Cr In Topsoil Research Articles

Contamination characteristics of heavy metals in a small-scale tanning area of southern China and their source analysis.

Tanning industry has been identified as a significant source of heavy metals; however, heavy metals contamination in farmland soil due to small-scale tanning activities remains unstudied. Here, samples from topsoil, profile soil, water and sediments in the vicinity of a small-scale tanning area in Nanning, Guangxi Zhuang Autonomous Region, southern China, were collected to explore the contamination characteristics and source apportionment of Cd, Cr, Hg, As, Cu, Pb, Ni and Zn. The results show that the farmland soil was mainly contaminated by Cr and its content was 33.40-3830.00mgkg-1. The highest level of Cr, Cd and Hg was above their thresholds, while the average contents of Cd, Cr, Pb and Hg exceeded the corresponding background levels. Moreover, enrichment of Cr in soil profiles and stream sediments were also observed, whose concentrations varied from 11.50 to 2590.00mgkg-1 and 738.00 to 11,200.00mgkg-1, respectively. Concentrations of Cr in top soils and soil profiles from farmland surrounding the stream were significantly higher than those from other areas, and the soils surrounding the stream were moderately to heavily polluted. The multivariate statistical analysis indicated that the heavy metals originated from traffic (Cu, Ni, Zn, Hg, and Pb), agriculture (Cr and Cd) and nature (As). Source apportionment with PMF model results showed that the relative contribution rates of heavy metals by traffic, tanning, agriculture, other industrial activities and natural sources were 16.00%, 18.88%, 20.88%, 22.04% and 22.20%, respectively. These findings indicate that small-scale tanning activities could also lead to heavy metal accumulation in the surrounding environment, which requires decision-makers to pay more attention and to develop effective remediation procedures.

Heavy metal uptake by wastewater irrigated potato plants grown on contaminated soil treated with hydrogel based amendments

Heavy metal uptake by food crops and the potential for groundwater contamination are of major concern in areas where untreated wastewater is used for irrigation. To minimize heavy metal uptake by wastewater irrigated food crops and to minimize its transport to deeper soil layers, the use of polyacrylamide super absorbent polymer (SAP) and SAP-gasified plantain peel biochar mix (SAP+GBC), as soil amendments, is proposed in this study. A sorption test was conducted to determine the ability of the treatments to adsorb heavy metals (Cd, Cr, Cu, Fe, Pb and Zn). Field experiment was conducted by growing synthetic wastewater irrigated potato plants ( Solanum tuberosum L.) in lysimeters packed with sandy soil, contaminated with heavy metals. Prior to conducting the study, heavy metals Cd, Cr, Cu, Fe, Pb and Zn were present in top 0.10 m of lysimeter soil within ranges of 15.6–23.9, 23.3–27.6, 30.3–62.2, 11538.6–10847.7, 64.9–131.3 and 38.7–46.8 mg kg −1 , respectively. Irrigation occurred eight times, at an interval of 10 days, based on the crop water requirement. After every irrigation, soil samples were collected from different depths (surface, 0.10, 0.30 and 0.60 m) for heavy metal analysis. Upon maturity, potato tubers, plant root, stems, leaf, tuber flesh and tuber peel tissues were sampled separately for heavy metal analysis. Soil samples, collected at the end of the experiment, were also subjected to pH and cation exchange capacity (CEC) analysis. Compared to the control, treatment SAP+GBC was able to retain significantly higher amounts of Cd, Cr and Fe in topsoil (0–0.10 m depth; p<0.05), whereas, the SAP treatment retained significantly higher amounts of Cd, Cu, Fe and Zn in topsoil (p<0.05). Both hydrogel based treatments (SAP and SAP+GBC) were able to significantly (p<0.10) reduce Cd uptake in tuber flesh (1.98 and 1.54 mg kg −1 , respectively) and peel tissue (20.75 and 23.89 mg kg −1 , respectively), as compared to the control (2.63 mg kg −1 in flesh and 43.87 mg kg −1 in peel). Concentrations of Zn in tuber flesh tissue for both, SAP (8.30 mg kg −1 ) and SAP+GBC (8.65 mg kg −1 ) treatments were found to be significantly (p<0.05) lower than that of the control (15.28 mg kg −1 ), indicating the effectiveness of the treatments in reducing Zn uptake by potato tubers. Treatment SAP+GBC was also able to significantly (p<0.05) reduce Pb uptake in tuber flesh (0.05 mg kg −1 ) and peel tissue (1.64 mg kg −1 ), as compared to control (0.09 mg kg −1 in flesh and 4.99 mg kg −1 in peel). Overall, it was found that tuber peels had significantly higher levels of heavy metals, as compared to tuber flesh. The present study indicates that the hydrogel based amendments have the potential to reduce the uptake of Cd, Pb and Zn metals, by wastewater irrigated potato tubers grown on sandy soils. • Irrigating potato with wastewater led to accumulation of heavy metals in soil. • Both treatments led to reduced Cd and Zn uptake by potato tubers. • Treatment SAP+GBC led to reduced Pb uptake in potato tubers. • SAP+GBC treated soil retained higher levels of Cd, Cr and Cr in topsoil. • SAP treated soil retained greater amounts of Cd, Cu, Fe and Zn in topsoil.

