Accumulation and spatial distribution of Cd, Cr, and Pb in mulberry from municipal solid waste compost following application of EDTA and (NH4)2SO4

Municipal solid waste compost can be used to cropland as soil amendment to supply nutrients and improve soil physical properties. But long-term application of municipal solid waste (MSW) compost may result in accumulation of toxic metals in amended soil. Phytoremediation, especially phytoextraction, is a novel, cost-effective, and environmentally friendly approach that uses metal-accumulating plants to concentrate and remove metals from contaminated soils. Ethylenediaminetetraacetate (EDTA) was applied to metal-contaminated soil to increase the mobility and phytoavailability of metals in soil, thereby increasing the amount of toxic metals accumulated in the upper parts of phytoextracting plants. The objectives of this study were (1) to investigate the accumulation and spatial distribution of toxic metals (Cd, Cr, and Pb) in mulberry from MSW compost with the application of EDTA and (NH₄)₂SO₄, (2) to examine the effectiveness of EDTA and (NH₄)₂SO₄ applied together on toxic metals (Cd, Cr, and Pb) removal by mulberry under field conditions, and (3) to evaluate the potential of mulberry for phytoextraction of toxic metals from MSW compost. The tested plant—mulberry had been grown in MSW compost field for 4 years. EDTA solution at five rates (0, 50, 100, 50 mmol L^?1?+?1 g?L^?1 (NH₄)₂SO₄, and 100 mmol L^?1?+?1 g?L^?1 (NH₄)₂SO₄) was added into mulberry root medium in September 2009. Twenty days later, the plants were harvested and separated into six parts according to plant height. Cd, Cr, and Pb contents in plant samples and MSW compost were analyzed using an atomic absorption spectrophotometer. In the same treatment, Cd, Cr, and Pb concentrations in mulberry shoot were all higher than those in root, and Cd and Pb concentrations in shoot increased from lower to upper parts, reaching the highest in leaves. Significant increases were found in toxic metal concentration in different parts of mulberry with increasing EDTA concentration, especially when combined with (NH₄)₂SO₄. Mulberry exhibited high ability to accumulate Cd with bioconcentration factors (BCFs) higher than 1. EDTA application also significantly increased Cd BCFs. More than 30 % of metal uptake was concentrated in mulberry branches (stem of above 100 cm height) and leaves. Results presented here show that mulberry is a woody plant that has the potential of Cd phytoextraction from MSW compost by removing leaves and cutting branches. The application of EDTA combined with (NH₄)₂SO₄ significantly enhanced the efficiency of mulberry in removing Cd from the compost medium. Adding (NH₄)₂SO₄ into the compost will lower the risk of the exposure of environment to excessive non-biodegradable EDTA in a large-scale EDTA-assisted phytoextraction by reducing the dosage of EDTA. In China, the need for sod is increasing day by day. Sod is often produced on arable soil and sold together with soils. This would lead to the soil being infertile and the soil layer thin. After several times’ production, the soil can no longer be used for cultivating crops and be destroyed. In order to fully utilize MSW compost resources and save valuable soil resources, MSW compost can be used to replace arable soil to produce sod after extraction of toxic metals in it.     

淋洗法去除城市生活垃圾堆肥中重金属

采用淋洗法研究了淋洗剂酸度、螯合剂与表面活性剂对生活垃圾堆肥中重金属的去除效果.结果表明,淋洗剂的酸度对堆肥中重金属的淋出效果不明显,螯合剂与表面活性剂的影响较为显著.随着螫合剂、表面活性剂浓度增加,Mn、Zn和Cu的淋出量有增加的趋势,当DL-苹果酸、柠檬酸浓度为30 mmol/L,Mn的淋出量分别为对照的87和22...     

Sorption of apolar and polar organic contaminants by waste tire rubber and its chars in single- and bi-solute systems

Single- and bi-solute sorption of organic compounds [1,3-dichlorbenzene (DCB), 1,3-dinitrobenzene (DNB) and 2,4-dichlorophenol (DCP)] on ground tire rubber and its chars was studied. The chars were prepared by pyrolyzing tire rubber at different temperatures (200-800 °C). Their surface area, aromaticity and hydrophobicity increase greatly with pyrolytic temperature, and the polymeric phase is partly converted into a condensed phase. The sorption of DNB and DCP increases with pyrolytic temperature and is characterized by a transition from a partition dominant to an adsorption dominant process. However, the sorption of DCB linearly decreases with the pyrolytic temperature. The enhanced adsorption of DNB and DCP on carbonized phase is primarily attributed to nonhydrophobic interactions such as π-π electron-donor-acceptor interactions and/or H bonding. The higher partition of DCB to polymeric phase is attributed to its high hydrophobicity. Competitive sorption between DCB and DCP on the tire chars is highly dependent on dissociation of the latter.     

