Temporal-spatial Variations And Chemical Characteristics Of Atmospheric Aerosol Over The East China Marginal Seas

Atmospheric aerosol can place a significant influence on the earth’s radiationbudget and then the partial or even global climate through their direct and indirectradiative force. The East Asia region can be seriously polluted by human activity andthen will lead to high loadings of aerosol from anthropogenic source. These aerosolparticles with high levels can be transported to the remote ocean over the East ChinaMarginal Seas from a long-range distance, which can bring about obvious impact onthe atmospheric quality and oceanic environment. In this dissertation we choose theEast China Sea （ECS）, the Bohai Sea （BS） and the Yellow Sea （YS） as the objects,which is of great importance because aerosol particles have to pass these marginalseas before reaching the Pacific Ocean. The aerosol samples were collected over theECS during spring in2011and summer and autumn in2010, the BS and the SouthYellow Sea （SYS） during spring and autumn in2010and summer and winter in2011.The distribution, seasonal and spatial variations as well as source analysis of aerosolcomposition are analyzed, the main results are presented as follows:（1） The total concentration of water soluble ions （WSI） during spring over the BS was54.2±17.1μg·m^-3and secondary ions occupy79.9%of the total concentration. Theconcentration of every single ion follows the order of NO₃^-> nss-SO₄^2-> NH₄⁺> Cl^->nss-Ca²⁺> Na⁺> nss-K⁺> Mg²⁺. The concentration of WSI follows the order ofnss-SO₄^2-> Cl^-> Na⁺> NO₃^-> Mg²⁺> nss-Ca²⁺> NH₄⁺> nss-K⁺. The totalconcentration was43.8±9.59μg·m^-3and the secondary ions (nss-SO₄^2-, NO₃^-andNH₄⁺) occupies about47.7%. The total concentration in autumn over the BS was36.4±12.9μg·m^-3and the level of single ion follows nss-SO₄^2-> NO₃^-> NH₄⁺> Cl^->nss-Ca²⁺> Na⁺> Mg²⁺> nss-K⁺. The secondary ions occupy85.4%of the totalconcentration during this cruise. The maximum of total concentration appeared inwinter over BS, with mean of64.5±12.2μg·m^-3. The single ion in aerosol samples follows the order of nss-SO₄^2-> NO₃^-> NH₄⁺> Na⁺> Cl^-> nss-Ca²⁺> nss-K⁺> Mg²⁺.The concentration of measured trace metals shows the same order in spring andsummer, Al> Fe> Zn> Mn> Pb> Cu. This order indicated Al> Fe> Zn> Pb> Mn> Cu in autumn and winter cruise over the BS. The level of MSA also presents theseasonal variation in aerosol samples, with the means of0.0636±0.0142μg·m^-3,0.0490±0.0403μg·m^-3,0.0398±0.0230μg·m^-3and0.0101±0.0039μg·m^-3duringspring, summer, autumn and winter, respectively.（2） The total concentration of WSI in spring over the SYS was24.2±6.57μg·m^-3andthe secondary ions occupy about68.6%. The concentration of single ion follows theorder of nss-SO₄^2-> Cl^-> Na⁺> NO₃^-> Mg²⁺> nss-Ca²⁺> NH₄⁺> nss-K⁺. The totalconcentration of WSI was36.8±16.4μg·m^-3during summer over the SYS and thisorder shows nss-SO₄^2-> NO₃^-> Cl^-> Na⁺> NH₄⁺> Mg²⁺> nss-Ca²⁺> nss-K⁺. Insummer cruise, the secondary ions occupy59.7%of the total concentrations and theproportion of sea-salt ions indicates the rising tendency. The minimum concentrationof WSI appears in autumn over the SYS, with the mean of20.5±14.5μg·m^-3. Thesecondary ions occupy67.8%and the single concentration follows the order ofnss-SO₄^2-> NO₃^-> Cl^-> NH₄⁺> Na⁺> Mg²⁺> nss-Ca²⁺> nss-K⁺. The totalconcentration of WSI shows the maximum in winter, with the mean of54.2±13.4μg·m^-3. The secondary ions accounts for67.4%of total level and the order of WSI isNO₃^-> nss-SO₄^2-> NH₄⁺> Cl^-> nss-Ca²⁺> Na⁺> nss-K⁺> Mg²⁺. The concentration ofmeasured trace metals shows the same order during spring, autumn and winter cruises,following the order of Al> Fe> Zn> Pb> Mn> Cu. This order appears as Al> Fe>Zn> Mn> Pb> Cu during summer cruise.