Trace Elements In Agricultural Soils Research Articles

Effects of anthropogenic and natural environmental factors on the spatial distribution of trace elements in agricultural soils

The concentrations of trace elements in agricultural soils directly affect the ecological security and quality of agricultural products. A comprehensive study aimed at quantitatively analyze the effects of anthropogenic and natural environmental factors on the spatial distribution of heavy metals (HMs) and selenium (Se) in agricultural soils in a typical grain producing area of China. Factors considered in this study were parent rock, soil physicochemical properties, topography, precipitation, mine activity, and vegetation. Results showed that the median values of Zn, Cd, Cr, and Cu of 111 topsoil samples exceeded the background values of Guangxi province but were lower than the relevant national soil quality standards, and 85% of soil samples were classified as having rich Se levels (0.40 −3.0 mg kg−1). The potential ecological risk index of soil heavy metals as a whole was low, with Cd in 9% of the samples posing moderate ecological risk. The concentrations of heavy metals and Se were relatively high in soils from shale rock. Soil properties, mainly Fe2O3 and Mn played a dominant role on soil HMs and Se concentrations. Based on GeoDetector, we found that the interaction effects of two factors on the spatial differentiation of soil HMs and Se were greater than their sum effect. Among the factors, Mn enhanced the explanatory power of the model the most when interacting with other factors for soil Zn; the greatest interactive effect was between distance from mining area and Mn for Cd (q = 0.70); Fe2O3 significantly promoted the spatial differentiation of soil Cr, Cu and Se when interacting with other factors (q > 0.50). These findings contribute to a better understanding of the factors that drive the distribution of HMs and Se in agricultural soils.

Trace Elements in Agricultural Soils of Saanich Peninsula, Vancouver Island: Concentrations Trend Over Time, Mobility in Soils and Their Sources

Trace Elements in Agricultural Soils of Saanich Peninsula, Vancouver Island: Concentrations Trend Over Time, Mobility in Soils and Their Sources

Assessment of bioavailability and mobility of major and trace elements in agricultural soils collected in Port St Johns, Eastern Cape, South Africa using single extraction procedures and pseudo-total digestion.

The aim of this study was to evaluate the applicability of ultrasound assisted single extraction and pseudo-total digestion procedures to investigate the bioavailability and mobility of major and trace elements collected from agricultural soil collected in Mzimvubu farmstead area located in Port St Johns, Eastern Cape Province (South Africa). The potential metal availability was assessed using complexing agent (ethylenediaminetetraacetic acid (EDTA)), mild (cacium chloride (CaCl2) and ammonium nitrate (NH4NO3)), deionized water and acidic (CH3COOH) extractants with the assistance of ultrasound to evaluate mobility and bioavailability of metals. The ultrasound radiation was used to assist the single extraction of major and trace metals from agricultural soils as well shortening the extraction time. The pseudo-total metal content in agricultural soils was obtained using pseudo-total digestion employing aqua-regia. The results obtained using different solvents for single extraction procedures, revealed that higher extraction of Al (256-681mgkg-1), Fe (172-430mgkg-1) and Mn (35-136mgkg-1), was observed compared to other metals. Among the investigated solvents, deionized water, acetic acid and EDTA proved to be the most aggressive extractants. The geo-accumulation index (2-6) and contamination factor (3-6) demonstrated that Fe, Cr, Mn, Co, Cu, Ni, and Zn could pose significant environmental contamination risk. Based on the results obtained, it can be concluded that the high levels of some studied metals was due to anthropogenic activities. The online version contains supplementary material available at 10.1007/s40201-020-00581-x.

