Elements Analysis Of PM_2.5 And Health Risk Of Giant Panda Habitat In The Qinling Mountains

As a unique biological species in China,the giant panda is considered the flagship species for species diversity protection.It is known as a national treasure and living fossil.The giant panda in the Qinling Mountains has attracted increasing attention due to its distinctiveness,biological significance,and ecological value.The giant panda habitat in the Qinling Mountains is seldom frequented and the reserve is strictly managed.There is no source of anthropogenic pollution in the reserve.However,the giant panda is subject to varying degrees of threat from environmental pollutants that can infiltrate the reserve through atmospheric movement and particulate matter deposition.Therefore,it is particularly important to carry out relevant atmospheric environment research and health risk assessment in the wild panda habitat.This research is based on giant panda in the Qinling Mountains,and relevant scientific research work has been carried out in Shaanxi Foping National Nature Reserve.The research contents include:long-term monitoring of PM_2.5 in Shaanxi Foping National Nature Reserve;Analysis of PM_2.5 and its elements concentration;Analysis of elements enrichment factor;Source analysis of elements in PM_2.5;Potential source analysis of PM_2.5;Morphology and distribution of bamboo in Shaanxi Foping National Nature Reserve;and potential health risk assessment of PM_2.5 on wild giant pandas in the Qinling Mountains.The specific results are as follows:（1）From July 1,2021 to June 30,2022,the annual concentration of PM_2.5 in Shaanxi Foping National Nature Reserve was 11.3±7.9μg/m³.The PM_2.5concentration decreased month by month from July to September 2021 and from March to June 2022.From September 2021 to March 2022,the PM_2.5 concentration increased month by month.During the sampling period,the PM_2.5 concentration in the reserve was the lowest in September 2021 and the highest in March 2022.According to the limit standard of PM_2.5 concentration（15μg/m³）in the National Standard GB3095-2012,22.7%of the PM_2.5 concentration in the reserve during the sampling period exceeded the limit standard.The concentration of elements in the PM_2.5 is less than the corresponding limit standard.The variation of PM_2.5 concentration in Shaanxi Foping National Nature Reserve is consistent with that in the towns around the habitat,but the concentration is significantly lower than that in the towns around the habitat.Therefore,the Qinling Mountains not only provide suitable living environment for wild giant pandas,but also reduce the threat of environmental pollutants to wild giant pandas.（2）In the PM_2.5 of Shaanxi Foping National Nature Reserve,S,Si,Cl and P are the main non-metallic elements,accounting for 99.6%of the total non-metallic elements;Na,Mg,Al,K,Ca and Fe are the main metallic elements,accounting for 96.4%of the total metallic elements.According to the results of the enrichment factor analysis of each element,the elements that are less affected by human activities in PM_2.5 include Ti,Al,Ca and Sr.The elements most affected by human activities include As,Zn,Pb and Se;Cu,Ni,Mn,V,Ba,Ga and Co are the next most affected by human activities.（3）Sources of elements in PM_2.5 and potential sources of PM_2.5 in Shaanxi Foping National Nature Reserve were analyzed by using PMF receptor model and the Hybrid Single-Particle Lagrangian Integrated Trajectory（HYSPLIT）Model.The results are as follows:There are four main sources of elements in PM_2.5 in the reserve,which are natural sources of dust,emission sources of coal burning,emission sources of biomass combustion and emission sources of transportation.Among the above three anthropogenic pollution emission sources,coal burning emission source contributed the most to the total elements in PM_2.5 in the reserve,followed by biomass combustion emission,and transportation emission was the least.The areas that contributed the most to the PM_2.5 concentration were mainly distributed in the surrounding areas of the reserve,including Xi’an,Baoji,Xianyang,Hanzhong,Shangluo and Ankang.Based on the results,measures were proposed to improve the daily energy structure of residents around the reserve（increase the use of natural gas and photovoltaic power generation,reduce coal and biomass combustion）and encourage the upgrading of vehicles to reduce the emission of atmospheric environmental pollutants.（4）The distribution,living environment and morphology of bamboo have significant differences in Shaanxi Foping National Nature Reserve.From 1000 m to1700 m,the main bamboo species in the reserve is Banshania fargesii.From 1700 m to1900 m,the distribution of Banshania fargesii gradually decreases,while that of Fargesia qinlingensis gradually increases.The two bamboo species form a transition zone within this altitude gradient.Above 1900 m,the main bamboo species distributed in the reserve is Fargesia qinlingensis.The leaf area of Banshania fargesii was 55.1±8.5 cm²,and the leaf mass was 0.7±0.1 g.The leaf area of Fargesia qinlingensis was5.6±0.7 cm²,and the leaf mass was 0.039±0.002 g.Under the same mass,the leaf area of Fargesia qinlingensis was about 1.89 times that of Banshania fargesii.（5）The annual exposure dose of PM_2.5 through feeding and respiration was72787.1 mg and 98.4 mg,respectively,and the adsorption amount of giant panda fur was about 5350 mg.S,Mg,Si,Na,Al,K,Ca,Fe and Cl were the main elements of PM_2.5 ingest by wild pandas in the reserve,and nine elements accounted for more than95%of the total.The intake of atmospheric particulate matter attached to the staple bamboo leaves is the main way to endanger the health of giant pandas.As,Cr and Mn have higher non-carcinogenic risk,and As,Co,Cr and Ni have higher carcinogenic risk.（6）Climate warming will affect the habits of wild giant pandas,so that their habitat time in high altitude areas will be prolonged,increasing the proportion of the Fargesia qinlingensis mass ate by giant pandas throughout the year.Due to the larger area per unit mass of Fargesia qinlingensis,wild pandas ingest more environmental pollutants attached to the leaf surface through Fargesia qinlingensis when eating the same mass of bamboo leaves.Therefore,climate warming will indirectly increase the exposure dose of atmospheric particulate matter through the feeding of pandas,increasing the threat of environmental pollutants to wild pandas.In combination with the study on PM_2.5 and the ecological investigation on bamboo in Shaanxi Foping National Nature Reserve,we analyzed the main process of environmental pollutants affecting the health of giant pandas through atmospheric transmission,and put forward corresponding suggestions to reduce the threat of environmental pollutants to wild giant pandas according to the analysis results of pollutant sources.It is also pointed out that feeding is not only the main way for pandas to ingest atmospheric particulate matter,but also will increase the threat to panda health due to climate warming.