Spatial enrichment assessment, source identification and health risks of potentially toxic elements in surface sediments, Central Asian countries

Abstract

Purpose Potentially toxic elements (PTEs), particularly metallic elements, are some of the most dangerous pollutants found in surface sediments due to their toxicity and persistence. Given the contamination-related issues for sediments in Central Asian countries (CACs), a combination of risk assessment and source apportionment was used in characterizing the pollution sources and source-specific risks of metallic elements in the sediments of CACs. Materials and methods Surface sediment samples collected from 254 sites across the CACs were analysed for PTEs. The calculation of enrichment factor (EF) and the assessments of health risks were devoted to identifying contamination and risk characteristics, including geomorphic-and watershed-driven variability. Multivariate statistical analyses were applied to quantitatively identify contamination sources. Results and discussionThe results suggested that Cr, Cu and Ni were minimally enriched, Pb was moderately enriched, and Zn was significantly enriched. Interestingly, the EF of Pb was considerably higher in the northwest plain of the CAC region, but that of Zn was distributed across the study area. Source apportionment indicated that natural and anthropogenic sources accounted for 40.42% and 59.58% of the total contamination, respectively. Overall, the non-carcinogenic risks caused by PTEs were acceptable, but Cr and Pb exhibited higher non-carcinogenic effects in the Caspian Sea-Ural River and Ishim River regions. Moreover, fuel combustion, atmospheric deposition and industrial activities made higher contributions than other sources to the ecological risk of PTEs in the CACs. Conclusions This study will advance our knowledge of spatial differences, contamination risks and source identification for PTEs in sediments and provide a scientific basis for policy makers to design environmental strategies in the CACs.

Baseline determination, pollution source and ecological risk of heavy metals in surface sediments of the Amu Darya Basin, Central Asia

“…Also, the average concentrations of HMs were compared with previous relevant studies for other regions in CA (Table 1). It was found that the HM concentrations in surface sediments of the ADB were close to those throughout the CA, except for Zn, Cu and Ni (Wang et al, 2021a). Compared to the surface samples from the Caspian Sea region (CSR) and Issyk-Kul Lake region (IKLR), however, the sediments in the ADB had the highest mean concentrations of Cd, Cu and Cr, especially Cd, while the topsoil in IKLR had the highest average concentrations of Pb and Zn, and the surface samples from the CSR had the relatively high abundance of Ni (De Mora et al, 2004;Ma et al, 2018).…”

“…Assessing the spatial distribution of metals in surface sediments can be a good way to determine positions with higher HM contents and provide evidence of anthropogenic impacts (Chen et al, 2019;Wang et al, 2021a;Yang et al, 2021). To reduce the influence of particle size, and better understand geochemical characteristics and anthropogenic inputs of met-al elements, the spatial distribution of metal concentrations with normalized values were essential (Zeng et al, 2014;Zhou et al, 2021).…”

“…Amu Darya Basin; 2 Caspian Sea region(De Mora et al, 2004); 3 Issyk-Kul Lake region(Ma et al, 2018); 4 Central Asia(Wang et al, 2021a); 5 Worldwide(CNEMC, 1990) …”