Source apportionment of and potential health risks posed by trace elements in agricultural soils: A case study of the Guanzhong Plain, northwest China

A comprehensive study aimed at improving the understanding of trace elements (TEs) pollution of agricultural soils on Guanzhong Plain, northwest China, was performed. We apportioned the sources of TEs using various methods, and assessed the health risks for inhabitants by exposure to TEs. The results showed that the mean concentration of 9 TE A, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn of 227 topsoil samples exceeded the background contents for the Guanzhong Plain but were lower than the relevant national soil quality standards. The total non-cancer risk values for adults and children were 4.3 and 9.5, respectively, and the total carcinogenic risks were 2.1 × 10−3 and 4.7 × 10−3, respectively. All these values were cause of the high health risk, and the results indicated that children were more susceptible than adults to environmental pollutants. Furthermore, Cr was the primary hazardous metal element to human health in agricultural soil, followed by Cu and As. Natural materials are the dominant sources of TEs to agricultural soil on the Guanzhong Plain, contributing 48% by mass of the total TE burden. Agricultural activities and traffic emissions contributed 29.4% and 22.6%, respectively, of the total TE burden. Even though natural source contributed most to the TE contents, anthropogenic sources contributed far more to the potential health risks posed to inhabitants of the study area. Our results show that health risk assessment in combination with TE source apportionment can serve as highly effective method in identification of primary harmfulness pollution source in the future.

Trace element concentrations in mineral phosphate fertilizers used in Europe: A balanced survey

Mineral phosphate (P) fertilizers contain trace elements (TE) and can be a long-term source of these elements in soil. This study aimed to survey TE concentrations in mineral P fertilizers consumed in 25 of the EU-28 countries plus Norway (EU-28+1), to improve estimates of the EU wide input of TEs in agricultural soils. Different mineral P fertilizers (n = 414) were collected from EU-28+1 with a consumption-balanced sampling strategy. The samples were analyzed by ICP-MS for 21 elements (Na, Mg, Al, P, S, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Cd, Pb, Sb and U) that had adequate analytical quality control. Trace element concentrations in the P fertilizers were positively correlated with the P content for Cd, U, V, Sb, Cr, As and Ni. In addition, two groups of rock phosphates are likely the basis of P fertilizers in EU-28+1, i.e., with a high TE/P (n = 288) and low TE/P ratio (n = 126). The TE concentrations, relative to the aqua regia soluble concentration in EU arable soils, were highest for U, followed by Cd and then by other TEs. The Cd and U concentrations showed strong association but suggest that rock phosphates with two different Cd/U ratio are used. The Cd/P2O5 ratio varied significantly among countries and averaged 28 mg Cd kg−1 P2O5. An EU weighted mean is 30 mg Cd kg−1 P2O5, based on country average data and P consumption. Both means are below earlier EU estimates, likely because of sampling bias in those surveys. About 10% of the fertilizers exceed the current European Cd limit (60 mg Cd kg−1 P2O5). This survey illustrates the importance of a consumption-balanced sampling strategy to estimate TE inputs at a large scale and provides the data necessary for risk assessment of TEs in agricultural soils.

Uptake of trace elements by vegetable plants grown on agricultural soils: Evaluation of trace metal accumulation and potential health risk

The current study investigated the concentration of trace elements in agricultural soils, water and agricultural produce collected from Port St. Johns, Eastern Cape (South Africa). Also, the potential health risk associated with consumption of vegetable crops contaminated with trace metals was investigated. The results obtained from the study revealed the presence of most trace metals in soil, water and vegetables samples (spinach). For instance, metals such as Zn, Se, Ni, Mn, Fe, Cu and Cr were detected in spinach samples and were found to be below maximum permissible level according to World Health Organization (WHO) guidelines. This implied that this agricultural produce was safe for human consumption. Similar results were obtained for soil samples, suggesting that the soil is not heavily contaminated by As, Cr, Co, Cu, Fe, Mn, Ni, Pb, Se and Zn. Furthermore, trace metals in water samples were found to be below the maximum allowed limit set by the Department of Water and Sanitation (South Africa). The calculated bioaccumulation factors (BF) from soil to leafy vegetables revealed that spinach excludes the As, Cd, Co, Cr, Cu, Ni and Pb were during metal transfer process while it accumulates Fe, Mn, Se and Zn. Furthermore, health risk index did not demonstrate any health risk to local consumers.

