Analysis of Hydrogeochemical Characteristics and Origins of Chromium Contamination in Groundwater at a Site in Xinxiang City, Henan Province

Hexavalent chromium contamination in groundwater has become a very serious and challenging problem. Identification of the groundwater chemical characteristics of the sites and their control mechanisms for remediation of pollutants is a significant challenge. In this study, a contaminated site in Xinxiang City, Henan Province, was investigated and 92 groundwater samples were collected from the site. Furthermore, the hydrogeochemical characteristics and the distribution patterns of components in the groundwater were analyzed by a combination of multivariate statistical analysis, Piper diagram, Gibbs diagram, ions ratio and hydrogeochemical simulation. The results showed that the HCO3-Cl-Mg-Ca type, SO4-HCO3-Na type, and HCO3-Mg-Ca-Na type characterize the hydrogeochemical composition of shallow groundwater and HCO3-Cl-Mg-Ca type, HCO3-Na-Mg type, and HCO3-SO4-Mg-Na-Ca type characterize the hydrogeochemical composition of deep groundwater. Ion ratios and saturation index indicated that the groundwater hydrogeochemical characteristics of the study area are mainly controlled by water–rock action and evaporative crystallization. The dissolution of halite, gypsum and anhydrite, the precipitation of aragonite, calcite and dolomite, and the precipitation of trivalent chromium minerals other than CrCl3 and the dissolution of hexavalent chromium minerals occurred in groundwater at the site. The minimum value of pH in groundwater at the site is 7.55 and the maximum value is 9.26. The influence of pH on the fugacity state of minerals was further investigated. It was concluded that the saturation index of dolomite, calcite, aragonite and MgCr2O4 increases with the increase of pH, indicating that these minerals are more prone to precipitation, and the saturation index of Na2Cr2O7, K2Cr2O7 and CrCl3 decreases with the increase of pH, implying that Na2Cr2O7, K2Cr2O7 and CrCl3 are more prone to dissolution. The saturation index of the remaining minerals is less affected by pH changes. The study can provide a scientific basis for groundwater remediation.

Chromium Laden Soil, Water, and Vegetables nearby Tanning Industries: Speciation and Spatial Distribution

This study investigates the spatial distribution and speciation of chromium in water, soil, and edible plants in tannery-contaminated areas at Modjo city, Ethiopia. Modjo city is one of the industrial zones in the country, which is dominated by tanneries due to the ease of effluent discharge and water use from the nearby Modjo River crossing the city. The river, which received chromium-containing effluent from the tanneries, is also used for urban gardening of edible plants besides other domestic purposes. 12 water and 12 soil samples from contaminated areas and 6 samples from different edible plants grown nearby tanneries were collected following the standard procedure to predict the level of chromium contamination in the environment and its health risk. The total chromium in Modjo River was 20.6 mg L−1 in the upstream region which later was significantly reduced (r = –0.93, p < 0.05 ) to 0.126 mg L−1 in the very downstream region. However, the Cr (VI) concentration ranges from 0.23 ± 0.032 to 2.82 ± 0.02 mg L−1 with a statistically insignificant decrease (r = -0.76, p > 0.05 ) to the downstream sampling points. The lowest Cr (III) and Cr (VI) concentrations in the soil were 2.78 ± 0.37 and 4.57 ± 1.01 mg kg−1, respectively, which are higher ( p < 0.05 ) than the control and the guideline values. Similarly, the chromium concentration in the edible plants was also 7.98 ± 0.63 mg kg−1 for green pepper to 14.45 ± 0.34 mg kg−1 for carrot with a trend of carrot > beetroot > lettuce > cabbage > tomato > green pepper. The chromium in the plants from the contaminated area was significantly higher ( p < 0.05 ) than the control area, which is between 0.14 mg kg−1 for lettuce and 0.31 ± 0.01 mg kg−1 for tomato. It is also confirmed that the root part of plants accumulates more chromium than the leaf and the fruits. It is concluded that water and soil in tannery surroundings and edible plants grown in the area contain chromium concentrations higher than the recommended amount for a healthy environment and human consumption. Therefore, appropriate wastewater treatment, stringent regulations, and public awareness are recommended to reduce chromium contamination and its impact on public health and the environment.

Phytoremediation

This chapter includes the sources of cadmium and chromium contamination of soil and various detrimental effects on plants and animals. Ecofriendly approach of soil clean up by phytoremediation is the main focus of the author. Heavy metal-induced oxidative stress of plants and their detoxification potentiality has been discussed here to create a wholesome idea about the basic and acute need of phytoremediation. Both enzymatic and non-enzymatic antioxidative defense mechanisms and various other biochemical parameters of metal hyperaccumulator plants are mentioned.