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51.
Metal mobility at an old, heavily loaded sludge application site 总被引:8,自引:0,他引:8
Richards BK Steenhuis TS Peverly JH McBride MB 《Environmental pollution (Barking, Essex : 1987)》1998,99(3):365-377
This study was undertaken to determine the present distribution and mobility of sludge-applied metals at an old land application site. Trace metals concentrations were determined for soils (using 4 M HNO3 extracts), soil leachates (collected with passive wick lysimeters over a 2.5-year period), and plant tissue from a field site which received a heavy loading of wastewater sludge in 1978 and an adjacent control plot. Blue dye was used to indicate preferential percolate flowpaths in the sludge plot soil for sampling and comparison with bulk soil metals concentrations. After nearly 20 years, metals in the sludge plot leachate were found at significantly greater concentrations than in the control plot, exceeding drinking water standards for Cd, Ni, Zn, and B. Annual metals fluxes were only a fraction of the current soil metal contents, and do not account for the apparent substantial past metals losses determined in a related study. Elevated Cd, Cu, and Ni levels were found in grass growing on the sludge plot. Despite heavy loadings, fine soil texture (silty clay loam) and evidence of past and ongoing metals leaching, examination of the bulk subsoil indicated no statistically significant increases in metals concentrations (even in a calcareous subsoil horizon with elevated pH) when comparing pooled sludge plot soil profiles with controls. Sampling of dyed preferential flow paths in the sludge plot detected only slight increases in several metals. Preferential flow and metal complexation with soluble organics apparently allow leaching without easily detectable readsorption in the subsoil. The lack of significant metal deposition in subsoil may not be reliable evidence for immobility of sludge-applied metals. 相似文献
52.
北京市西北城区取暖期环境大气中PM10的物理化学特征 总被引:5,自引:0,他引:5
根据监测资料探讨了北京市西北城区取暖期PM10 的逐日变化规律和日变化规律 .分别使用X射线衍射仪(XRD)和扫描电镜 (SEM)研究PM10 中的矿物成分及其微观形貌特征 .结果表明夜间PM10 浓度普遍高于白天 .XRD分析显示颗粒物粒度越细 ,其中所含的矿物种类越少 .SEM研究得出 ,单个PM10 颗粒类型可初步分为有链状集合体、簇状集合体、圆球状、片状和不规则形状等 5类 .从数量上看 ,PM10 主要来自燃煤和汽车尾气 相似文献
53.
Chow JC Watson JG Lowenthal DH Richards LW 《Environmental monitoring and assessment》2002,79(1):29-45
Particle light scattering and PM2.5 (particles with aerodynamic diameters less than 2.5 m) concentration data from air quality studies conducted over the past ten years wereexamined. Fine particle scattering efficiencies were determinedfrom statistical relationships among measured light scattering and fine and coarse mass concentrations. The resulting fine particle scattering efficiencies ranged from 1.7 m2 g-1at Meadview in the Grand Canyon to over 5 m2 g-1 in Mexico City. Most of the derived fine scattering efficiencieswere centered around 2 m2 g-1, which is considerablylower than most values reported from previous studies. 相似文献
54.
R. Peter Richards David B. Baker Jack W. Kramer D. Ellen Ewing Barbara J. Merryfield Nancy L. Miller 《Journal of the American Water Resources Association》2001,37(2):423-438
ABSTRACT: A computerized technique was developed to identify storm runoff episodes and calculate storm discharges, storm loads, and storm average concentrations for each event in datasets with up to 10,000 records. This technique was applied to four watersheds within the Lake Erie drainage basin and identified between 160 and 250 runoff events in each. Storm event loads and storm event mean concentrations were calculated for each runoff event for suspended solids, total phosphorus, soluble reactive phosphorus, nitrate, and total Kjeldahl nitrogen. The basic characteristics of the resulting data are described, as are systematic differences as a function of watershed size, seasonal differences, and trends over time. Many of the results of this study reflect the importance of nonpoint processes and improvements in agricultural best management practices in these watersheds. 相似文献
55.
New highly fluorinated monodentate and bidentate phosphine oxide compounds of the type {CF(3)(CF(2))(n)CH(2)CH(2)}(3)PO (n = 5, 9) and [{CF(3)(CF(2))(5)CH(2)CH(2)}(2)P(O)CH(2)CH(2)P(O){CH(2)CH(2)(CF(2))(5)CF(3)}] have been prepared. Their ability to extract a number of metals and radionuclides from aqueous solutions into perfluorinated solvents has been established and the extractable species investigated. All extractants extract the metals As(V), Cd(II), Co(II), Cr(VI), Hg(II), Pb(II), and Sn(II) with >75% removal. In addition, the radioisotopes (90)Sr(II), (133)Ba(II), and U(VI) have been investigated, whilst (59)Fe(III) has been used to model the extraction of plutonium. (133)Ba(II) shows a high distribution ratio for monodentate phosphine oxides, whilst for UO(2)(2+) and (59)Fe(III) bidentate phosphine oxides are superior. 相似文献
56.
