Bioaccumulation, transfer characteristics of metals in six vascular plants, and soil pollution assessment from Wachangping karst bauxite residue areas

Bauxite residue (BR) is a large volume by-product generated during bauxite smelting process and metal pollution problem is becoming increasingly prominent in residue areas. Accumulation and transfer of metals in six vascular plants were analyzed and soil environment was evaluated. Results found levels of Al (2,110-26,280 mg kg-1), Fe (990 to 9,880 mg kg-1), Ca (8,020 to 49,250 mg kg-1), Mg (2,060 to 17,190 mg kg-1), K (16,840 to 39,670 mg kg-1), and Ti (80 to 1,240 mg kg-1) in plants. Metal concentrations in soils exceeded background levels. Bioconcentration factor (BCF) found that Al, Fe, and Ti in plants (roots, stems, and leaves) were relatively depleted (BCF <1). Transfer factor (TF) of Al, Fe, Ca, K, and Ti in plants was distinctly higher than 1 and mainly concentrated in stems and leaves. Pollution indices revealed that soil environment was at moderated to serious contaminated risk. Principal components analysis (PCA) showed that Artemisia caruifolia Buch. and Siegesbeckia orientalis L. plants had a good ability to absorb Al and Fe, which can be used as biological indicators and restoration materials.Novelty statementCurrently, soil environment was exposed to moderated to serious contaminated risk from Wachangping karst bauxite residue areas.Bioconcentration factor (BCF) analysis found that Al, Fe, and Ti in six vascular plants (roots, stems, and leaves) were relatively depleted (BCF <1).Transfer factor (TF) of Al, Fe, Ca, K, and Ti in vascular plants was distinctly higher than 1, which mainly concentrated in stems and leaves.PCA revealed that Artemisia caruifolia Buch. and Siegesbeckia orientalis L. plants had a good ability to absorb Al and Fe, which can be used as biological indicators and ecological restoration materials.

[Evaluation of Mercury Pollution in Soil of Different Land Use Types in Coal-fired Industrial Area]

The geo-accumulation index, potential ecological risk index, health risk model, and geographical detector were used to evaluate the soil mercury (Hg) concentrations and assess the health risks for various land use types to reveal the characteristics and spatial variability of soil Hg pollution under different land uses in the coal-fired industrial area of the Loess Plateau. The study area included seven counties in the western part of Xinzhou City, Shanxi province. The results showed that the average ω(Hg) in the agricultural land, grass land, wood land, and residential land were 0.48, 0.34, 0.58, and 0.52 mg·kg^-1, respectively, which were 16.00, 11.33, 19.33, and 17.33 times higher than the background value, respectively. The variation coefficients were ranked as residential land>agricultural land>grass land>wood land. The evaluation results of the geo-accumulation index and potential ecological risk index indicated a high ecological risk of Hg pollution in the entire study area with extreme pollution points in certain aeras. The health risk assessment results indicated no non-carcinogenic health risks for children and adults in the study area from Hg. Additionally, the geographical detection results revealed that the spatial variability in Hg was mainly impacted by industrial and agricultural activities in agricultural land, by soil organic matter and pH value in grass land, by soil salinity in wood land, and by soil salinity and organic matter in residential land. The spatial distribution pattern of Hg concentrations peaked in both the northern and southern edges, with a decreasing trend towards the middle and the majorly polluted areas being caused by human activities such as coal mining and industrial production.