Oral bioaccessibility and human health risk assessment of trace elements in agricultural soils impacted by acid mine drainage

Cultivated soils around the historic mine site of Tharsis (Spain) contain elevated concentrations of As (up to 621 mg kg−1), Cu (752 mg kg−1) and Pb (2395 mg kg−1), exceeding the regional background levels and the statutory limits set for agricultural use. A site-specific health risk assessment of occupational and environmental exposures was conducted using an approach based on guidelines from regulatory agencies, refined by combining bioaccessibility and bioavailability data.Oral bioaccessibility, as determined by simulating the human digestion process in vitro (Unified BARGE Method), was largely related to total trace element concentrations in soil. Arsenic seemed to be evenly distributed among the gastric and gastro-intestinal phases (about 31%), whereas the bioaccessible fraction of pH-dependent metal cations, like Pb and Zn, was noticeably higher in the stomach (nearly 50%) than in the gastro-intestinal tract (less than 10%). Bioaccessibility assessed by single extraction with 0.43 M HNO3 was overestimated by a factor of 1.2–1.4 relative to that obtained from the BARGE method.Site-specific relative bioavailability (RBA) values of As (27.7%) and Pb (42.6%), predicted from bioaccessibility measurements through linear regression models, had little effect on the overall risk estimates. For the ingestion pathway, the RBA-adjusted cancer risk values (9.7E-05 to 2.0E-04) exceeded the regulatory threshold in all plots, and the hazard index re-calculated after adjustment of oral dose was also above the allowable limit, with values ranging from 2.5 to 4.8. However, no detrimental health effects are expected to occur through inhalation of soil particles in nearby residents.

Pollution Assessment of Trace Elements in Agricultural Soils around Copper Mining Area

Agricultural soils from Dongchuan copper mining area were sampled and analyzed to determine the concentrations of selected trace elements, namely As, Cd, Cr, Cu, Hg, Ni, Pb and Zn. The main objectives of this study were: (1) To determine the levels of trace elements and their spatial distribution in soils; (2) to evaluate the potential ecological risk; and (3) to identify the main sources of risk element pollution. The environmental risks were assessed using five different contamination and pollution indexes. Descriptive and exploratory statistical analyses were performed to identify the relations among the trace elements in soils and possible sources of pollution. Although the values of As, Cu and Zn in the soils were significantly higher than Yunnan background values and exceeded the limits of the Chinese national standards in several sampling points, the most serious threat for the ecosystem and human health was represented by Cd. The main sources of Cu and As were identified mining activities, airborne particulates from smelters and the weathering of tailings, and partly also agricultural fertilizers. The major source of Cd was agricultural fertilizers and partly sources associated with mining and smelting activities.

Geochemical distribution of major and trace elements in agricultural soils of Castilla-La Mancha (central Spain): finding criteria for baselines and delimiting regional anomalies.

Castilla-La Mancha (central Spain) is a region characterized by significant agricultural production aimed at high-quality food products such as wine and olive oil. The quality of agricultural products depends directly on the soil quality. Soil geochemistry, including dispersion maps and the recognition of baselines and anomalies of various origins, is the most important tool to assess soil quality. With this objective, 200 soil samples were taken from agricultural areas distributed among the different geological domains present in the region. Analysis of these samples included evaluation of edaphological parameters (reactivity, electrical conductivity, organic matter content) and the geochemistry of major and trace elements by X-ray fluorescence. The dataset obtained was statistically analyzed for major elements and, in the case of trace elements, was normalized with respect to Al and analyzed using the relative cumulative frequency (RCF) distribution method. Furthermore, the geographic distribution of analytical data was characterized and analyzed using the kriging technique, with a correspondence found between major and trace elements in the different geologic domains of the region as well as with the most important mining areas. The results show an influence of the clay fraction present in the soil, which acts as a repository for trace elements. On the basis of the results, of the possible elements related with clay that could be used for normalization, Al was selected as the most suitable, followed by Fe, Mn, and Ti. Reference values estimated using this methodology were lower than those estimated in previous studies.

