Deposition and storage of solid-bound heavy metals in the floodplains of the River Geul (the Netherlands)

Because of past mining activities, the floodplains of the River Geul are polluted with heavy metals. The continuous supply of fresh sediments during floods has caused the floodplain soils to exhibit large quality variations in time. By measurements of ¹³⁷Cs deposition rates in part of the floodplain area were determined at 0.4 to 2.7 cm yr^–1. Analysis of soil metal concentrations at various depths at 65 locations, revealed that the upper 40 cm of the soil profile deposited during the past 30–45 yr, exhibit the highest metal levels. The geostatistical interpolation technique kriging was used to map actual and past pollution patterns. It was shown that, as a result of variable deposition rates, the spatial correlation structure of soil metal concentrations becomes less clear with increasing depth/age. Kriged maps of average metal concentrations in the upper 100 cm of the soil profile provided the basis for the calculation of the mass storage of heavy metals.     

Effect of biosludge and biofertilizer amendment on growth of Jatropha curcas in heavy metal contaminated soils

The pot experiments were conducted to evaluate the effect of different concentrations of arsenic, chromium and zinc contaminated soils, amended with biosludge and biofertilizer on the growth of Jatropha curcas which is a biodiesel crop. The results further showed that biosludge alone and in combination with biofertilizer significantly improved the survival rates and enhanced the growth of the plant. With the amendments, the plant was able to grow and survive upto 500, 250 and 4,000 mg kg(-1) of As, Cr and Zn contaminated soils, respectively. The results also showed that zinc enhanced the growth of J. curcas more as compared to other metals contaminated soils. The heavy metal accumulation in plant increased with increasing concentrations of heavy metals in soil, where as a significant reduction in the metal uptake in plant was observed, when amended with biosludge and biofertilizer and biosludge alone. It seems that the organic matter present in the biosludge acted as metal chelator thereby reducing the toxicity of metals to the plant. Findings suggest that plantation of J. curcas may be promoted in metal contaminated soils, degraded soils or wasteland suitably after amending with organic waste.     

Chemical, biochemical, and biological impact of untreated domestic sewage water use on Vertisol and its consequences on wheat (Triticum aestivum) productivity

In the peri-urban areas of central India, sewage water is a valuable resource for agricultural production. In this study, impact of domestic sewage water irrigation for 5 years on Vertisol with no previous history of sewage irrigation was investigated in an ongoing field experiment at Bhopal (India) under subtropical monsoon type climate. The wheat (Triticum aestivum) crop was grown during post-rainy winter season with 30 cm of irrigation (groundwater or sewage water) and four nutrient treatments (T₁, 0; T₂, 100%; T₃, 50%; and T₄, 50% of general recommended doses of NPK + FYM at 10 Mg/ha). Results showed that sewage irrigation of about 150 cm over a period of 5 years resulted significant increases in salinity as well as available fractions of N, P, K, and micronutrients, viz., Zn, Fe, and Mn in soils. Carbon and phosphorus applied through sewage water were accumulated more in subsoil layer compared to topmost plough layer. Soil microbiological activity, as indicated by soil respiration, microbial biomass C, as well as dehydrogenase enzyme activity was higher in sewage water-irrigated soils. There was also significant increase in fungal and actinomycetes as well as total coliform population in such soils. Nutrients supplied through sewage water were not able to raise the productivity of wheat to the level that obtained through fertilizers at the recommended level which indicated that additional nutrients through fertilizers are required to obtain higher productivity of wheat under sewage farming. Protein and Zn content in wheat grains were more when the crop was grown with sewage irrigation. Overall results show that except for increase in coliform population, short duration (5 years) of municipal sewage water irrigation did not have any appreciable harmful effect on soil quality as well as crop productivity; rather, it proved beneficial in improving soil fertility, wheat productivity, and produce quality.     

