Health risks of heavy metals in contaminated soils and food crops irrigated with wastewater in Beijing, China

Consumption of food crops contaminated with heavy metals is a major food chain route for human exposure. We studied the health risks of heavy metals in contaminated food crops irrigated with wastewater. Results indicate that there is a substantial buildup of heavy metals in wastewater-irrigated soils, collected from Beijing, China. Heavy metal concentrations in plants grown in wastewater-irrigated soils were significantly higher (P相似文献   

Influence of organic amendments on diuron leaching through an acidic and a calcareous vineyard soil using undisturbed lysimeters

The influence of different organic amendments on diuron leaching was studied through undisturbed vineyard soil columns. Two composts (A and D), the second at two stages of maturity, and two soils (VR and Bj) were sampled. After 1 year, the amount of residues (diuron + metabolites) in the leachates of the VR soil (0.19-0.71%) was lower than in the Bj soil (4.27-8.23%), which could be explained by stronger diuron adsorption on VR. An increase in the amount of diuron leached through the amended soil columns, compared to the blank, was observed for the Bj soil only. This result may be explained by the formation of mobile complexes between diuron and water-extractable organic matter (WEOM) through the Bj soil, or by competition between diuron and WEOM for the adsorption sites in the soil. For both soils, the nature of the composts and their degree of maturity did not significantly influence diuron leaching.     

锌精炼铅塔燃烧系统烟气温度模糊控制研究

针对锌精馏铅塔动态过程中的非线性、非最小相位特征、不稳定性、时滞和负荷干扰,基于模糊控制策略下给出了锌精馏铅塔燃烧系统新的控制方法.运用模糊控制系统对锌精馏铅塔的烟气温度进行仿真研究和实时控制结果表明,该研究所设计的模糊控制器能够克服许多干扰因素,产生了良好的控制效果.     

A2/O工艺中的反硝化除磷

A2/O工艺是一种最简单的同步脱氮除磷工艺,但由于其系统中固有的基质竞争和污泥龄等矛盾,在实际应用中特别是处理低C/N比污水时脱氮除磷效率较低.反硝化除磷工艺作为近年来颇受关注的污水生物处理新技术.由于在脱氮除磷过程中可以在碳源利用上耦合,可从一定程度上缓解A2/O工艺中的基质竞争矛盾,使得其在处理低C/N比污水时也能实现较高的脱氮除磷效率.就反硝化除磷的技术原理,结合其在A2/O工艺中的最新研究成果及其控制策略,对A2/O工艺中的反硝化除磷的实现、维持及影响因素进行了分析和探讨,并对其发展方向进行了展望.     

Relationships between organic matter, black carbon and persistent organic pollutants in European background soils: Implications for sources and environmental fate

Black carbon (BC) and total organic carbon (TOC) contents of UK and Norwegian background soils were determined and their relationships with persistent organic pollutants (HCB, PAHs, PCBs, co-planar PCBs, PBDEs and PCDD/Fs) investigated by correlation and regression analyses, to assess their roles in influencing compound partitioning/retention in soils. The 52 soils used were high in TOC (range 54-460 mg/g (mean 256)), while BC only constituted 0.24-1.8% (0.88%) of the TOC. TOC was strongly correlated (p < 0.001) with HCB, PCBs, co-PCBs and PBDEs, but less so with PCDD/Fs (p < 0.05) and PAHs. TOC explained variability in soil content, as follows: HCB, 80%; PCBs, 44%; co-PCBs, 40%; PBDEs, 27%. BC also gave statistically significant correlations with PBDEs (p < 0.001), co-PCBs (p < 0.01) and PCBs, HCB, PCDD/F (p < 0.05); TOC and BC were correlated with each other (p < 0.01). Inferences are made about possible combustion-derived sources, atmospheric transport and air-surface exchange processes for these compounds.     

Spatial variability of arsenic concentration in soils and plants, and its relationship with iron, manganese and phosphorus

Spatial distribution of arsenic (As) concentrations of irrigation water, soil and plant (rice) in a shallow tube-well (STW) command area (8 ha), and their relationship with Fe, Mn and P were studied. Arsenic concentrations of water in the 110 m long irrigation channel clearly decreased with distance from the STW point, the range being 68-136 μg L⁻¹. Such decreasing trend was also noticed with Fe and P concentrations, but the trend for Mn concentrations was not remarkable. Concerning soil As, the concentration showed a decreasing tendency with distance from the pump. The NH₄-oxalate extractable As contributed 36% of total As and this amount of As was associated with poorly crystalline Fe-oxides. Furthermore only 22% of total As was phosphate extractable so that most of the As was tightly retained by soil constituents and was not readily exchangeable by phosphate. Soil As (both total and extractable As) was significantly and positively correlated with rice grain As (0.296 ± 0.063 μg g⁻¹, n = 56). Next to drinking water, rice could be a potential source of As exposure of the people living in the As affected areas of Bangladesh.     

