College of Resources and Environment, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Agricultural Resources and Environment, Southwest University, Chongqing 400715, China.
College of Resources and Environment, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Bio-resource for Bioenergy, Southwest University, Chongqing 400715, China.
Ecotoxicol Environ Saf. 2021 Jan 15;208:111402. doi: 10.1016/j.ecoenv.2020.111402. Epub 2020 Oct 15.
It is of great importance to elucidate the mechanism of mercury (Hg) migration in the forest litterfall so as to clearly understand global Hg deposition. However, it is still unclear for the migration and transformation of Hg in different forest litters during long-term decomposition. Therefore, the dynamics of total Hg (THg), methylmercury (MeHg), carbon, nitrogen, microbial biomass carbon and nitrogen in the litterfall of the evergreen broadleaf (EB) and mixed broadleaf-conifer (MBC) forests, southwest China were investigated, aiming to understand the migration characteristics of Hg in the two-year decomposing litterfall. Results showed that carbon decreased, while nitrogen accumulated slightly in the process of litterfall decomposition. THg levels in the second year of the EB and MBC forests decreased by 16.9% and 11.3%, while MeHg levels reduced by 141.4% and 210.7% respectively comparing with those in the first year. The total percentage of hydrochloric acid-soluble mercury (Hg-h) and water-soluble mercury (Hg-w) had a significant impact on the migration of THg and MeHg in the two forest stands. The C/N ratio in the EB forest bore a positive correlation with THg and MeHg levels, whereas that in the MBC forest was adverse. Besides, microbial biomass C and N were positively related with THg and MeHg levels in both the EB and MBC forests. It is proposed that THg and MeHg accumulation in the second year drastically decreased probably due to finite nutritional conditions, which implies that Hg accumulation risks alleviate with degradation time.
阐明汞（Hg）在森林凋落物中的迁移机制对于清楚了解全球 Hg 沉积非常重要。然而，长期分解过程中不同森林凋落物中 Hg 的迁移和转化仍不清楚。因此，本研究调查了中国西南地区常绿阔叶林（EB）和针阔混交林（MBC）凋落物中总汞（THg）、甲基汞（MeHg）、碳、氮、微生物生物量碳和氮的动态变化，旨在了解两年分解凋落物中 Hg 的迁移特征。结果表明，凋落物分解过程中碳减少，氮略有积累。与第一年相比，EB 和 MBC 林第二年的 THg 水平分别下降了 16.9%和 11.3%，而 MeHg 水平分别下降了 141.4%和 210.7%。盐酸可溶汞（Hg-h）和水溶汞（Hg-w）的总百分比对两种林分中 THg 和 MeHg 的迁移有显著影响。EB 林的 C/N 比与 THg 和 MeHg 水平呈正相关，而 MBC 林的 C/N 比则相反。此外，EB 和 MBC 林的微生物生物量 C 和 N 均与 THg 和 MeHg 水平呈正相关。研究认为，第二年 THg 和 MeHg 的积累大幅减少可能是由于营养条件有限，这意味着 Hg 积累的风险随着降解时间的延长而减轻。
