Nutrient Characteristics And Source Apportionment In Atmospheric Deposition Of The Yellow Sea And East China Sea

In this study, aerosol and rainwater samples were collected in the Yellow Sea （QianliyanIsland） and East China Sea （Huanglong Island）, the nutrient concentrations were determined.Air mass back trajectories of aerosols and precipitation were used to track their sources andnutrient characteristics by using the NOAA HYSPLIT model. The re-circulation leachingsystem was developed to understand the dissolution dynamics of nutrients in aerosols.Dissolved nutrients (NO₂^-+NO₃^-, NH₄⁺, SiO₃^2-, PO₄^3-) were measured in wet deposition at twosites. Water-soluble nutrients (NO₂^-+NO₃^-, NH₄⁺, SiO₃^2-, PO₄^3-), acid-soluble nutrients （TINH4,TI（NO₂+NO₃）, TIP） and total particle phosphorus （TPP） were determined in aerosol samplesat Qianliyan Island.At Qianliyan Island, dry deposition showed seasonal variations, the total suspendedparticulates （TSP） contents and nutrient concentrations in aerosols had obvious seasonalvariation, which were higher in spring and winter while it were lower in summer. Comparednutrient levels in land-based with marine source aerosols, nutrient concentrations inatmospheric deposition should be affected by anthropogenic emissions and natural sand-duststorm.It was observed in leaching experiments that the reduction of pH had no effect ondissolution of NO₂^-+NO₃^-whatever in seawater or Milli-Q water. NH₄⁺of the aerosol samplesin spring was mostly dissolved in neutral condition （pH=7.8）, a little amount also wasdissolved in acidic conditions （pH=2）, while nothing was dissolved in acidic conditions foraerosol samples in winter. In neutral conditions （pH=7.8）, little amount of SiO₃^2-and PO₄^3-was dissolved, while a large amount was dissolved in acidic conditions （pH=2）.Rainfall was mostly neutral （5.6<pH≤7.0） and the rainfall weighted pH was6.21atQianliyan Island. At Huanglong Island, rainfall was mostly strong acid （pH≤4.5） and gentleacid（4.5<pH≤5.6）, average rainfall weighted pH was4.54. For wet deposition of Qianliyan andHuanglong Islands, the concentrations of nutrients had obvious seasonal variation, which werehigher in spring and winter than in summer and autumn. At Qianliyan Island, annual total atmospheric deposition fluxes of NO₂^-+NO₃^-, NH₄⁺, SiO₃^2-, PO₄^3-were83.1,68.0,3.04,0.71mmol m-2yr-1, respectively. Atmospheric dry and wet deposition of NH₄⁺, NO₂^-+NO₃^-, SiO₃^2-and PO₄^3-accounted for87%,53%,3%and50%of total terrestrial （atmospheric deposition andrivers） input respectively. At Huanglong Island, annual atmospheric wet deposition fluxes ofNH₄⁺, NO₂^-+NO₃^-, SiO₃^2-, PO₄^3-were29.5,22.6,1.95,0.11mmol m-2yr-1, respectively. Annualtotal atmospheric dry and wet deposition fluxes of NH₄⁺, NO₂^-+NO₃^-, SiO₃^2-, PO₄^3-were36.4,35.0,2.25and0.29mmol m-2yr-1, respectively.Based on comparison of nutrient concentrations in atmospheric wet deposition at differentregions in the world, inorganic nitrogen concentrations in rainwater decreased gradually fromcoastal urban stations to remote oceans. Nutrient concentrations in atmospheric deposition shouldbe affected by anthropogenic emissions and natural sand-dust storm. Atmospheric depositionfluxes showed considerable temporal and sptial variations, there was a dramatic increase with thereduction of the distance from sand-dust source area and human settlements. With thedevelopment of industry and agriculture, the influence of anthropogenic emissions can be moreand more significant in atmospheric deposition. NH₄⁺in atmospheric deposition was higher thanNO₃^-in China, but it was opposite for the developed countries. The value of NH₄⁺/（NO₂^-+NO₃^-）should be affected by conditions of industrial and agricultural development.