Changes in coal waste DOM chemodiversity and Fe/Al oxides during weathering drive the fraction conversion of heavy metals

Pinpeng Tuo; Zongpeng Zhang; Ping Du; Lijuan Hu; Renyou Li; Jie Ren

doi:10.1016/j.scitotenv.2024.172063

Changes in coal waste DOM chemodiversity and Fe/Al oxides during weathering drive the fraction conversion of heavy metals

Sci Total Environ. 2024 May 20:926:172063. doi: 10.1016/j.scitotenv.2024.172063. Epub 2024 Mar 28.

Authors

Pinpeng Tuo¹, Zongpeng Zhang¹, Ping Du², Lijuan Hu¹, Renyou Li³, Jie Ren⁴

Affiliations

¹ Collaborative Innovation Center for Grassland Ecological Security Jointly Supported by the Ministry of Education of China and Inner Mongolia Autonomous Region, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China.
² Technical Centre for Soil, Agricultural and Rural Ecology and Environment, Ministry of Ecology and Environment, Beijing 100012, China.
³ Collaborative Innovation Center for Grassland Ecological Security Jointly Supported by the Ministry of Education of China and Inner Mongolia Autonomous Region, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China; Technical Centre for Soil, Agricultural and Rural Ecology and Environment, Ministry of Ecology and Environment, Beijing 100012, China.
⁴ Collaborative Innovation Center for Grassland Ecological Security Jointly Supported by the Ministry of Education of China and Inner Mongolia Autonomous Region, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China. Electronic address: renie@mail.bnu.edu.cn.

PMID: 38552975
DOI: 10.1016/j.scitotenv.2024.172063

Abstract

The long-term accumulation of coal waste on the surface during natural weathering leads to the inevitable migration of heavy metals contained in the coal waste, which increases the likelihood of environmental contamination and health risks. Dissolved organic matter (DOM) and Fe/Al oxides play crucial roles in the transformation and bioavailability of heavy metals. Thus, we analyzed the Fe/Al oxide content and DOM molecular composition in coal waste with different degrees of weathering and explored the influence of DOM chemical diversity and Fe/Al oxides on the potential mobility of heavy metals. Results showed that weathering-driven decrease in Fe oxides (Fe_d, Fe_O, and Fe_p decreased from 82.4, 37.5, and 3.6 mg∙L^-1 to 41.3, 24.7, and 2.3 mg∙L^-1, respectively) led to decreases in the reducible fractions of V and Cr. The potential environmental risks of more toxic metals of Cd and As, also increased as a result of the residual fractions decreased to 32.6 % and 41.3 %, respectively. Weathering caused an increase in oxygen-to‑carbon ratio, double-bond equivalent, modified aromaticity index, nominal oxidation state of carbon, and molecular diversity and a decrease in (m/z)_w and (H/C)_w, suggesting that the DOM of highly weathered coal waste possessed high unsaturation, aromatic structures, hydrophilicity, and strong oxidative characteristics. Additionally, although V_MF and Cr_MF showed significant negative correlations with O/C ratio, polyphenolic, carbohydrates, and condensed aromatics, pH remained a key environmental factor determining the potential environmental risks of V and Cr by changing the residual fractions. The mobilities of Cd and As were significantly negatively correlated with those of Fe/Al oxides, particularly Fe_d, Fe_O, Fe_p, and Al_p. Our findings contribute to the understanding of the impact of weathering on the geochemical cycling of different coal waste components, providing priority options for environmental risk prevention and control in coal mining areas.

Keywords: DOM; FT-ICR MS; Fe/Al oxide; Heavy metal; Weathered coal waste.