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Monitoring and modeling dissolved oxygen dynamics through continuous longitudinal sampling: a case study in Wen‐Rui Tang River, Wenzhou, China
Author(s) -
Li Jun,
Liu Huixia,
Li Yancheng,
Mei Kun,
Dahlgren Randy,
Zhang Minghua
Publication year - 2012
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.9459
Subject(s) - biochemical oxygen demand , environmental science , water quality , sampling (signal processing) , hydrology (agriculture) , pollutant , surface water , chemical oxygen demand , environmental engineering , ecology , wastewater , computer science , geology , geotechnical engineering , filter (signal processing) , computer vision , biology
Synoptic water sampling at a fixed site monitoring station provides only limited ‘snap‐shots’ of the complex water quality dynamics within a surface water system. However, water quality often changes rapidly in both spatial and temporal dimensions, especially in highly polluted urban rivers. In this study, we designed and applied a continuous longitudinal sampling technique to monitor the fine‐scale spatial changes of water quality conditions, assess water pollutant sources, and determine the assimilative capacity for biochemical oxygen demand (BOD) in an urban segment of the hypoxic Wen‐Rui Tang River in eastern China. The continuous longitudinal sampling was capable of collecting dissolved oxygen (DO) data every 5 s yielding a ~11 m sampling interval with a precision of ±0.1 mg L −1 . The Streeter and Phelps BOD‐DO model was used to calculate: (1) the oxygen consumption coefficient ( K 1 ) required for calibration of water quality models, (2) BOD assimilative capacity, and (3) BOD source and load identification. In the 2014 m river segment sampled, the oxygen consumption coefficient ( K 1 ) was 0.428 d −1 (20°C), the total BOD discharge was 916 kg d −1 , and the BOD assimilative capacity was 382 kg d −1 when the minimum DO level was set to 2 mg L −1 . In addition, the longitudinal analysis identified eight major drainage outlets (BOD point sources), which were verified by field observations. This new approach provides a simple, cost‐effective method of evaluating BOD‐DO dynamics over large spatial areas with rapidly changing water quality conditions, such as urban environments. It represents a major breakthrough in the development and application of water quality sampling techniques to obtain spatially distributed DO and BOD in real time. Copyright © 2012 John Wiley & Sons, Ltd.