Dynamics of trace element enrichment in blue carbon ecosystems in relation to anthropogenic activities.

Abstract
Blue carbon ecosystems (BCEs), located at the land-sea interface, provide critical ecological services including the buffering of anthropogenic pollutants. Understanding the interactions between trace element (TE) loads in BCEs and socioeconomic development is imperative to informing management plans to address pollution issues. However, the identification of anthropogenic TE pollution in BCEs remains uncertain due to the complex geochemical and depositional processes and asynchronous socioeconomic development along continental coastlines. Here, priority-controlled TE (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) concentrations in the mangrove, saltmarsh and seagrass soils and plant tissues along the coastline of China were investigated while taking bare flat and upland soils as corresponding references. We demonstrate that blue carbon (BC) soils accumulated markedly higher concentrations of anthropogenic TEs than the reference soils, mainly due to the effective trapping of fine-grained particles and higher binding capacities. We identify the time course of TE changes over the last 100 years which shows increasing anthropogenic TE accumulation resulting from military activities (1930-1950) and the growth of industrial and agricultural activities (1950-1980), then reaching a maximum after national economic reform (1980-2000). Since the 2000s, decreases in TE discharges driven by socioeconomic reform and strengthened environmental regulations have led to a widespread reversal of anthropogenic TE concentrations in BC soils. Based on the current TE flux we estimate that BCEs can filter over 27.3-100 % of the TEs emitted in industrial wastewaters from Chinese coastal provinces annually. However, the uptake of these TEs by plants can be substantially reduced through various mechanisms offered by edaphic properties such as organic carbon, clay, and sulfur contents. Therefore, enhancing TE filtering while preventing TEs from entering food webs through the conservation and restoration of BCEs will greatly aid in achieving the sustainable development goal of the coastal zone under intensified anthropogenic activities.

Citation
Fu, C., Li, Y., Tu, C., Hu, J., Zeng, L., Qian, L., Christie, P., & Luo, Y. (2023). Dynamics of trace element enrichment in blue carbon ecosystems in relation to anthropogenic activities. Environment International, 180, 108232. https://doi.org/10.1016/j.envint.2023.108232

Acknowledgements
The authors are grateful for funding provided by the National Natural Science Foundation of China (Grant No. 42007022, 41991330, and 42141014), the Chinese Postdoctoral Science Foundation (2021T140682), and the Department of Human Resources and Social Security of Jiangsu Province, China (2021K130B). We thank Prof. Bo Li, Prof. Hangqing Fan, Prof. Chuan Tong, Prof. Guo Wang, Prof. Qiuying Han, Dr. Zhijian Jiang, and Prof. Guangxuan Han for their assistance in field sampling, Dr. Xiaoli Wang for help in climate data processing, Mo Li for the laboratory analysis of trace elements, Jessica Breavington for linguistic assistance, and Prof. Carlos M. Duarte for his kind support.

Publisher
Elsevier BV

Journal
Environment international

DOI
10.1016/j.envint.2023.108232

PubMed ID
37778288

Additional Links
https://linkinghub.elsevier.com/retrieve/pii/S0160412023005056