Sensitivity of isolated eggs of pond snails: a new method for toxicity assays and risk assessment

The concentration of heavy metals in the environment is normally low. We here address whether using the development of isolated pond snail Radix auricularia eggs would provide a more sensitive endpoint and whether the gelatinous matrix of the egg mass surrounding the eggs indeed protects the snail embryos. In the present study, artificial removal of the gelatinous matrix of egg masses greatly increased the sensitivity of developing eggs to a heavy metal (cadmium). The sensitivity of isolated eggs to cadmium was determined using several convenient endpoints, including mortality, hatching rate, and heart rate, with an acute toxicity test and a subchronic test. In the acute toxicity test, a 96-h LC₅₀ value of 58.26 μg/L cadmium was determined. In the subchronic toxicity test, sublethal effects in terms of a significant reduction in hatching rate could be found in the 25-μg/L treatment, and a significant decrease of heart rate was observed in both treatments (5 and 25 μg/L). The high sensitivity of isolated eggs indicates that such tests can be efficient for toxicity assays and risk assessment, although one needs to keep in mind that the ecologically relevant measure of toxicity will be how eggs are affected when they are still inside the egg mass.     

Nitrogen enrichment in runoff sediments as affected by soil texture in Beijing mountain area

Enrichment ratio (ER) is widely used in nonpoint source pollution models to estimate the nutrient loss associated with soil erosion. The objective of this study was to determine the ER of total nitrogen (ER_N) in the sediments eroded from the typical soils with varying soil textures in Beijing mountain area. Each of the four soils was packed into a 40 by 30 by 15 cm soil pan and received 40-min simulated rainfalls at the intensity of 90 mm h^?1 on five slopes. ER_N for most sediments were above unity, indicating the common occurrence of nitrogen enrichment accompanied with soil erosion in Beijing mountain area. Soil texture was not the only factor that influenced N enrichment in this experiment since the ER_N for the two fine-textured soils were not always lower. Soil properties such as soil structure might exert a more important influence in some circumstances. The selective erosion of clay particles was the main reason for N enrichment, as implied by the significant positive correlation between the ER of total nitrogen and clay fraction in eroded sediments. Significant regression equations between ER_N and sediment yield were obtained for two pairs of soils, which were artificially categorized by soil texture. The one for fine-textured soils had greater intercept and more negative slope. Thus, the initially higher ER_N would be lower than that for the other two soils with coarser texture once the sediment yield exceeded 629 kg ha^?1.     

Flotability and flotation separation of polymer materials modulated by wetting agents

The surface free energy, surface tension and contact angles were performed to investigate the properties of wetting agents. Adsorption of wetting agents changes wetting behavior of polymer resins. Flotability of polymer materials modulated by wetting agents was studied, and wetting agents change significantly flotability of polymer materials. The flotability decreases with increasing the concentration of wetting agents, and the wetting ability is lignin sulfonate (LS) > tannic acid (TA) > methylcellulose (MC) > triton X-100 (TX-100) (from strong to weak). There is significant difference in the flotability between polymer resins and plastics due to the presence of additives in the plastics. Flotation separation of two-component and multicomponent plastics was conducted based on the flotability modulated by wetting agents. The two-component mixtures can be efficiently separated using proper wetting agent through simple flotation flowsheet. The multicomponent plastic mixtures can be separated efficiently through multi-stage flotation using TA and LS as wetting agents, and the purity of separated component was above 94%, and the recovery was more than 93%.     

A bibliometric analysis of solid waste research during the period 1993–2008

This study is a bibliometric analysis of solid waste research to evaluate the current trends, using the literature in the Science Citation Index (SCI) database from 1993 to 2008. Analyzed aspects included document type, language, and publication output as well as distribution of journals, subject category, countries, institutes, title-words, author keywords, and ‘Keywords Plus’. An evaluating indicator, h-index, was applied to characterize the solid waste publications. The trend of publication outputs during 1993–2008 coincided with a power and an exponential model. Based on the exponential model during 2001–2008, the number of articles on solid waste in 2013 is predicted to be twice that in 2008. The most common subject category is environmental science and the most productive journal is Waste Management. The USA with most publications and China with the highest growth rate were compared. Finally, author keywords, words in title, and ‘Keywords Plus’ were analyzed to provide research emphasis. The results showed that mainstream research was centered on the following methods: recycling, landfilling, composting and waste-to-energy. Heavy metals, fly ash and sewage sludge were considered recent research hotspots.     

镍的作物效应及临界值研究

在三种紫色土（酸性，中性，石灰性）上添加Ｎｉ（０，１０，３０，６０，１００，２００ｍｇ／ｋｇ土）进行莴笋盆栽试验，结果表明：低浓度的Ｎｉ能刺激作物生长，而高浓度的Ｎｉ则阻碍作物生长，使叶片黄化。三种土因性质及本身肥力水平的差异，使酸性紫色土上作物Ｎｉ最敏感，石灰性紫色土上次之，中性紫色土上最不敏感，且Ｎｉ在作物体内分配规律也有所不同，比较了土壤全Ｎｉ，有效Ｎｉ，植株根Ｎｉ作为的临界值的优越性，结果     

中国生态农业与绿色食品

本文从农业环境问题和食品安全性出发，阐述了中国生态农业的兴起及特点，绿色食品生产的要求，生态农业与绿色食品的关系。介绍了几种可用于开发绿色食品的优化生态模式。     

机械工业职业卫生状况研究

对１２２４个工种（岗位）的工人接触生产性毒物、粉尘、高温的状况以及部分工种（岗位）的工人体力劳动强度状况进行了调研，初步了解到机械工业的主要职业危害因素、危害分布、危害程度和特征。     

五氯酚对环境污染及居民健康影响研究

中国长期以来使用五氯酚纳盐杀灭亡血吸虫的中间宿主──—钉螺．为评价它对环境的污染及居民健康危害，１９９０－１９９３年在我省开展了五氯酚环境污染及对居民健康影响研究．在研究区采集环境样品（空气、水体、土壤及底泥、蔬菜、肉、蛋、鱼等）共１７３份；生物材料（人血、尿）共４５７份，分析五氯酚浓度．结果在明，在五氯酚使用区，环境中ＰＣＰ浓度稍高于对照区，而生物材料尿、血中ＰＣＰ浓度明显高于对照区．全血胆碱脂酶活性用药区明显低于对照区，统计学分析有显著差异（Ｐ＜０．００１），证实了长期低剂量使用可造成环境及生物蓄积．     

土壤侵蚀信息系统的结构设计

本文介绍了黄土地区土壤侵蚀信息系统的建造原理与方法。分析探讨了土壤侵蚀各因子计算机自动提取的算法，以及土壤侵蚀预测模型的构造方法，并用灰色控制系统的原理确定了模型的参数。并以山西省离石县王家沟流域羊道沟为例进行了试验研究。     

地面水中叶枯灵的高效液相色谱测定

本文采用反相高效液相色谱法，在质控条件下，对河水，塘水两种地面水中叶枯灵的检验方法进行了测试，用Shimapck ODS柱为分析柱，以甲醇：水＝50：50为流动相，并用冰醋酸调PH至4－5，紫外检测波长281nm，两种水样的平均回收率分别为91．7－96．3％，90－95．8％，相对标准偏差为4．3％，最低检出限为0．0261mg/l，为地面水中叶枯灵卫生标准的实施提供了简便，灵敏，正确的配套测试手段。