Municipal sludge management: Health aspects of crop uptake of cadmium from sludge-amended soil and recommendations for regulation

Regulations have been proposed by the United States Environmental Protection Agency to promote the proper management of sludge disposal on croplands. The application of municipal sludge to croplands raises serious questions concerning the increase in dietary levels of metals resulting from metal uptake by crops. A model is presented that affords a quantitative estimate of the dietary increase of metals when foods are derived from sludge-amended soil. If a diet or part of a diet is derived completely from sludge-amended soil, it is likely to be excessive in cadmium and pose a clear health hazard. Recommendations designed to reduce the potential health threat of excessive metals in the diet are presented.     

FORESTED WETLANDS IN EASTERN CONNECTICUT: THEIR TRANSITION ZONES AND DELINEATION1

ABSTRACT: The delineation of inland wetlands requires close field examination of the biological and physical gradients (transition zones) between wetlands and bordering uplands. As part of a study on the detection and delineation of inland wetlands in eastern Connecticut by remote sensing techniques, this effort was designed to investigate vegetation distribution and composition and selected physical and chemical properties of the soils of wetland to upland transition zones in deciduous wetland forests. Field research was conducted during the growing season of 1975 within a test area consisting of the 45 mi² Town of Mansfield, Connecticut. Changes in vegetation composition and structure, soil pH, and soil water content were determined along line transects extended over wetland to upland transition zones. Differences in soil pH occurred along the transects but were of such magnitude that they probably have little impact on plant distribution. There were significant changes in soil water content along the wetland to upland gradients. Discriminant analysis applied to statistical “index of abundance” data describing vegetation distribution among the various zones (wetland, transition, upland) showed which plant species best distinguish wetlands from uplands. Of the criteria studied, vegetation composition and distribution, soil water content, and relief are the most useful criteria for delineating deciduous wetland forests.     

ESTIMATION OF SOIL MOISTURE WITH API ALGORITHMS AND MICROWAVE EMISSION1

Large area soil moisture estimations are required to describe input to cloud prediction models, rainfall distribution models, and global crop yield models. Satellite mounted microwave sensor systems that as yet can only detect moisture at the surface have been suggested as a means of acquiring large area estimates. Relations previously discovered between microwave emission at the 1.55 cm wavelength and surface moisture as represented by an antecedent precipitation index were used to provide a pseudo infiltration estimation. Infiltration estimates based on surface wetness on a daily basis were then used to calculate the soil moisture in the surface 0–23 cm of the soil by use of a modified antecedent precipitation index. Reasonably good results were obtained (R²= 0.7162) when predicted soil moisture for the surface 23 cm was compared to measured moisture. Where the technique was modified to use only an estimate of surface moisture each three days an R² value of 0.7116 resulted for the same data set. Correlations between predicted and actual soil moisture fall off rapidly for repeat observations more than three days apart. The algorithms developed in this study may be used over relatively flat agricultural lands to provide improved estimates of soil moisture to a depth greater than the depth of penetration for the sensor.     

SATELLITE MICROWAVE OBSERVATIONS OF SOIL MOISTURE VARIATIONS1

ABSTRACT: Results from studies in the Illinois-Indiana and Texas-Oklahoma areas indicate that satellite microwave observations at the 1.55 cm wavelength are responsive to relative moisture variations in the near surface layer of the soil. Because significant vegetation cover absorbs the 1.55 cm microwave emission from the soil, the target area must be predominately bare soil or low density vegetation cover for meaningful measurements to result. The 25 km resolution of the satellite sensor limits application of the microwave techniques to large areas such as watersheds or agricultural districts rather than individual fields. In general, at 1.55 cm. there is an inverse relationship between microwave brightness temperature and changes in soil moisture levels (as indicated by antecedent rainfall) in agricultural regions before the planting of crops or during the early growing season when vegetation cover is sparse. Even early season observations should be of great value in deciding on the time and type of crop planting and for initial irrigation scheduling when the root zone is still in close proximity to the surface.     

Metabolic fate of the 14C-labeled herbicide clodinafop-propargyl in soil

The metabolic fate of ¹⁴C-phenyl-labeled herbicide clodinafop-propargyl (CfP) was studied for 28 days in lab assays using a soil from Germany (A_p horizon, silt loam, and cambisol). Mineralization amounted to 12.40% of applied ¹⁴C after 28 days showing a distinct lag phase until day 7 of incubation. Portions of radioactivity extractable by means of 0.01 M CaCl₂ solution (bioavailable fraction) decreased rapidly and were 4.41% after 28 days. Even immediately after application, only 57.31% were extracted with the aqueous solvent. Subsequent extraction using accelerated solvent extraction (ASE; acetonitrile/water 4:1, v/v) released 39.91% of applied ¹⁴C with day 0 and 26.16% with day 28 of incubation from the samples. Non-extractable portions of radioactivity thus, increased with time amounting to 11.99% (day 0) and 65.00% (day 28). A remarkable increase was observed between 14 and 28 days correlating with the distinct increase of mineralization. No correlation was found throughout incubation with general microbial activity as determined by DMSO reduction. Analysis of the CaCl₂ and ASE extracts by radio-TLC, radio-HPLC and GC/MS revealed that CfP was rapidly cleaved to free acid clodinafop (Cf), which was further (bio-) transformed; DT₅₀ values (based on radio-TLC detection of the parent compound) were far below 1 day (CfP) and about 7 days (Cf). TLC analysis pointed to 2-(4-hydroxyphenoxy)-propionic acid as further metabolite. Due to fractionation of non-extractable residues, most of the ¹⁴C was associated with fulvic and humic acids, portions in humin fractions and non-humics were moderate and low, respectively. Using a special strategy, which included pre-incubation of the soil with CfP and then mineralization of ¹⁴C-CfP as criterion, a microorganism was isolated from the soil examined. The microorganism grew using CfP as sole carbon source with concomitant evolution of ¹⁴CO₂. The bacterium was characterized by growth on commonly used carbon sources and by 16S rDNA sequence analysis. The sequence exhibited high similarity with that of Rhodococcus wratislaviensis (99.56%; DSM 44107, NCIMB 13082).     

