Abstract
Abstract Nitrate and organic contamination from Midwest rivers, including the White River at Muncie, IN, has been an on-going concern and contributes to the hypoxic zone in the Gulf. Despite rich data, recent water quality changes have rarely been investigated. This study employed 16 years of continuous monitoring data, including biochemical oxygen demand (BOD), dissolved oxygen (DO), and nitrate–nitrite as nitrogen (NN) from five sites near Muncie, and analyzed the water quality trend and pollution sources. A novel approach, Weighted Regression on Time, Discharge and Seasons (WRTDS) that allows for the representation of long-term water quality patterns by considering seasonal variance and discharge-related effects over time, is adopted. Flow-normalized BOD and NN concentration and flux both increased, and DO concentration and flux decreased. However, the changes vary among sites. Muncie wastewater treatment plant and combined sewage outflows (CSOs) contribute remarkably to NN pollution during low-flow seasons. Urban and agricultural runoff, and CSOs impact BOD levels. Agricultural runoff contribution to BOD is increasing in recent years. Seasonal patterns of nitrate and BOD in the river are also analyzed. The results are helpful for watershed managers to re-think conservation practices and have indications to water quality management beyond the study area.
Highlights
Water quality degradation has been a significant concern in the US Midwest
With long-term monitoring data and the employment of WRTDS, the current study aims to investigate the long-term trends and seasonal variations of White River water quality and analyze the sources of organic and nitrogen pollutants upstream of the White River at Muncie
The NN concentration increase does not differ much in the first three sites but is much higher at the Nebo and 575 W sites, and the results indicate that wastewater treatment plants (WWTPs) effluent contribution is significant during low-flow seasons
Summary
Water quality degradation has been a significant concern in the US Midwest. As a consequence of industrial, domestic, and urban/agricultural runoff, the White River was heavily contaminated prior to the 1970s (Tiffany 2018). Downstream aquatic environment degradation including the so-called ‘dead zone’ in the Gulf of Mexico where fish and marine life is affected by the low level of dissolved oxygen (DO) level could potentially be traced back to the nutrient and biochemical oxygen demand (BOD) load in the upstream river basins including the White River watershed (Bargu et al 2019). BOD originates from various point and non-point sources, including the organic-rich discharge from domestic wastewater treatment plants (WWTPs); stormwater runoff from agricultural land, parking lots, and livestock operations; combined sewage outflows (CSOs), and septic and wastewater pipeline leakages. Potential sources include surface drainage, discharge from WWTPs, CSOs, agricultural runoff, decomposition of plant and animal tissue, and the complex nitrogen cycle (Ghane et al 2016)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
