case study applied to northern hardwood stands in Québec, Canada. SaMARE is a stochastic single tree-based model that was designed for these types of stands. Using a Monte Carlo approach, the model can provide a mean predicted value and its confidence limits for some plot-level attributes.The mean predicted values were compared to observed values in terms of bias and accuracy. In addition to these common statistics, we compared nominal coverage of Monte Carlo-simulated confidence intervals with real (observed) coverage to verify the adequacy of the simulated uncertainty. A comparison was made using several plot-level attributes, which exhibited an increasing discriminative complexity. This complexity ranges from coarse attributes, such as all-species basal area, up to more complex ones, such as basal area for stems of a particular species and with sawlog potential.The results showed that in terms of absolute value, biases were small, but could be relatively high with respect to the average observed value when the discriminative complexity of the attribute increased. The comparison between nominal and real coverage of confidence intervals gave satisfactory results for all-species plot-level attributes. However, for some species-specific attributes, the Monte Carlo-simulated confidence intervals overestimated the real coverage.     

A Monte Carlo study of radon detection in cylindrical diffusion chambers

The functioning of radon diffusion chambers was studied using the Monte Carlo code RAMMX developed here. The alpha particles from radon are assumed randomly produced in the volume of the cylinder, and those from the progeny are assumed to originate randomly at the cylindrical surface. The energy spectrum, the distribution of incident angles, and the distribution of path lengths of the alpha particles on the detector were obtained. These quantities vary depending on input parameters such as initial alpha particle energy, radius and depth of the diffusion chamber, detector size and atmospheric pressure. The calculated energy spectrum for both ²²²Rn and ²²⁰Rn was compared with experiment, permitting the identification of each peak and its origin, and a better understanding of radon monitoring. Three aspects not considered in previous calculations are progeny alphas coming from surfaces of the monitor, taking into account the atmospheric pressure, and including the isotope ²²⁰Rn.     

UNCERTAINTY ANALYSIS OF BMP EFFECTWENESS FOR CONTROLLING NITROGEN FROM URBAN NONPOINT SOURCES1

ABSTRACT: The effectiveness of urban Best Management Practices (BMPs) in achieving the No-Net-Increase Policy (NNTP), a policy designed to limit nonpoint nitrogen loading to Long Island Sound (US), is analyzed. A unit loading model is used to simulate annual nitrogen exported from the Norwalk River watershed (Connecticut) under current and future conditions. A probabilistic uncertainty analysis is used to incorporate uncertainty in nitrogen export coefficients and BMP nitrogen removal effectiveness. The inclusion of uncertainty in BMP effectiveness and nitrogen export coefficients implies that additional BMPs, or BMPs with a greater effectiveness in nitrogen removal, will be required to achieve the NNIP. Even though including uncertainty leads to an increase in BMP implementation rates or BMP effectiveness, this type of analysis provides the decision maker with a more realistic assessment of the likelihood that implementing BMPs as a management strategy will be successful. Monte Carlo simulation results indicate that applying BMPs to new urban developments alone will not be sufficient to achieve the NNIP since BMPs are not 100 percent effective in removing the increase in nitrogen caused by urbanization. BMPs must also be applied to selected existing urban areas. BMPs with a nitrogen removal effectiveness of 40–60 percent, probably the highest level of removal that can be expected over an entire watershed, must be applied to at least 75 percent of the existing urban area to achieve the NNIP This high rate of application is not likely to be achieved in urbanized watersheds in the LIS watershed; therefore, additional point source control will be necessary to achieve the NNIP     

A WATER QUALITY‐BASED APPROACH FOR WATERSHED WIDE BMP STRATEGIES1

ABSTRACT: Watershed management strategies generally involve controlling nonpoint source pollution by implementing various best management practices (BMPs). Currently, stormwater management programs in most states use a performance‐based approach to implement onsite BMPs. This approach fails to link the onsite BMP performance directly to receiving water quality benefits, and it does not take into account the combined treatment effects of all the stormwater management practices within a watershed. To address these issues, this paper proposes a water quality‐based BMP planning approach for effective nonpoint source pollution control at a watershed scale. A coupled modeling system consisting of a watershed model (HSPF) and a receiving water quality model (CE‐QUAL‐W2) was developed to establish the linkage between BMP performance and receiving water quality targets. A Monte Carlo simulation approach was utilized to develop alternative BMP strategies at a watershed level. The developed methodology was applied to the Swift Creek Reservoir watershed in Virginia, and the results show that the proposed approach allows for the development of BMP strategies that lead to full compliance with water quality requirements.     

杭州啤酒厂清洁生产示范工程回顾评价和追踪评价

通过对杭州啤酒厂清洁生产示范工程的回顾评价和追踪评价，不仅可再现以往的成果，而且可了解该示范工程的进一步发展情况，有利于对示范工程长期效益进行评估和示范工程的成败进行总结，因此，这是一项务实的制度。     

贵州喀斯特地区旅游资源的变异与可持续利用

喀斯特景观与民族文化是不可再生的旅游资源,其开发在促进喀斯特地区经济、文化发展的同时,也加剧了环境的损耗和地方特色的消失,旅游资源变异现象普遍发生。文中分析了资源变异的几种情况,并指出控制资源变异,实现可持续利用的途径     

Using Sediment Budgets to Investigate the Pathogen Flux Through Catchments

We demonstrate a materials budget approach to identify the main source areas and fluxes of pathogens through a landscape by using the flux of fine sediments as a proxy for pathogens. Sediment budgets were created for three subcatchment tributaries of the Googong Reservoir in southeastern New South Wales, Australia. Major inputs, sources, stores, and transport zones were estimated using sediment sampling, dam trap efficiency measures, and radionuclide tracing. Particle size analyses were used to quantify the fine-sediment component of the total sediment flux, from which the pathogen flux was inferred by considering the differences between the mobility and transportation of fine sediments and pathogens. Gullies were identified as important sources of fine sediment, and therefore of pathogens, with the pathogen risk compounded when cattle shelter in them during wet periods. The results also indicate that the degree of landscape modification influences both sediment and pathogen mobilization. Farm dams, swampy meadows and glades along drainage paths lower the flux of fine sediment, and therefore pathogens, in this landscape during low-flow periods. However, high-rainfall and high-flow events are likely to transport most of the fine sediment, and therefore pathogen, flux from the Googong landscape to the reservoir. Materials budgets are a repeatable and comparatively low-cost method for investigating the pathogen flux through a landscape.