Responses Of Carbonyl Sulfide And Dimethyl Sulfide From Soil To Different Factors

Carbonyl sulfide(COS)and dimethyl sulfide(DMS)are the two most abundant volatile organic sulfur compounds(VOSCs)in the atmosphere.They can not only directly influence human health,but also participate in photochemical reactions to promote the formation of acid rain,destruct the Earth's radiation balance and the ozone layer.Soil is one of most important source of atmospheric COS and DMS,while global sulfur cycle is difficult to estimate due to COS and DMS from soil are vulnerable to various factors(i.e.,temperature,soil water content,carbon dioxide(CO2)concentration and nitrogen deposition).For the past few years,global warming,rainfall pattern and atmospheric nitrogen deposition had a tendency to change significantly,which demands us to understand the response of COS and DMS to various environmental factors.This study was divided into two parts:Using dynamic chamber and GC-MS method,this study investigated the effects of major environmental factors(i.e.,gas concentration,soil water content,temperature and carbon dioxide(CO2)concentration)on subtropical dryland soil.While parts of the soil cores were collected without disturbance(i.e.,intact soil cores),the rest were broken and mixed after passing through 8 mm mesh sieve(i.e.,disturbed soil cores).The results were listed as follows:(1)COS and DMS uptake rates were reduced dramatically after sterilization,which indicated that it is mainly controlled by biological processes.Soil COS uptake rates from intact soils were higher than those from the disturbed soils under high air conditions,while DMS had little significant correction under none of air conditions.Soil COS and DMS uptake rates increased positively with the high atmospheric concentration.(2)Temperature had significant effects on soil COS and DMS.For intact soil,the highest COS emission rate(15.20 pmol·M-2·s-1)occurred at 25 ?,while disturbed soil appeared the lowest COS uptake(-100.37 pmol·m-2·s-1).The highest intact soil DMS uptake(-3330.21 pmol·m-2·s-1)occurred at 35?.Soil water content also had significant effects on soil COS and DMS,the lowest intact soil COS emission(0.90 pmol·m-2·s-1)occurred at 50%water holding capacity and the highest disturbed soil DMS uptake(-2175.06 pmol·m-2·s-1)occurred at 20%water holding capacity.High ambient CO2 concentration would significantly inhibit soil COS emission.In this part,two nitrogen levels(0 and 60 kg-N·ha-1·a-1 ammonium nitrate)and two types litter(Pinus massoniana and Cunninghamia lanceolate)were added to forest soil to carry out the experiment.We wanted to find the effects of simulated nitrogen addition on soil COS and DMS flux during process of litter decomposition.The results were listed as follows:(1)The types of litters and its decomposition process would affect the COS and DMS flux.Soil COS increased significantly with the litters of Pinus massoniana and Cunninghamia lanceolate addition.For ventilation with no exogenous nitrogen,the COS cumulative flux of soil with Pinus massoniana(33.23 mg·S·m-2)and Cunninghamia lanceolate(29.63 mg·S·m-2)litters were significantly increased than those soil without litters(23.95 mg·S·M-2).While DMS cumulative flux of soil with Ctunninghamia lanceolate(-13.16 mg·S·m-2)litters was significantly decreased than those without litters(9.49 mg·S m-2)and with Pinus massoniana litters(10.21 mg·S·m-2).(2)Nitrogen addition would affect soil DMS directly.For ventilation with exogenous nitrogen,the DMS cumulative flux of soil(14.96 mg·S·m-2)was signif1cantly higher than that with no exogenous nitrogen(9.49 mg·S·m-2).Respectively with exogenous nitrogen the COS cumulative flux of soil with Pinus massoniana(57.68 mg·S·m-2)and Cunninghamia lanceolate(44.16 mg·S·m-2)litters were significantly higher than those with no exogenous nitrogen(33.23 and 29.63 mg·S·m-2)ventilation.Nitrogen application would also affect the decomposition of litters,resulting in different stages of COS and DMS flux.(3)The soil physical and chemical properie also changed with the decoposition of litter leaves under the exogenous nitrogen.Soil pH dropped at the early stage and then remained stable,with soil organic matter and total nitrogen decreased and then increased,while with C/N ratio decreased all the stage.Soil respiration rate decreased gradually all the stage,for ventilation with no exogenous nitrogen the MBC/MBN ratio dropped all the stage,while for ventilation with exogenous nitrogen MBC/MBN ratio dropped at the early stage and then remained stable.COS and DMS fluxes showed significantly positive correction with soil pH,total nitrogen,MBC/MBN and CO2 flux,while significantly negative correction with soil C/N ratio respectively.All in all,the temperature,soil water content,gas concentration,nitrogen deposition and litters would directly or indirectly affect soil COS and DMS.