Monitoring The Atmospheric Heavy Metals And Nitrogen Deposition By Using The Moss Haplocladium Microphyllum(Hedw.)Broth.

Bryophytes have simple structure and no real vascular tissue.The pseudoroots with filamentous structure only play a role of fixation but not absorption.The stems and leaves are usually composed of only one layer or a few layers of cells.There is no waxy cuticle or underdeveloped cuticle on the surface of the plant,so it abtains most nutrients and pollutants from the atmosphere and is an effective indicator for monitoring air pollution.In China,the emissions of heavy metals（HMs）and nitrogen（N）in the atmosphere caused by human activities have increased sharply with economic boom since the late 1970s,and the environmental pollution in Yancheng,a coastal city in central Jiangsu Province,has also becomes increasingly serious.Due to the high cost of conventional monitoring methods,the number of atmospheric HMs and N deposition monitoring stations established in China is very limited,and it is impossible to determine the changes of atmospheric HMs and N deposition with higher spatial resolution.To date,there have been no public reports on atmospheric HMs and N deposition in Yancheng.This study used European moss reference samples M2 and M3 to ensured the quality control of the concentration determination results of HMs in mosses in the laboratory.We investigated the HMs concentrations and Pb isotope compositions in the moss Haplocladium microphyllum（Hedw.）Broth from Yancheng,and analyzed their main sources in the atmosphere.We determined the atmospheric N deposition at 18 sites from geographic suitable distribution areas of the moss H.microphyllum in China and compared this value to the N concentration in mosses collected<1000m from these sites.Based on the N concentration andδ¹⁵N value of the mosses,the atmospheric N deposition in Yancheng was evaluated.This study aims to provide supplementary methods for the quantification of atmospheric N deposition in different regions of China,and provide scientific basis for environmental pollution prevention,environmental quality assessment and management in Yancheng.The main fingdings of this thesis are as follows:1.The European moss reference materials M2 and M3 can be used for quality control to the analytical performance of the participating laboratories.The quality control exercise make the data obtained comparable.2.The concentrations of heavy metals in the mosses from Yancheng were higher than that in pollution-free areas.The contamination factor（CF）value indicated that the pollution levels of heavy metals Cd and Pb were the highest to the whole territory under investigation.The pollution load index（PLI）and potential ecological risk index（RI）indicated the extremely contamination with heavy metals Cd,Cr,Pb,Zn,V,Ni and Cu,and the presence of a high ecological risk.The PMF model was used to identify the contamination sources of the heavy metals and apportion their source contributions in the mosses.The results showed that the source contributions of the natural source and manufacturing and construction,metal processing and chemical industries,traffic emissions and fuel burning in industrial activities,and agricultural activities accounted for 53%,33%,12%and 2%,respectively.The Pb isotope ratios of the mosses(1.125-1.164 for ²⁰⁶Pb/²⁰⁷Pb,2.059-2.148 for ²⁰⁸Pb/²⁰⁶Pb)further proved that metal processing and traffic emission were the main sources of Pb.3.The Spearman rank correlation analysis showed that the total N concentration in mosses and measured dry and wet/bulk and total N deposition were significantly correlated（0.599≤r_s≤0.75,P<0.01）.There was no significant relationship between the total N concentration in mosses and precipitation and population density.A significant linear correlation（y=0.0373x+1.1429,R²=0.61,P<0.0001）between the total N concentration（y,%）in mosses and total nitrogen deposition(x,kg N ha^-1 yr^-1)was found.The difference in the distance between the atmospheric nitrogen deposition monitoring site and the moss sampling site was significant for the relationship between nitrogen concentration in mosses and atmospheric nitrogen dry deposition,wet/bulk deposition and total nitrogen deposition.The total nitrogen concentration in mosses can help to identify areas in China at risk from high nitrogen deposition at a high spatial resolution.4.The average N concentration in mosses from Yancheng was 1.68±0.28%,and the total N deposition in the atmosphere was estimated 18.18 kg N ha^-11 yr^-1.Hotspots of moss N concentration（1.0-2.52%）and,thus total N deposition（TN）,were found in the northeast and west,with an overall decreasing tendency from west to east.Mossδ¹⁵N varied between-7.76‰and 1.28‰,with an overall increase from the center to surrounding areas.Negative mossδ¹⁵N values revealed that NH₃from agriculture and urban sewage was the main sources of atmospheric N deposition.Based on mossδ¹⁵N values,it could be concluded that wet deposition of NO₃^--N and NH₄⁺-N accounted for 20%(3.56 kg N ha^-1 yr^-1)and 66%(12.07 kg N ha^-11 yr^-1)of TN,respectively.Overall,30%of the region exceeded the critical N deposition load for terrestrial ecosystems(10-20 kg N ha^-1 yr^-1),and given average trends in increasing N deposition coinciding with the Yangtze River Drainage Basin,all areas in the Yancheng region are predicted to surpass the critical load within the next 19years.Our data supports the moss monitoring method as an effective complement means to assess atmospheric heavy metals and nitrogen deposition,allowing for higher spatial resolution to determine changes in atmospheric heavy metals and nitrogen deposition,including in countries or areas where atmospheric heavy metals and nitrogen deposition monitoring networks are not established.