Physical And Chemical Characteristics And Emission Flux Of Sea Salt Aerosol In Fujian Province

Throughout the world,sea-salt aerosol is the largest natural source of atmospheric particle.They have profound effects on atmospheric chemical processes,global climate change and ecosystem of estuary.Sea-salt aerosol can react with acidic species such as HNO3,H2SO4 in the coastal urban atmosphere,resulting in more atmospheric particles and size distribution change.Quantifying the emission flux of sea salt aerosol is an important basis for assessing the impact of sea salt particles on environment.In this study,the emission flux of sea salt aerosol was estimated for Fujian based on appropriate sea salt aerosols(SSA)source function,combined with the local parameter in Fujian.Based on the actual monitoring results,the estimation results were verified.The results of this study can update and supplement the local atmospheric pollutant emission inventory,and provide the important basic data for the improvement of regional air quality.The measured results showed the seasonal distribution characteristic of atmospheric particle about the average concentration is higher in spring and winter than in summer and autumn.The contributions of sea salts to PM at the coastal cities ranged from 2.7%to 21.2%were commonly lower than those over sea ranged from 15.4%to 89.3%,and the concentration of sea salts decreased with the distance away from the coastline.In the coastal cities,Na+ exhibited typical coarse mode with peaks at 2.5?10 ?m,but the peaks of Cl-were 0.44?1.0 ?m and 2.5?10 ?m which indicate that there are sources other than sea salt for Cl-.Due to the influence of land-sea transport,the concentration of Cl-in fine mode decreased over sea.The good correlation between Na+ and Cl-over sea but coarse Na+ better correlated with NO3-supported the deduction that sea salts in the coastal cities were aged.The results of Scanning Electron Microscope(SEM)showed that the coastal areas of Fujian have sea salt particles,both fresh and aging.The size of sea salts was different but more concentrated in>2.5 ?m rang.According to selecting Gong(2003)and Smith(1993)formula to calculate the emission flux of sea salt aerosol over sea(The area of open sea is 46856 km2)at Fujian area in 2016 and 2017 were 8.85×108?1.16×109 kg and 9.20×108?1.19×109 kg respectively.In the open ocean,the emission intensity of sea salt aerosol had obvious spatial and temporal distribution but the annual variation of total sea salt discharge was smaller.Meanwhile,by choosing De Leeuw(2000)formula to estimate the emission flux of sea salt aerosol in the surf zone(The area of surf zone is 30.2 km2)at Fujian area in 2016 was 1.90×106 kg slightly higher than 1.64×106 kg in 2017.At last,the estimated results were validated by the measured data.The measured data verify the comparability of the estimated results from the different aspects of the relationship between sea salt emissions and topographic conditions,seasonal distribution,particle size distribution,and comparison with the measured results and literature results.