Characteristics And Sources Of Trace Elements In Atmospheric Deposition

In order to study the morphology of different diameter particles in atmospheric dry deposition and the concentration levels and change said of the inorganic elements in atmospheric precipitation, To explore the scouring effect of rainfall of inorganic elements, Dry wet subsidence flux and the source of inorganic elements, This paper choose Shanghai as a sampling point, Because Shanghai is a typical background site of the Yangtze river delta,and also the most developed economy, the most populous, the most serious pollution of city. In May 2015, June, July and September a total 4 months, According to before the rain, in the rain after the rain of the sampling method to collect the rainfall sample and different size particles samples, Particulate matter sample including dust, rain residue, PM10 and PM2.5, classifying the samples, Eventually collected 244 samples, Put the collected samples according to before the rain, in the rain, after the rain ways into nine cycles. Using SEM and EDS to observe and analyze the appearance characteristics and the kinds of inorganic elements of a single particle or a region particulate matter of dust, rain sample residue, PM10, PM2.5 and PM1.0(select 5 ~ F samples as PM1.0 samples in classifying the samples). And using ICP-MS to four cycles of 88 samples of rainfall, PM10 and PM2.5, classifying the samples Ni, Cr, Mn, Cu, As, V, Cd, Sb, Pb, Al, Ti, Fe, Zn, Se, Ba, P, Br, I, Si, SO of 20 kinds of inorganic element concentration are measured and analyzed, The results show that:(1) From the picture of particulate matter`s scanning electron microscopy(SEM) can be seen,The Morphology characteristics of Rain sample residue, dust, PM10, PM2.5 and PM1.0 were very similar, Most of them are different shapes, different particle sized and rough surface, Most of them are the chain, the spherical and the irregular shape, And the Sampling filter membrane surface is not uniform attached to the particles, but stick to loose, void clearly visible, rom the perspective on aggregation degree between particles, the rain sample residue accumulation is sparse, and the rain sample residue of particle size is smaller than the dust as a whole. And the other of different size particles are with the decrease of the particle size,The particles the gathered more and more intensive, and with the decrease of the particle size,The spherical particles more and more.(2)From sample residue rain, dust, PM10, PM2.5 and PM1.0 particles energy spectrum diagram found, The element types and the atomic percentage of each element in different point is not the same, The elements of each particle composition is not the same, All of the particles are particularly high oxygen content, and almost no other anion,Therefore Various metal elements of particulate matters should be exist in the form of oxide, Followed by C elements, Through comprehensive analysis that dust is soil dust, construction dust and the Marine aerosols, as well as the comprehensive automobile exhaust dust source, affected by soil dust, construction dust is larger. Most of the elements in the Rain residue are the same with the elements of the particulate matter, Only element number has decreased, which shows that the elements of rain residue sample are from the atmospheric aerosol, PM10 samples are the automobile exhaust dust, industrial coal dust, soil dust, and construction of large particles of dust mixed dust, PM2.5 amples in addition to car exhaust dust, industrial coal dust, soil dust and construction dust mixed, but also affected by other factors; The elements in the PM1.0 sample compare with PM1.0 elements were increased, And all the heavy metal element increased, Illustrated that with the decrease of particle size, the less affected by the construction dust, The bigger affected by automobile exhaust and industrial dust, coal, etc.And in the rain sample residue, dust, PM10 and PM2.5 and PM1.0 particles, Only in PM2.5 and PM1.0 particles contain element of N, This suggested that N element mainly concentration on the small particles.(3)When detection the volume concentration of rainfall samples and mass concentration of PM10 samples、PM2.5 samples、grading samples, Each element of rainfall samples, PM10 and PM2.5 samples were all detected, Only Fe, Ti, Ba three elements in grading samples were not detected, In the Rain samples, PM10 samples, PM2.5 samples and sample classification are all SO element’s concentration high, An order of magnitude or two orders of magnitude as other elements, In addition the concentration of different elements measured value difference is very big, In rain samples SO element volume concentration maximum was 459.58μg/l, Cd element volume concentration minimum was 0.09μg/l; In PM10 samples SO element mass concentration maximum was 728.19 ng/m3, Ti element mass concentration minimum was 0.21 ng/m3; In the PM2.5 samples SO element mass concentration maximum was 131.76 ng/m3, Ti element mass concentration minimum was 0.20 ng/m3; In classification samples, The concentration of each element in particulate matter in the same series are not the same, The concentration of the same element in different series of particles are not the same. Comprehensive comparison of rainfall samples, PM10 samples, PM2.5 samples all P, Fe, Al, Zn, Si, SO et al the crust elements’ concentration are higher, but Cd, Cr, Ni, Sb, Ti, Se, As, Pb, Cu, V, I, Mn, Br, Ba et al pollution elements’ concentration are lower, Grading samples in each level all SO, Si, P, I, Zn Al, Br et al elements’ mass concentration are higher, other Mn, As, Pb, Se, Ni, Cu, Cr, Cd, Sb, V, Ti, Fe, Ba et al pollution elements’ mass concentration are lower.