A proposed methodology to determine accuracy of location and extent of geographically isolated wetlands

The disposal of industrial and sewage water is a problem of increasing importance throughout the world. In India, and most of the developing countries untreated sewage and industrial wastes are discharged on land or into the running water streams which is used for irrigating crops. These wastes often contain high amount of trace elements which may accumulate in soils in excessive quantities on long term use and enter the food chain through absorption by the plants. Among the trace metals, Cd has received the greater attention because of its easy absorption and accumulation in plants and animals to levels toxic for their health. The objective of this study conducted in three industrially different cities viz., Ludhiana, Jalandhar and Malerkotla was to monitor the extent of Cd accumulation in soils and plants receiving untreated sewage water. Plant and soil samples were collected from sewage and tubewell irrigated areas. Soil samples were analysed for texture, pH, EC, organic carbon (OC), CaCO(3), bioavailable DTPA-Cd and plant samples were analysed for total Cd. In sewage irrigated soils, the mean values of pH were lower but organic carbon and electrical conductivity were generally higher both in surface and sub-surface layers of all the three cities as compared to tubewell irrigated soils. The mean DTPA- extractable Cd in sewage irrigated soil was 6.3- and 4.36-fold in Ludhiana, 3.38- and 1.71-fold in Jalandhar and 3.35- and 6.67-fold in Malerkotla in 0-15 and 15-30 cm soil depth, respectively, compared with the values in tubewell irrigated soils. The accumulation of DTPA-Cd in sewage irrigated soils was restricted to 30 cm depth after which the values were generally close to values in tubewell irrigated soils. Soil pH, OC, CaCO(3), clay and silt collectively accounted for 37.1%, 65.1% and 53.9% DTPA-extractable bioavailable Cd in soils of Ludhiana, Jalandhar and Malerkotla, respectively. Lower R(2) values in Ludhiana suggest that factors other than the ones mentioned may be affecting Cd availability. At all sites plants receiving sewage irrigation had elevated levels of Cd as compared to the plants receiving tubewell irrigation. The mean Cd content of sewage irrigated plants irrespective of the city was 5.96 microg g(-1) dry matter as compared to 0.98 microg g(-1) dry matter in tubewell irrigated plants. The results suggest that the intake of Cd obtained from consumption of crops grown on sewage irrigated soils would be much higher than the tolerable limits set by WHO and may, therefore, prove potentially toxic leading to various health ailments to humans and animals.     

Regional monitoring of lead and cadmium contamination in a tropical grazing land site,Thailand

An investigation was carried out to monitor Pb and Cd contamination in grazing land located near a highway. Environmental media at different distances fromhighway (soil, grass, water, cow's forage, fertilizer,manure and milk samples) were collected from three samplinglocations. Soil and grass were characterized by high metalmobility (soil with Pb: 5.25±0.71–14.59±1.17 mgkg^-1, dry mass and Cd: 0.038–0.33±0.04 mg kg^-1, dry mass and grass with Pb: 0.76±0.05–6.62±0.18 mg kg^-1, dry mass and Cd: 0.17±0.01–0.73±0.09 mg kg^-1, dry mass). One-way analysis of variane (ANOVA) was applied to find out the correlation between metal (total and bioavailable) concentrationsin the soil and the distance from roadside. In most cases, the finding showed that plants growing nearer to the highway are usually exposed to more heavy metal accumulations than those awayfrom the highway. In addition, a correlation was established between plant available metal concentrations and plant metaluptake concentrations.Analysis of fertilizer and manure showed considerable amountof metals (fertilizer with Pb: 1.53±0.06 mg kg^-1 andCd: 0.038 mg kg^-1 and manure with Pb: 2.55–3.34 mgkg^-1 and Cd: 0.14–0.31 mg kg^-1). Long termsimultaneous application of fertilizer and manure on thecommercial farm showed higher metal accumulation in the soiland plants than those of co-operative farm Considerableconcentrations of metals (Pb: 1.60–2.94 mg kg^-1 andCd: 0.025–0.19 mg kg^-1) were observed in fodder. The finding clearly demonstrated that there are seasonalvariation in total daily metal intake by individual cow (Pb:109.37 mg day^-1 (dry), 273.47 mg day^-1 (rainy) andCd: 2.02 mg day^-1 (dry), 19.62 mg day^-1 (rainy)).The provisional tolerable weekly intake of heavy metals incows is 390 g Pb and 28 g Cd per kg bodyweight in the rainy season and 156 g Pb and 2 gCd per kg body weight in the dry season. The levels of metals (Pb: 0.014 mg L^-1 and Cd: not detectable) and bio-transferfactor (10^-5–10^-4) in raw milk were found to be well below the Codex Alimentarius Commissions Draft (1997). Ouranalysis revealed that improvements on farm management give significant reduction in elevated levels of Pb and Cdin soil and plants, and however leads to minimize the amountof Pb and Cd in consumed milk.     

