Levels Of Heavy Metals In Soil Research Articles

Heavy Metals Accumulation in Soil Irrigated with Industrial Effluents of Gadoon Industrial Estate, Pakistan and Its Comparison with Fresh Water Irrigated Soil

Wastewater mixed with industrial effluents is used for irrigation in Gadoon Industrial estate and thus contaminating soil. This soil was tested for heavy metal content by using atomic absorption spectrophotometer (perkin elmer 700) and compared with control soil irrigated with tube well water at seven selected spots. Accumulation of the toxic metal was significantly greater in the soil irrigated with industrial effluent than control soil (p < 0.05). Manganese (Mn) was the most significant pollutant, accumulated up to 9.95 ppm in the soil irrigated with industrial waste water. It was found that the samples were containing Zn in the range of 1.596 - 6.288, Cu 0.202 - 1.236, Co 0.074 - 0.115, Ni 0.0002 - 0.544, Cr 0.243 - 0.936, Mn 3.667 - 9.955 and Pb 0.488 - 1.259 ppm. No sample was containing the heavy metal above the critical level mentioned in typical and unsafe heavy metal levels in soil.

Exploration of the spatial-Composite Risk Index (CRI) for the characterization of toxicokinetics in petrochemical active areas

The spatial modeling of the petrochemical active regions in the Niger Delta (ND), Nigeria was carried out through the analysis exploration and extraction of geospatial data and resultant risk maps were generated. The pollutants assessed include; heavy metals, polychlorinated aromatic hydrocarbons (PAHs), benzene–toluene–ethylene–xylene (BTEX), and total petroleum hydrocarbons (TPHs) and properties of the pollutants such as bioaccumulation, persistence and toxicity were used to calculate the Hazard Index (HI) and thus created a ranking system. The Composite Risk Index (CRI) was developed successively considering the concentrations of all pollutants and the computed HI using the samples collected in ND areas of Nigeria. The carcinogenic PAHs showed spatial abundance in the areas sampled and elevated levels of soil heavy metals were also observed. In this study, mathematical tool such as the artificial neural network (ANN) self-organizing map (SOM) and geostatistical analysis such as kriging were applied to develop the risk map of the areas which represent the spatial spread of the CRI. The results show that the application of spatially developed integral risk map for pollutant assessment is effective and facilitates with decision making with regards the environment and humans exposed in this region.

Potential risk effect from elevated levels of soil heavy metals on human health in the Niger delta

An analysis of the soil quality in the Niger Delta Area (NDA) was carried out to determine the severity of soil contamination. The United States Environmental Protection Agency (US EPA) risk assessment model was used in determining the potential health risk due to lifetime exposure (by means of ingestion, dermal contact and inhalation) of the population to heavy metal contents in the soil. Substantial levels of contamination were found indicating elevated levels of heavy metals above background concentrations from controlled samples in the areas. Median topsoil metal concentrations (0–15cm) in the NDA measured in mg/kg were: Zn 58.3±37.0, Cd 1.3±1.0, Cr(VI) 13.2±5.5, Cu 28.3±31.5, Pb 895.1±423.9, Ni 42.7±20.3, Mn 201.8±77.5 and Fe 1303.5±2028.6. Pb, Ni, Zn, Cd, Cr(VI), Fe and Mn exceeded some guideline and standard values; while the comprehensive levels of total metals contamination exceeded the environmental action level for soils, which could potentially affect human health. The collective total risk (carcinogenic and non-carcinogenic) for minors and adults were established from the model using the slope factors and reference dose of the compounds respectively. The study has shown that soil contamination in the industrial and residential regions are similarly significant; while the risk assessment proved that based on the pollutants concentration in the soil, metals with the highest cancer risk values (Pb=2.62E-02 and Cr(VI)=1.52E-02) have the potential of affecting the health status of the residents, especially for children in the region. The chronic daily intake of the metals are of major concern as their cumulative effect could result to several health complications of children and adults in the region.

