Isotopic signatures unveil the lead sources and migration in surface mangrove sediments

Mangrove sediments act as both sinks and secondary sources for lead (Pb), yet the sources, migration, and transformations of Pb in mangrove environments are poorly understood. In this study, Pb concentration in three mangrove sediments adjacent to different land-use types was evaluated. The Pb sources were quantitatively identified using Pb isotopes. Our data indicated minor Pb contamination in the mangrove sediments, possibly due to the relative lack of developed industry in this region. The Pb isotopic ratios suggested, on average, natural sources, coal combustion, agricultural activities, and traffic-related emissions respectively contributed approximately 61.4 %, 18.8 %, 14.0 %, and 5.8 % of the Pb accumulation in the mangrove sediments, suggesting that coal combustion and agriculture were important anthropogenic Pb sources. Significant relationships were observed between the 206Pb/207Pb ratios and total organic content (TOC) in mangrove sediments, which implied contrasting Pb cycling in two mangrove environments. We further suggested that organic matter and sulfur content significantly reduced Pb mobility and bioavailability in mangrove sediments. Our study provides isotopic method to investigate the Pb sources and migration in the mangrove environment.

Automated summary

This study evaluated lead concentrations in three mangrove sediments adjacent to different land-use types and identified the sources of lead using lead isotopes. The data showed minor lead contamination in the sediments, possibly due to the lack of industrial development in the region. The lead isotopic ratios indicated that natural sources, coal combustion, agricultural activities, and traffic-related emissions contributed to the lead accumulation in the sediments, with coal combustion and agriculture being important anthropogenic sources of lead. Significant relationships were observed between the 206Pb/207Pb ratios and total organic content in the sediments, suggesting contrasting lead cycling in different mangrove environments. Organic matter and sulfur content were found to reduce lead mobility and bioavailability in the sediments. This study provides an isotopic method to investigate lead sources and migration in mangrove environments.