Pollution Characteristics Of Water Soluble Ions And Water Soluble Organic Carbon In PM_2.5 And PM₁₀ In Dust And Non Dust Days In Hotan

Dust weather is a kind of weather phenomenon that dust is blown by the wind,which makes the air turbid and atmospheric visibility significantly reduced.Its formation is the product of climate,environment and human activities.Hotan city is located in the middle of the Yangtze River.In addition,with the increase of industrial construction in recent years,the atmospheric particulate pollution is more serious.Therefore,it is of great significance to study the pollution characteristics and source apportionment of PM_2.5and PM₁₀ in Hotan City,which can provide scientific basis for the scientific prevention and effective management of local atmospheric particulate pollution.In this paper,PM_2.5 and PM₁₀ samples were collected from two sampling sites（Kunlun lake and Meteorological Bureau）in Hotan city in spring and summer of 2020,and the water-soluble ions and water-soluble organic carbon in PM_2.5 and PM₁₀were analyzed under the framework of dust days and non dust days.Finally,PCA（principal component analysis）was used to determine the possible sources of PM_2.5 and PM₁₀ in dust and non dust days.The main conclusions are as follows:（1）The total average mass concentrations of PM_2.5and PM₁₀ were289.6μg/m³and 752.3μg/m³ in sand dust days,111.9μg/m³and 355.7μg/m³in non sand dust days,3.86 times and 5.02times higher than the secondary daily average mass concentration limits of PM_2.5 and PM₁₀ in sand dust days,1.49 times and 4.74 times higher than those in non sand dust days,respectively The standard rate was 100%,while it was 59%-96%in non dust days.Atmospheric particulate matter pollution is serious.The concentration of particulate matter in dust days is generally higher than that in non dust days.（2）The average concentration of total water-soluble ions in PM_2.5 was 58.30%in dust days65μg/m³ in non dust days.The average concentration of total water-soluble ions in PM₁₀was93.79μg/m³ in dust days 72μg/m³ in non dust days Ca²⁺,SO₄^2-,Cl^-,and Na⁺are the important components of water-soluble ions in PM_2.5 and PM₁₀ of dust and non dust days in Hotan city.The proportion of these four ions to the total ion concentration in PM₁₀ and PM_2.5 is more than 80%.（3）It is found that Ca²⁺,Mg²⁺and Cl^-have a good correlation with most ions.The correlation between K⁺and other ions is higher in dust days than that in non dust days,and the correlation between NH₄⁺and other ions is lower than that in non dust days.（4）The analysis of cation and anion showed that the anions were depleted in different degrees in dust days and non dust days,and the particles were alkaline as a whole.The values of sor and nor in PM_2.5 and PM₁₀ were 0.76 and 0.69,0.15 and 0.14,0.79 and 0.79,0.1 and 0.12,respectively;in non dust days,the values of sor and nor in PM_2.5 and PM₁₀ were 0.52 and 0.52,0.1and 0.12,0.63 and 0.62,0.15 and 0.09,respectively.The results show that the secondary conversion of NO₃^-in PM₁₀ and PM_2.5is not obvious during the whole sampling period,while the secondary conversion of SO₄^2-is obvious.（5）The values of TC,IC and WSOC in sand dust days were significantly higher than those in non sand dust days,and the concentration of WSOC was higher than that in some developed cities at home and abroad;the correlation between WSOC and SO₄^2-was good,indicating that WSOC mainly came from secondary generation.The correlation coefficient between WSOC and meteorological factors is generally better in dust days than in non dust days,which may be due to more active photochemical reaction,resulting in increased correlation;the coefficient of relative humidity is very high,which may be caused by strong wind.（6）Principal component analysis was used to analyze the sources of water-soluble ions and water-soluble organic carbon in PM_2.5 and PM₁₀ in dust and non dust days.The results showed that soil source was the main pollution source in PM_2.5 and PM₁₀,followed by industrial source;In non dust days,the main pollution sources of PM_2.5and PM₁₀were secondary sources,followed by mobile sources.