Spatial and temporal modeling of microbial contaminants on grazing farmlands

This paper introduces an integrated spatial and temporal modeling system developed mathematically for assessing microbial contaminants on animal-grazed farmlands. The model uses fecal coliform, specifically Escherichia coli, as an indicator of fecal contamination and describes the sources, sinks, transport processes, and fate of E. coli contaminants in catchments and associated streams. Spatial features include grazing location, land topography, distance to a nearby stream, and distance through the stream network to the outlet. Temporal features are population dynamics on the land surface, in flow, and on streambeds. The model applies the principles of conservation of mass balance on two different types of pools: grid cells on land surfaces and networked stream segments. The model aims to improve the prediction of the effects of different land management strategies on the fecal contamination of waterways. This is achieved by characterizing the movement of fecal contaminants from land to streams and in-stream mobilization. Processes of attenuation, diffusion, and transport govern the movement. Our study site is a hill land catchment with an area of 140 ha and is used exclusively for animal grazing. The model was calibrated with previous research results, and then tested using the data collected at the outlet of the catchment. The sensitivity of the model predictions was analyzed for different scenarios: effect of stock rate, attenuation rate, and flow volumes. The similar pattern between monitored and predicted E. coli concentration proved that the model captures the key features that control the population dynamics of fecal contaminants. Further experiments are required to expand the model's functionality for covering more mitigation options.     

估算天津环境中γ-HCH归宿的逸度模型

以全天津市为研究区域,利用稳态假设的逸度模型,用Matlab软件计算了γ-HCH(林丹)在环境各相中的浓度和相间迁移通量.γ-HCH在天津气、水、土壤、沉积物、鱼、作物、蔬菜各相中的浓度分别为1.57×10^-11、7.95×10^-7、1.17 × 10^-4、4.58×10^-4、6.03×10^-4、1.60×10^-4和6.42×10^-5mol/m³,在数量级上与实测值吻合很好.估算结果表明农业施用和农药厂废水是该地区环境中γ-HCH最主要的来源,最大的汇是土壤和沉积相(占环境中总量的99%),最主要的迁移过程是水-沉、气-土的扩散和沉降,土壤和沉积物中的降解是γ-HCH消失的最主要途径.     

安全风险预警技术研究

安全风险预警技术是一种预防事故、提高安全管理的效率和水平的有效手段.对安全风险预警技术的研究是实现现代化安全管理的迫切要求.本文提出了实施安全风险预警的具体方法,即选用危险态(第二类危险源)作为预警要素,通过对所有预警要素的实时监控,并将监控结果进行综合评价,以警示色的形式发出预警信号,提示相关部门采取应对措施的方法.最后,本文以首都机场的应用实例展示该技术的具体应用过程和其有效性.     

垃圾堆放发酵机理与应用工艺研究

对垃圾的发酵机理进行了实验研究,对渗沥液的析出量及其酸碱度、堆酵后垃圾热值的变化以及堆内温度的变化进行了观测,并对堆酵过程的机理进行了初步分析,给出了垃圾堆酵应用工艺的建议.     

基于层次分析法的秦皇岛市垃圾填埋场选址评价

城市垃圾填埋场场址的选择,受到当地经济、交通、气候条件,自然地理条件,环境保护条件,水文地质工程地质条件等诸多因素影响,是一项十分复杂的工程。本文总结了秦皇岛市现有垃圾填埋场的基本情况、存在问题及其产生原因。鉴于层次分析法在多目标决策分析方面的成效,将其运用到秦皇岛市垃圾填埋场选址评价中,对研究区进行适宜性分区,依次划分为最佳场地区、适宜场地区、较适宜场地区、不适宜场地区。     

云南宁洱6.4级地震灾区范围的快速判断

采用云南175个历史强震的等震线图、云南数字等震线模型和云南1：400万活动断裂资料,对常规正圆法灾区范围量化与数字等震线模型灾区范围量化得到的云南宁洱6．4级地震灾区范围进行了对比,分析了地震等震线长轴方向与活动断裂的关系。结果表明,灾害地震的灾区范围用等震线模型来量化比常规用正圆来量化更加符合地震的客观情况。     

Mercury uptake by Paspalum distichum L. in relation to the mercury distribution pattern in rhizosphere soil

Environmental Science and Pollution Research - Paspalum distichum L. was tested to evaluate their phytoremediation capacity for Hg contaminated soil through analyzing the dissipation of Hg in soil...     

Shellac-coated iron oxide nanoparticles for removal of cadmium(II) ions from aqueous solution

This study describes a new effective adsorbent for cadmium removal from aqueous solution synthesized by coating a shellac layer, a natural biodegradable and renewable resin with abundant hydroxyl and carboxylic groups, on the surface of iron oxide magnetic nanoparticles. Transmission Electron Microscopy (TEM) imaging showed shellac-coated magnetic nanoparticle (SCMN) adsorbents had a core-shell structure with a core of 20 nm and shell of 5 nm. Fourier Transform Infrared Spectroscopic analysis suggested the occurrence of reaction between carboxyl groups on the SCMN adsorbent surface and cadmium ions in aqueous solution. Kinetic data were well described by pseudo second-order model and adsorption isotherms were fitted with both Langmuir and Freundlich models with maximum adsorption capacity of 18.80 mg/g. SCMN adsorbents provided a favorable adsorption capacity under high salinity conditions, and cadmium could easily be desorbed using mild organic acid solutions at low concentration.     

都江堰市红色村干沟泥石流活动特征及危险性评估

"5·12"四川汶川大地震导致灾区地质灾害危险性大大增强,严重影响了周边居民的生命财产安全。都江堰市虹口乡红色干沟泥石流灾害隐患点是其中之一。根据泥石流的成因、类型、规模,以及泥石流的活动特征,对泥石流活动进行了危险性评估,指出泥石流防治工程方案应采用以排为主,适当拦挡的原则,建拦挡坝用以消能、调节泥石流流量;建防护堤用以限制泥石流漫流,对居民区进行有效防护。     

含砷废水净化剂的制备及其应用研究

本文描述了用黄铁矿和还原铁粉或其代用品为原料制备含砷废水净化剂－硫化亚铁的新方法，获得了制备的最佳条件，探讨了其在含砷废水处理中的应用条件和影响因素，结果表明，该净化剂的生产及其处理含砷废水的工艺简单，经济高效，具有良好的开发应用前景。