Pollution of intensively managed greenhouse soils by nutrients and heavy metals in the Yellow River Irrigation Region,Northwest China

The present study aimed to assess the potential ecological risk of heavy metals and nutrient accumulation in polytunnel greenhouse soils in the Yellow River irrigation region (YRIR), Northwest China, and to identify the potential sources of these heavy metals using principal component analysis. Contents of available nitrogen (AN), phosphorus (AP), and potassium (AK) in the surface polytunnel greenhouse soils (0–20 cm) varied from 13.42 to 486.78, from 39.10 to 566.97, and from 21.64 to 1,156.40 mg kg^?1, respectively, as well as AP, soil organic matter (SOM) and AK contents tended to increase significantly at the 0–20- and 20–40-cm soil layers. Heavy metal accumulations occurred in the polytunnel greenhouse soils as compared to arable soils, especially at a depth of 20 cm where Cd, Zn and Cu contents were significantly higher than arable soil. Cd and As were found to be the two main polluting elements in the greenhouse soils because their contents exceeded the thresholds established for greenhouse vegetable production HJ333-2006 in China and the background of Gansu province. It has been shown that Cd, Cu, Pb and Zn at the 0–20-cm soil layer were derived mainly from agricultural production activities, whereas contents of Cr and Ni at the same soil layer were determined by ‘natural’ factors and As originated from natural sources, deposition and irrigation water.     

Contamination assessment of arsenic and heavy metals in a typical abandoned estuary wetland—a case study of the Yellow River Delta Natural Reserve

Coastal and estuarine areas are often polluted by heavy metals that result from industrial production and agricultural activities. In this study, we investigated the concentration trait and vertical pattern of trace elements, such as As, Cd, Ni, Zn, Pb, Cu, and Cr, and the relationship between those trace elements and the soil properties in coastal wetlands using 28 profiles that were surveyed across the Diaokouhe Nature Reserve (DKHNR). The goal of this study is to investigate profile distribution characteristics of heavy metals in different wetland types and their variations with the soil depth to assess heavy metal pollution using pollution indices and to identify the pollution sources using multivariate analysis and sediment quality guidelines. Principal component analysis, cluster analysis, and pollution level indices were applied to evaluate the contamination conditions due to wetland degradation. The findings indicated that the concentration of trace elements decreased with the soil depth, while Cd increases with soil depth. The As concentrations in reed swamps and Suaeda heteroptera surface layers were slightly higher than those in other land use types. All six heavy metals, i.e., Ni, Cu, As, Zn, Cr, and Pb, were strongly associated with PC1 (positive loading) and could reflect the contribution of natural geological sources of metals into the coastal sediments. PC2 is highly associated with Cd and could represent anthropogenic sources of metal pollution. Most of the heavy metals exhibited significant positive correlations with total concentrations; however, no significant correlations were observed between them and the soil salt and soil organic carbon. Soil organic carbon exhibited a positive linear relationship with Cu, Pb, and Zn in the first soil layer (0–20 cm); As, Cr, Cu, Ni, Pb, and Zn in the second layer (20–40 cm); and As, Cr, Cu, Ni, Pb, and Zn in the third layer (40–60 cm). Soil organic carbon exhibited only a negative correlation with Cd (P?I _geo values), which averaged less than 0 in the three soil layers, this finding indicates that the soils have remained unpolluted by these heavy metals. The mean concentrations of these trace elements were lower than Class I criteria. The degradation wetland restoration suggestions have also been provided in such a way as to restore the reserved flow path of the Yellow River. The results that are associated with trace element contamination would be helpful in providing scientific directions to restore wetlands across the world.     

