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- Title
Factors characterizing phosphate oxygen isotope ratios in river water: an inter-watershed comparison approach.
- Authors
Ide, Jun'ichiro; Ishida, Takuya; Cid-Andres, Abigail P.; Osaka, Ken'ichi; Iwata, Tomoya; Hayashi, Takuya; Akashi, Masanori; Tayasu, Ichiro; Paytan, Adina; Okuda, Noboru
- Abstract
We compared the oxygen isotope ratio of dissolved phosphate δ 18 O PO 4 in two rivers with different land-cover and geological features (Ado River and Yasu River) within Lake Biwa basin, central Japan, to explore what factor primarily characterizes the δ 18 O PO 4 . Mean values of δ 18 O PO 4 in river water were 19.0 ± 2.4‰ (n = 7) in Ado River and 13.1 ± 2.3‰ (n = 15) in Yasu River, which were significantly different. Comparisons of δ 18 O PO 4 between river water and potential sources of phosphate revealed that in the Ado River, the δ 18 O PO 4 was similar to that in rocks from the accretionary complex and decreased with increasing sedimentary rock coverage. In the Yasu River, the δ 18 O PO 4 was low in the upper forested areas, but increased with paddy field coverage. These results demonstrate that river δ 18 O PO 4 strongly reflects inputs from geological substances, but is also impacted by land-use activities and varies with anthropogenic land coverage in the watershed. Thus, river δ 18 O PO 4 relates to land or bedrock coverage differentially in each river. Regression analysis showed that residuals of the δ 18 O PO 4 tended to converge to zero with increasing drainage area, suggesting that river δ 18 O PO 4 more explicitly reflects land-cover and geological features on a larger watershed scale.
- Subjects
JAPAN; WATERSHEDS; SEDIMENTARY rocks; RIVERS; NONPOINT source pollution; PADDY fields; OXYGEN isotopes; PHOSPHATES; ACCRETIONARY wedges (Geology)
- Publication
Limnology, 2020, Vol 21, Issue 3, p365
- ISSN
1439-8621
- Publication type
Article
- DOI
10.1007/s10201-020-00610-6