Chromium Concentrations In Soils Research Articles

Human cancer risk due to chromium and its bioaccumulation in physids in Central Punjab, Pakistan.

The present study aims to assess the ecological risk of chromium [Cr(VI)] in the water and soil of Central Punjab and its natural bioremediation through physids. Members of the genus Physa are cosmopolitan as they are resistant to various pollutants. The snails of the genus Physa were sampled from October through March. Three species, i.e., P. acuta, P. fontinalis, and P. gyrina, were identified. The foot, shell, water, and soil samples were tested for the presence of the hexavalent chromium, using ICP-MS. The maximum mean concentration of chromium in soil was found in GB(R8), i.e., 2.66ppb. The maximum mean concentration of chromium in water was found in RB(R4), 1.627ppb. The highest maximum average daily dose (ADD) was found in RB:R6, with a hazard quotient (HQ) of 32.32 and a carcinogenic risk (CR) of approximately 20 in every 100 children as a result of water pollution which is quite similar to RB:R5 showing these are extremely polluted area due to chromium. The pollution level of chromium in soil of Faisalabad is less than zero and safe while water is unsuitable for drinking as the value of water quality index (WQI) is higher than 100. No significant difference among the three species was found regarding bioaccumulation of chromium, in the snail shell and body. Physids play an active role in the bioremediation of soil and water yet may become cancer-causing tablets in the food chains of the region.

Effects of Chromium Pollution on Soil Bacterial Community Structure and Assembly Processes

With the rapid development of industry, chromium (Cr) has become one of the main soil heavy metal pollutants in China, seriously affecting the soil ecological environment and health of residents. In this study, contaminated soil samples were taken around the tannery sludge yard area in Heibei Province. The Illumina MiSeq high-throughput sequencing technology was employed to analyze the structure and assembly processes of soil bacterial communities at different pollution levels. Results showed that chromium pollution significantly influences soil properties and soil bacterial communities. The composition and structure of bacterial communities were significantly shifted at different pollution levels. Furthermore, the α diversity of bacterial communities may decrease with relatively high concentrations of chromium. Bacterial communities in chromium polluted soil can be divided into 55 phyla, where Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, and Firmicutes are the dominant phyla (relative abundance>5%). Moreover, the soil bacterial communities were dominated by the deterministic assembly process (homogeneous selection) and the stochastic ratios decreased with increases in the concentration of chromium in soil. The total concentration of chromium, soil moisture, pH, and organic matter were significantly correlated (P<0.05) with the bacterial communities. Therefore, these soil properties might be the driving factors affecting the structure of bacterial communities.

Geogenic Cr oxidation on the surface of mafic minerals and the hydrogeological conditions influencing hexavalent chromium concentrations in groundwater

This study aims to specify the source minerals of geogenic chromium in soils and sediments and groundwater and to determine the favorable hydrogeological environment for high concentrations of Cr(VI) in groundwaters. For this reason, chromium origin and the relevant minerals were identified, the groundwater velocity was calculated and the concentrations of Cr(VI) in different aquifer types were determined. Geochemical and mineralogical analyses showed that chromium concentrations in soils and sediments range from 115 to 959mg/kg and that serpentine prevails among the phyllosilicates. The high correlation between chromium and serpentine, amphibole and pyroxene minerals verifies the geogenic origin of chromium in soils and sediments and, therefore, in groundwater. Manganese also originates from serpentine, amphibole and pyroxene, and is strongly correlated with chromium, indicating that the oxidation of Cr(III) to Cr(VI) is performed by manganese–iron oxides located on the surface of Cr–Mn-rich minerals. Backscattered SEM images of the soils revealed the unweathered form of chromite grains and the presence of Fe–Mn-rich oxide on the outer surface of serpentine grains. Chemical analyses revealed that the highest Cr(VI) concentrations were found in shallow porous aquifers with low water velocities and their values vary from 5 to 70μg/L. Cr(VI) concentrations in ophiolitic complex aquifers ranged between 3 and 17μg/L, while in surface water, karst and deeper porous aquifers, Cr(VI) concentrations were lower than the detection limit of 1.4μg/L.