Transversal immission patterns and leachability of heavy metals in road side soils

Today there is consensus concerning the road traffic's role as a metal source. However, there are so far only a few studies which focus on the road side immission patterns regarding distance from roads, and especially in combination with the leachability of heavy metals down the soil profile. In this study, the aim was to analyse concentrations of traffic related metals in road side soils, at different depths and distances from roads, both to analyse the immission patterns as well as to explain the importance of the road construction design of the road side terrain. The BCR sequential extraction procedure was performed to be able to address the environmental risk in terms of metal mobility. Approximately 80 soil samples were analysed for seven metals; antimony (Sb), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), nickel (Ni) and zinc (Zn). The results showed that, depending on metal, the total metal concentrations in road side soils have increased 3-16 times compared to regional background during the last decades. Each metal had a limited dispersal distance from the roads as well as down in the soil profile and the road construction significantly affected the metal immission distance. Elevated metal concentrations were mostly found for top soils and down to 10 cm in the soil profiles. The labile fractions counted for more than 40% of the total concentrations for Cd, Cu, Ni, Pb and Zn, indicating a potential mobilization of the metals if the road side soils become disturbed. The present soil metal concentration levels are not alarming, but metals with a high accumulation rate might gradually be an upcoming problem if nothing is done to their emission sources.     

Use of sequential extraction to assess the influence of sewage sludge amendment on metal mobility in Chilean soils

In Chile, the increasing number of plants for the treatment of wastewater has brought about an increase in the generation of sludge. One way of sludge disposal is its application on land; this, however involves some problems, some of them being heavy metal accumulation and the increase in organic matter and other components from sewage sludge which may change the distribution and mobility of heavy metals. The purpose of the present study was to determine the effect of sewage sludge application on the distribution of Cr, Ni, Cu, Zn and Pb in agricultural soils in Chile. Three different soils, two Mollisols and one Alfisol, were sampled from an agricultural area in Central Chile. The soils were treated with sewage sludge at the rates of 0 and 30 ton ha(-1), and were incubated at 25 degrees C for 45 days. Before and after incubation, the soils were sequentially extracted to obtain labile (exchangeable and sodium acetate-soluble), potentially labile (soluble in moderately reducing conditions, K4P2O7-soluble and soluble in reducing conditions) and inert (soluble in strong acid oxidizing conditions) fractions. A two-level factored design was used to assess the effect of sludge application rate, incubation time and their interaction on the mobility of the elements under study. Among the metals determined in the sludge, zinc has the highest concentration. However, with the exception of Ni, the total content of metals was lower than the recommended limit values in sewage sludge as stated by Chilean regulations. Although 23% of zinc in sludge was in more mobile forms, the residual fraction of all metals was the predominant form in soils and sludge. The content of zinc only was significantly increased in two of the soils by sewage sludge application. On the other hand, with the exception of copper, the metals were redistributed in the first four fractions of amended soils. The effect of sludge application rate, incubation time and their interaction depended on the metal or soil type. In most cases an increase in more mobile forms of metals in soils was observed as the final effect.     

