Distribution Characteristics Of SO₄^2-,NO₃^-and Gaseous SO₂ And NO_x In Atmospheric Particulates And Rainfall Scavenging

In order to study the removal efficiency of SO₄^2-,NO₃^-and gaseous SO₂, NO_x and its influencing factors,In this study,the sampling of precipitation in the new urban area of Nanchang was carried out,and the simultaneous sampling of atmospheric particles and gaseous pollutants during precipitation was carried out,The distribution characteristics of pH,conductivity?EC?,SO₄^2-,NO₃^-and the distribution characteristics of SO₄^2-,NO₃^-and SO₂, NO_x in atmospheric particulates during precipitation were discussed:?1?Compared to the whole precipitation,the precipitation can better reflect the true process of precipitation.Sub samples of precipitation rate of acid rain 75%,71.4% higher than that of the entire sample;subsection EC > precipitation samples 14.8 uS/cm total of 36.5% samples,19% higher than the whole sample;sample concentration > 1.15 mg/L SO₄^2-segment accounted for the total sample 59%,lower than the whole sample 85.7%;NO₃^-> 0.51mg/L piecewise sample concentration of total samples 71.8%.The whole sample below 95.2%,reflecting the initial precipitation ion concentration and precipitation concentration followed by a huge difference.?2?The pH value,EC,SO₄^2-and NO₃^-in the precipitation samples had some variation with the precipitation.Nanchang city spring precipitation samples pH value with the continued precipitation time gradually rising trend;summer with continued precipitation time decreased first,then increased gradually;winter precipitation samples pH value and similar to that of summer,but there is no dramatic changes in summer precipitation pH value;EC,SO₄^2-,NO₃^-segment with precipitation the continuous precipitation time,showing the overall downward trend.?3?The values of pH,EC,SO₄^2-and NO₃^-in the precipitation samples varied greatly with time.The pH value?5.49?of precipitation in spring and summer was generally higher than that in autumn and winter?5.03?.Precipitation of EC performance for 5-6 month 2016< November 2016< April 2016 < 2-3 months 2017,namely the spring and summer < autumn and winter precipitation;like SO₄^2-,NO₃^-segment in autumn and winter is higher than the concentration in spring and summer,autumn and winter SO₄^2-,NO₃^-concentration values were 3.5 times,3.93 times of the spring and summer,autumn and winter reflect the pollution degree of air particulate matter SO₄^2-,NO₃^-and its precursors is much higher than that in spring and summer.Long time precipitation and short-time precipitation differences in pH,EC: the short-time precipitation?segment number < 4?pH value changed little,long time precipitation piecewise pH value of precipitation changes,easily affected by meteorological conditions;short-time precipitation of EC is high,and long time precipitation of EC was relatively low,Shows that the erosion of the atmospheric pollutants by the short-term rainfall is rapid,but because of flushing time is shorter,leading to incomplete,and long-term precipitation of atmospheric pollutant scouring more thoroughly,leading to a lower overall precipitation samples EC.?4?On the whole,the ionic concentration of precipitation samples was SO₄^2-> NO₃^-.SO₄^2-accounted for 60.6% of the ion concentration;NO₃^-accounted for the concentration of ion concentration of 39.4%;the rate of the overall order of SO₄^2-<NO₃^-.The removal efficiency of atmospheric particles in SO₄^2-and NO₃^-(SO₄^2-inTSP average of 60.2%;the average [NO₃^-inTSP] was 58.0%)is higher,The SO₄^2-and NO₃^-which are washed into the precipitation under the cloud are mainly in the form of scouring the atmospheric particles,while the erosion of the gaseous SO₂, NO_x is less?SO2 average of 9%,with an average of 14% NO_x?;in spring and summer,the SO₄^2-,NO₃^-precipitation on the particle removal efficiency is higher than that in autumn and winter,reflected in the atmospheric particulate SO₄^2-,the particle size distribution of NO₃^-in different seasons are different.?5?The precipitation cloud of long term precipitation is acidic: Eight times of the pH in long term persistant percipitation are 6.37?5.36?5.65?5.59? 5.61?4.34?5.44?5.2;The EC are 4.99?5.16?3.96?5.76? 2.87?20.03?4.76?11.50?S/cm;SO₄^2-in cloud water are 0.7?0.46?0.65?0.39?0.12?2.12?1.51?2.23 mg/L,NO₃^-are 0.29?0.16?0.52?0.11?0.10?0.63?0.71?3.54 mg/L.Under the cloud,the contribution to precipitation EC is low,averaging 38%.The average contribution value of SO₄^2-in eight times erosion under the cloud,which named FSO₄^2-,is 50%.The average value of FNO₃^-is 57%;erosion under the cloud is the main source of SO₄^2-?NO₃^-in precipitation.?6?The SO₄^2-and NO₃^-in atmospheric particulate matter decreased gradually with the continuous precipitation,there are significantly reduction rate in the initial state,and the reduction rate guadually slow down with the precipitaion continued,while begin to rise with the formation of new pollutants.The SO₂ and NO_x of gaseous pollutants gradually decreased along with the continuous precipitation,it is began to rise gradually because of the accumulation of pollutants.However,the reduction rate is slower than the atmospheric particulate matter.?7?Atmospheric particulate matter present SO₄^2->NO₃^-totally.The value of [SO₄^2-inPM2.5]/ [SO₄^2-inTSP]?[NO₃^-in PM2.5]/ [NO₃^-inTSP] rise gradually along with the continuous precipitation.It began to stabilize after a long period of precipitation.The value of [SO₄^2-inTSP]/ [NO₃^-inTSP]?[SO₄^2-inPM2.5]/ [NO₃^-in PM2.5]present the decrease rate,There are some differences in the particle size distribution of SO₄^2-and NO₃^-in the atmospheric particles,and there will be more SO₄^2-on the large particles distribution.?8?The average precipitation scavenging efficiency of [SO₄^2-inTSP] is 60.2%;The average precipitation scavenging efficiency of [SO₄^2-inPM2.5] is 59.3%;The average precipitation scavenging efficiency of [NO₃^-in PM2.5] is 56.7%;the precipitation scavenging efficiency of SO₄^2-higher than NO₃^-,the scavenging efficiency of SO₄^2-?NO₃^-higher than PM2.5;the average precipitation scavenging efficiency of SO₂ is 21.3%,the average precipitation scavenging efficiency of NO_x is 19.8%.And it is evident that the average precipitation scavenging efficiency of SO₂ is higher than NO_x,the unit precipitation removal of SO₄^2-?NO₃^-in particles when autumn and winter is higher than it when spring.The removal rate of SO₂ unit rainfall is higher than that of NO_x unit rainfall.On the whole,it can be seen that the precipitation scavenging of SO₂ is more efficient than NOX.?9?The scavenging efficiency of SO₄^2-?NO₃^-in atmospheric particles have a good correlation with rainfall.While the correlation between precipitation intensity and the concentration of SO₄^2-and NO₃^-in the atmosphere is not good.The correlation among gaseous pollutants SO₄^2-?NO₃^-and rainfall,precipitation intensity,gaseous pollutant concentration is not significant.?10?SO₄^2-?NO₃^-in precipitation mainly comes from in-cloud scavenging and cloud removal of SO₄^2-?NO₃^-in gaseous particles,the contribution of gaseous pollutants are very low.