Combined amendment reduces soil Cd availability and rice Cd accumulation in three consecutive rice planting seasons

The scientific application of stabilized materials has been considered an effective method for the in situ remediation of Cd-contaminated soil. This study aimed to investigate the persistence of the effect of a combined amendment of limestone and sepiolite(LS) on soil Cd availability and accumulation in rice grown in a mildly Cd-contaminated paddy field(0.45 mg/kg of Cd) over three consecutive rice seasons. 1125–4500 kg/ha of LS was applied to the soil before the first rice planting season and 5...     

Primary production and rain use efficiency across a precipitation gradient on the Mongolia Plateau

Understanding how the aboveground net primary production (ANPP) of arid and semiarid ecosystems of the world responds to variations in precipitation is crucial for assessing the impacts of climate change on terrestrial ecosystems. Rain-use efficiency (RUE) is an important measure for acquiring this understanding. However, little is known about the response pattern of RUE for the largest contiguous natural grassland region of the world, the Eurasian Steppe. Here we investigated the spatial and temporal patterns of ANPP and RUE and their key driving factors based on a long-term data set from 21 natural arid and semiarid ecosystem sites across the Inner Mongolia steppe region in northern China. Our results showed that, with increasing mean annual precipitation (MAP), (1) ANPP increased while the interannual variability of ANPP declined, (2) plant species richness increased and the relative abundance of key functional groups shifted predictably, and (3) RUE increased in space across different ecosystems but decreased with increasing annual precipitation within a given ecosystem. These results clearly indicate that the patterns of both ANPP and RUE are scale dependent, and the seemingly conflicting patterns of RUE in space vs. time suggest distinctive underlying mechanisms, involving interactions among precipitation, soil N, and biotic factors. Also, while our results supported the existence of a common maximum RUE, they also indicated that its value could be substantially increased by altering resource availability, such as adding nitrogen. Our findings have important implications for understanding and predicting ecological impacts of global climate change and for management practices in arid and semiarid ecosystems in the Inner Mongolia steppe region and beyond.     

Temporal analysis of population genetic composition in the overexploited Japanese eel <Emphasis Type="Italic">Anguilla japonica</Emphasis>

The Japanese eel has dramatically declined in Asia since the 1970s. Over the past two decades, glass eel productivity in Taiwan has decreased, but is highly variable among each year catch, though the cause for this is unknown. The impact of both population decline and instability on genetic diversity, however, is unknown. In this study, we investigated changes in allele frequencies of Japanese eel recruitment events over the past 20 years using six polymorphic microsatellite DNA loci. Specimens of glass eels were collected yearly from a single location in northern Taiwan from 1986 to 2007. Overall genetic differentiation among all samples was very low but significant (F_ST = 0.002, P = 0.002), and only 2 out of 120 pairwise tests were significant. The relationship between genetic and temporal distance showed a slight but insignificant correlation (R² = 0.03, P = 0.0504). There were no overall significant differences in allelic richness (P = 0.35) or genetic heterozygosity (P = 0.73) among annual recruitment events. No apparent loss of genetic diversity and occurrence of a genetic bottleneck for eel populations were observed. Estimates of the effective population size (N_e) generally exceeded 500, although confidence intervals were very wide. While El Niño /Southern Oscillation (ENSO) events had little impact on genetic diversity, they may account for the annual fluctuation in glass eel catch. These results indicate long-term stability of genetic diversity in the Japanese eel with little evidence for sweepstakes recruitment.     