Assessment of the effects of Cr, Cu, Ni and Pb soil contamination by ecotoxicological tests

This study aimed to assess soil quality by chemical and ecotoxicological investigations and to check the correspondence between soil metal concentrations and ecotoxicity. For these purposes, surface soils collected at four adjacent roadside urban parks and at a former industrial area were characterized for C/N, organic matter content, texture, and pH. Cr, Cu, Ni and Pb, chosen among the most representative soil metal contaminants, were measured as total content and as available and water soluble fractions. In addition, the total concentrations of the investigated metals were used to calculate two chemical indices: the contamination and the potential ecological risk factors. The toxicity of the investigated soils was evaluated by an ecotoxicity test battery carried out on both soil samples (Vibrio fischeri, Heterocypris incongruens and Sinapis alba) and elutriates (Vibrio fischeri, Daphnia magna and Selenastrum capricornutum). The findings, both by the chemical and ecotoxicological approaches, would suggest that the soils with high metal contamination pose ecological risks. On the other hand, moderately metal contaminated soils did not exclude soil ecotoxicity. In fact, toxic effects were also highlighted in soils with low metal content, toxicity being affected by metal availability and soil characteristics. Moreover, the results suggest the importance of using a battery of tests to assess soil ecotoxicity.     

Effect of new organic supplement (Panchgavya) on seed germination and soil quality

We studied the suitability of Panchgavya (five products of cow), new organic amendment, application on seed germination, plant growth, and soil health. After characterization, Panchgavya was mixed with water to form different concentration and was tested for seed germination, germination index, and root and shoot growth of different seedlings. Four percent solution of Panchgavya was applied to different plants to test its efficacy. Panchgavya and other two organic amendments were incorporated in soil to test the change of soil chemical and microbiological parameters. Panchgavya contained higher nutrients as compared to farm yard manure (FYM) and vermicompost. Its application on different seeds has positively influenced germination percentage, germination index, root and shoot length, and fresh and dry weight of the seedling. Water-soluble macronutrients including pH and metal were positively and negatively correlated with the growth parameters, respectively. Four percent solution of Panchgavya application on some plants showed superiority in terms of plant height and chlorophyll content. Panchgavya-applied soil had higher values of macro and micronutrients (zinc, copper, and manganese), microbial activity as compared to FYM, and vermicompost applied soils. Application of Panchgavya can be gainfully used as an alternative organic supplement in agriculture.     

Heavy Metal Load Of Soil, Water And Vegetables In Peri-Urban Delhi

Peri-urban lands are often used for production of vegetables for better market accessibility and higher prices. But most of these lands are contaminated with heavy metals through industrial effluents, sewage and sludge, and vehicular emission. Vegetables grown in such lands, therefore, are likely to be contaminated with heavy metals and unsafe for consumption. Samples of vegetables i.e., spinach (Spinacia oleracea L.) and okra (Abelmoschus esculentus L.); soil and irrigation water were collected from 5 peri-urban sites of New Delhi to monitor their heavy metal loads. While heavy metal load of the soils were below the maximum allowable limit prescribed by the World Health Organization (WHO), it was higher in irrigation water and vegetable samples. The spinach and okra samples showed Zn, Pb and Cd levels higher than the WHO limits. The levels of Cu, however, were at their safe limits. Metal contamination was higher in spinach than in okra. Spatial variability of metal contamination was also observed in the study. Bio-availability of metals present in soil showed a positive relationship with their total content and organic matter content of soil but no relationship was observed with soil pH. Washing of vegetables with clean water was a very effective and easy way of decontaminating the metal pollution as it reduced the contamination by 75 to 100%.     

