The Study On The Ecological Effects Of Atmospheric Nitrogen And Sulfur Deposition Around Ningdong Coal-fired Power Plants Based On Stoichiometry

With the accelerating development of industrialization,the increase of atmospheric acid deposition has caused serious impact on the terrestrial ecosystems.In recent years,with the implementation of air pollutant emission control measures,the acid deposition rate in most regions of China tends to be stable or even reduced.However,it has been speeded up in northwest China by the transformation of industrial pattern.Coal-fired power plant is one of the main industrial emission sources of acid precursors(mainly nitrogen oxides and sulfur dioxide).In order to clarify the ecological effect of acid deposition around the coal-fired power plants in the industrial park,three typical coal-fired power plants in Ningdong Energy and Chemical Industry Base were taken as monitoring points,the bulk acid deposition of rainfall and dustfall were monitored from January to June in 2019,the soils and common plant leaves were collected in July,the spatiotemporal dynamics of N and S deposition in rainfall and dustfall were studied,the C:N:P ecological stoichiometry in soil-plant-microbe systems and their influencing factors were explored.The purpose of this paper is to provide a new insight into evaluating the environmental effect of acid deposition around industrial emission sources under current emission measures.The main results are as follows:(1)SO42-was the main form of acid deposition in the bulk deposition of rainfall and dustfall,while NO3-was the main form of N deposition,reflecting the emission characteristics of industrial source dominated by coal-fired power plants.There were great differences in SO42-deposition,NO3-deposition,NH4+ deposition,inorganic N deposition,SO42-/NO3-,and NO3-/NH4+ among different power plants,sampling distances,and sampling months,especially SO42-deposition.The six indices ranged from 0.19 kg·hm-2·month-1 to 5.80 kg·hm-2·month-1,from 0.16 kg·hm-2·month-1 to 3.24 kg·hm-2·month-1,from 0.10 kg·hm-2·month-1 to 0.63 kg·hm-2·mouth-1,fron 0.29 kg·hm-2·month-1 to 3.61 kg·hm-2·month-1,from 0.17 to 19.15,and from 0.94 to 16.10,and the mean value of each index was 2.51±0.07 kg·hm-2·month-1,1.17±0.05 kg·hm-2·month-1,0.23±0.01 kg·hm-2·month-1,1.40±0.05 kg·hm-2·montth-1,3.82±0.26,and 5.34±0.21,respectively;(2)there were great differences in the C:N:P ecological stoichiometry in soil-plant-microbe system among different power plants and sampling distances,however,lacking of consistent patterns.Compared with microbes and soils,the variation coefficients of leaf C:N:P ecological stoichiometry were smaller.The mean values of orgainc C content,total N content,total P content,C:N,C:P,and N:P in 0-60 cm soil were 4.09±0.41 g·kg-1,0.44±0.05 g·kg-1,0.44±0.03 g·kg-1,9.84±0.31,8.81±0.46,and 0.94±0.06,respectively.The mean value in plant leaves was 429.85±3.11 mg·g-1,23.41±0.50 mg·g-11.95±0.03 mg·g-1,19.86±0.39,230.62±3.86,and 12.33±0.27,respectively.The mean value in microbes was 55.00±4.27 mg·kg-1,11.11±1.14 mg·kg-1,2.38±0.24 mg·kg-1,5.74±0.33,28.39±2.06,and 5.01±0.26,respectively;(3)both N and S deposition changed the ecological stoichiometric relationships between C,N,and P in the soil-plant-microbe system.There were lack of significant linear relationships between C and N and between C and P in leaves,while significant relationship was found between N and P.Comparatively,significant relationships between the three elements were detected either in microbes or in soils.The homeostasis of total N,total P,and N:P in leaves were high.The homeostasis of biomass N and P were lower while that of N:P was higher in microbes.The result of RDA revealed that the factors,which had greater impacts on soil-plant-microbe C:N:P ecological stoichiometry,were monthly mean SO42-depostion,monthly mean inorganic N deposition,monthly mean NO3-deposition,soil urease activity,soil phosphatase activity,soil Ca2+concentration,and soil water content.In conclusion,the mean SO42-deposition of the three power plants was equivalent to the mean value at national level,but lower than the critical load of S deposition in the study area.That of N deposition was higher than the mean value of northwestern China and exceeded the acceptable N deposition of soils in the study area;compared with leaves,there were closer relationships among biomass C,N,and P in microbes,but biomass N,P,and N:P in microbes were more sensitive to environmental factors.Consequently,biomass C:N:P stoichiometric balance in microbes could better reflect the changes in atmospheric acid deposition and soil environments around the studied coal-fired power plants;SO42-deposition increased soil enzyme activities,stimulated microbial activities,and promoted soil organic C and N and P accumulation,whereas N deposition had strong negative effects on the above soil properties.The collected bulk deposition was total wet deposition plused part dry deposition,therefore,the measured N and S deposition would be lower than the total acid deposition in the studied power plants.Considering the time accumulation and coupling effect of N and S deposition,it is still necessary to limit the N and S emission in the coal-fired power plants of Ningxia and very important to pay more attention to their ecological effects,especially that of N deposition.