Some physico-chemical and Heavy metal levels in soils of waste dumpsites in Port Harcourt Municipality and Environs

Various physico-chemical techniques were used to investigate the characteristics and heavy metal concentration of soils in some selected waste dumpsites in Port Harcourt. This is because the soils act asvehicles for the permeability of leachates into various levels of aquifers in the environment. The results show that the soils are moderately acidic with a mean pH value of 5.5 for the 1m subsoil and 5.8 for 30cm soil depth in the various dumpsites, while the total organic carbon (TOC) levels show that it was low with 3.41% and 2.90% for depths 30cm and 1m respectively. The cation exchange capacity (CEC) of the soils showed a range of 21.36 – 28.79 meq/100g for a depth of 30cm and 20.94 – 26.44meq/100g for a depth of 1m soil level acrossthe waste dumpsites. The textural class of the soils was observed to be a mixture of sand, clay and loam in all the sites. Low sand fractions (>40%) was observed for almost all sites except for Elekahia and Eleme roads that had 64.7% and 56.4% respectively. The results of the heavy metal concentration in all the locations of the wastedumpsites were above permissible limits. In this study, the soil did not meet up the moisture requirement for a waste land filling and could therefore be prone to porosity, surface flooding and underground water pollution. It is therefore suggested that the use of impermeable geomembrane is necessary for all dumpsites to minimizeseepage of leachates from causing pollution of both surface and groundwater resources taking into account the possibility that the containment system may be threatened by any disaster.

Heavy metal concentrations in soils and plants in the vicinity of Arufu lead-zinc mine, Middle Benue Trough, Nigeria

This study focused on the influence of base metal mining on heavy metal levels in soils and plants in the vicinity of Arufu lead-zinc mine, Nigeria. Soil samples (0–15 cm depth) and plant samples were collected from cultivated farmlands in and around the mine, the unmineralized site and a nearby forest (the control site). The samples were analyzed for heavy metals (Fe, Zn, Mn, Cu, Pb, Cr and Cd) by Atomic Absorption Spectrophotometry (AAS). The physical properties of soils (pH and LOI) were also measured. Results showed that soils from cultivated farmlands have neutral pH values (6.5–7.5), and low organic matter contents ( cassava tubers>peelings. In the same plant species, metal levels decreased in the order of Zn>Fe>Mn>Cu>Pb>Cr>Cd. Most heavy metals were found in plant parts at average concentrations normally observed in plants grown in uncontaminated soil, however, elevated concentrations of Pb and Cd were found in a few cassava samples close to the mine dump. A stepwise linear regression analysis identified soil metal contents, pH and LOI as some of the factors influencing soil-plant metal uptake.

Comparative analysis of heavy metal concentration in secondary treated wastewater irrigated soils cultivated by different crops

The use of treated urban wastewater for irrigation is a relatively recent innovation in Botswana and knowledge is still limited on its impact on soil heavy metal levels. The aim of this study is to analyze and compare heavy metal concentration in secondary wastewater irrigated soils being cultivated to different crops: olive, maize, spinach and tomato in the Glen Valley near Gaborone City, Botswana. The studied crop plots have been cultivated continuously under treated wastewater irrigation for at least 3 years. Most crop farms have sandy loam, loamy sand soils. Based on food and agriculture organization, heavy metal threshold values for crop production have been studied. Results showed that the wastewater irrigated soils in the Glen Valley have higher cadmium, nickel and copper than desirable levels, while the levels of mercury, lead and zinc are lower than the maximum threshold values recommended for crop production. The control sites show that the soils are naturally high in some of these heavy metals (e.g copper, zinc, nickel) and that crop cultivation under wastewater irrigation has actually lowered the heavy metal content. Comparing between the crops, mercury and cadmium levels are highest in soils under maize and decline linearly from maize to spinach to olive to tomato and control site. By contrast, concentrations of the other metals are at their lowest in maize and then increase from maize to spinach to olive to tomato and to control site.

Characterization of PM2.5/PM2.5–10 and source tracking in the juncture belt between urban and rural areas of Beijing

Coarse (PM2.5–10) and fine (PM2.5) atmospheric particulate samples were collected in summer and winter during 2005–2007 in the juncture belt between urban and rural areas of Beijing. Elements, ions, organic/elemental carbon (OC/EC) and polynuclear aromatic hydrocarbons (PAHs) were determined to obtain some latest information about the particulate pollution in the juncture belt of Beijing. Particulate matter levels at this site were high as compared with the levels at other sampling sites in Beijing. Pollution elements, secondary ions and PAHs were enriched in fine particles rather than in coarse particles. An obvious seasonal variation of the chemical composition of PM was observed. Source apportionment results showed that secondary components were the largest mass contributor of PM2.5, accounting for 28%; whereas soil-related sources were the largest contributor of PM2.5–10, explaining about 49% of the total mass. The abnormal levels of soil heavy metals at the electronic waste disassembly site in the upwind villages suggested the potential impact of such activities to the environment.