Status of heavy metals in agricultural soils as affected by different patterns of land use

This study was conducted to determine status of heavy metals in agricultural soils under different patterns of land use. A total of 38, 40 and 45 soil samples for bare vegetable field, greenhouse vegetable field, and grain crop field were respectively taken from surface layer (0–20 cm) from selected experimental areas away from suburbs of ten counties (or districts or cities) in four provinces or municipalities of Huabei plain in north China. Information of crop production history, including varieties, rotation systems and fertilizer use, at the corresponding sampling sites was surveyed. Soil total Cu, Zn, Cd, Pb, Cr, As and Hg were measured. The results showed that the contents of total Cu, Zn, Cd, Pb, Cr, As, and Hg in the soil samples, especially soil total Cu and Zn contents, were higher in the bare vegetable field and the greenhouse vegetable field than that in the grain crop field. Long-term use of excessive chemical fertilizers and organic manures in the bare vegetable field and the greenhouse vegetable field contributed to the accumulation of Cu, Zn, and other heavy metals in the soils. The contents of total Cu, Zn, and other heavy metals in soils increased with increasing vegetable production history of the research areas. In comparison with the grain crop field, the comprehensive pollution indices of the seven soil heavy metals and the single-factor pollution indices of soil Zn, Cu, Cd, Cr, and Hg based on the second criterion of Environmental Quality Standard for Soils were significantly higher in the bare vegetable field and the greenhouse vegetable field. Soils from the greenhouse vegetable field were slightly contaminated according to the comprehensive pollution index, and soils from the bare vegetable field and the grain crop field were at the warning heavy metal pollution level. The soils were contaminated with Cd according to the single-factor pollution index. The Cd pollution was relatively more serious in the bare vegetable field and the greenhouse vegetable field than that in the grain crop field. The soils selected with different land use patterns were not contaminated with Zn, Cu, Pb, Cr, As and Hg.     

Spatial variation of salts in a Gyanpur canal command area

This study was aimed to establish background and reference values of total heavy metals in soils from a representative area of Albania (Tirana). Thirty-eight soil samples collected from genetic horizons of major soil types of Tirana were analyzed for important physicochemical properties by standard methods and for total contents of Cd, Cr, Ni, Pb, Zn, and Cu by atomic absorption spectrometer, after extraction with aqua regia. The results showed that the total contents of Cd, Cr, Ni, Pb, Zn, and Cu in surface horizons varied widely with respective mean values of 0.3 (??0.6), 174.2 (??63.7), 305.9 (??133.0), 19.7 (??12.4), 95.5 (??26.3), and 42.7 (??6.8) mg/kg. The highest metal contents were found in two soils developed in limestone. The depth distribution of metals showed a tendency for accumulation of Cd and Pb in the surface horizons of three soils, suggesting that these metals partially come from anthropogenic inputs. Correlation analysis indicated that the metal contents of soils were controlled by soil properties, including pH, CaCO₃, clay, organic matter, cation exchange capacity, and Fe oxides. The background values (given as the 90th percentile) were much higher than those reported in the literature, showing that the levels of respective metals were naturally higher. The total metal contents of some soils were above background levels, suggesting metal pollution. The reference values for all the analyzed metals were quite consistent with those of the Dutch system. The proposed background and reference values can be used to evaluate the soil pollution with these elements.     

Long-term variability of metals from fungicides applied in amended young vineyard fields of La Rioja (Spain)

The long-term variability of total Cu content from fungicides applied in a certified wine region of Spain (La Rioja) and of other metals (Cd, Cr, Ni, Pb, and Zn) was evaluated in three young vineyard soils and subsoils unamended and amended with spent mushroom substrates (SMS) over a 3-year period (2006–2008). SMS is a promising agricultural residue as an amendment to increase the soil organic matter content but may modify the behaviour of metals from pesticide utilisation in vineyards. Fresh and composted SMS was applied each year at a rate of 25 t ha⁻¹ (dry-weight). Copper concentrations in the three unamended soils were 21.2–88.5, 25.5–77.1, and 29.4–78.4 mg kg⁻¹. They exceeded natural Cu concentrations of the region and reference sub-lethal hazardous concentration for soil organism. The concentrations of Cd, Ni, Pb, and Zn were largely below the sub-lethal limits. Thus, although Cu levels were lower than those of established vineyards, vine performance, and productivity might be affected. The variation in behaviour between different amendments for each soil was high, so a generic conclusion could not be drawn. The amendment practice seemed to have caused temporarily Cu mobilization respect to untreated soils. Total zinc concentrations fall within the range of the natural soil of La Rioja and were significantly affected (p < 0.05) especially by fresh state SMS addition, with increasing up to 75% respect to untreated specimen. The results indicated a build-up of fresh sites for metal retention at both surface and subsurface level, although no accumulation of metals was observed in the short-term period. However, the benefit for soils and the negative effects need to be monitored in the long run.     

