Geochemistry of Flood Waters from the Tar River, North Carolina Associated with Hurricane Matthew

Charles Humphrey,Jamil Blackmon,Christa Sanderford,Guy Iverson,Caitlin Skibiel

doi:10.3390/resources8010048

Charles Humphrey, Jamil Blackmon + Show 3 more

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https://doi.org/10.3390/resources8010048

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Abstract

Hurricane Matthew caused flooding in Eastern North Carolina that was categorized as a one in 500-year frequency event. Matthew was the second such event in less than 20 years, following Hurricane Floyd in 1999. The frequency of intense storms is projected to increase for many coastal areas, including North Carolina, because of climate change. The goal of this study was to gain a better insight into the geochemistry of flood waters associated with major flood events. Water samples (n = 22) from the Tar River in Greenville, North Carolina were collected over a two-week period after Matthew moved across the state. Results show that total Kjeldahl nitrogen, dissolved organic carbon, phosphate, and Escherichia coli concentrations and exports were significantly (p < 0.05) higher when the river was above flood stage relative to below. Isotopic analyses of δ15N and δ18O in NO3 in flood waters suggest that wastewater, possibly from sanitary sewer and confined animal feeding operation overflows, was the major source of nitrate associated with flood waters. Regulatory efforts to reduce nutrient loading to coastal waters may be complicated by contributions associated with intense storm events, given that such storms are becoming more frequent.

Highlights

Stream concentrations and watershed exports of common water quality contaminants including nitrogen, phosphorus, and Escherichia coli often increase in response to rain events [1,2,3,4]
Nutrient and E. coli concentrations in water samples collected from the Tar River during the flood stage were variable (TDN: 1.25 to 1.54 mg L−1 ; Total Kjeldahl nitrogen (TKN): 0.79 to 1.22 mg L−1 ; PO4 -P: 0.015 to 0.112 mg L−1 : dissolved organic carbon (DOC): 14.3 to 19.2 mg L−1 ; E. coli: 21 to 354 most probable number (MPN) 100 mL−1 ), but most concentrations were higher during flood stage relative to below flood stage (Figures 2–4, Table 1.)
The river dropped below flood stage during the afternoon of 21 October 2016, and samples collected after that time had median concentrations of E. coli (45 MPN 100 mL−1 ), PO4 -P (0.002 mg L−1 ), Dissolved nitrogen (DON) (0.44 mg L−1 ), TKN

Summary

Introduction

Stream concentrations and watershed exports of common water quality contaminants including nitrogen, phosphorus, and Escherichia coli often increase in response to rain events [1,2,3,4]. While the influence of stormwater runoff on water quality has been extensively documented, less information is available with regards to pollutant concentrations and exports from rivers during extreme weather events such as hurricanes. During such events, the focus is providing shelter and necessities for residents in affected areas, and routine water quality sampling locations may be inaccessible during these events [15]. Over the past two decades, the frequency and intensity of tropical cyclones has increased for the Pacific and Atlantic Basins [16,17], causing extensive flooding

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