Variable relationships between the hydrophobic fraction of dissolved organic matter and metals in Scottish freshwater before the estuarine mixing zone
The organic-Fe association in Scottish freshwater rivers has received little attention compared with in the estuarine mixing zone. We collected 201 water samples from rivers and lakes in Scotland across different sampling years and seasons. Relationships among the hydrophobic (HPO) fraction of dissolved organic matter (DOM), specific UV absorbance (SUVA254), and dissolved metals (Al and Fe) were examined to better understand their co-transportation in Scottish waters. The average DOM, HPO fraction, Fe, and Al concentrations for all the samples co-varied and were lower during winter than during summer. There was a strong positive correlation between DOM and HPO fraction concentrations (R2 = 0.99, p < 0.0001). A significant positive correlation was also found between the HPO fraction and Fe and Al concentrations. The regression slope indicating the overall relationships between the HPO fraction and Fe concentrations differed by as much as 12 times depending on both the sampling period and the river. These slope differences were not significantly determined by the chemical structures of DOM, SUVA254, or Al and Cu concentrations. These results suggest that the Fe transport capacities vary among the Scottish rivers because of other factors such as seasonal effects (temperature and the level of water table) and a suspended solid concentration in the water column.
KeywordsComplex DOM Iron Peat SUVA254
This work was supported by JSPS KAKENHI Grant Number JP15H02805.
Compliance with ethical standards
Conflict of Interest
The authors declare that they have no conflict of interest.
- Kikuchi T, Fujii M, Terao K et al (2017) Correlations between aromaticity of dissolved organic matter and trace metal concentrations in natural and effluent waters: a case study in the Sagami River Basin, Japan. Sci Total Environ 576:36–45. https://doi.org/10.1016/j.scitotenv.2016.10.068 CrossRefGoogle Scholar
- Martin JM, Windom H (1991) Present and future role of ocean margins in regulating marine biogeochemical cycles of trace elements. In: Mantoura R, Martin J, Wollast R (eds) Ocean margine processes in global change. Wiley, New York, pp 45–67Google Scholar