Geology topics

Durelle T. Scott

Publications and source records attributed to Durelle T. Scott.

4 recordsLinked to original sources

USGS2019

Floodplain inundation spectrum across the United States

Floodplain inundation poses both risks and benefits to society. In this study, we characterize floodplain inundation across the United States using 5800 stream gages. We find that between 4% and 12.6% of a river’s annual flow moves through its floodplains. Flood duration and magnitude is greater in large rivers, whereas the frequency of events is greater in small streams. However, the relative exchange of floodwater between the channel and floodplain is similar across small streams and large rivers, with the exception of the water-limited arid river basins. When summed up across the entire river network, 90% of that exchange occurs in small streams on an annual basis. Our detailed characterization of inundation hydrology provides a unique perspective that the regulatory, management, and research communities can use to help balance both the risks and benefits associated with flooding.

Nature Communications↗

USGS2014

Floodplain biogeochemical processing of floodwaters in the Atchafalaya River Basin during the Mississippi River flood of 2011

The 2011 flood in the Lower Mississippi resulted in the second highest recorded river flow diverted into the Atchafalaya River Basin (ARB). The higher water levels during the flood peak resulted in high hydrologic connectivity between the Atchafalaya River and floodplain, with up to 50% of the Atchafalaya River water moving off channel. Water quality samples were collected throughout the ARB over the course of the flood event. Significant nitrate (NO 3 -) reduction (75%) occurred within the floodplain, resulting in a total NO 3 - reduction of 16.6% over the flood. The floodplain was a small but measurable source of dissolved reactive phosphorus (SRP) and ammonium (NH 4 +). Collectively, these results from this large flood event suggest that enhancing river-floodplain connectivity through freshwater diversions will reduce NO 3 - loads to the Gulf of Mexico during large annual floods.

Louisiana↗

USGS2012

Anthropogenic aerosols as a source of ancient dissolved organic matter in glaciers

Glacier-derived dissolved organic matter represents a quantitatively significant source of ancient, yet highly bioavailable carbon to downstream ecosystems. This finding runs counter to logical perceptions of age–reactivity relationships, in which the least reactive material withstands degradation the longest and is therefore the oldest. The remnants of ancient peatlands and forests overrun by glaciers have been invoked as the source of this organic matter. Here, we examine the radiocarbon age and chemical composition of dissolved organic matter in snow, glacier surface water, ice and glacier outflow samples from Alaska to determine the origin of the organic matter. Low levels of compounds derived from vascular plants indicate that the organic matter does not originate from forests or peatlands. Instead, we show that the organic matter on the surface of the glaciers is radiocarbon depleted, consistent with an anthropogenic aerosol source. Fluorescence spectrophotometry measurements reveal the presence of protein-like compounds of microbial or aerosol origin. In addition, ultrahigh-resolution mass spectrometry measurements document the presence of combustion products found in anthropogenic aerosols. Based on the presence of these compounds, we suggest that aerosols derived from fossil fuel burning are a source of pre-aged organic matter to glacier surfaces. Furthermore, we show that the molecular signature of the organic matter is conserved in snow, glacier water and outflow, suggesting that the anthropogenic carbon is exported relatively unchanged in glacier outflows.

Nature Geoscience↗

USGS2003

Transport and cycling of iron and hydrogen peroxide in a freshwater stream: Influence of organic acids

An in‐stream injection of two dissolved organic acids (phthalic and aspartic acids) was performed in an acidic mountain stream to assess the effects of organic acids on Fe photoreduction and H 2 O 2 cycling. Results indicate that the fate of Fe is dependent on a net balance of oxidative and reductive processes, which can vary over a distance of several meters due to changes in incident light and other factors. Solution phase photoreduction rates were high in sunlit reaches and were enhanced by the organic acid addition but were also limited by the amount of ferric iron present in the water column. Fe oxide photoreduction from the streambed and colloids within the water column resulted in an increase in the diurnal load of total filterable Fe within the experimental reach, which also responded to increases in light and organic acids. Our results also suggest that Fe(II) oxidation increased in response to the organic acids, with the result of offsetting the increase in Fe(II) from photoreductive processes. Fe(II) was rapidly oxidized to Fe(III) after sunset and during the day within a well‐shaded reach, presumably through microbial oxidation. H 2 O 2 , a product of dissolved organic matter photolysis, increased downstream to maximum concentrations of 0.25 μM midday. Kinetic calculations show that the buildup of H 2 O 2 is controlled by reaction with Fe(II), but this has only a small effect on Fe(II) because of the small formation rates of H 2 O 2 compared to those of Fe(II). The results demonstrate the importance of incorporating the effects of light and dissolved organic carbon into Fe reactive transport models to further our understanding of the fate of Fe in streams and lakes.

Water Resources Research↗