Distribution Assessment and Source Identification Using Multivariate Statistical Analyses and Artificial Neutral Networks for Trace Elements in Agricultural Soils in Xinzhou of Shanxi Province, China

Multivariate statistical analyses were used to assess the contents and distributions of trace elements in agricultural soils in Xinzhou of Shanxi Province, China, and to identify their sources. Samples with high levels of trace elements were concentrated in eastern Xinzhou, with contents declining from the east to west. Principal component and redundancy analyses revealed strong correlations among Co, Cu, Mn, Ni, Se, V, and Zn contents, suggesting that these elements were derived from similar parent materials. There were also strong correlations between the contents of these elements and soil properties. Contents of Cd and Pb were significantly higher in the agricultural soil samples than in the background soil samples (P < 0.05), and were higher in areas with higher levels of gross domestic product but decreased with distance to the nearest road. Therefore, human activities appear to have a strong influence on the Cd and Pb distribution patterns. A novel artificial neural network (ANN) model, using environmental input data, was used to predict the soil Cd and Pb contents of specified test dates. The performances of the ANN model and a traditional multilinear model were compared. The ANN model could successfully predict Cd and Pb content distributions, projecting that soil Cd and Pb contents will increase by 128% and 25%, respectively, by 2020. The results thus indicated that the economic condition of an area has a greater effect on trace element contents and distributions in the soil than the scale of the economy itself.

Identifying the Sources and Contamination Status of Potentially Toxic Trace Elements in Agricultural Soils

ABSTRACTElevated concentrations of potentially toxic trace elements in agricultural soils contribute to soil pollution affecting food quality and safety. We assessed pollution levels in agricultural systems, lowland rice (LL) and highland cash crops (HL), by comparing with non-agricultural soils (NA). Correlation analysis and principal component analysis (PCA) were performed, and geo-accumulation index (Igeo) and pollution loading index (PLI) were calculated. Zinc in LL, and Cd in LL and HL, were significantly higher than in NA. The Igeo values of cooper (Cu), lead (Pb), nickel (Ni), zinc (Zn), and cadmium (Cd) ranged from uncontaminated to moderately contaminated (Class 0 to 2) for LL, HL, and NA. Overall, trace element levels were categorized as unpolluted based on PLI. Soil properties significantly correlated with Cu, Pb, Ni, and Zn concentrations but not with Cd. Based on PCA, sources of origin for Cu, Pb, Ni, and Zn were lithogenic, while the sources for Cd was anthropogenic in the studied agricultural soils.

Fractionation of trace elements in agricultural soils using ultrasound assisted sequential extraction prior to inductively coupled plasma mass spectrometric determination

The main objectives of this study were to determine the concentration of fourteen trace elements and to investigate their distribution as well as a contamination levels in selected agricultural soils. An ultrasonic assisted sequential extraction procedure derived from three-step BCR method was used for fractionation of trace elements. The total concentration of trace elements in soil samples was obtained by total digestion method in soil samples with aqua regia. The results of the extractable fractions revealed that most of the target trace elements can be transferred to the human being through the food chain, thus leading to serious human health. Enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), risk assessment code (RAC) and individual contamination factors (ICF) were used to assess the environmental impacts of trace metals in soil samples. The EF revealed that Cd was enriched by 3.1–7.2 (except in Soil 1). The Igeo results showed that the soils in the study area was moderately contaminated with Fe, and heavily to extremely polluted with Cd. The soil samples from the unplanted field was found to have highest contamination factor for Cd and lowest for Pb. Soil 3 showed a high risk for Tl and Cd with RAC values of greater than or equal to 50%. In addition, Fe, Ni, Cu, V, As, Mo (except Soil 2), Sb and Pb posed low environmental risk. The modified BCR sequential extraction method provided more information about mobility and environmental implication of studied trace elements in the study area.