Bioaccessibility and health risk of arsenic, mercury and other metals in urban street dusts from a mega-city, Nanjing, China

The oral bioaccessibility and the human health risks of As, Hg and other metals (Cu, Pb, Zn, Ni, Co, Cd, Cr, Mn, V and Fe) in urban street dusts from different land use districts in Nanjing (a mega-city), China were investigated. Both the total contents and the oral bioaccessibility estimated by the Simple Bioaccessibility Extraction Test (SBET) of the studied elements varied with street dusts from different land use districts. Cd, Zn, Mn, Pb, Hg and As showed high bioaccessibility. SBET-extractable contents of elements were significantly correlated with their total contents and the dust properties (pH, organic matter contents). The carcinogenic risk probability for As and Cr to children and adults were under the acceptable level (<1 × 10⁻⁴). Hazard Quotient values for single elements and Hazard Index values for all studied elements suggested potential non-carcinogenic health risk to children, but not to adults.     

工业LNG储罐泄漏扩散数值模拟

针对工业LNG储罐泄漏问题,基于Fluent软件结合UDF修正风速模型,研究不同工况下泄漏发展情况,并对泄露口下风向沿直线距离上的泄漏气体浓度进行分析,得出准确气体扩散浓度范围.研究结果表明,泄漏孔口越接近地面,横向扩散距离越大.相同风速下,泄漏路径上气体浓度具有相似的变化趋势,风速越高泄漏气体沿扩散路径的稀释作用越强...     

材料性能劣化对刚构桥地震易损性的影响分析∗

为了揭示山区服役环境下材料性能劣化对桥梁抗震安全性的影响,根据混凝土碳化和钢筋锈蚀规律得到山区环境下材料劣化时变模型,采用基于需求能力比(D/C)的动力增量分析(IDA)方法,提出了桥梁时变地震易损性分析流程。围绕某山区典型高墩刚构桥,研究了桥梁构件和体系两个层次的地震易损性时变规律。结果表明:构件塑性发展程度越高,材料劣化的影响越不利,构件曲率延性系数也越大;相比于横桥向,材料劣化对构件纵向地震易损性的影响更大,且服役时间越长,构件地震损伤概率越高;桥梁体系的损伤概率上限高于任意构件,材料劣化的不利影响也主要体现于纵桥向,该方向上 0.8g 时,服役 100 年的严重受损概率相比新桥增大 100.86%;材料劣化对桥梁地震易损性的影响不容忽视,且构件层面的易损性评估不足以反映桥梁体系的易损性。     

A systematic approach for the comparative assessment of stormwater pollutant removal potentials

This paper describes the development of a methodology to theoretically assess the stormwater pollutant removal performances of structural best management practices (BMPs). The method combines the categorisation of the relative importance of the primary removal processes within 15 different BMPs with an evaluation of the ability of each process to remove a pollutant in order to generate a value representing the pollutant removal potential for each BMP. The methodology is demonstrated by applying it separately to a set of general water quality indicators (total suspended solids, biochemical and chemical oxygen demand, nitrates, phosphates and faecal coliforms) to produce a ranked list of BMP pollutant removal efficiencies. Given the limited amount of available monitoring data relating to the differential pollutant removal capabilities of BMPs, the resulting prioritization will support stakeholders in making urban drainage decisions from the perspective of pollutant removal. It can also provide inputs to existing urban hydrology models, which aim to predict the treatment performances of BMPs. The level of resilience of the proposed approach is tested using a sensitivity analysis and the limitations in terms of BMP design and application are discussed.     

锐劲特对原生动物群落的急性毒性试验

以PFU法采集的淡水原生动物群落为试验对象 ,对锐劲特的急性毒性进行研究 .结果表明 ,锐劲特对原生动物群落的 48h LC50 为 35 83mg·l- 1 ;原生动物群落结构参数和功能参数随加入锐劲特的量而变化 ;在种类组成上 ,虽然鞭毛虫、纤毛虫、肉足虫的种类均随着毒物浓度的增大而下降 ,但是其减少的程度各不相同 ,纤毛虫所受损伤最大 ;在试验浓度范围内 ,功能类群发生显著变化 ,光合作用自养者和食藻者原生动物的物种逐渐消失 ,而一些食菌 碎屑类原生动物具有较高的耐受性 ,随着锐劲特浓度的增加 ,其在群落中的优势度更加明显