| This study aimed to evaluate the spatio-temporal distributions and sources of nitrogen (N) and phosphorous (P) in the atmospheric deposition of ChangLe River Watershed and its contribution to the recycling of regional nutrients in this area. The atmospheric N and P depositions at four sampling sites in ChangLe River Watershed were monitored from March 2009 to December 2011. A no-power quantitative rain collector (Application number 201010269542.0) was designed and applied to collect rain samples once a month. The wet and dry atmospheric N and P deposition fluxes, their spatio-temporal distributions and contribtutions to total nutrient balance for the entire watershed were discussed and evaluated. The main results were summarized as followings:(1) The mean concentration of TN in rains was 4.0±1 mg/L, and ammonium, nitrate and dissolved organic N formed 48%,20% and 32% of TN in precipitation. The mean concentration TP in rains was low with 0.05±0.02 mg/L.(2) The mean concentration of N and P in precipitation decreased with increasing rainfall. Abount 81% TN and 86% TP wet depositions derived from the rains with <40mm/d.(3) The annual atmospheric N (R2=0.826) and P (R2=0.784) wet deposition flux were both depended on the rainfall, which provided a simpl way to obtain the fluxes on the period with no monitoring data.(4) The annual atmospheric N wet deposition flux and dry deposition accounts for 69% and 31%of total atmospheric N deposition flux (81.8 kg·hm-2), respectively. However, total atmospheric P deposition is in lower level (1.98 kg·hm-2) and dry deposition accounts for 64% of total P deposition flux.(5) Atmospheric N and P deposition both had remarkable seasonal variations. The average deposition fluxes among different seasons followed:summer> spring> autumn> winter. The sum of N deposition amount in summer and spring accounted for 70% annual atmospheric N deposition amount. The sum of P deposition amount in summer and spring accounted for about 66% annual atmospheric P deposition amount.(6) The total emission quantity of N and TP was 12830 yr-1 and 2971 t yr-1 in ChangLe River Watershed in 2009, repectively. Fertilizer application, atmospheric deposition, domestic and animal wastes accounted for 47%,30%,14% and 9% of total N emission quantities, respectively. The contribution of atmospheric deposition for N input in the entire watershed should not be ignored. However, atmospheric deposition only accounted 1% of P emission quantities in the entire watershed.(7) Due to the similar processes from lands to the streams for N derived from the atmospheric dry deposition and chemical fertilizer, the average export ratio (0.21) of chemical fertilizer was used to estimate the N export load of the atmospheric N dry deposition for different catchments. The export of atmospheric N wet deposition was consided to be related with the processes of runoff and the proximity to streams. Moreover, the average concentration of N in the runoff (4.1-6.9 mg/L) was higher than that in the rains.The export ratio for the atmospheric N wet deposition was estimated as 0.308-0.405 for different catchments.(8) Total N export load from watershed to the streams was 2221 yr-11 for the ChangLe River Watershed. Export N load derived from dry and wet deposition was 239 t yr-1 and 802 t yr-1, respectively. Their sum accounted for about 47% of total export load, with dry deposition and wet deposition contributing 11% and 36%, respectively. |
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