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Characteristics of Dissolved Organic Matter from a Transboundary Himalayan Watershed: Relationships with Land Use, Elevation, and Hydrology
journal contribution
posted on 2020-02-19, 15:22 authored by Meilian Chen, Chen Zeng, Fan Zhang, Shichang Kang, Chaoliu LiHimalayan rivers play pivotal roles
in regional water and food
supplies, global sediments, and carbon budgets. We studied a transboundary
mountainous Kosi River in the Himalayas by utilizing ultraviolet–visible
spectroscopy and excitation–emission matrix coupled with parallel
factor analysis. We have found that agricultural land use promoted
the production of abundant proteinlike fluorescence in the surface
waters [∼1.1–1.8 Raman unit (RU) for two proteinlike
components that accounts for ≥97% of relative abundance] as
opposed to natural vegetation land cover (e.g., forests and grasslands),
despite the low dissolved organic carbon (DOC, 0.50–1.02 mg
L–1), implying more reactive fluorescent dissolved
organic matter (FDOM) that can potentially cause more CO2 outgassing. Furthermore, we observed a decreasing trend of slope
ratio (SR) and proteinlike fluorescence
with elevation as opposed to a humiclike component, potentially due
to more concentrated croplands and consequent nutrient inputs to rivers
at lower elevations. In addition, poststorm samples shifted to more
humiclike FDOM and chromophoric DOM (CDOM) sides compared to baseflow
water. These findings highlighted the importance of land uses and
other environmental conditions, such as elevation and hydrology, on
DOM characteristics and dynamics and water quality, which can potentially
be amplified due to the steep gradients in mountainous watersheds.
Measures should be taken for proper and sustainable land uses to mitigate
river water eutrophication and pollution and to protect drinking water
sources for millions of populations.