2 research outputs found
Influence of Leaching Solution and Catchment Location on the Fluorescence of Water-Soluble Organic Matter
Organic matter (OM) plays a significant
role in biogeochemical
processes in soil and water systems. Water-soluble organic matter
(WSOM) leached from soil samples is often analyzed as representative
of potentially mobile OM. However, there are many WSOM extraction
methods in the literature with no clear guidelines for method selection.
In this study, four common leaching solutions (0.5 M K<sub>2</sub>SO<sub>4</sub>, 0.01 M CaCl<sub>2</sub>, 2 M KCl, and H<sub>2</sub>O) were used to extract WSOM from various locations within a forested
catchment. Fluorescence spectroscopy was used to analyze the impact
of extraction method on WSOM chemistry. While all four methods consistently
identified chemical differences between WSOM from a north-facing slope,
south-facing slope, and riparian zone, there were clear differences
in fluorescence signals between the leaching methods. All three salt
solutions contained WSOM with a higher fluorescence index and humification
index than WSOM leached with H<sub>2</sub>O, suggesting the presence
of salts releases different fractions of the soil organic matter.
A parallel factor analysis (PARAFAC) model developed from the leachates
identified a distinctive soil humic fluorophore observed in all samples
and fluorescent artifacts present in H<sub>2</sub>O-leached samples
Persistent Urban Influence on Surface Water Quality via Impacted Groundwater
Growing urban environments stress
hydrologic systems and impact
downstream water quality. We examined a third-order catchment that
transitions from an undisturbed mountain environment into urban Salt
Lake City, Utah. We performed synoptic surveys during a range of seasonal
baseflow conditions and utilized multiple lines of evidence to identify
mechanisms by which urbanization impacts water quality. Surface water
chemistry did not change appreciably until several kilometers into
the urban environment, where concentrations of solutes such as chloride
and nitrate increase quickly in a gaining reach. Groundwater springs
discharging in this gaining system demonstrate the role of contaminated
baseflow from an aquifer in driving stream chemistry. Hydrometric
and hydrochemical observations were used to estimate that the aquifer
contains approximately 18% water sourced from the urban area. The
carbon and nitrogen dynamics indicated the urban aquifer also serves
as a biogeochemical reactor. The evidence of surface water–groundwater
exchange on a spatial scale of kilometers and time scale of months
to years suggests a need to evolve the hydrologic model of anthropogenic
impacts to urban water quality to include exchange with the subsurface.
This has implications on the space and time scales of water quality
mitigation efforts