Environmental contamination of heavy metals from zinc smelting areas in Hezhang County, western Guizhou, China

Total heavy metal (Cd, Cr, Cu, Pb and Zn) concentrations were evaluated in smelting waste, soil, crop and moss samples collected from the Hezhang artisanal zinc smelting areas, Guizhou, China. Soil samples from the cornfield near the smelting sites contained extremely high Cd (5.8–74 mg kg−1), Pb (60–14,000 mg kg−1) and Zn (260–16,000 mg kg−1) concentrations. Elevated heavy metal concentrations were also found in corn plants and total Pb (0.80–1.5 mg kg−1) and Cd (0.05–0.76 mg kg−1) concentrations in corn grain have totally or partially exceeded the national guidance limits for foodstuff. Thus, the soil-to-crop transfer of heavy metals might pose a potential health risk to the local residents. Similar to the high heavy metal levels in soil and corn, Cd, Cr, Cu, Pb and Zn concentrations in moss samples collected from the smelting sites ranged from 10 to 110, 10 to 55, 26 to 51, 400 to 1200 and 330 to 1100 mg kg−1, respectively, exhibiting a local spatial pattern of metals deposition from the atmosphere. Based on examination of Zn/Cd and Pb/Cd ratios of the analyzed samples, we have distinguished between the flue gas dust derived and smelting waste derived metals in different environmental compartments.

The use of town refuse ash in urban agriculture around Jos, Nigeria: health and environmental risks

This paper reports on a study that examines the health and environmental risks of using town refuse ash in urban vegetable production in Jos, Nigeria, in terms of heavy metal accumulation in the food chain. Soil and crop samples, collected from five study farms, and samples of the river water used for irrigation, were analysed for seven heavy metals Fe, Mn, Zn, Cu, Ni, Cd and Pb. On the basis of the field data the paper discusses: (1) the potential soil deficiencies and toxicities; (2) the probable links between soil heavy metal levels and fertilisation practices; (3) the heavy metal concentrations in crop tissue in relation to crop growth and human health. The findings suggest that soil concentrations of the seven metals fall within ‘typical’ soil levels, and that there should not be any problems of either toxicities or deficiencies for crop growth. There was evidence of slight accumulation of Zn, Cu and Cd on some of the farms with a history of town refuse ash use. However, in all farms lettuce crops contained very large concentrations of Fe, and Pb concentrations that were 20 to 40 times higher than the WHO/FAO maximum recommended level in leafy vegetables for human consumption. The Cd content of carrot tissue was 10 times higher than the WHO/FAO recommended limit. The relatively small number of soil and crop samples precluded any formal attempt at correlating the concentrations of heavy metals found in the vegetable crops with the farm levels. Nevertheless, the data suggested that these were not linked. The paper goes on to consider various potential sources of the metals found in the crops, including irrigation water, town refuse ash and air-borne dust, and discusses additional health and environmental risks pertaining to the use of town refuse ash. Undoubtedly, the heavy Pb and Cd contamination of certain crops indicates the urgent need for future studies to ascertain the precise source of these metals, and although the practice of using town refuse ash does not appear to have resulted in large-scale contamination of soil in the farming area, there are a number of unsafe practices associated with it that call for the identification of strategies for the safe utilisation of urban waste in Jos.

Assessment of metals in soil extracts and their uptake and movement within Tamarix nilotica at Lake Nasser banks, Egypt

This study aims to determine heavy-metal levels in soil from the banks of Lake Nasser, the ability of Tamarix nilotica to accumulate such metals from soil and hence its potential for phytoextraction. Soil and Tamarix samples were collected from the banks of four bights around Lake Nasser and analysed for Fe, Mn, Ca, Mg, Cr, Cu, Ni, Zn, Cd and Pb by atomic absorption spectrometry, whereas Na and K were measured by atomic emission spectrophotometry. Three different methods of extraction were used for the soil samples. Lead, copper and zinc were equally distributed between the exchangeable phase and Fe/Mn oxide-bound form, while other measured metals were mainly present in the Fe/Mn oxide fraction. With the exception of iron, all metals studied showed total concentrations within the geochemical background values. T. nilotica exhibited elevated concentrations of Na (36.2–48.5 mg g−1) and K (2.74–4.33 mg g−1) in stems, and relatively high concentrations of Pb, Cd and Co (0.39–1.03 µg g−1, 0.24–1.3 µg g−1 and 1.94–5.3 µg g−1, respectively) are found in plant leaves. Bioaccumulation factors of Na and K (9.3 and 12.63, respectively) were high in T. nilotica stems. While the bioaccumulation of Pb, Cd, Co and Ni (2870.1, 2035.4, 10.5 and 5313.2, respectively) was high in plant leaves, Fe, Mn, Ca and Mg were accumulated relatively equally in plant stems and leaves. T. nilotica was found to secrete high amounts of Na, Ca and K, in addition to small amounts of all accumulated metals except Cd and Cu. These secreted metals appeared as salt crystals (67.5% Na; 25.8% Ca; 5% Mg; 1.5% K and 0.16% trace and minor elements) on the plant surface. The concentrations of all the metals studied in T. nilotica were higher than in the salt crystals. Statistical analysis of the database suggests bioaccumulation of these metals from soil to T. nilotica. This reflects the importance of using T. nilotica as a model in the phytoremediation process as an established environmental clean-up technology.