（3） The concentrations of major WSI follow the order of nss-SO₄^2-> NH₄⁺> NO₃^->Cl^-> nss-Ca²⁺> Na⁺> Mg²⁺> nss-K⁺in the TSP during spring over the ECS. Theorder of WSI during summer over the ECS shows almost same as the spring,indicating nss-SO₄^2-> NH₄⁺> NO₃^-> Cl^-> nss-Ca²⁺> Na⁺> Mg²⁺> nss-K⁺. Thesecondary ions occupy the most part of WSI during spring and summer, with averagesof17.5±5.7μg·m^-3and28.1±7.3μg·m^-3，respectively, contributing over80%of thetotal WSI concentrations. The concentrations of WSI follow the order of nss-SO₄^2-> Cl^-> NO₃^-> Na⁺> nss-Ca²⁺> Mg²⁺> NH₄⁺> nss-K⁺during autumn over the ECS.The total concentrations of WSI accounts to39.5±20.4μg·m^-3, and the secondarycompositions occupy56.8%showing a lower tendency. The concentrations of tracemetals collected over the ECS during spring and autumn are7.178±2.164μg·m^-3and1.068±0.537μg·m^-3，respectively. The concentration of trace metals in spring andautumn follows the same order of Al> Fe> Zn> Mn> Pb> Cu. The totalconcentration of trace metals during summer over the ECS was1.490±1.646μg·m^-3and it follows the order of Al> Fe> Zn> Pb> Mn> Cu. There exists a significantseasonal difference in the concentration of Methanesulfonic acid （MSA）, with meanconcentrations of0.0748±0.0328μg·m^-3，0.0392±0.0416μg·m^-3and0.0722±0.0523μg·m^-3during spring, summer and autumn, respectively.（4） Based on the correlation analysis, there exists a good correlation between thesecondary ions in aerosol samples. This result indicates the secondary ions have thesimilar source, which can be mainly ascribed to the human activities. The meanNa⁺/Mg²⁺mass ratios was very close to the ratio in bulk seawater, indicating the samesource between Na⁺and Mg²⁺. Besides the transport from ocean, the terrestrial inputcan contribute to the concentration of Cl^-. The correlation analysis presents nss-K⁺andnss-Ca²⁺are mostly derived from crust.（5） Biogenic contribution to nss-SO₄^2-are13.2%，5.2%and10.0%during spring,summer and autumn cruise over the ECS, respectively; while over the BS the biogeniccontributions during spring, summer, autumn and winter are9.4%，7.5%，4.9%and0.6%, respectively. In the samples collected over SYS, the contributions account to20.9%,13.1%,8.1%and1.6%during spring, summer, autumn and winter,respectively. Biogenic contributions appear higher during spring than other seasons,since in spring the higher primary productivity contributes higher DMS in surfaceseawater, which can lead to the higher atmospheric MSA concentration and thenhigher biogenic contribution. Generally speaking, the nss-SO₄^2-in aerosol samplesover the China marginal seas can mostly be ascribed to anthropogenic source,however, the biogenic contribution should also be obvious, especially when theprimary productivity is relatively higher during spring bloom. （6） Because of the strong input from human activities, much more acidic ions havebeen transported to sampling areas than alkaline ions. This difference can result in theacidic nature of aerosol samples collected over China marginal seas. Obvious Cl^-deficits are observed in the samples collected over the ECS and the SYS, however,this phenomenon does not appear in aerosol samples collected over the BS.