(4)From the various samples of each element on the proportion of the total, In the rainfall, PM10 and PM2.5 samples all mainly are earth crust elements, And in the earth’s crust elements are mainly for SO, Si two elements, the pollution are the main elements for Ba, Br, Mn, I, Cu et al elements. But the proportion of crustal elements and pollution elements in the sample are not same, In rain samples crust element is accounted for 96% of total element, pollution elements is accounted for only 4%; The crust elements in PM10 samples is accounted for 91% of total element, pollution elements is accounted for 9%; In PM2.5 samples crust element is accounted for 81% of total element, pollution elements is accounted for 19%; In grading samples mainly for SO Si, Zn et al high concentration elements accounted for 97% of total element, low concentration elements accounts for only 3% of total element, and follow the particle size decreases,the proportion of high concentration elements gradually reduce. Comprehensive analysis, the elements in the rainfall sample mainly comes from atmospheric particulates,and with the decrease of the particle size, the proportion of pollution elements gradually rise.(5)In the research on the effects of rainfall on trace elements in the PM10, PM2.5 and grading samples, PM10 and PM2.5 samples in each cycle each element’s concentration were mostly below each element’s concentration of before the rain and after the rain, To illustrate that rainfall have a flushing action for most of the elements in PM10 and PM2.5 samples, And in the research of classification samples did not show the rainfall have the flushing action on it, Additional rainfall on the various elements in PM10 and PM2.5 removal efficiency are not the same, After the rain the formation rate of each element in PM10 and PM2.5 is also different, In PM10 samples, The clear rate of rainfall on the Al, Pb, Fe, Ni, Cu, Cr, Mn et al elements is bigger, After the rain Ti, Al, Cd, Pb, Sb, As and Si element formation rate is bigger, In PM2.5 samples, The clear rate of rainfall on the Cu, Ba, Cd, Zn,Sb and Ti elements is bigger, After the rain Cu, Sb, Pb, Cd, Br, Si, Mn and Fe element formation rate is bigger, But the grading samples has not found a similar rule, For the influence of rainfall on each element of different particle size distribution and same particle size distribution of different elements in grading samples need to be researched.(6) Rainfall and concentration of each element in the period of rainfall are negative correlation, proved that the rainfall has the scouring effects of trace elements in aerosol particles, rainfall and the element of Ba, I, V, Br is significant correlation, also illustrates the rainfall flushing action are different of different elements.(7) Rainfall and rainfall duration and negative correlation between PM10 and PM2.5 by correlation analysis, proved that the rainfall of PM10 and PM2.5 are flushing action, and flushing action of PM10 is more than PM2.5. Rainfall duration and the mass concentration of PM10 and PM2.5 is significant negative correlation, that with the increase of rainfall during long, the stronger the rainfall of PM10 and PM2.5 washout. The quality of the mass concentrations of PM2.5 and PM10 concentration has significantly positive correlation, Interaction and reciprocal transformation between PM2.5 and PM10 of concentration.(8) Analysis on dry wet subsidence fluxes, each element in the dry deposition fluxes is bigger than wet deposition in atmospheric particulates, Informed that the most elements in rainfall are derived from the atmospheric aerosol. SO, Si and other elements are higher in dry wet subsidence, in addition, Si, Zn, Al, Fe and Mn in the dry wet subsidence occupies a significant proportion of proportion. Shanghai atmospheric particulate matter is mainly affected by soil such as dust, construction dust. Heavy metal elements in wet subsidence occupy certain proportion, due to the heavy metal element potential dangers to the environment, its pollution are not allowed to be ignored.(9)The source of trace elements in the samples of rainfall, PM10 and PM2.5 was discovered by the principal factor analysis method. The main source of rainfall, PM10 and PM2.5 are soil source, automobile exhaust, ocean source and industry, coal source. The main source of rainfall is industry producing, coal burning and car exhaust(43.9%), ocean source(20.6%), soil source(13.5%). The main source of PM10 is mineral industry, smelting, burning, car exhaust, coal burning(65.6%), earth crust(16.6%) and ocean source(6.5%). The main source of PM2.5 is earth crust, ocean source, car exhaust, oil burning(39.3%), industry, coal burning(20.2%) and car exhaust(13.8%).