基于数量化理论Ⅱ的鄂西北山区坡面土壤侵蚀强度评价

水土流失既是资源问题，又是生态环境问题。土壤侵蚀对人类生存和发展构成了严重威胁，成为制约可持续发展的障碍因素。以鄂西北丹江口库区郧西县坡面径流小区为试验点，通过分析小区的实地观测数据，建立坡面土壤侵蚀定性评价指标体系，并将数量化理论II作为有效的数学方法，建立郧西县坡面径流小区土壤侵蚀强度评价模型，对参与建立模型的样本进行回归分析，其准判率达到800%以上，并且利用该模型对其他年份坡面土壤侵蚀强度实测数据进行对比验证，得到土壤侵蚀强度分级的精度较高。研究表明，建立的郧西县坡面径流小区土壤侵蚀强度评价模型有较好的适用性与可靠性，可为郧西县及类似自然地理环境的其他区域水保工作起到一定指导意义     

基于参与式社区评估法的泾河流域景观管理问题分析

参与式社区评估法既兼顾了景观管理中的地理变量,同时还将社会经济因素纳入了考虑范畴,是深入进行问题分析客观有效的方法之一。本文采用参与式社区评估法,运用问题矩阵和问题树分析,对泾河流域景观管理中存在的问题和利益相关者的认知进行了分析。研究发现,绝大多数利益相关者认为土壤侵蚀已成为第一严重的问题,其次是土地生产力低下、自然灾害、植被破坏等。尽管当地公众已经认识到了土壤侵蚀的严重危害,但在安排土地利用方式时,却很少考虑土壤侵蚀带来的危害,仍然从事着自给自足的粮食生产活动。     

Stochastic Transfer Function Model and Neural Networks to Estimate Soil Moisture1

Abstract: A practical methodology is proposed to estimate the three‐dimensional variability of soil moisture based on a stochastic transfer function model, which is an approximation of the Richard’s equation. Satellite, radar and in situ observations are the major sources of information to develop a model that represents the dynamic water content in the soil. The soil‐moisture observations were collected from 17 stations located in Puerto Rico (PR), and a sequential quadratic programming algorithm was used to estimate the parameters of the transfer function (TF) at each station. Soil texture information, terrain elevation, vegetation index, surface temperature, and accumulated rainfall for every grid cell were input into a self‐organized artificial neural network to identify similarities on terrain spatial variability and to determine the TF that best resembles the properties of a particular grid point. Soil moisture observed at 20 cm depth, soil texture, and cumulative rainfall were also used to train a feedforward artificial neural network to estimate soil moisture at 5, 10, 50, and 100 cm depth. A validation procedure was implemented to measure the horizontal and vertical estimation accuracy of soil moisture. Validation results from spatial and temporal variation of volumetric water content (vwc) showed that the proposed algorithm estimated soil moisture with a root mean squared error (RMSE) of 2.31% vwc, and the vertical profile shows a RMSE of 2.50% vwc. The algorithm estimates soil moisture in an hourly basis at 1 km spatial resolution, and up to 1 m depth, and was successfully applied under PR climate conditions.     

城市老工业区土壤重金属污染状况与健康风险评价

本文对西部某老工业区土壤中As、Pb、Cr、Cd、Hg、Zn的含量、空间分布状况展开了研究,并依据《污染场地风险评估技术导则》对该老工业区的健康风险进行了评价。研究结果表明,该老工业区土壤重金属污染严重,6种元素与陕西土壤背景值相比超标100%,表明其不适宜作为居住用地开发。健康风险评价结果显示,As、Pb、Cr、Cd元素的非致癌风险值分别为3.83、1.7、1.94、1.09,均超过非致癌风险可接受值1,表明该老工业区对人们存在非致癌健康风险;对于致癌风险,As、Cr、Cd元素的致癌风险值远大于致癌风险边界值,分别超过致癌风险值的2个数量级(2.64×10-4)、4个数量级(1.94×10-2)、1个数量级(6.12×10-5),表示As和Cr已经达到了显著致癌风险的水平。     

铅锌冶炼厂周边农田土壤、苕子与荠菜的重金属污染特征

在云南某铅锌矿冶炼厂周边农田,采集当地主要绿肥(苕子)与野菜(荠菜)的植株和根部土壤样品,测定重金属(Pb、Zn、Cu和Cd)的全量和DTPA提取的有效态质量比,并进行污染评价.结果表明:1)综合污染指数评价显示,铅锌冶炼厂周边农田土壤以重度和中度重金属污染为主,Cd质量比为GB 15618-1995《土壤环境质量标准》三级标准限值的1.94～8.30倍,污染程度最重,其次为Pb和Zn;2)荠菜植株Pb、Zn和Cd质量比的最大值、平均值均大于苕子;荠菜对Cd的富集系数大于1,对Pb、Zn和Cd的转移系数大于或接近1;3)苕子和荠菜地上部与土壤的Cd、Pb质量比,苕子地下部与土壤的Pb质量比,荠菜地上部与土壤的Zn质量比均呈显著或极显著正相关.研究表明:铅锌冶炼厂周边农田存在严重的重金属污染,Cd是主要污染因子;苕子和荠菜植株重金属质量比高,且荠菜对重金属的富集能力大于苕子.