Expansion of cropland area and formation of the eastern farming-pastoral ecotone in northern China during the twentieth century

Land cover changes induced by historical cultivation in ecologically fragile areas involving important issues such as environmental change, ecology, and human sustainability are particularly worthy of attention. This paper reconstructs the spatial distribution of cultivated areas at the county level in the eastern farming-pastoral ecotone of northern China for four time periods during the twentieth century. The paper also analyzes how the location of cultivation ratio contours of 15 and 30 %, representing the boundaries of agricultural areas, have moved and the formation process of farming-pastoral ecotone patterns during this period. The study concludes that the area and ratio of cultivated land fluctuations increased during the twentieth century. The boundaries of the cultivation ratio contours of 15 and 30 % continually moved west and north. Moving north took priority over the other directions during the period of 1916–1940, when its center moved the farthest during the twentieth century, and the boundaries primarily moved westward during 1940–1980 and northwestward during 1980–2000. The distance, direction, and extent of the movement of the cultivation boundaries are all related to agricultural area expansion processes during this period, finally resulting in the creation of the modern farming-pastoral ecotone pattern.     

Heavy metal contamination in a vulnerable mangrove swamp in South China

Concentrations of six heavy metals (Cu, Ni, Zn, Cd, Cr, and Pb) in sediments and fine roots, thick roots, branches, and leaves of six mangrove plant species collected from the Futian mangrove forest, South China were measured. The results show that both the sediments and plants in Futian mangrove ecosystem are moderately contaminated by heavy metals, with the main contaminants being Zn and Cu. All investigated metals showed very similar distribution patterns in the sediments, implying that they had the same anthropogenic source(s). High accumulations of the heavy metals were observed in the root tissues, especially the fine roots, and much lower concentrations in the other organs. This indicates that the roots strongly immobilize the heavy metals and (hence) that mangrove plants possess mechanisms that limit the upward transport of heavy metals and exclude them from sensitive tissues. The growth performance of propagules and 6-month-old seedlings of Bruguiera gymnorhiza in the presence of contaminating Cu and Cd was also examined. The results show that this plant is not sufficiently sensitive to heavy metals after its propagule stage for its regeneration and growth to be significantly affected by heavy metal contamination in the Futian mangrove ecosystem. However, older mangrove seedlings appeared to be more metal-tolerant than the younger seedlings due to their more efficient exclusion mechanism. Thus, the effects of metal contamination on young seedlings should be assessed when evaluating the risks posed by heavy metals in an ecosystem.     

混凝沉淀-高级氧化联合处理垃圾转运站污水的实验研究

城市生活垃圾转运站污水具有水质水量变化大、有机污染负荷高、具有强烈恶臭、色度高等显著特点,已成为城市重要的点源污染。为有效消减转运站污水有机负荷,探讨了混凝沉淀-高级氧化联合使用的物化处理方法,考察了联合处理过程中双氧水/亚铁、亚铁投加量、酸化后pH值、混凝剂投加量、中和后pH值等因素对处理效果的影响。小试研究结果表明,在混凝剂投加400 mg/L,亚铁0.06 mol/L,酸化后pH为3,双氧水/亚铁=4∶1,中和后pH为7.5的条件下,污水COD消减量达到60%以上,色度去除率98%,恶臭基本消除。     

硫化法制备废水处理用光催化剂La3NbS2O5

采用高温硫化法制备了具有可见光活性的La3 NbS2 O5光催化剂,运用X射线衍射谱图、扫描电子显微镜照片、比表面积和紫外-可见漫反射光谱对La3 NbS2 O5的结构、物理性质和光吸收性能进行了表征.以亚甲基蓝为目标降解物,考察了硫化温度、催化剂加入量和制备方法对亚甲基蓝降解率的影响.实验结果表明,当硫化温度为800...     

Organochlorine pesticides and PCBs in fish from lakes of the Tibetan Plateau and the implications

High mountains may play significant roles in the global transport of persistent organic pollutants (POPs). This work aims to investigate the levels, patterns and distribution of semi-volatile organoclorine pollutants and to improve the understanding of the long-range atmospheric transport and fate of contaminants on the Tibetan Plateau. A total of 60 fish samples were collected from eight lakes located between 2813 and 4718 m above sea level across the Plateau. Concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) including dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were measured in fish muscle. The results showed that concentrations of DDT, HCH and HCB were comparable to or lower than those found in remote mountains of Europe, Canada and US, while PCB concentrations in fish were, on average, about 4-150 times lower on Tibet than at other mountain areas. The transport and fate of contaminants in the Plateau are significantly influenced by the unique climatological and meteorological conditions, particularly by the summer Indian monsoon and winter westerly jet stream.     

解磷微生物肥料的研究与进展

磷是植物生长必需的矿物质元素之一，在土壤中易被固定降低其有效性，目前，研究和生产含有解磷功能的微生物有机肥料是转化土壤中无效磷、提高磷肥利用率的有效途径之一。叙述了解磷微生物犯料中微生物的种类、生态分布规律和影响高效解磷微生物选育的外部因素，概述了解磷微生物菌肥的应用和研究进展，探讨了解磷微生物肥料的应用价值。为解磷微生物未来的研究重点提出理论依据。．     

微生物絮凝剂改善城市污水厂浓缩污泥脱水性能的研究

采用酱油曲霉(Aspergillus sojae)产生的微生物絮凝剂(MBF)作为污泥絮凝脱水剂，对城市污水处理厂浓缩污泥进行调理，确定该絮凝剂对浓缩污泥脱水的处理工艺参数为：微生物絮凝液最佳投加体积为6%～8%（体积比），发挥絮凝作用的最适污泥温度为28～32℃，最适pH为6～7。经微生物絮凝剂调理的污泥在3 000 r/min离心9 min，污泥脱水率高达82.7%，滤饼含水率降低至77.3%，污泥脱水后体积减至原来的1/5左右。     

竹林土壤中甲基对硫磷降解菌的降解效果及其与土壤物理特性的关系

采用实验室控制试验研究了甲基对硫磷降解菌在竹林土壤生态系统中的降解效果及其与土壤物理特性的关系。试验结果表明，邻单胞菌（DLL-1）具有高效性，甲基对硫磷初始浓度为15 mg/kg干土，第5 d竹林土壤上、中和下层的降解率分别为88.6%、85.9%和79.2%，相应的半衰期为2.5、2.84与3.79 d。甲基对硫磷在土壤中的不同粒径范围吸附情况是不同的，从而影响DLL-1菌的降解效果，表现为土壤中粘粒含量与降解率呈显著正相关。孔隙度也是影响降解效果的一个因素，上中下3层的降解率随着孔隙度的减小而降低。     

电解-水生植物-软隔离带复合技术治理重污染河流的中试研究

为了探索重污染河流的治理技术，2011年3月在无锡市新区鸿山镇徐塘桥河开展生态治理示范工程，通过电解技术、种植高等水生植物和构建软隔离带复合工程技术改善河流水质。实验结果表明，通过电解技术，可以迅速降低TP、氨氮（NH4＋-N）和COD；但较难减少TN。通过软隔离带可以有效隔离外源污染，在较短时间内改善河流TN、TP、COD的平均水平，但是难以提高河流的生态系统稳定性。电解能够有效的降解大分子有机物，为水生植物提供良好的生长环境，之后再种植水生植物，能够进一步降低的TN、TP。通过电解一水生植物一软隔离带复合技术不仅能够全面改善河流水质的平均水平，而且能够修复水生生态系统，提高生态系统稳定性。