Strong Acid Mixture and Sequential Geochemical Arsenic Extractions in Surface Sediments from the Santa Maria La Reforma Coastal Lagoon, Mexico: A Bioavailability Assessment

Bibliometric Analysis of the Influencing Factors, Derivation, and Application of Heavy Metal Thresholds in Soil

The study of threshold levels of heavy metals in soil is essential for the assessment and management of soil environmental quality. This study reviewed the influencing factors, the derivation, and application aspects of heavy metals' threshold values comprehensively by a combination of bibliometric analysis and scientific knowledge mapping. A total of 1106 related studies were comprehensively extracted from the Web of Science database during the period from 2001 to 2020. The results showed that the publication output has been growing strongly. An analysis on the subject, journal, country, and institution was carried out to demonstrate the development and evolution of this research branch during the two decades. According to high-frequency keywords analysis, external factors (e.g., soil physicochemical properties) and internal factors (e.g., crop genotype) can affect heavy metal threshold values in the soil-crop system. The current methods mainly include the Point model (e.g., evaluation factor method), the Probability model (e.g., species sensitivity distribution method), and the Empirical model (e.g., ecological environment effect method). A threshold study can be applicable to the risk assessment for soil heavy metal contamination in order to determinate the soil pollution degree and its spatial and temporal distribution characteristics. Moreover, challenges and prospects of the study of heavy metal threshold values are proposed, indicating that research should focus on the relationships between human health risks and the established threshold values of heavy metals in the soil, long-term field trials and bioavailability of heavy metals for the derivation of the thresholds, and the establishment of more scientific and rational soil environmental benchmarks.

Subtotal content and geochemical fractionation of potential toxic elements in agricultural soils from Mocorito River basin in NW Mexico: environmental and health implications

Agricultural soils were collected from Mocorito river basin, to determine potentially toxic elements (PTEs) subtotal concentrations and geochemical fractionation, and evaluate their environmental and health risks. All sites showed low As and Cr concentrations. Subtotal concentrations (mg/kg) ranged between 6.8 and 25.6 for As, 1.9 and 2.5 for Cd and 22.5 and 55.1 for Cr. These values were classified as moderately contaminated for As, while a considerable contamination was presented for Cd and Cr. Geochemical partitioning revealed that PTEs are strongly linked with residual phase. Arsenic was associated with amorphous Fe-oxyhydroxides. Ecotoxicological indices showed from low (As and Cr) to considerable (Cd) potential ecological risk factors; potential non-carcinogenic risks by As, Cd and Cr, and potential carcinogenic risks by As and Cr. Lithogenic and anthropogenic sources were identified. Arsenic and Cr showed lithogenic influence, while Cd increased, caused by nearby activities, representing an environmental and health risk.