The transportation,time-dependent distribution of heavy metals in paddy crops

Sixteen experimenmtal plots (5 m x 6 m = 30 m2) were designed with four different levels of heavy metals (HMs) concentration in soil. The concentrations of heavy metals in soils, and paddy plant during the different periods of growth were investigated. A relationship between the total HM content in plants and the HM level in soil was found for a wide range of concentrations. The exchangeable fraction of HMs extracted with 1 M MgCl2 solution according to Tessier's method increased correlation with the dosage of supplemented HMs, then decreased as time went on. The time-related variation of exchangeable HMs in soil demonstrated that the amount of effective HMs taken up by paddy differed at various growth phases. The amount of HMs accumulated in different parts of paddy followed the order of root > stem > grain, leaf. The transportation potential of the HMs in paddy in present study followed the order of Zn, Cr > Cd, Cu > Pb. The HM content in root, stem and leaf of paddy plant (dry weight) was low at time of seedling. The concentration in the root increased sharply at time of tillering, decreased thereafter. The concentrations in stem and leaf reached the highest at time of tillering, then decreased, while rose slightly at following time.     

重金属废水处理中磁分离技术的应用现状研究

论述了重金属废水的来源及危害,简要概述了当前重金属废水的处理技术,着重阐述了磁分离技术的基本原理及其在重金属废水处理中的应用情况,指出磁分离技术具有高效、短时、占地少、成本低、耐冲击负荷能力强及不产生二次污染等优点,是一项极具发展前景的技术。最后还指出了磁分离技术在重金属废水处理中面临的问题,针对这些问题展望了磁分离技术在废水处理领域的三个主要研究趋势,一是制备高效、可再生磁种;二是开发磁回收工艺;三是研究磁种与重金属及其他污染物的作用机理。     

Overqualification and counterproductive work behaviors: Examining a moderated mediation model

The current study examined the effect of employees' perceived overqualification on counterproductive work behaviors (CWBs). Building on person–job fit theory and prior research on such organizational phenomena, we conceptualized overqualification as a type of poor person–job fit. Drawing on the dual‐process model, we further suggested that in processing their person–job misfit, overqualified employees might cognitively appraise themselves as less worthy organizational members and experientially feel angry toward the employment situation. We also suggested that to the extent that overqualified people are sensitive to justice, they may react more or less strongly to being overqualified. We tested our predictions using time‐lagged data from a sample of 224 workers and their supervisors employed in a large manufacturing company in China. Consistent with our theoretical framework, we found that organization‐based self‐esteem (OBSE) and anger toward employment situation mediated the positive relationships between perceived overqualification and both self‐rated and supervisor‐rated CWBs. In addition, justice sensitivity moderated the relationship between perceived overqualification and the mediators (i.e., OBSE and anger) and the indirect relationship between perceived overqualification and CWB. The theoretical and practical implications of these findings as well as future research directions are discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Molecular toxicity of earthworms induced by cadmium contaminated soil and biomarkers screening

Earthworms (Eisenia fetida) were used to study the impact of low-dose cadmium in treated artificial soil (0, 0.6, 3, 6, 15, 30 mg/kg) and contaminated natural soil (1.46 mg/kg). The changes of earthworms' physiological related gene expressions of metallothionein (MT), annetocin, calreticulin and antimicrobial peptides were detected using real-time PCR after a 70-day incubation period. The results showed that low doses of cadmium could up regulate earthworms' MT and down regulate annetocin gene expression and show a significant positive and negative correlation respectively. The expression of two other genes, calreticulin and anti-microbial peptides, was induced at low doses of cadmium (highest gene expression at 0.6 mg/kg for calreticulin and 6 mg/kg for anti-microbial peptides) and inhibited at high doses. No significant correlation was found for these two genes. This study shows that MT and annetocin genes expression found in earthworms in contaminated soil have the potential to be developed as biomarkers of soil cadmium pollution.     

铁盐改性砂制备及其吸附Zn~(2+)的性能研究

通过改变石英砂表面的物理化学性质,提高石英砂的吸附效率,考察其对废水中的Zn~(2+)去除效果.以石英砂为载体,分别用反复高温加热法和反复碱性沉积法制备了三氯化铁改性砂、硝酸铁改性砂,测定2种方法制备的铁盐改性砂的表面含铁量、铁盐的酸稳定性及比表面积,并比较2种铁盐改性砂对Zn~(2+)的吸附效果.结果表明,三氯化铁改性砂、硝酸铁改性砂的比表面积分别为2.468、4.247 m~2/g,比石英砂比表面积分别提高6.910、12.612倍;在pH为中性条件下,石英砂对Zn~(2+)去除率为43%左右,三氯化铁改性砂对Zn~(2+)去除率达到70%左右,硝酸铁改性砂对Zn~(2+)去除率达到85%左右,表明铁盐改性砂对Zn~(2+)去除能力比石英砂有很大提高;铁盐改性砂对Zn~(2+)的吸附有一定容量,表面的活性中心越多,吸附能力越大;铁盐改性砂对Zn~(2+)的去除率随着pH的升高而增加,当pH>8.5时,Zn~(2+)去除率可达90%左右.     

