Atmospheric Phosphorus Deposition in Ashiu, Central Japan – Source Apportionment for the Estimation of True Input to a Terrestrial Ecosystem

Atmospheric bulk depositions of soluble reactive phosphorus (SRP), soluble unreactive phosphorus (SUP), particulate inorganic phosphorus (PIP), particulate organic phosphorus (POP), total phosphorus (TP) and some other dissolved and particulate components were monitored for 3 years in Ashiu, Central Japan. The mean bulk depositions of SRP, SUP, PIP, POP, TP, dissolved components (Na, Mg, nss-Ca, K, V, Mo, nss-SO4) and particulate components (Al, Fe, Ti, Ca, Mg, Mn, Ba, Sr, Zn) were 175, 76, 136, 397, 783, 156,000, 10,900, 7450, 5470, 10.3, 1.52, 40,100, 13,200, 3590, 2630, 576, 624, 42.3, 30.2, 17.4, 8.2 μmol m−2 year−1, respectively. The value for TP deposition was in the lower range of previous literature. The low P deposition probably reflected the method applied to reduce the contribution of local particles, including (1) placement of samplers off the ground surface, (2) installation of multiple samplers, and (3) rejection of contaminated samples. Al data suggested that 15 ± 5% of TP was brought by lithogenic dust from East Eurasia. Nss-SO4 and Mo data and air-mass backward trajectories suggested that 39 ± 4% of TP was derived from coal combustion in China. It was speculated that the rest (47 ± 6%) of the TP deposition might be predominantly attributed to the contribution of local biogenic particles. Net atmospheric TP input (lithogenic dust and fossil fuel combustion) was almost equal to the TP outflow from Japanese forests on granitic soils.