Peat Deposit And Its Past200-year Records Of Environmental Changes In Mountain Peatlands, Northeast China

An ombrotrophic peat bog is a domed peatland in which the surface peat layersare hydrologically isolated from the influence of local ground and surface water, andare fed exclusively by atmospheric deposition consisting of both solid particles andmineral substances dissolved in rain water. It has been proven to be a good continentalgeochemical archive, and has the unique advantage of a wide global distribution.Motianling ombrotrophic peat bog in Great Hinggan Mountain and the ChangbaiMountain peatlands in northeast China are valuable outdoor laboratories for studies ofatmospheric deposition because they are covered with a complete vegetation systemand are affected slightly by human beings directly.This study analyzed mainly the sedimentation information of mountain peatlandswhich were dated by²¹⁰Pb and¹³⁷Cs to build a high precision chronology. Afterunderstanding the core's structure and the history of peat evolution throughphysicochemical analysis (e.g. dry bulk density, water content, et al.), we analyzed thegrain-size parameter, magnetic susceptibility, chemical elements (e.g. Al, As, Hg, Pb,Ti), and organic pollutants (PAHs and PCBs) to reconstruct the dust evolution andenvironmental pollution history over the past150years in northeast China. In addition,the recent hot issue on carbon accumulation in peatlands was also involved. Therefore,the main conclusions are as followings:Firstly, the recent chronologies were constructed using²¹⁰Pb and¹³⁷Cs from3cores in Motianling, Great Hinggan Mountain, and12cores in Changbai Mountainpeatlands. The mean sedimentation rates of these peatlands are0.56-0.68cm yr^-1forMotianling peat bog, and0.21-1.81cm yr^-1for Changbai Mountain peatlands.Secondly, the150-year history of soil dust evolution were characterized bygrain-size parameter, magnetic susceptibility and typical earth-crust elements (e.g. Al,Fe, Ti). Data obtained from Changbai Mountain peatlands allowed us to estimate theinput rate of atmospheric soil dust (ASD) at5-40g m^-2yr^-1, and the correspondingvalue for the Motianling peat at13.4-68.1g m^-2yr^-1. The temporal variation of ASDfor the last60years well coincided with the meteorological records of dust storm frequency during1954-2002in northern China, suggesting that the reconstructed fluxof ASD from peat is reasonable. There were also soil dust storms in the late Qingdynasty, but the frequency and intensity were smaller than those occurred after1949.The impacts of soil dust storms on the western region were greater than that on theeastern region in northeast China.Thirdly, we reconstructed the environmental pollution history over the past150years in northeast China through the chemical elements (e.g. As, Cd, Hg, Pb, Sb)analysis. Lead deposition rate in Great Hinggan Mountain was estimated to be24.6-55.8mg m^-2yr^-1,and the variation pattern is consistent with increasingindustrialization over the past150years. In addition to Pb, several other traceelements including As, Cd, Hg and Sb were also estimated and analyzed. The study ofPAHs and PCBs in Motianling peat bog also revealed the variation of the influencesof human activities on the natural environment.Lastly, we discussed the carbon accumulation in these peatlands. The recent rateof carbon accumulation (RERCA) in Changbai Mountain peatlands ranged from124.2to292.8g C m^-2yr^-1(averaged199.6±60.9g C m^-2yr^-1). The carbon pool forthe past200years in Changbai Mountain peatlands was38.5-52.1kg C m^-2. TheRERCA in Motianling peat bog was166.64-259.31g C m^-2yr^-1with an average of203g C m^-2yr^-1.Accordingly, this study revealed the evolution of natural soil dust and thevariation of the influences of human activities on the natural environment. The resultswere not only helpful in supporting the decision-making process regarding sustainabledevelopment, improved the global database of peat archives of atmospheric metaldeposition, but also enriched the domain of environmental evolution research.