Mineralogical and Heavy Metal Assessment of Iraqi Soils from Urban and Rural Areas

The concentrations of Cu, Ni, Pb, Zn, and Cr in top soils (0-15 cm) from urbanized and rural areas of Iraq were measured by X-ray fluorescence analysis (XRF). The results revealed that soil samples located in urban areas had higher metal contents than did soil samples from rural areas. This was probably due to local pollution from increased population and other industrial sources. The comparison with the soil quality guidelines showed that metal concentrations in all the studied locations are lower than the permissible levels admitted by the World Health Organization (WHO). The mineralogical composition of the top soils, identified by X-ray diffraction (XRD), was predominantly Quartz, Calcite and minor minerals such as Dolomite, Feldspar and clay minerals. Total clay minerals in the soil samples, ranged from 3-10%, were found to be dominated by Montmorillonite, Kaolinite and Feldspar. The highest clay content was observed in Diala soils near the river Tigris.

Forensic investigation of a chromium(VI) groundwater plume in Thiva, Greece

A forensic investigation was conducted with the aim of decoupling the contribution of geogenic and anthropogenic Cr(VI) sources in the wider area of Thiva. Groundwater and topsoil samples were collected from two Cr(VI) groundwater plumes of 160μg/L and 75μg/L. A series of evidence support the view that the origin of Cr(VI) detected in groundwater is mainly geogenic. These are: (a) the presence of Cr in topsoil of the wider area, (b) the moderate Cr(VI) groundwater concentrations, (c) the high Ni levels within the Cr(VI) plumes, (d) the predominance of Mn(IV), which is a prerequisite for Cr(III) oxidation to Cr(VI), and (e) the absence of co-contaminants. The present study also revealed that, although both Cr(VI) plumes are clearly of geogenic origin, the plume with the elevated Cr(VI) values, in the north of Thiva town, exhibits also an anthropogenic component, which can potentially be attributed to the alkaline environment associated with the old uncontrolled landfill of Thiva and the industrial cluster located in this area.

Trace Element Soil Quality Status of Mt. Cameroon Soils

The concentrations of Cu, Co, Zn, Ni, V, and Cr in topsoils at six sites located along the lower slopes of Mt. Cameroon were assessed for their potential toxicity to humans and the ecosystem. Soils were collected from horizons down to a depth of 70 cm and analysed for trace element concentration by ICP-MS technique. The Dutch soil quality standards which use %clay/silt and organic matter content to derive target values were used to assess the contamination levels of the soils. The content of these soils was also compared to the United Kingdom ICRCL “soil trigger” values. Zinc and Cu values were persistently below the normal value (A) and occurred in the lower elevation, the region of extreme weathering, while Cr and V values were above the intervention (C) values. The high content of Cr in common fertilisers poses a potential risk in toxicity in the higher elevations experiencing lower weathering rates, where soil Cr levels are elevated.

Studies on the chromium concentrations in topsoils and subsoils of two rapidly industrialized cities in the Yangtze River Delta in east China

A total of 782 topsoil samples (0-20 cm) and 371 subsoil samples (20-40 cm) were collected from agricultural land in two rapidly industrialized areas with a large number of small rural industries in southeast China, Zhangjiagang City (ZJG) and Changshu City (CS), to measure soil chromium (Cr) concentrations. Kriging and cokriging were used to predict the spatial distribution of Cr in the topsoils and subsoils. Paired-samples t test and spatial distribution maps were used to compare the Cr concentrations in topsoils and subsoils. The mean Cr concentration in ZJG topsoils was significantly higher than that in ZJG subsoils and the mean Cr concentration in CS topsoils showed no significant difference from that in CS subsoils. The Cr concentrations in topsoils were higher than those in subsoils over most of the area of ZJG and part of CS, suggesting that Cr accumulation had occurred in these areas and extrinsic factors have an important role controlling the distribution of Cr in topsoils. Semivariogram/cross-semivariogram was used to evaluate soil Cr spatial variability. The Cr in ZJG topsoils, ZJG subsoils, and CS topsoils had moderate spatial dependence and the Cr in CS subsoils had strong spatial dependence. Cr in ZJG subsoils had longer effective range than Cr in ZJG topsoils, suggesting that the anthropogenic factors affecting Cr distribution in ZJG topsoils; and Cr in CS topsoils had longer effective range than Cr in CS subsoils, indicating that soil formation may be the major explanation for the decrease in the variation of Cr in topsoils. A significant correlation was found between the Cr in topsoils and Cr in subsoils, indicating that natural factors also play an important role as extrinsic factors that control the distribution of Cr in topsoils.

Spatial distribution of chromium in soils contaminated by chromium-containing slag

To evaluate the metal chromium (Cr) contamination of soil at a chromium-containing slag site by ferrochromium production, the contaminated sites, under slag heap, in the vicinity of slag heap and arable soils near the outlet of sewer channel, and unpolluted site 5 km away from one ferroalloy plant in Hunan Province, China, were selected. The concentrations of total Cr and water soluble Cr in bulk soil samples and profile depth samples were determined. The results show that the soils in the vicinity of slag heap have the highest total Cr content followed by the soils under the slag heap and near the outlet of sewer channel of the factory. The mean concentrations of total Cr in the top soils at above three contaminated locations exceed the critical level of Secondary Environmental Quality Standard for Soil in China by 3.5, 5.4 and 1.8 times. In most Cr polluted soils, total Cr has a relative accumulation in soil depth of 40–60 cm, but this trend is not found in unpolluted soils. The average concentrations of water soluble Cr (VI) in top soils under slag heap and in the vicinity of slag heap are 176.9 times and 52.7 times higher than that in the uncontaminated soils, respectively. However, water soluble Cr (VI) contents in soils near sewer channel are all low and the values are close to that in the uncontaminated soils. Although water soluble Cr (VI) content in soil profiles decreases with soil depths, it in soils under slag heap maintains a high level even at a depth of 100–150 cm. The results imply that the transportation of Cr (VI) can result in a potential risk of groundwater system in this area.