| As economy and society developed rapidly,people’s living standard has undergone significant improvement,which is partially on expense of the environment goodness.Increasingly severe environmental problems are and will be emerging,which will in return affect human health and survival.Therefore,environmental issues ought to be taken seriously.Understanding the environmental conditions of various regions lies on the fundamental process for conducting relevant research and further targeted solutions,while it can also provide reference for relevant environmental protection departments to understand the level of pollutants and formulate corresponding policies,so as to effectively repair and protect the environment.Aiming at further understanding of atmospheric particulate matter in forest areas,this study collected the atmospheric particulate matter(PM2.5)sample from typical forest areas in central Hainan.The samples collected from four points were analyzed for the mass concentration of atmospheric particulate matter.Also,content of water-soluble anions(F-,Cl-,NO3-,PO43-,SO42-)and cations(K+,Ca2+,Na+,Mg2+,NH4+)of three samples are detected.The main research results obtained are as follows:（1）The concentration level of atmospheric pollutants such as atmospheric particulate matter(PM2.5)in typical forest areas in central Hainan is excellent in general.According to national first-level standard for 24-hour average concentration of the PM2.5（35μg/m3）,the figures in four samples in the forest area in each season are all within the national first-level standard,ranging from 8.3±0.8μg/m3～25.6±2.0μg/m3.The concentration shows a seasonal characteristic of being higher in autumn and winter while lower in spring and summer;During a period of 304 days of investigation,Baisha and Baoting were proved to be under a slightly polluted situation caused by O3in 10 and 6 days respectively,suggesting that O3is the main contaminant in typical forest areas in central Hainan.（2）Ten kinds of ions were detected in the samples from three sampling regions.The PM2.5samples from three sampling regions in typical forest areas in central Hainan were detected and analyzed by ion chromatography.Five anions(F-,Cl-,NO3-,PO43-,SO42-)and five cations(K+,Ca2+,Na+,Mg2+,NH4+)had been found.Generally,the total concentration of anions is higher than that of cations.For anions,SO42-,NO3-,and PO43-account for a relatively high proportion,while the content of F-and Cl-is lower.In terms of cations,the content of Na+and NH4+is higher comparing with that of K+,Ca2+and Mg2+.（3）Water-soluble ions content of PM2.5in air in typical forest areas in centralHainan varies in different season.The figure of sample collected in winter stood at the highest position（8.118±0.459μg/m3）,followed by that of autumn sample（7.970±0.456μg/m3）and spring sample（5.255±0.599μg/m3）,while the summer sample occupied the lowest position（3.491±0.973μg/m3）.The proportion of PM2.5is autumn（38.81%）>spring（36.84%）>winter（32.47%）>summer（31.35%）,the concentration of SO42-is the highest among all ions in four seasons,while the concentration of Mg2+is the lowest.（4）The water-soluble ions’structure characteristics of atmospheric particulate matter(PM2.5)in a typical forest area in central Hainan.Through the analysis of structure characteristics of the water-soluble ion of atmospheric particulate matter PM2.5in a typical forest area in central Hainan,our study concluded that the AE/CE ratio is above 1in spring and autumn,while the particulate matter is relatively acidic.However,the AE/CE ratios in winter and summer are both beneath 1,and the particulate matter prefer to be alkaline.The average content of SNA of sample collected in winter stands at the highest position（6.193±0.518μg/m3,24.71%）,followed by that of autumn sample（4.939±0.359μg/m3,24.41%）and spring sample（3.394±0.401μg/m3,23.69%）,while the summer sample occupied the lowest position（1.534±0.368μg/m3,13.82%）.The proportion of SNA in winter（69.30%～80.27%）outweighed that of autumn（47.94%～78.93%）,and the figure in spring（62.51%～67.77%）outstripped that of summer（42.51%～52.85%）;the ratio of[NO3-]/[SO42-]stood at a relatively low level which is associated with a trend of higher in spring（0.38～0.42）and lower in summer（0.13）while less than 0.5 regardless of areas and seasons.（5）The correlation of water-soluble ions of atmospheric particulate matter(PM2.5)in typical forest areas in central Hainan shows seasonal differences.Statistic analysis resulting from SAS and R shows that atmospheric particulate matter(PM2.5)in a typical forest area in central Hainan has a strong relationship with other seven ions,except for the weak correlation with NO3-and K+in spring.In autumn,interestingly,there are five ions that are strongly related to PM2.5,and it is observable that only a few strong relationships between PM2.5and each ion in winter and summer,but they are all strongly related to NH4+.（6）The main sources of water-soluble ions in atmospheric particulate matter(PM2.5)in typical forest areas in central Hainan are soil dust and biomass combustion.The principal component analysis shows that the soil dust and biomass combustion is the main sourse of PM2.5all year round.Apart from soil dust and biomass combustion,car fume emission also plays a role in contributing to PM2.5produce in spring and summer.However,sea salt contributes to PM2.5in autumn while the transmission of external pollutants is the main source for PM2.5production in winter.Strengthening source control is the most fundamental way to reduce PM2.5concentration.According to the source analysis results,it is recommended that government departments further optimize the energy structure,while take actions to protect forest from forest fires;in terms of external pollution transmission,comprehensive regional air pollution management should be strengthened,which means that joint prevention and governance with surrounding areas be promoted. |
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