Emergy Assessment of a Wheat-Maize Rotation System with Different Water Assignments in the North China Plain

Sustainable water use is seriously compromised in the North China Plain (NCP) due to the huge water requirements of agriculture, the largest use of water resources. An integrated approach which combines the ecosystem model with emergy analysis is presented to determine the optimum quantity of irrigation for sustainable development in irrigated cropping systems. Since the traditional emergy method pays little attention to the dynamic interaction among components of the ecological system and dynamic emergy accounting is in its infancy, it is hard to evaluate the cropping system in hypothetical situations or in response to specific changes. In order to solve this problem, an ecosystem model (Vegetation Interface Processes (VIP) model) is introduced for emergy analysis to describe the production processes. Some raw data, collected by investigating or observing in conventional emergy analysis, may be calculated by the VIP model in the new approach. To demonstrate the advantage of this new approach, we use it to assess the wheat-maize rotation cropping system at different irrigation levels and derive the optimum quantity of irrigation according to the index of ecosystem sustainable development in NCP. The results show, the optimum quantity of irrigation in this region should be 240–330 mm per year in the wheat system and no irrigation in the maize system, because with this quantity of irrigation the rotation crop system reveals: best efficiency in energy transformation (transformity = 6.05E + 4 sej/J); highest sustainability (renewability = 25%); lowest environmental impact (environmental loading ratio = 3.5) and the greatest sustainability index (Emergy Sustainability Index = 0.47) compared with the system in other irrigation amounts. This study demonstrates that application of the new approach is broader than the conventional emergy analysis and the new approach is helpful in optimizing resources allocation, resource-savings and maintaining agricultural sustainability.     

Heavy metal contamination of urban soils and dusts in Guangzhou, South China

The heavy metal concentrations of soil and dust samples from roadside, residential areas, parks, campus sport grounds, and commercial sites were studied in Guangzhou, South China. Heavy metals in samples were determined by inductively coupled plasma atomic emission spectrophotometer following acidic digestion with HClO₄ + HF + HNO₃. High concentrations, especially of Cd, Pb, and Zn, were found with mean concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the urban dusts being 4.22?±?1.21, 62.2?±?27.1, 116?±?30, 31.9?±?12.6, 72.6?±?17.9, and 504?±?191 mg/kg dry weight, respectively. The respective levels in urban soils (0.23?±?0.19, 22.4?±?13.8, 41.6?±?29.4, 11.1?±?5.3, 65.4?±?40.2, and 277?±?214 mg/kg dry weight, respectively), were significantly lower. The integrated pollution index of six metals varied from 0.25 to 3.4 and from 2.5 to 8.4 in urban soils and dusts, respectively, with 61 % of urban soil samples being classified as moderately to highly polluted and all dust samples being classified as highly polluted. The statistical analysis results for the urban dust showed good agreement between principal component analysis and cluster analysis, but distinctly different elemental associations and clustering patterns were observed among heavy metals in the urban soils. The results of multivariate statistic analysis indicated that Cr and Ni concentrations were mainly of natural origin, while Cd, Cu, Pb, and Zn were derived from anthropogenic activities.     

近十年水磨河水质变化特征研究

利用水磨河2001—2010年各断面实测资料,采用单因子法和综合污染指数法分析了近十年该流域各断面主要污染物超标情况,沿程变化特征及年际、季节变化趋势。结果表明,搪瓷厂泉断面、七纺桥断面水质有所好转,下游联丰桥断面、米泉桥断面污染程度逐渐加重,超标污染项目逐年增加。高锰酸盐指数、氨氮、总磷浓度值在联丰桥断面直线上升,石...     

Preparation of a new Fenton-like catalyst from red mud using molasses wastewater as partial acidifying agent

Using molasses wastewater as partial acidifying agent, a new Fenton-like catalyst (ACRM _sm ) was prepared through a simple process of acidification and calcination using red mud as main material. With molasses wastewater, both the free alkali and the chemically bonded alkali in red mud were effectively removed under the action of H₂SO₄ and molasses wastewater, and the prepared ACRM _sm was a near-neutral catalyst. The ACRM _sm preparation conditions were as follows: for 3 g of red mud, 9 mL of 0.7 mol/L H₂SO₄ plus 2 g of molasses wastewater as the acidifying agent, calcination temperature 573 K, and calcination time 1 h. Iron phase of ACRM _sm was mainly α-Fe₂O₃ and trace amount of carbon existed in ACRM _sm . The addition of molasses wastewater not only effectively reduced the consumption of H₂SO₄ in acidification of red mud but also resulted in the generation of carbon and significantly improved the distribution of macropore in prepared ACRM _sm . It was found that near-neutral pH of catalyst, generated carbon, and wide distribution of macropore were the main reasons for the high catalytic activity of ACRM _sm . The generated carbon and wide distribution of macropore were entirely due to the molasses wastewater added. In degradation of orange II, ACRM _sm retained most of its catalytic stability and activity after five recycling times, indicating ACRM _sm had an excellent long-term stability in the Fenton-like process. Furthermore, the performance test of settling showed ACRM _sm had an excellent settleability. ACRM_sm was a safe and green catalytic material used in Fenton-like oxidation for wastewater treatment.

     

三种环境动力学模型建模方式的比较

在农药和化学品的风险评估工作中,环境动力学模型正得到越来越多的应用。采用Stella软件、Matlab M文件和Matlab Simulink 组件3种建模方式分别构建了微宇宙、湖泊和海湾系统的多介质环境动力学模型,并对3种方式的建模难度、计算耗时及模型直观性进行了比较。研究结果表明：Stella模型最直观,但提供的计算方法有限,更适用于微分方程数量不多且计算周期短的模型;M文件模型建模速度最快,但在直观性和计算速度上没有优势,不建议在环境动力学模型中使用;Simulink模型兼具直观性和计算速度快的优点,无论微分方程数量多少,在需要进行长周期计算的模型中都最具优势。