黄海近岸大气降水中磷溶解度及其影响因素

于2020年6~9月在黄海近岸城市青岛采集31场降水69个样品，分析其中总磷（TP）、溶解态总磷（DTP）及溶解态无机磷（DIP）和有机磷（DOP），探讨P浓度和溶解度的变化特征及其影响因素.降水中TP浓度为（6.2±1.0）μg/L，DTP浓度为（3.8±0.6）μg/L，P溶解度为（64.8±18.0）%.DTP中以DIP为主，其贡献为（56.5±21.6）%.降水中TP和DTP与降水量呈负幂指数关系，TP清除指数大于DTP.降水量<10mm时，降水对气溶胶P的清除和稀释作用显著影响降水中P浓度，但降水量>40mm时，这种作用对P浓度的影响不大.降水对气溶胶P的清除作用以云下清除为主，占总清除效率的70%~85%.酸化作用显著促进降水中颗粒态P溶解，且无机P溶解效率高于有机P.对降雨量<5mm及>30mm降水，pH值是影响P溶解度的主要因素，降水量和气团来源对P溶解度也有一定影响.当pH值相近时，降水量越大，P溶解度越高；当pH值相近且降水量<5mm时，海洋源贡献越大，P溶解度越高.对降水量5~30mm的降水，P溶解度受到降水量、pH值及气团来源等因素的共同影响.

Solubility of phosphorus in rainwater collected in the coastal area of the Yellow sea and influencing factors

69 rainwater samples were collected in Qingdao during 31precipitation events from Jun. to Sep. 2020. Total phosphorus (TP), dissolved total phosphorus (DTP), dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) were characterized in terms of concentrations, solubility and influencing factors. The averaged concentrations of TP and DTP in rainwater were (6.2±1.0)μg/L and (3.8±0.6)μg/L, respectively, with the P solubility at (64.8±18.0)%. DIP dominantly contributed to DTP with the percentage of (56.7±15.7)%. Both TP and DTP had a negative power correlation with precipitation while the TP scavenging index was larger. For rainwater samples collected at the precipitation <10mm, precipitation significantly affected the P concentrations via scavenging and dilution effects. However, these effects were not detectable in samples collected at precipitation >40mm. The measured P in rainwater was derived from the washout process, which scavenged 70%~85% of particulate P to rainwater. Acidification processes significantly promoted the dissolution of particulate P with a higher efficiency of inorganic P than that of organic P. For the recorded two types of precipitation, i.e., <5mm and >30mm, pH mainly determined the P solubility with precipitation and backward air mass history to some extent. For the rainwater samples with a similar pH, the P solubility increased with increasing precipitation. For the rainwater samples with a similar pH and collected at the precipitation <5mm, the P solubility was higher with air mass history from oceans to the continent. For rainwater samples collected at 5~30mm precipitation, the single factor effect, e.g., precipitation, pH, and air mass source, on the P solubility cannot be isolated out.