Prediction of the solubility of zinc, copper, nickel, cadmium, and lead in metal-contaminated soils

Risk assessment of metal-contaminated soil depends on how precisely one can predict the solubility of metals in soils. Responses of plants and soil organisms to metal toxicity are explained by the variation in free metal ion activity in soil pore water. This study was undertaken to predict the free ion activity of Zn, Cu, Ni, Cd, and Pb in metal-contaminated soil as a function of pH, soil organic carbon, and extractable metal content. For this purpose, 21 surface soil samples (0–15 cm) were collected from agricultural lands of various locations receiving sewage sludge and industrial effluents for a long period. One soil sample was also collected from agricultural land which has been under intensive cropping and receiving irrigation through tube well water. Soil samples were varied widely in respect of physicochemical properties including metal content. Total Zn, Cu, Ni, Cd, and Pb in experimental soils were 2,015?±?3,373, 236?±?286, 103?±?192, 29.8?±?6.04, and 141?±?270 mg kg^?1, respectively. Free metal ion activity, viz., pZn²⁺, pCu²⁺, pNi²⁺, pCd²⁺, and pPb²⁺, as estimated by the Baker soil test was 9.37?±?1.89, 13.1?±?1.96, 12.8?±?1.89, 11.9?±?2.00, and 11.6?±?1.52, respectively. Free metal ion activity was predicted by pH-dependent Freundlich equation (solubility model) as a function of pH, organic carbon, and extractable metal. Results indicate that solubility model as a function of pH, Walkley–Black carbon (WBC), and ethylenediaminetetraacetic acid (EDTA)-extractable metals could explain the variation in pZn²⁺, pCu²⁺, pNi²⁺, pCd²⁺, and pPb²⁺ to the extent of 59, 56, 46, 52, and 51 %, respectively. Predictability of the solubility model based on pH, KMnO₄-oxidizable carbon, and diethylenetriaminepentaacetic acid-extractable or CaCl₂-extractable metal was inferior compared to that based on EDTA-extractable metals and WBC.     

杭州地区农业土壤中重金属的分布特征及其环境意义

为了分析杭州地区农业土壤重金属的分布特征及其环境意义,通过现场采样和室内分析检测的方法,对杭州市各区县不同作物农业土壤表层土中的Hg、As、Cu、Pb、Cr、Cd 6种重金属元素进行检测,并对其分布特征进行了分析。结果表明,杭州地区农业土壤中除As外,其他5种重金属的平均含量均低于且接近浙江省土壤背景值,个别采样点的重金属含量超过了土壤环境质量国家二级标准。总体上,杭州地区农业土壤处于安全水平。通过重金属的区域分布特征分析表明,余杭区和富阳市农业土壤中重金属平均含量普遍高于其他区域。萧山区和建德市部分农业土壤则存在Cu和Hg含量较高的情况,而淳安县农业土壤中重金属含量差异较大,土壤中出现了As、Cr和Cd含量最大值。不同作物的农业土壤重金属含量存在一定的差异,但不明显。水稻田和蔬菜地的土壤中,重金属含量较其他作物种植类型的土壤中含量高;叶菜类(蔬菜、茶叶)作物土壤中的Cd含量要比根茎类(水稻)、茄果类(水果)及其他作物种植类型的土壤中的含量低。目前杭州地区土壤中6种重金属含量均对作物的直接危害不大,但由于萧山区个别采样点Cu含量严重超标,淳安县土壤中Cd受外源性来源影响也已较明显,需要相关部门加大监管力度,防止污染事件发生。同时,为防止农业土壤中重金属含量进一步升高,需要加大大气降尘监测与治理、废气污染监管与控制治理。     