Effects of long-term irrigation with untreated municipal wastewater on soil properties and crop quality.

Irrigating crops with untreated wastewater leads to elevated concentrations of heavy metals both in soil and cultivated crops. The current study was designed to determine heavy metal (i.e., Pb, Cd, Cr, Cu, Ni, Zn, Hg) accumulation in Konya soils in selected nine sites irrigated with wastewater for over 40 years. Non-irrigated soil samples and soil samples irrigated with well water were taken as control samples. Transport of these pollutants to the wheat samples cultivated in the investigated site was also examined. The obtained results reveal that high alkaline properties and clay structure of Konya soil reduce the mobility of contaminants and cause accumulation in the top layer of soil. Intense effect of wastewater irrigation on soil EC was determined. The highest concentrations of Pb, Cr, Cu, Cd, Zn, Ni, and Hg in wastewater irrigated soil were 5.32, 37.1, 31.5, 11.4, 91.5, 134, and 0.34 mg kg(-1), respectively. Wastewater irrigated soils were strongly polluted by means of Cd (8.23-11.6 mg kg(-1)) and moderately to strongly polluted by means of Ni (47.7-134 mg kg(-1)), exceeding Maximum Admissible Concentrations for Trace Elements in Agricultural Soils and Sewage Sludge Regulation limit values of Turkey. Maximum concentrations found for Pb, Cr, Cu, Cd, Zn, and Ni in wastewater irrigated wheat grain were 8.44, 1.30, 9.10, n.d, 29.31, and 0.94 mg kg(-1), respectively. Besides, Hg was not detected in any samples of wheat grain. Based on the regulation of Turkish Food Codex, Pb contamination in wheat samples grown in the sampling site was evidenced.

Investigation of trace elements in agricultural soils by BCR sequential extraction method and its transfer to wheat plants

In this study, soil samples were collected from Edirne, Turkey in both summer and winter seasons and subjected to the modified Community Bureau of Reference (BCR) sequential extraction procedure in order to investigate the chemical partitioning of metals in soils and to predict heavy metals uptake by wheat grains which grown at the same soils. The samples were subjected to a three stage extraction procedure proposed by the BCR. The three phases that were separated out in the following order: (1) carbonate, exchangeable, (2) Fe-Mn oxides, and (3) organic matter. Metal concentrations of soil fractions and grain samples were determined by inductively coupled plasma atomic emission spectroscopy. The wheat samples were prepared to analysis using microwave acid digestion procedure. The pseudo-total concentrations of metals were determined after aqua regia digestion. The analytical accuracy of the method was evaluated by using the Standard Reference Materials (BCR 142R Light Sandy Soil, NIST 2711 Montana Soil, and NIST 2704 Buffalo River Sediment). The sum of the metal contents obtained from the modified BCR sequential extraction procedure and pseudo-total metal contents for soil samples were used to calculate recovery values. In order to evaluate the bioavailability of metals, the relationships between the wheat-metal and soil-extractable metal concentrations were compared.

Using Multivariate Statistical and Geostatistical Methods to Identify Spatial Variability of Trace Elements in Agricultural Soils in Dongguan City, Guangdong, China