Use of dairy-industry sludge as fertiliser for grasslands in northwest Spain: heavy metal levels in the soil and plants

The suitability of dairy-plant sludge for fertilisation of a Cambisolic soil was investigated in northwest Spain. Soil properties (pH, electrical conductivity, organic matter content, NO3−, P, Ca, Mg, Na, K and Al) and soil and plant tissue heavy metal contents (Hg, Pb, Cd, Cu, Zn, Ni and Cr) were determined in 12 grassland plots fertilised over a 1–4-year period with dairy sludge and conventional fertiliser (cattle slurry and mineral fertilisers), and in six meadows fertilised with conventional fertilisers only. Heavy metal contents were also determined in plant tissues from different plots. There were no significant differences in soil heavy metal concentrations between the sludge-amended plots and the control plots, except for Pb concentration, which was significantly lower in the sludge-amended plots. A significant correlation between metal content in the soil and total sludge dose applied was detected only for Cr. Even in plots to which the dairy-plant sludge had been applied for 4 years, heavy metal levels in both soil and plants were within European Union and Spanish legislative limits (Council of the European Communities Council Directive of 12 June 1986 on the protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture (86/278/EEC), Official J. Eur. Communities 1986;L 181:6–12; Royal Decree 1310/1990, del 29 de octubre por el que se regula la utilizacion de los lodos de depuracion en el sector agrario, BOE 1990;262:32339–32340.) However, a number of significant metal-metal correlations (Ni–Zn, Ni–Cr, Ni–Cu, Cu–Cr, Zn–Cr and Pb–Cd) were detected in both the sludge and the sludge-amended soils, but not the non-amended soils, suggesting that the sludge is an important source of these metals. In addition, soils that had received the dairy-plant sludge had significantly higher conductivity, probably because of the NaOH used for cleaning in dairy plants. Salinity-related variables (K, NO3−) were significantly correlated with Cr and Zn concentrations in plant tissues. These findings suggest a need to assess the possible long-term effects of dairy sludge application, with the aim of developing guidelines for its use as a fertiliser.

Ectomycorrhizal diversity and community structure in oak forest stands exposed to contrasting anthropogenic impacts

We compared the ectomycorrhizal community structure of oak forest stands located in either an urban or a rural area. Urban stands had higher N deposition rates, soil heavy metal levels, and earthworm counts than rural stands. Ectomycorrhizal types were quantified on roots of mature oak (Quercus) in soil cores and on Quercus rubra L. seedlings grown in soil cores in the glasshouse. Twenty-six ectomycorrhizal types were distinguished on mature oak in rural soils versus 16 in urban soils. Nine ectomycorrhizal types were distinguished on Q. rubra seedlings grown in rural soils versus seven in urban soils. Despite fewer ectomycorrhizal types in urban soils, richness of ectomycorrhizal types per centimetre fine root of mature oak or Q. rubra seedlings did not differ between urban and rural soils. Ectomycorrhizal colonization (ectomycorrhizal tips/m fine root) was lower in urban than rural soil cores but higher on Q. rubra seedlings grown in urban versus rural soils. Fine root length per unit soil volume was higher in urban than rural stands. No difference in fine root length was observed between Q. rubra seedlings grown in urban and rural soils. These differences in ectomycorrhizal community structure between the urban and rural stands are likely due to anthropogenic impacts.Key words: air pollution, anthropogenic impacts, community structure, diversity, ectomycorrhiza, Quercus rubra.

Compost use in viticulture: Effect on heavy metal levels in soil and plants

The purpose of this study was to examine the long‐term effect of compost application on the heavy metal content in soil, leaves, and fruit of grape (Vitis vinifera). Two types of compost were tested in a vineyard. One was compost with a low heavy metal content, which was derived from sewage sludge and bark (SB compost). The other type was compost with a higher concentration of metals, which was derived from municipal solid waste (MSW compost). For 6 years, the levels of zinc (Zn), copper (Cu), nickel (Ni), lead (Pb), cadmium (Cd), and chromium (Cr) in their total (aqua regia digestion), EDTA‐extractable, and DTPA‐extractable forms were monitored in soil, leaves, musts, and wines. The resulting data clearly demonstrate that SB compost did not cause any significant increase in heavy metal levels in the soil and the plants. Thus, this type of compost can be used for soil fertilization with no danger either to the environment or to crops. In contrast, the use of MSW compost caused a significant accumulation of Ni, Pb, Cd, and Cr in the soil, in vegetation, and in musts. Skin‐contact fermentation dramatically decreased the heavy metal content of the wines. The concentration of heavy metals in plant tissues was found to be positively correlated with the DTPA‐extractable form of the metals in the soil, but not correlated with the total or the EDTA‐extractable forms.

