Recent Atmospheric Deposition of Natural Dust and Heavy Metals in An Ombrotrophic Peat Bog of Great Hinggan Mountain, Northeast China.

An ombrotrophic bog is a domed peatland in which the surface peat layers are hydrologically isolated from the influence of local ground and surface waters, and are fed exclusively by atmospheric deposition consisting of both solid particles and mineral substances dissolved in rain water. It has proved to be a good continental geochemical archive. We studied the use of peat bog as an archive of atmospheric deposition and reconstructed environmental changes in deposition of dust and heavy metals over the past 150-200 years using ²¹⁰Pb-dated, Sphagnum-derived peat sequences from the Great Hinggan Mountain peatlands in northeast China. Large cores (15 × 15 × 64 cm) were collected in October 2008 and May 2009, and were sectioned on-site into horizontal layers and stored in polyethylene bags until the laboratory analysis. Physiochemical indexes of peat were measured including loss on ignition (LOI), grain size, magnetic susceptibility, dry bulk density and humification degree. Acid-insoluble concentration of conservative, lithogenic metals (Al and Ti), and total concentration of heavy metals (As, Cd, Hg, Pb, and Sb) were measured using ICP-AES (Shimadzu Co., Japan) and PF6-2 AFS (Beijing Purkinje General Instrument Co. Ltd., China). The average input rate of atmospheric soil dust (ASD) was estimated to be 13.4-68.1 g m^-2 yr^-1. Recent atmospheric metal deposition rates were 93.5-158.4 ng m^-2 yr^-1 for As, 0.7-1.1 ng m^-2 yr^-1 for Cd, 4.1-10.9 ng m^-2 yr^-1 for Hg, 24.6-55.8 mg m^-2 yr^-1 for Pb, and 10.7-16.3 ng m^-2 yr^-1 for Sb, respectively. The variations of metal concentrations show a dramatic increase with time, especially during the past 50 years, which corresponds to the intense industrial development and population growth in northeast China. However, the increasing trend of these metals accumulation rates is not obvious. Further analyses on these geochemistry data are ongoing. This study will complement global database of peat bog archive of atmospheric deposition.  The results will reflect the patterns of local environmental change and pollution and will be helpful to formulating policy to achieve sustainable and healthy development.