Laboratory-polluted soils: a methodological approach to establish equilibrium conditions for different metal chemical forms in soils

An approach based on the number of extractions performed over time was applied to study the time necessary to attain equilibrium conditions between the different chemical forms present in two natural soils laboratory-loaded with heavy metals (Cu(II), Pb(II), Zn(II)). The influence of some soil parameters, such as pH value, cation exchange capacity and organic matter content, on the equilibrium time was evidenced both by the different nature of the soils and by the treatment of soils with paper mill sludge. Equilibrium conditions were determined by studying the metal partitioning in the soil on a case by case basis. The behaviour of the three metals was not the same, and the conditions of equilibrium among the different chemical forms were the result of the amount of heavy metals added as well as of the nature of the soil.     

Sources and the distribution of heavy metals in the particle size of soil polluted by gold mining upstream of Miyun Reservoir,Beijing: implications for assessing the potential risks

Mining has been carried out upstream of Miyun Reservoir, Beijing, for several decades, and has caused metal emissions to the environment, threatening human health. We conducted a soil survey to assess metal contamination in this area and to determine distribution of heavy metals in the particle size. We attempted to determine the possible sources of the metals and the significance of metals in the fine particle fractions to soil risk assessments. Thirty-four soil samples were collected, and eight samples were partitioned into seven size fractions. Most of the metal concentrations in the soils were higher than the background levels in Beijing, and the metal concentrations and total organic matter (TOC) contents generally increased as the particle size decreased. Each metal except Hg significantly positively correlated with the TOC. The metals in the coarse-grained soils were mainly derived from parent materials, but the metals in the fine fractions were mostly anthropogenic. Statistical analyses showed that there were three metal sources: Cd, Cu, Hg, Pb, and Zn had anthropogenic sources; Co, Cr, Ni, and V had mixed anthropogenic and natural sources; and As and Be had natural sources. The trace metals were primarily in the clay and fine silt fractions, and they might pose health risks through the inhalation of resuspended soil particles (PM10 and PM2.5). The elevated accumulation factors, enrichment factors, and ecological risk indices for the metals in the fine fractions suggest that risk assessments should be based on the fine particle size.     

Soil Contamination Due to Heavy Metals from an Industrial Area of Surat, Gujarat, Western India

The pollution of soil is a source of danger to the health of people, even to those living in cities. The anthropogenic pollution caused by heavy industries enters plants then goes through the food chain and ultimately endangers human health. In the context, the knowledge of the regional variability, the background values and anthropogenic vs. natural origin of potentially harmful elements in soils is of critical importance to assess human impact. The present study was undertaken on soil contamination in Surat, Gujarat (India). The aims of the study were: i) to determine extent and distribution of heavy metals (Ba, Cu, Cr, Co, Ni, Sr, V and Zn) ii) to find out the large scale variability, iii) to delineate the source as geogenic or anthropogenic based on the distribution maps and correlation of metals in soils. Soil samples were collected from the industrial area of Surat from top 10 cm layer of the soil. These samples were analysed for heavy metals by using Philips PW 2440 X-ray fluorescence spectrometer. The data reveal that soils in the area are significantly contaminated, showing higher levels of toxic elements than normal distribution. The heavy metal loads of the soils in the study area are 471.7 mg/kg for Ba, 137.5 mg/kg for Cu, 305.2 mg/kg for Cr, 51.3 mg/kg for Co, 79.0 mg/kg for Ni, 317.9 mg/kg for Sr, 380.6 mg/kg for V and 139.0 mg/kg for Zn. The higher concentrations of these toxic metals in soils need to be monitored regularly for heavy metal enrichment.