Abstract:

The Hg pollution is a global problem. The lacustrine sediment in remote area is sensitive to atmospheric Hg deposition by long-distance transportation and they are ideal materials for studying atmospheric Hg cycling. The Badain Jaran Desert is located in the Northwest China where there are about 142 permanent inter-dune lakes, and lacustrine sediments from these lakes are ideal materials for study atmospheric Hg deposition in remote desert region due to less human activities. The inter-dune lake， the Baoritaolegai， in the southeast of the Badain Jaran Desert， was selected for this study. The sediment core (BR-2) was dated by ²¹⁰Pb_uns and ¹³⁷Cs. Results derived from the sediment core BR-1 suggest that: (1) THg concentration ranges from 1.5 to 17.5 ng/g，the flux ranges from 2.9 to 38.9 μg/(cm²·a)and EF ranges from 0.3 to 4.5, respectively, and the THg content enriched in the recent decades;(2) The flux of THg in the Core BR-1 is composed of background (THg_lithogenic) and atmospheric fractions (THg_atmospheric). The flux variety of the THglithogenic fraction during 400 years is relative stable which are controlled mainly by nearby material source supply and regional aeolian activities. Gradually increasing flux of the THg_atmospheric fraction since 1930s， to a great extent， indicates the growth of anthropocentric THg in the recent decades. To the low background THg in the Badain Jaran Desert lake and the natural fluctuation affected by climate or the environmental change of the lacustrine sediment are considered. Peaks of the TH_gatmospheric flux occurring in the Core BR-1 after 1930s may be relating with global warming and increasing lake productivity while TH_gatmospheric flux changes may link with the nearby material source and aeolian activities before 1930s. Signals revealed by the 400 years’THg_atmospheric flux from the inter-dune lacustrine sediment in the Badain Jaran Desert is consisting with global Hg production and a THg record from ice core from North American, which can be regarded as a reliable record of the desert region atmospheric THg.

Key words: Hg, ²¹⁰Pb, ¹³⁷Cs, atmospheric deposition, LOI, the inter-dune lake in the Badain Jaran Desert