Extent and causes of 3D spatial variations in potential N mineralization and the risk of ammonium and nitrate leaching from an N-impacted permanent grassland near York, UK

Changes in the dynamics of inorganic N species transformations with depth have been investigated for seven soil profiles from a nitrogen-impacted ancient grassland on a nature reserve outside York in the UK, using incubation experiments. In five of the profiles, both ammonification and nitrification are occurring below the rooting zone, probably partly in response to the low C:N ratio in the soils. This contributes to elevated nitrate concentrations found in an adjacent stream. Accumulation of ammonium during incubation in the sub-soils of these five profiles suggests a high probability of ammonium leaching down the profiles as ammonium inputs and outputs at a given depth approach equilibrium. This ammonium may also be nitrified at depth. However, in the two profiles with the most acidic surface horizons, net mineralization was negligible or negative; some initial ammonium-N and ammonium-N produced during incubation were nitrified, so the loss in ammonium-N was closely balanced by nitrate-N production.     

Long term changes in atmospheric N and S throughfall deposition and effects on soil solution chemistry in a Scots pine forest in the Netherlands

In a Scots pine forest the throughfall deposition and the chemical composition of the soil solution was monitored since 1984. (Inter)national legislation measures led to a reduction of the deposition of nitrogen and sulphur. The deposition of sulphur has decreased by approximately 65%. The total mineral-nitrogen deposition has decreased by ca. 25%, which is mainly due to a reduction in ammonium-N deposition (−40%), since nitrate-N deposition has increased (+50%). The nitrogen concentration in the upper mineral soil solution at 10 cm depth has decreased, leading to an improved nutritional balance, which may result in improved tree vitality. In the drainage water at 90 cm depth the fluxes of NO₃⁻ and SO₄²⁻ have decreased, resulting in a reduced leeching of accompanying base cations, thus preserving nutrients in the ecosystem. It may take still several years, however, before this will meet the prerequisite of a sustainable ecosystem.     

Sorption of polar and nonpolar aromatic compounds to four surface soils of eastern China

Improved predictions on the fate of organic pollutants in surface environments require a better understanding of the underlying sorption mechanisms that control their uptake by soils. In this study, we monitored sorption of nine aromatic compounds with varying physicochemical properties (hydrophobicity, electron-donor/acceptor ability and polarity), including two polycyclic aromatic hydrocarbons, two chlorobenzenes, two nitroaromatic compounds, dichlobenil, carbaryl and 2,4-dichlorophenol in aqueous suspension of four surface soils of eastern China. The tested soils were characterized with respect to organic carbon (OC) content, black carbon content, mineralogy, morphology and size fraction to assess the role of the diverse soil characteristics in sorption. The results of this study show that not only the solute hydrophobicity and the OC content of soil are important to the retention of organic pollutants, but also the solute molecular structure and the soil nature.     

Use of USLE/GIS Methodology for Predicting Soil Loss in a Semiarid Agricultural Watershed

The Universal Soil Loss Equation (USLE) is an erosion model to estimate average soil loss that would generally result from splash, sheet, and rill erosion from agricultural plots. Recently, use of USLE has been extended as a useful tool predicting soil losses and planning control practices in agricultural watersheds by the effective integration of the GIS-based procedures to estimate the factor values in a grid cell basis. This study was performed in the Kazan Watershed located in the central Anatolia, Turkey, to predict soil erosion risk by the USLE/GIS methodology for planning conservation measures in the site. Rain erosivity (R), soil erodibility (K), and cover management factor (C) values of the model were calculated from erosivity map, soil map, and land use map of Turkey, respectively. R values were site-specifically corrected using DEM and climatic data. The topographical and hydrological effects on the soil loss were characterized by LS factor evaluated by the flow accumulation tool using DEM and watershed delineation techniques. From resulting soil loss map of the watershed, the magnitude of the soil erosion was estimated in terms of the different soil units and land uses and the most erosion-prone areas where irreversible soil losses occurred were reasonably located in the Kazan watershed. This could be very useful for deciding restoration practices to control the soil erosion of the sites to be severely influenced.