Dongguan City, located in the Pearl River Delta, South China, is famous for its rapid industrialization in the past 30 years. A total of 90 topsoil samples have been collected from agricultural fields, including vegetable and orchard soils in the city, and eight heavy metals (As, Cu, Cd, Cr, Hg, Ni, Pb, and Zn) and other items (pH values and organic matter) have been analyzed, to evaluate the influence of anthropic activities on the environmental quality of agricultural soils and to identify the spatial distribution of trace elements and possible sources of trace elements. The elements Hg, Pb, and Cd have accumulated remarkably here, incomparison with the soil background content of elements in Guangdong Province. Pollution is more serious in the western plain and the central region, which are heavily distributed with industries and rivers. Multivariate and geostatistical methods have been applied to differentiate the influences of natural processes and human activities on the pollution of heavy metals in topsoils in the study area. The results of cluster analysis (CA) and factor analysis (FA) show that Ni, Cr, Cu, Zn, and As are grouped in factor F1, Pb in F2, and Cd and Hg in F3, respectively. The spatial pattern of the three factors may be well demonstrated by geostatistical analysis. It is shown that the first factor could be considered as a natural source controlled by parent rocks. The second factor could be referred to as “industrial and traffic pollution sources”. The source of the third factor is mainly controlled by long-term anthropic activities, as a consequence of agricultural activities, fossil fuel consumption, and atmospheric deposition.

Inputs of trace elements in agricultural soils via phosphate fertilizers in European countries

Mineral fertilizers are sources of diffuse metal enrichment of agricultural soils. A survey of phosphate fertilizers (blends or raw) sold on the European market was undertaken to quantify metal input via fertilizers in European agricultural soils. A total of 196 phosphate fertilizer samples from 12 European countries were analyzed for trace metals. Analytical quality was controlled with a certified rock phosphate sample. The average metal concentrations (mg kg−1) in the fertilizers were 14.8 (Ni), 7.4 (Cd), 166 (Zn), 2.9 (Pb), 7.6 (As), and 89.5 (Cr). The trace metal concentrations were positively correlated with the P concentrations confirming that the rock phosphate was the major source of these elements. Lowest metal concentrations were generally found in samples from Scandinavian countries. At average P use, the trace metal input via fertilizers was similar to or even larger than the metal input via atmospheric deposition in European agricultural soils for Cd, As, and Cr, whereas the reverse was true for Zn, Ni, and Pb. The input of Cd in European agricultural soils has decreased from previously estimated values and the soil Cd mass balance was close to steady state on an average basis.

A multivariate analysis of the accumulation and fractionation of major and trace elements in agricultural soils in Hidalgo State, Mexico irrigated with raw wastewater

We evaluated the accumulation and distribution of major and trace elements in agricultural soils of District 03 (DR03) in the State of Hidalgo, Mexico, irrigated with raw wastewaters for an average of 20 years. Samples of topsoils (0–30 cm depth) were extracted using a modified Tessier method. Total concentrations of the species tested were in the ranges of 675−1176 mg K kg −1, 277.9–1001 mg Na kg −1, 6,708−81,854 mg Ca kg −1, 23,800−106,974 mg Mg kg −1, 9.2−123.8 mg B kg −1, 0.6−1.9 mg Cd kg −1, 11.6−27.4 mg Cr kg −1, 3.9–47.0 mg Pb kg −1. Concentrations of As and Hg were very low. Concentrations of total Cd, Cr and Pb were generally below the maximum permissible levels set by the regulations of the European Union except for cadmium, which was in the middle of the maximum European range allowed for two soils. Regarding lead, one soil (S5) could reach the maximum permissible level of the EU in 6 more years of continued irrigation. On the other hand, contents of Pb in the most mobile fractions (“e” in this work) were significant (range: 3–28%). This distribution translated into concentrations of soluble plus exchangeable lead of approximately 2 mg Pb kg −1 in three of six soils, significantly higher than the Swiss tolerance limit of 1.0 mg Pb kg −1 for mobile fractions of lead in soils. Multivariate analysis of the data (Pearson correlation and principal component analysis) quantitatively confirmed that: (i) there is a strong covariance between boron contents and several variables representing the salinity of soils (electrolytic conductivity, a variety of alkaline and alkaline−earth total and fraction concentrations). It appears that there is a problem with high boron content in soils, although the salinity is high only for one of the soils (S3); (ii) a significant correlation among irrigation time, lead content (total, fraction easily exchangeable and bound to organic matter and sulfides) and organic carbon in soils was found; (iii) another association among irrigation time, total contents of cadmium, chromium and boron, and organic carbon was observed.

