Effects of Wastewater Irrigation on Physicochemical Properties of Soil and Availability of Heavy Metals in Soil and Vegetables

The present study investigated the impact of irrigation with wastewater on nutritional property and heavy‐metal concentrations in the soil and consequent accumulation in vegetables at sites having long‐term uses of wastewater for irrigation. Samples of irrigation water, soil, and root and shoot parts of palak plants were analyzed to determine the concentration of heavy metals. Wastewater irrigation led to increases in the total and phytoavailable heavy‐metal concentrations in the soil at all the sites. Heavy‐metal concentrations in soil under wastewater irrigation were negatively and positively correlated with soil hydrogen potential (pH) and organic carbon (OC), respectively. The enrichment factor and metal pollution index were higher at wastewater‐irrigated sites as compared to the clean water–irrigated ones. The study concludes that wastewater irrigation modified the physicochemical properties of the soil, leading to more availability of heavy metals in the soil and consequently to the plant.     

六种野草对土壤中菲的降解研究

研究了六种野草对菲污染土壤的修复作用和降解途径。通过60 d的温室盆栽试验,观察到:对菲浓度为100 mg kg-1的污染土壤,六种野草表现出了不同的去除能力:狐尾草>狗尾草>蟋蟀草>稗草>高羊茅>碱蓬。其中种植狐尾草、狗尾草、蟋蟀草的菲污染土壤菲去除率分别达到了:81.53%,78.02%和76.01%,碱蓬仅为42.86%。利用GC-MS联用仪初步研究了菲的降解途径,结果表明:菲主要按照邻苯二甲酸途径进行降解,降解产物主要有:长链正代烷烃、邻苯二甲酸酯类、长链正代醛和长链有机酸。中间产物最终进入TCA循环,降解为二氧化碳和水。     

A technique for the correction of measurements of iron in alfalfa tops contaminated with soil

Abstract

A technique is described for the correction of abnormally high iron concentrations measured by X‐ray fluorescence spectrometry in alfalfa tops contaminated with soil. By adding to alfalfa samples, known amounts of different soils representative of the textural types occurring in the sampling area, the concentration of iron and aluminium in the contaminating soil was determined by subtracting the concentrations of the elements in the uncontaminated controls. A single regression equation relating concentrations of iron in the contaminating soil as a function of soil aluminium was suitable for correcting iron concentrations measured in all plants contaminated with soils of a loamy texture. Another regression equation was derived to correct values of iron in plants contaminated with sandy soils.     

Characterization of soil heavy metal pools in paddy fields in Taiwan: chemical extraction and solid-solution partitioning

