Water Quality Estimation Using Combined Water Chemistry and Field Spectroscopy in the Shenandoah River, Virginia

Water Quality Estimation Using Combined Water Chemistry and Field Spectroscopy in the Shenandoah River, Virginia

Mbongowo J. Mbuh (George Mason University, Fairfax, VA, USA), Paul R. Houser (George Mason University, Fairfax, VA, USA) and Ako Heidari (George Mason University, Fairfax, VA, USA)
Copyright: © 2016 |Pages: 24
DOI: 10.4018/ijagr.2016040102
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Abstract

This study investigated the spatial dynamics of water quality across the Shenandoah River basin using spectroscopy and chemometrics to estimate chlorophyll (Chl), colored dissolved organic matter (CDOM) and turbidity using three band combinations and nutrients (total nitrogen and total phosphorous) in the Shenandoah River. The mean Chl a concentration for 555 nm, 560 nm and 640 nm were; 0.31 µg/l, 0.33 µg/l, and 0.51 µg/l respectively. Chlorophyll a showed strong correlations at band 640 (r = 0.92). The bands centered at 670/490 were the best in predicting CDOM and turbidity in the Shenandoah River Basin with an r2 = 0.56. Chemometrics analysis show that total phosphorous, nitrogen and turbidity can be predicted between 450 to 555nm and 670 to 710 nm, the range of wavelengths which indicated better predictability for spectroscopic analysis. The resultant concentration is used to develop predictive models to determine sensitive spectral variables for nitrogen, phosphorous, Chl-a, and CDOM.
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1. Introduction

Water is one of the most essential and valuable and essential resources for life on earth and there is an ever-increasing stress on water resources as population increases, there is an ever-increasing stress exerted on water resources (McGwire et al., 2000). Sustainable water resources management requires continuous and accurate monitoring. Satellite observations has provided data for such monitoring for several years (Landgrebe, 1999) and has served as a time and the cost-effective way to carry out large-scale monitoring (Okin et al., 2001), “which can be used to determine the quality, quantity, and geographic distribution of this resource” (Govender et al., 2006). Water pollution is a significant environmental issue, further limiting the availability of water for human and environmental use. In the Shenandoah River, several natural and anthropogenic processes affect the quality of streams and ground water. According to the Virginia Department of Environmental Quality the Shenandoah River is also “under the under stress from a variety of human uses and influences, from water supply demands, waste disposal and irrigation, to hydropower, transportation and recreation”. Common major chemicals found in the Shenandoah Basin include nutrients (nitrogen and phosphorous), “pesticides, trace elements, volatile organic compounds and chlorinated industrial compounds” (USGS, 1998). Although nutrients are essential for plant and animal growth and nourishment, an overabundance of some nutrients in water can disturb the river (Mueller & Helsel, 1996). Pollution incidents in the Shenandoah have been reported by the Environmental Quality Department, between 1929 and 1950, where mercury waste from a now-defunct DuPont Co. facility contaminated the South Fork from Waynesboro to Front Royal. McGovern (2014), in a recent article on the Rockbridge report, stated that mercury levels have mostly settled and do not appear to pose a significant health threat, although its concentrations have not declined. The report also indicates that the river continues to maintain mercury advisory, the sponsorship of scientists by DuPont to monitor fish health and water quality has remained in place (McGovern S., http://rockbridgereport.washingtonandlee.net/?p=7053).

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