William H. Richards ‡ David O. Wallin Nathan H. Schumaker† 《Conservation biology》2002,16(5):1409-1421
57.
Redox probes are typically constructed by soldering Pt wire to a metal wire or rod, such as copper or brass. The junction between the Pt and wire or rod is often sealed with an epoxy resin and hardener or with heat-shrink tubing. Microcracks (small cracks invisible to the unaided eye) can form in the hardened resin and result in incorrect readings. The hardened resin is not easily removed, making repairs difficult. Heat-shrink tubing is thin, lacks rigidity, and can be damaged in the soil. The method described in this paper used a thick-walled, adhesive-lined terminal insulator to seal the junction. The terminal insulators were easily applied and removed, which made faulty probes easy to repair. Two-hundred forty probes were made with this method and eight were made with a marine epoxy resin. The probes were tested with a redox buffer solution (Light Solution) and were usable if they read +476 +/- 10 mV. The probes were installed 0.76 and 1.5 m deep in the soil. The ability of the probes to provide reliable redox readings was examined by testing selected probes after 10 mo of use and testing all of the probes after completion of the study (19 mo). Ten of the twelve probes tested after 10 mo worked satisfactorily, while the other two clearly malfunctioned before testing. After the study was completed, 236 of the 240 of the probes worked satisfactorily. These results indicate that the construction method presented produces reliable, long-lasting probes. 相似文献
58.
A Brief Overview of Carbon Sequestration Economics and Policy 总被引:2,自引:0,他引:2
Richards KR 《Environmental management》2004,33(4):545-558
This article provides an overview of the issues and challenges involved in analyzing the costs and program design for carbon sequestration. The first section examines some of the pitfalls of comparing the results of carbon sequestration cost studies and suggests some simple ways in which analysts could make their results more useful. The pitfalls in comparing studies include different definitions for the summary statistic dollars per ton, differences in the type of costs that are estimated, and differences in underlying assumptions regarding program design and implementation. Future cost studies will benefit from improved treatment of leakage, general equilibrium interactions, and public finance interactions. The second section reviews issues related to the implementation of a carbon sequestration program, including which policy tools are available and which have received the most attention, some of the challenges for using those policy tools, and one alternative that has received little attention, but may become necessary. The discussion also provides an overview and analysis of the bills introduced in the last two congresses and considers the general policy implications of those proposals. 相似文献
59.
Trends in water quality in four northwest Ohio rivers over the period 1975-1995 were identified using datasets of daily concentrations containing 4500 to 6800 observations per river during the study period. Concentrations were log-transformed prior to analysis, and adjusted for flow using a locally weighted scatterplot smoother (LOWESS) fit between log(concentration) and log(flow). Seasonality was modeled using one- and two-cycle sinusoidal oscillations and monthly additive constants. Substantial decreases in total and soluble reactive phosphorus were documented at all stations. Smaller but highly significant decreases in total Kjeldahl nitrogen were documented at all stations, and significant decreases in total suspended solids were documented at three of the four stations. Nitrate did not show significant trends at the two stations draining major watersheds, and showed significant trends in opposite directions at the two stations on smaller watersheds. Comparisons using nonparametric, nonlinear trend fits (LOWESS) suggest that changes in fertilizer and manure application rates are the most important cause of trends in phosphorus and total Kjeldahl nitrogen; point sources are insufficient to account for the phosphorus trends. The conflicting trends for nitrate are enigmatic, but may reflect diverging land use in the two smaller watersheds. 相似文献
60.
Peter Richards 《补救:环境净化治理成本、技术与工艺杂志》2002,12(4):65-79
In June 2001, the Massachusetts Department of Environmental Protection (DEP) installed a permeable reactive barrier (PRB) within a roadway in Needham, Massachusetts, to treat a plume of chlorinated solvents migrating toward two public water‐supply wells located in the adjacent town of Wellesley, Massachusetts. The solvents originated from an electronics manufacturer located approximately 2,300 feet upgradient of the roadway and 5,200 feet upgradient of the public supply wells. Chlorinated solvents, primarily trichloroethene (TCE), had migrated past the roadway to within 300 feet of the public supply wells. Two contaminant transport models prepared by the DEP's design contractor and the EPA indicated that the plume would reach the well field if no response actions were taken. To mitigate the future impact to the municipal well field, the DEP decided to install a PRB composed of zero‐valent granular iron across the path of the plume along Central Avenue in Needham. Though several dozen PRBs have been installed at sites worldwide and the technology is no longer considered innovative, the application of the technology in a roadway that receives 17,000 vehicles per day within a residential neighborhood is unique and presented difficulties not typically associated with PRB installations. The Needham PRB was also one of the first zero‐valent iron PRBs installed using the slurry trench method to treat chlorinated compounds. © 2002 Wiley Periodicals, Inc. 相似文献