Comparative Phytoremediation of Chromium-Contaminated Soils by Alfalfa (Medicago sativa) and Sorghum bicolor (L) Moench

A study was carried out to investigate the potential of alfalfa and sorghum for phytoremediation of soil contaminated chromium. Soil samplings of 0-10 cm depths were taken. The experiment consisted of five treatments in which chromium concentration varied from 0 to 10 mg/kg soil (blank (T1), soil contaminated with 2 mg/kg concentration of chromium (T2), soil contaminated with 4 mg/kg concentration of chromium (T3), soil contaminated with 8 mg/kg concentration of chromium (T4), soil contaminated with 10 mg/kg concentration of chromium (T5). Alfalfa and sorghum were grown for 50 days after seeding in pots containing 5 kg of these soils. Chromium concentrations in soil after phytoremediation by alfalfa were 0.74, 1.16, 2.08, and 4.00 in T2, T3, T4, and T5, respectively. Chromium concentrations in soil after phytoremediation by sorghum were 0.84, 1.36, 2.44, and 5.12 in T2, T3, T4, and T5, respectively. Concentration of chromium in soil in all treatments after phytoremediation by alfalfa was decreased between 60-74%, and after phytoremediation by sorghum was decreased between 51.2-69.5%. The evidence provided by this experiment indicated that alfalfa and sorghum are effective accumulator plants for phytoremediation of chromium, but the potential of alfalfa was more than sorghum for phytoremediation of chromium polluted soils.

The influence of old leather tannery district on chromium contamination of soils, water and plants

The paper demonstrates the actual level of chromium contamination at the site of the old tannery waste lagoon in Serniki community (SE Poland). Despite the fact that since 1994 this area is not exploited, the chromium presence is still detected in soil, water and plants. The current study is the 4th phase (after 1989, 2001 and 2004) of checking and controlling the chromium concentration in this territory. The chromium content was assessed after soil and plant mineralization using FAAS method. Total chromium concentrations in soil samples reached values of 2.25 - 18.25 mg·kg-1 dry mass. Levels of chromium in water samples ranged between 0.008 and 0.017 mg·dm-3 for Wieprz River and the trough, situated in the tannery centre, respectively. Absorption of chromium by plants depended from the plant species. The highest Cr content in the stalks of Oenothera biennis, whilst the lowest in Phragmites australis were detected. Finally, it was assumed that soil chromium content noted in 2009 was by 42% - 83% lower in relation to the data from 2004. Consequently, nowadays the tannery waste lagoon site is not so threat to the health of local residents and to the surrounding ecosystem.

Cr(VI) genesis and dynamics in Ferralsols developed from ultramafic rocks: The case of Niquelândia, Brazil

Despite high chromium concentrations in soils developed on ultramafic rocks, Cr availability is generally low, as Cr-bearing minerals are considered stable in supergene conditions. However, KH2PO4 extractions have shown high hexavalent chromium availability in Ferralsols developed on the ultramafic massif of Niquelândia (Brazil). A study combining mineralogical, geochemical, μSXRF and XANES approaches was performed to assess the solid speciation of Cr and to understand its genesis. Chromium is mostly present in the trivalent form and is included in chromites and Fe-oxides. Nevertheless, a large amount of Cr(VI) is associated with the clay-sized fraction in the mineral horizons. Mn-oxides, the only natural Cr(III) oxidants, are also present in these horizons. Microscale investigations revealed the close association of Cr(VI) with Mn-oxides and strongly suggest that Mn-oxides can oxidize Cr(III) into Cr(VI). The XANES analyses show the occurrence of Cr(VI), which is removed by KH2PO4 extraction, demonstrating that the Cr(VI) is completely sorbed onto the soil matrix, i.e., Fe-oxides. Finally, the high mobility of Cr(VI), associated with the finest Fe-oxide particles mobilized during runoff following rainy events, may have harmful environmental consequences. This approach of combining direct and indirect observations allows us to characterize the total extractable Cr(VI) pool of these soils and to give key information on its mobility and localization.