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This study provides a 16.2-kyr record of mercury (Hg) deposition derived from a lacustrine sedimentary sequence in Dahu Swamp, eastern Nanling Mountains. Results indicate that changes in climatic conditions had a significant effect on Hg concentrations (Hg – C) and accumulation rates (Hg -AR). Multi-proxy records including dry density, grain size, geochemical elements, organic matter and pollen indicators were compared with Hg accumulation. The results revealed that the contributions of detrital input and atmospheric deposition were minor, and Hg accumulation in the sediments was closely related to changes in climatic conditions: relatively drier and colder climate would result in shrinkage of the lake water body thus favoring increased formation of organic-rich peat or gyttja and leading to enhanced absorption of Hg by organic matter and result in increases of Hg – C and Hg -AR in sediments, and vice versa. Our results indicate that variations of Hg accumulation in Dahu Swamp were greatly impacted by climate under the influences of solar insolation changes and shrinkage or expansion of ice sheets in high latitudes to the north. The results of this study provide an insight into the response of Hg accumulation to low latitude climate processes in the East Asian summer monsoon region. [ABSTRACT FROM AUTHOR]

There are differences in the response of long-term mercury (Hg) deposition to climate change, so it is necessary to clarify the influencing factors of Hg deposition in different locations. The Dahu and Daping Swamps are located in the eastern and western parts of the Nanling Mountains in South China, respectively. They are asynchronous variations of Hg deposition reflected by the two swamps since the last deglaciation. Based on the comprehensive comparative analysis of physical, chemical, and biological proxies, it is indicated that Hg deposition changes in the Dahu and Daping mainly record the changes in Hg content in the catchment input from organic matter. The differences in organic matter sources, core surrounding environment, Hg sources and atmospheric sedimentation contribution are reasons associated with the catchment environment for the observed differences in swamp Hg deposition and the response to climate. In cold/dry periods, Hg adsorption by terrestrial organic matter in Dahu Swamp were more significant, while in warm/humid periods, Hg adsorption by endogenous organic matter in Daping Swamp and wet deposition of nearby Hg sources, were the main climate-related processes for their asynchronous response. In addition, Dahu and Daping Swamps show similarities and differences in their Hg deposition variations. In both swamps, multi-millennial (∼1000−2200yr) and multi-centennial cycles (∼300–500yr) were observed and may be related to the harmonic period of the Earth's precession cycle and the solar activity cycle. This study helps to understand the differences in response between sedimentary Hg and climate, and to understand the regional and global proxies used to record climate and environmental changes. • Hg deposition investigated in two swamps in the Nanling Mountains in South China. • Hg deposition in subtropical swamps responds to climate changes since the Last Deglaciation. • Changes in Hg deposition are asynchronous in the two swamps. • Low latitude climate processes affect EASM strength and Hg deposition in South China. • Millennial and centennial scale cycles in Hg deposition are also recorded. [ABSTRACT FROM AUTHOR]

Previous multi-proxy records have revealed the advantages of well-preserved and long-scale geological archives from the lake sediments of Daping swamp in the western Nanling Mountains in South China. However, the exact organic matter (OM) sources in the sediments and their response to climatic variability still remain unclear. In this study, we present a 15.3-kyr n -alkane record extracted from lacustrine sediments in this swamp to explore the OM sources and the relationship between OM input and climatic changes. The results indicated that the n -alkane composition in sediments was dominated by long-chain n -alkanes (C 27 -C 31), implying that the OM mainly originated from the terrestrial higher plants and emergent aquatic plants. The n -alkane data further verified that changes in OM sources were related to the surface erosion-transportation-deposition processes controlled by climatic changes. Lake level change, which was also regulated by climate conditions, played an important role in impacting OM accumulation; warmer and wetter conditions would result in rising lake levels that favored more aquatic OM and less terrestrial OM input, and vice versa. Variability of the Asian summer monsoon intensity regulated by the dynamic variations in low-latitude processes (e.g., solar insolation, intertropical convergence zone, and El Niño/Southern Oscillation), as well as high-latitude processes (e.g., meltwater input in the North Atlantic), was closely related to the OM accumulation in sediments. • A 2.36-m n -alkane records from the subalpine Daping Swamp in western Nanling Mountains (South China) were reported. • n -Alkane proxies revealed the OM source mainly originated from terrestrial higher plants and emergent aquatic plants. • The OM accumulation is closely related to climatic/environmental conditions. • The warm and wet conditions favor increased aquatic/autochthonous and decreased terrestrial/allochthonous OM input, and vice versa. [ABSTRACT FROM AUTHOR]