Background, aim, and scope  Ongoing industrialization has resulted in an accumulation of metals like Cd, Cu, Cr, Ni, Zn, and Pb in paddy fields across Southeast Asia. Risks of metals in soils depend on soil properties and the availability of metals in soil. At present, however, limited information is available on how to measure or predict the directly available fraction of metals in paddy soils. Here, the distribution of Cd, Cu, Cr, Ni, Zn, and Pb in 19 paddy fields among the total, reactive, and directly available pools was measured using recently developed concepts for aerated soils. Solid-solution partitioning models have been derived to predict the directly available metal pool. Such models are proven to be useful for risk assessment and to derive soil quality standards for aerated soils. Material and methods  Soil samples (0–25 cm) were taken from 19 paddy fields from five different communities in Taiwan in 2005 and 2006. Each field was subdivided into 60 to 108 plots resulting in a database of approximately 3,200 individual soil samples. Total (Aqua Regia (AR)), reactive (0.43 M HNO₃, 0.1 M HCl, and 0.05 M EDTA), and directly available metal pools (0.01 M CaCl₂) were determined. Solid-solution partitioning models were derived by multiple linear regressions using an extended Freundlich equation using the reactive metal pool, pH, and the cation exchange capacity (CEC). The influence of Zn on metal partitioning and differences between both sampling events (May/November) were evaluated. Results  Total metals contents range from background levels to levels in excess of current soil quality standards for arable land. Between 3% (Cr) and 30% (Cd) of all samples exceed present soil quality standards based on extraction with AR. Total metal levels decreased with an increasing distance from the irrigation water inlet. The reactive metal pool relative to the total metal content is increased in the order Cr << Ni = Zn < Pb < Cu < Cd and ranged from less than 10% for Cr to more than 70% for Cd. Despite frequent redox cycles, Cd, Pb, and Cu appear to remain rather reactive. The methods to determine the reactive metal pool in soils yield comparable results, although the 0.43 M HNO₃ extraction is slightly stronger than HCl and EDTA. The close correlation between these methods suggests that they release similar fractions from soils, probably those reversibly sorbed to soil organic matter (SOM) and clay. The average directly available pool ranged from less than 1% for Cu, Pb, and Cr to 10% for Ni, Zn, and Cd when compared to the reactive metal pool. For Cd, Ni, Zn, and to a lesser extent for Cu and Pb, solid-solution partitioning models were able to explain up to 93% (Cd) of the observed variation in the directly available metal pool. CaCl₂ extractable Zn increased the directly available pool for Ni, Cd, and Cu but not that of Pb and Cr. In the polluted soils, the directly available pool was higher in November compared to that in May. Differences in temperature, rainfall, and changes in soil properties such as pH are likely to contribute to the differences observed within the year. The solid-solution partitioning model failed to explain the variation in the directly available Cr pool, probably because Cr is present in precipitates rather than being adsorbed onto SOM and clay. Despite obvious differences in parent material, source of pollution, climate, and land use, solid-solution partitioning of Cd in paddy fields studied here was similar to that in soils from Belgium and the Netherlands. Discussion  To assess risks of metals in soils, both analytical procedures as well as models are needed. The three methods tested here to determine the reactive metal pool are highly correlated and either of these can be used. The directly available pool was predicted most accurately by the 0.43 M HNO₃ method. The similarity of metal partitioning in paddy soils compared to well-drained soils suggests that changing redox conditions in paddy fields have a limited effect on the geochemical behavior of metals like Cd, Ni, and Zn. Small but significant differences in the directly available metal pool during the year suggest that redox cycles as well as differences in rainfall and temperature affect the size of the directly available metal pool. The large observed spatial heterogeneity of contaminant levels requires ample attention in the setup of soil monitoring programs. Conclusions  The directly available pool (0.01 M CaCl₂) of Cd, Zn, and Ni in paddy fields can be described well by an extended Freundlich model. For Cu and Pb, more information on dissolved organic carbon is needed to obtain a more accurate estimate of the directly available pool. Recommendations and perspectives  Soil testing protocols and models used in risk assessment consider the availability of pollutants rather than the total metal content. Results from extensive testing indicate that approaches developed for nontropical regions can be applied in paddy fields as well for metals like Cd, Ni, and Zn. This study shows that the chemical behavior under drained conditions in paddy fields is comparable to that observed in soils across the European Union, which allows regions with large scale soil pollution including Taiwan to apply such concepts to derive meaningful experimental protocols and models to assess risks of metals in soils.     

