Distribution of Hg in mangrove trees and its implication for Hg enrichment in the mangrove ecosystem

• Published in: Applied geochemistry 2011-02, Vol.26 (2), p.205-212
• Main Authors: Ding, Zhenhua, Wu, Hao, Feng, Xinbin, Liu, Jinling, Liu, Yang, Yuan, Yanting, Zhang, Ling, Lin, Guanghui, Jiayong, Pan
• Format: Article
• Language: English
• Subjects: Aegiceras corniculatum; Avicennia marina; Earth sciences; Earth, ocean, space; ecosystems; Engineering and environment geology. Geothermics; Exact sciences and technology; Geochemistry; Kandelia candel; leaves; mercury; methylmercury compounds; plant litter; Pollution, environment geology; Rhizophora; Rhizophora stylosa; sediments; trees
• ISSN: 0883-2927; 1872-9134
• DOI: 10.1016/j.apgeochem.2010.11.020

► Mangrove plants concentrate high contents of Hg and MeHg. ► Different distribution of Hg and MeHg in mangrove plants relates to their environmental and physiological properties. ► THg content of mature leaves was always higher than that in juvenile leaves, but MeHg showed a contrasting trend. ► The litterfall leads to high Hg content in mangrove ecosystem. The aim of this study was to evaluate Hg distribution in mangrove plants and changes of Hg content during leaf aging; the contribution of litterfall to Hg enrichment in mangrove ecosystems is also discussed. Contents of total Hg (THg) and methylmercury (MeHg) in mangrove plants and sediments were determined. Contents of THg and MeHg in the sediments were 225 ± 157 ng/g and 0.800 ± 0.600 ng/g. Concentrations of THg and MeHg in the mangrove plants were 1760 ± 1885 ng/g and 0.721 ± 0.470 ng/g (dry weight), respectively, which were much higher than those in terrestrial plants. Enrichment of THg in mangrove plants was different, following the order Rhizophra apiculata > Rhizophora stylosa > Kandelia candel > Aegiceras corniculatum > Avicennia marina; while MeHg contents in mangrove plants decreased in the order of R. stylosa > K. candel > A. corniculatum > R. apiculata > A. marina. There were obvious interspecies differences, regional differences, individual differences and tissue differences between THg and MeHg contents of mangrove plants, all of which were closely related to the environmental and the physiological characteristics of mangrove plants. In juvenile leaves, mature leaves and leaf litter, THg contents ranged 55.3–1760 ng/g, 204–1800 ng/g, and 385–2130 ng/g (dry weight), respectively; MeHg contents ranged 0.17–2.39 ng/g, 0.01–1.28 ng/g, and 0.13–1.47 ng/g (dry weight), respectively. Except for A. corniculatum and Bruguier gymnorrhiza, THg content of mature leaves was always higher than that in juvenile leaves, but MeHg showed a contrasting trend. THg content of litter leaves was between that of juvenile leaves and mature leaves, while MeHg content was generally lower than that of juvenile leaves and mature leaves. In the mangrove ecosystem, Hg enrichment contributed by the litterfall decreased in the order of K. candel > A. corniculatum > A. marina.