Use of sorption and extraction tests to predict the dynamics of the interaction of trace elements in agricultural soils contaminated by a mine tailing accident

Over 2000 ha of agricultural soils were contaminated by a pyritic sludge and acidic waste waters coming from a spill from a mining exploitation. The affected soils were acidic with sandy-loam texture (SL), loamy with neutral pH (L), and calcareous, saline, with clay texture (Cs). The Cs soils were contaminated only with acidic waste waters. Sorption and extraction tests were applied to examine the medium-term dynamics of the interaction of trace elements (As, Cd, Cu, Pb and Zn) in the soils. The solid–soil solution distribution coefficient ( K D) was determined in soil samples taken 3 months (initial stage, 3M samples) and then nearly 2 years (final stage, 21M samples) after the accident. Distribution coefficient values ranged from the lowest values in the SL samples (from 0.2 l kg −1 for Cd and Zn to 25 l kg −1 for As) to higher values in the L and Cs soils. Lead and As had the highest K D in all soils (over 10 5 l kg −1 in the L soils). No clear dynamics pattern could be derived from these data because of the low heavy metal concentrations in the soil solution. As a complementary approach, four single extractions (0.01 and 1 mol l −1 CaCl 2; 0.05 mol l −1 EDTA; 0.43 mol l −1 CH 3COOH) were applied to soil and sludge samples. Samples derived from submitting field 3M samples to drying-wetting (DW) cycles were included to define a complete laboratory approach to predict field dynamics. Results from extraction tests indicated that changes of the trace element interaction over time depended on the soil pH and on the source of contamination. For those soils affected only by the acidic waste waters, where an increase in fixation occurred, natural processes such as diffusion controlled dynamics. For those soils contaminated by a mixed source, the dynamics of the interaction was the resultant process of the combination of the natural attenuation and the oxidation of the pyritic sludge. This latter process led to an increase in the remobilisation for those elements associated with soluble secondary minerals (Cd and Zn) and to an increase in the fixation for those elements coprecipitating with insoluble secondary minerals (Pb and As). Drying–wetting cycles were useful to predict the dynamics in the field at month–year scale. The CH 3COOH was recommended as the best test among those studied here to derive conclusions about dynamics pattern because it provided significant desorption yields in most scenarios. Acidic soils with sludge contamination represented the scenarios with the highest risk, while calcareous soils better attenuated contamination. In a longer time scale, the depletion of calcareous components needs to be controlled.

Status of trace elements in agricultural soils of Bangladesh and relationship with soil properties

An investigation was undertaken to examine the levels of various trace elements in agricultural soils of Bangladesh and to analyze their relationship with some soil properties. Trace elements under study included Cu, Zn, Mn, As, Mo, Cd, Sb, and Pb. Forty samples of top soils were collected from farmers' fields in two major agroecological regions (AEZs) of the country. The two AEZs represented separately non-calcareous (pH around 6.5, free CaCO3 absent) and calcareous (pH around 7.6, free CaCO3 present) soils. Soil samples were digested with HF-HNO3 followed by the determination of the levels of the elements by ICP-MS. Levels of trace elements varied considerably between the locations and soil types. The clay content of the non-calcareous and the organic matter plus clay content of the calcareous soils were mainly responsible for such a variation. The total contents of all the trace elements except for As in calcareous soils were much lower than the maximum acceptable limit for agricultural soils. Generally, the concentration of each trace element in calcareous soils was considerably higher than that in non-calcareous soils. The total amount of trace elements in both non-calcareous and calcareous soils followed the order: Mn ≫ Zn > Pb, Cu >As ≫ Mo, Sb > Cd.