Human health risk assessment of explosives and heavy metals at a military gunnery range

In this research, a risk assessment was undertaken in order to develop the remediation and management strategy of a contaminated gunnery site, where a nearby flood controlling reservoir is under construction. Six chemicals, including explosives and heavy metals, posing potential risk to environmental and human health, were targeted in this study. A site-specific conceptual site model was constructed, based on effective, reasonable exposure pathways, to avoid any overestimation of the risk. Also, conservative default values were adapted to prevent underestimation of the risk when site-specific values were not available. The risks posed by the six contaminants were calculated using the API’s Decision Support System for Exposure and Risk Assessment, with several assumptions. In the crater-formed-area (Ac), the non-carcinogenic risks (i.e., HI values) of tri-nitro-toluene (TNT) and Cd were slightly larger than 1, but for RDX (Royal Demolition Explosives) was over 50. The total non-carcinogenic risk of the whole gunnery range was calculated to be 62.5, which was a significantly high value. The carcinogenicity of Cd was estimated to be about 10⁻³, while that for Pb was about 5 × 10⁻⁴, which greatly exceeded the generally acceptable carcinogenic risk level of 10⁻⁴–10⁻⁶. It was concluded from the risk assessment that there is an immediate need for remediation of both carcinogens and non-carcinogens before construction of the reservoir. However, for a more accurate risk assessment, further specific estimations of the changes in environmental conditions due to the construction of the reservoir will be required; and more over, the effects of the pollutants to the ecosystem will also need to be evaluated.     

建筑物结构变化对大气污染影响的试验研究

通过风洞实验对大气污染物扩散特性进行了模拟试验研究,重点讨论了建筑物结构形式变化对周围环境污染浓度的影响,在此基础上对影响污染浓度的各个要素进行了分析与讨论,得到了大气污染物在复杂结构建筑物之间扩散的一般规律。     

厌氧颗粒污泥膨胀床原理特征分析

从污泥床层流态、生化反应动力学、体系物相平衡角度分析了以循环为特征的厌氧颗粒污泥膨胀床反应器的结构特点,基质代谢和酸碱平衡特征,进而得出:高面积(H /A)和回流比(R)是实现反应器较高上升流速的结构和运行指标;回流引起反应器基质代谢特征的变化,同时使反应器处理增强;厌氧颗粒污泥膨胀床的运行方式对调解、平衡系统的碱度、pH值起着积极的作用。     

交联阳离子淀粉的合成及其对重金属离子的吸附

通过正交实验合成了取代度为0．568的交联阳离子淀粉。考察了溶液pH、螯合剂用量、重金属离子初始浓度对交联阳离子淀粉去除重金属离子效果的影响。当重金属离子初始质量浓度为50mg／L、螯合剂投加量为0．5g／U时,Pb^2 ,Cu^2 ,Cr^3 在溶液pH为6时的去除率达到最高,分别为97．94％,99．46％,84．30％,而Cd^ 在溶液pH为7时的去除率达到最高,为99．36％。实验结果表明,交联阳离子淀粉是一种有效去除废水中重金属的处理剂。     

阻抑动力学光度法测定痕量邻二硝基苯

研究发现,在盐酸介质中,痕量邻二硝基苯能灵敏地阻抑溴酸钾氧化甲基红褪色的反应。研究了该阻抑褪色反应的最佳条件,建立了一种测定痕量邻二硝基苯的新方法。该方法线性范围为0.0～0.16μg,检测限为1.15×10-10gmL。用于环境水样中邻二硝基苯的测定,结果满意。     

城市生态环境与可持续发展评价指标体系研究

本文从探讨城市生态环境与可持续发展的战略关系入手,在进行调查研究的基础上,提出了城市生态环境与可持续发展评价指标体系,旨在为城市的全面、协调、可持续发展提供一点科学管理依据。     

餐饮废水的化学处理方法研究

以聚硅酸铝为混凝剂,用化学法絮凝处理餐饮废水。考查了酸度、混凝剂加入量、搅拌速度、搅拌时间、沉降时间对CODCr去除率的影响。结果表明酸度在pH9～11范围内,每100mL污水中聚硅酸铝加入量为02mL,搅拌速度为45r/min,搅拌15s,沉降15min后,测上清液的化学耗氧量,CODCr去除率可达88%左右。该方法效果好、工艺简单、易于操作管理,有实际应用价值。