The oxygen isotopic composition of phosphate as an effective tracer for phosphate sources in Hongfeng Lake

作     者：Yongxue Ji Jingan Chen Runyu Zhang Yong Liu Jingfu Wang 

作者机构：State Key Laboratory of Environmental GeochemistryInstitute of GeochemistryChinese Academy of SciencesGuiyang 550081China University of Chinese Academy of SciencesBeijing 100049China 

出 版 物：《Acta Geochimica》 (地球化学学报（英文）)

年 卷 期：2017年第36卷第4期

页      面：619-625页

核心收录：

学科分类：0709[理学-地质学] 0819[工学-矿业工程] 08[工学] 0708[理学-地球物理学] 0815[工学-水利工程] 

基　　金：financially supported by the National Key Research and Development Project by MOST of China(No.2016YFA0601003) the National Natural Science Foundation of China(Nos.U1612441 and 41173125) Science and Technology Project of Guizhou Province 

主　　题：Phosphate source δ18Op Eutrophication Hongfeng Lake 

摘      要：In order to characterize the oxygen isotopic composition of internal phosphate and explore the possibility of using these data to identify phosphate sources, we measured oxygen isotopic compositions of phosphate(δ^(18)O_p) in sediment pore water in Hongfeng Lake, a typical deep-water lake in a mountainous area. These data, in combination with δ^(18)O_p in surface water samples and water column samples, were successfully used to identify phosphate sources. The δ^(18)O_p value of sediment pore water ranged from 15.2% to 15.8%, with an average value of 15.5%—the δ^(18)O_p value of internal phosphate. The δ^(18)O_p values decreased gradually through the water column from 19.4% in surface water to 16.4% in deeper water, implying that internal phosphate had more negative δ^(18)O_p values than external phosphate. This finding was substantiated by horizontal variations in δ^(18)O_p values, which decreased with increasing distance from inflowing rivers. All collected evidence suggests that external and internal phosphate have distinctly different isotopic signatures and that these signatures have not been considerably altered by biological mediation in Hongfeng Lake. Therefore, δ^(18)O_p can be used to distinguish phosphate sources. A two-endmember mixing model showed that internal phosphate had an average contribution of 40%, highlighting the influence of internal phosphorus loading on aqueous phosphate and eutrophication. This study illustrates the need to reduce the internal phosphorus load from sediment and provides guidance for nutrient management and in-lake restoration treatment in Hongfeng Lake. The data presented here are limited, but serve to highlight the great potential of δ^(18)O_p as an effective tracer for identifying phosphate sources. Systematic investigations of the oxygen isotopic compositions of external phosphate, internal phosphate, and phosphate through the water column, in combination with in-lake P biogeochemical cycle study, would be desirable in fu