Publication Date:
2012-07-08
Description:
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 seconds 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 o 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.
Print ISSN:
0885-6087
Electronic ISSN:
1099-1085
Topics:
Architecture, Civil Engineering, Surveying
,
Geography
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