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.     

Bioaccumulation of zinc,lead, copper,and cadmium from contaminated sediments by native plant species and Acrida cinerea in South China

This research was conducted to search and identify spontaneously growing heavy metal-tolerant plant species that are potentially useful for phytoremediation in contaminated sediment. Five sites were selected for collection of plants growing on polluted shore (river bank) sediment of the Xiang River, China. The concentrations of Zn, Pb, Cu and Cd in plants, sediments, and grasshoppers were determined using flame atomic absorption spectrophotometer (AAS700, Perkin-Elmer, USA). Considering translocation factor and bioaccumulation factor, Rumex crispus (Polygonaceae), Rumex dentatus (Polygonaceae), and Lagopsis supina (Labiatae) could be potentially useful for phytostabilization of metals. R. crispus can be considered potentially useful for phytoextraction of Cd. In light of the biomagnification factors, grasshoppers are deconcentrators for Pb and Cd, microconcentrators for Zn and macroconcentrators for Cu to the plants, respectively. To the best of our knowledge, the present study is the first report on Zn, Pb, Cu and Cd accumulation in R. crispus and L. supina, providing a pioneer contribution to the very small volume of data available on the potential use of native plant species from contaminated sediments in phytostabilization and phytoremediation technologies.     

Effects of prenatal exposure to bisphenols on newborn leucocyte telomere length: a prospective birth cohort study in China

Environmental Science and Pollution Research - Telomere length (TL) at birth is related to diseases that may arise in the future and long-term health. Bisphenols exhibit toxic effects and can cross...     

环境电磁污染和防治

本文对环境电磁污染的现状,危害及产生作了部份介绍;同时阐述了污染的防治技术和目前该项工作尚存在问题。     

基于神经网络的温度预测

室内温度与诸多影响因素之间的非线性、复杂性等关系 ,给建模、预测带来了难度 ,引入了人工神经网络 ;利用人工神经网络的非线性、并行计算和自学习特性进行建模 ,实现了对温度模拟     

萍乡市农用土壤重金属含量及其分布特征分析

以江西省萍乡地区农用土壤为研究对象,分析研究了萍乡市农用土壤中重金属的含量、分布特征。结果表明:萍乡地区农用土壤中重金属的平均含量均未超过国家土壤环境质量二级标准,但其中锌、镍、铬、铜、镉、砷、铅、锰、汞的含量均超过了江西省土壤重金属相应元素的背景值。从空间分布来看,在全市5个县区布置的29个测点中,有14个测点的重金属含量超标;其中上栗县有8个测点超标,明显多于其他县区,出现了不同的污染特征。     

Research on transesterification parameters for producing plant sterols with supercritical methanol

The supercritical fluid method, regarded as a type of individual production process in the course of preparing plant sterols, has become a promising technology, which possesses advantages of high conversion rate without any pretreatment and need of a catalyst. This study examined the reaction process of the deodorizer distillate (DOD), which mainly included the direct transesterification of DOD to convert into free sterols. The effects of the ratio of methanol to DOD, reaction temperature and time on transesterification were studied. Furthermore, the interactions between different factors were also assessed using the response surface methodology. The optimal conditions obtained were as follows: reaction temperature 553 K, reaction time 80 min, and CH₃OH: DOD = 25:1 (mass ratio). Under these conditions, 36.42% sterol concentration was obtained, which is significantly higher in comparison with the initial sterols’ concentration in raw material (22.45%).     

基于Matlab分析的台阶式场地平整方案优化设计

在某市餐厨垃圾处理厂场地平整设计中,利用Matlab软件对台阶式场地平整方案进行优化设计,即在Auto CAD环境下用等高线法计算各级台阶的土方量,用Matlab软件拟合出台阶设计高程和土方量的函数关系式,在约束条件下求解,得到了最优设计高程和基于土方挖填平衡条件下场地平整的最小土方工程量,为工程总平面布置提供优化方案。其分析设计方法可为工业企业台阶式场地的总平面布置设计提供借鉴。