Compost mulch effects on soil fertility, nutritional status and performance of grapevine

Two composts were tested as mulching materials in a vineyard: one was a sewage sludge and bark compost with a low heavy metal content, the other was a municipal solid waste compost with a higher concentration of metals. Both compost mulches increased organic matter content, available phosphorous and exchangeable potassium of soil and improved the porosity and water retention capacity of the soil. They also reduced soil temperature fluctuations, reduced evaporation of soil water, and influenced the levels of some nutrients measured in leaf samples. The data obtained show that the nutrients uptake was more influenced by the physical conditions of the soil (temperature, moisture) than by the availability of nutrients in the soil. The sewage sludge and bark compost did not cause any significant increase in heavy metal levels in soil and plants. In contrast, the municipal solid waste compost led to a notable accumulation of metals in the soil, in the vegetation and in the musts. Both the compost mulch materials had considerable advantages for the soil management on the grapevine rows, by reducing chemical weed control and allowing for the substitution of chemical fertilisers with no loss in vigour, yield or quality of musts.

The use of compost: its effects on heavy metal levels in soil and plants

Three organic soil conditioners were tested in 14 different Malus domestica orchards: cattle manure, SB compost (from sewage sludge and poplar barks) and MSW compost (from municipal solid waste not source separated). These materials differed notably in their heavy metal content: the SB compost contained greater amounts of Zn, Cu and Pb than did the cattle manure, while the MSW compost had higher concentrations of all the metals studied. For 6 years the Zn, Cu, Ni, Pb, Cd and Cr content were monitored in the soil—both in ‘total’ and EDTA extractable form—and in leaves and fruits. The resulting data demonstrate that the SB compost did not cause any significant increase in heavy metal levels in soil and plants; this compost can thus be used to fertilise the soil with no danger in the short/medium term either to the environment or to crops. In contrast, the experiment clearly demonstrates that the MSW compost, used over a 6 year period, increased concentrations of Zn, Cu, Ni, Pb, Cd and Cr in the soil—both in ‘total’ and EDTA extractable form—and in the case of Pb and Cd also in the vegetation and the fruits.

Heavy metal levels in apple orchards after the application of two composts

Two composts were tested in eleven different Malus domestica orchards: one was a sewage sludge and bark compost with a low heavy metal content, the other was a municipal solid waste compost with a higher concentration of metals. For six years the zinc (Zn), copper (Cu), nickel (Ni), lead (Pb), cadmium (Cd), and chromium (Cr) content were monitored in the soil, both in ‘total’ and EDTA extractable form, and in leaves and fruits. The resulting data demonstrate clearly that the sewage sludge and bark compost did not cause any significant increase of heavy metal levels in soil and plants; this compost can thus be used to fertilize the soil with no danger either to the environment or to crops. In contrast, the municipal solid waste compost led to a notable accumulation of all the metals examined in the soil and, above all in the case of Pb and Cd, also in the vegetation and the fruits.

Relations between heavy metal levels in soil, detritophagous and phytophagous invertebrates

Heavy metal (HM) levels in soil samples taken from surface soil horizon (up to 30 cm depth) and in the bodies of two invertebrate groups (earthworms as detritophagous and snails as phytophagous) were investigated during the vegetation period of 1993 in Central Moravia. Within the frame of large scale monitoring the above samples were taken repeatedly in ten selected habitats, mostly Protected Landscape Areas (PLA) and forests, and heavy metal levels of seven elements (Cd, Pb, Cr, Mn, Cu, Zn, Fe) were estimated by AAS after laboratory treatment. In soil samples three HM forms (fixed, soluble and available) were differentiated. Results indicated that the individual HM are distributed in a characteristic way both in soil and in invertebrate bodies. A relative comparison indicated that soil is the main depot for Pb, Cr, Mn and Fe, whereas biomass accumulates mainly Zn, Cu and Cd (related to kg dry matter). Characteristic differences were also found in the HM levels between detritophagous (earthworms) and phytophagous (snails) invertebrates. Elevated HM levels in several Protected Landscape Areas should be considered as warning symptoms.