Time:2019-04-11(Thursday) 14:30-17:00
Speaker:Chuanyu Gao
Institution:University of Münster, Germany; Chinese Academy of Sciences
Venue:C2-207，Xiping Bldg
Host:Steven A. Kuehl，Fengling Yu
Contact:Chen Jingyan, chenjy@xmu.edu.cn
Brief CV:
Education:
10/2015---present University of Muenster PhD Candidates in Landscape Ecology
09/2012---06/2015 Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences Master of Science in Environmental Science
09/2009---07/2010 Dalian University of Technology Exchanging student
09/2008---06/2012 Jilin University Bachelor of Science in Environmental Science
Interested topics:
Redox properties of solid OM (organic matter) in anoxic environmental systems (wetlands)
Biogeochemical processes for carbon cycle under the anoxic environmental systems.
Black carbon deposition process in wetland and its response to regional human activities
Anthropogenic heavy metals pollution history in wetlands
Abstract:
Palaeoenvironmental implication of black carbon. Black carbon (BC) is produced by incomplete combustion of fossil fuels and biomass, and it is strongly influenced by human activities in recent hundreds years. Due to its refractory nature, BC is stored in sedimentary archives (e.g. wetland, lake sediments) and provides an ideal proxy to show historical fire frequency and regional BC emission. Increased slash-and-burn of pastures and forests during reclamation increases fire frequency, and thus influences regional BC emission and storage. However, few study investigated the influence of land use and land use change on regional BC deposition. To address this gap, we investigated BC deposition, and regional land use and settlement history in four wetland regions in Northeast of China: Sanjiang Plain, Changbai Mountain, Songnen Plain and Great Hinggan Mountain. People were encouraged by the government to settle in these regions and exploit natural resources after 1895. Our results showed that BC deposition fluxes in the different wetlands regions were around 10 (from 1 to 15) mg cm-2 yr-1 during the last 150 years, and were thus similar with results of studies on forest soils and higher than fluxes derived from other sedimentary archives. Wetland degradation caused by human reclamation and desertification in the surrounding landscape due to improper land use change BC storage and may also lead to BC losses in wetland soils. On the other hand, higher frequency of fire events caused by exploitation of resources lead to several peaks in BC deposition in the surrounding wetlands before the 1980s. After the 1980s, wild fires were controlled and forest protection policies were implemented by the government. This decreased regional fire frequency and thus BC deposition in the western region of Northeast of China. However, in the eastern regions, increasing anthropogenic impacts (e.g. industry sources) became the dominant factors on BC deposition and kept BC deposition fluxes increasing here.
Anaerobic carbon decomposition processes in peat soils. Peatlands, peat-accumulation wetland, are major sources of atmospheric CH4 and hold a third of all soil carbon despite representing only 3–4 % of the global land surface. Controls on CH4 production in water logged, anaerobic peatlands have been studied for several decades. Most importantly, temperature, substrate quality, water table position and availability of electron acceptors for organic carbon oxidation have been identified. However, many studies found that inorganic electron acceptors did not suffice to explain the observed production of CO2 and suppression of methanogenesis. Only recently suitable electrochemical techniques became available to access stocks and changes in electron accepting capacities (EAC) of dissolved and particulate natural organic matter (NOM), which can potentially serve as an additional electron acceptor. Here, we studied turnover of electron acceptors including NOM, and if CO2 production in anoxic incubation of peat can be balanced by methanogenesis or consumption of inorganic and organic electron acceptors. Moreover, we tested the influence of temperature on EAC turnover and the potential of oxidation by ambient oxygen to replenish capacities of EAC of NOM. Results shown that 54 - 80% of CO2 stemmed from methanogenesis. Of all remaining, 0.4 – 0.6% of non-methanogenic CO2 was explained by inorganic EA. The consumption of EAC of particulate organic matter (EACPOM) was closely related to the observed production of non-methanogenic CO2. Moreover, the contribution of EACPOM by far exceeded EACDOM. EAC of organic matter (EACPOM + EACDOM) could explain around 25 % of CO2 production of a weakly decomposed peat, around 30 % in a well decomposed peat. Except methanogenic and electron acceptors, only 15 – 31% of CO2 production remained unexplained. In addition, we incubated a highly oxidized peat material rich in sulfate. In this peat, non-methanogenic CO2 production could be explained by 70%, of which EAC of organic matter contributed 55% and inorganic EA contributed 15%. As expected, EACPOM consumption rates increased with temperature, and Q10 values were around 2.0. Moreover, exposing the peat material to oxic conditions under ambient air, EACPOM could be regenerated completely within 12 hours after 8 weeks of anoxic incubation. The results show that the EACPOM is the major electron acceptor in peat controlling CO2 production and suppression of methanogenesis. DOM likely only acted as a mediator for electron transfer. Short time exposure to air showed that EACPOM can readily be renewed by atmospheric oxygen and thus suppress CH4 production under again anaerobic conditions.