Accuracy of seven vapour intrusion algorithms for VOC in groundwater

Background, aim and scope  During the last decade, soil contamination with volatile organic contaminants (VOC) received special attention because of their potential to cause indoor air problems. Moreover, research has shown that people spend 64% to 94% of there time indoors; therefore, the indoor air quality is of a primary importance for exposure to VOC. Human health risks to VOC—in cases of soil contamination—are often dominated by the exposure route ‘inhalation of indoor air’. Exposure is often a result of vapour transport from the soil or groundwater to the indoor air of the building. Within human health risk assessments, a variety of algorithms are available that calculate transfer of soil gas to the indoor air. These algorithms suffer from a relatively high uncertainty due to a lack of representation of spatial and temporal variability. For such an application, these algorithms need to be further verified empirically against field observations so that they can be sufficiently reliable for regulatory purposes. This paper presents the accuracy for seven algorithms by using observed and predicted soil and indoor air concentrations from three sites, where the groundwater had been contaminated with aromatic and chlorinated VOC. Materials and methods  The algorithms for vapour intrusion that are frequently used in European countries were included in this study and were Vlier–Humaan (Flanders), CSoil (Netherlands), VolaSoil (Netherlands), Johnson & Ettinger (USA), Risc (United Kingdom), and the dilution factor (DF) algorithms from Sweden and Norway. Three sites were investigated in more detail and samples were taken synoptically from the groundwater, soil and indoor air on four occasions. On the petroleum sites, the aromatic hydrocarbons benzene, toluene, ethylbenzene and xylenes were analysed and, on the dry cleaning sites, the chlorinated hydrocarbons tetrachloroethylene, trichloroethylene and cis 1,2-dichloroethene. To increase spatial resolution, measurements in groundwater and soil air were taken in three different zones at each site, in the close proximity of or in the building. During sampling, several relevant soil properties were measured like the bulk density, water and air filled porosity, soil temperature and depth of the groundwater. Also, building properties like the dimensions of the building and the quality of the floor were registered. The seven algorithms were applied to compare that observed with the predicted concentrations in soil and indoor air. The groundwater concentrations were used as a source contamination. The results from the algorithms were compared by using performance criteria to assess the accuracy of each algorithm. Results  All calculations are presented in a box plot that contains the predicted soil or indoor air versus the observed concentrations. Results from the applied criteria are presented for each algorithm. Discussion  Differences between predictions and observations were up to three orders of magnitude and can be partially related to the amount of parameters included in each algorithm and the mathematical concept used. For example, the inclusion or exclusion of a capillary fringe or temperature correction for the Henry constant: it is not clear why all algorithms tend to over-predict the soil air concentration. The prediction mostly starts with the calculation of a soil air concentration related to the Henry constant, followed by diffusive and/or convective transport to the soil surface and zone of influence around the building foundation. Further research is needed to investigate the over-predictions and the use of the Henry constant to calculate the soil air concentration should be reviewed. Conclusions  The algorithms with the highest accuracy were the Johnson and Ettinger and the Vlier–Humaan algorithms. The DF algorithms from Sweden and Norway resulted in higher over- and underpredictions than others. Results for the indoor air showed that all the algorithms calculate high and low concentrations in the indoor air when compared to observations. The algorithms with the highest accuracy were JEM, Vlier–Humaan and CSoil. The DF algorithm from Norway calculated concentrations that were frequently higher than observed concentrations and the Swedish DF algorithm showed frequent higher and lower concentration than observed. The conservatism of the most accurate algorithms is sufficient for regulatory purposes, and they can trigger an integrated programme of field observations (monitoring) or/and modelling. Recommendations and perspectives  The dataset used for this paper was derived from three sites with groundwater contamination and further verification of these algorithms should be done for other sites that have a vadose zone contamination.     

老工业基地环境污染形成机制研究——以株洲市清水塘工业区为例

在株洲市清水塘地区环境污染现状的基础上,从政策体制、地理分布格局、能源结构及产业结构4个方面分别对污染的原因进行了分析,从而为老工业基地如何解决其自身矛盾,减轻环境污染,在新时期如何实现可持续发展提供了依据。     

河北省农药安全使用影响因素及对策研究

对河北省农村地区农药污染和安全使用的调查显示,经济效益、安全意识、农药管理和残留检测以及植物保护技术水平是影响河北省农村地区农药安全使用的主要因素。在此基础上提出了相应的对策和建议。     

复合微生物制剂对糙皮侧耳菌丝生长和子实体产量的影响

试验结果表明，复合微生物制剂能促进糙皮侧耳菌丝生长，降低污染率，改善子实体品质，显著提高生物学效率。生料栽培中，添加1．0％复合微生物制剂可使污染率下降31．7％，生物学效率提高79．6％。发酵料栽培中，添加0．5％复合微生物制剂可使污染率下降12．5％，生物学效率提高42．4％。     

犬体表犬弓首蛔虫虫卵的污染调查

对 30只肉用犬和护院犬以及 2 5只伴侣犬体表犬弓首蛔虫虫卵的污染情况进行调查 ,结果表明 ,肉用犬和护院犬的污染率为 30 % ,伴侣犬的污染率为 1 6% ,并以丙硫咪唑对患犬或带虫犬进行了驱虫试验 ,效果为 1 0 0 %。     

南宁市蔬菜基地土壤重金属含量及评价

通过调查和采样分析结果表明,南宁市蔬菜基地土壤重金属平均含量分别为Cd 0.33 mg/kg、Hg 0.15 mg/kg、As 27.7 mg/kg、Pb 46.7 mg/kg、Cr 133 mg/kg。部分蔬菜基地土壤受到不同程度重金属污染,主要污染物为Cd,其平均单项污染指数为1.10。全市平均综合污染指数为0.91。