Dissolved oxygen and its response to eutrophication in a tropical black water river

• Published in: Journal of environmental management 2010-08, Vol.91 (8), p.1730-1737
• Main Authors: Rixen, Tim, Baum, Antje, Sepryani, Harni, Pohlmann, Thomas, Jose, Christine, Samiaji, Joko
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; anthropogenic activities; Applied ecology; Applied sciences; Biological and medical sciences; Bioremediation; Black water river; Carbon; Channels; color; Conservation, protection and management of environment and wildlife; Dissolution; dissolved organic carbon; Dissolved organic matter; Dissolved oxygen; Environmental Monitoring - methods; Eutrophication; Exact sciences and technology; Freshwater; Fundamental and applied biological sciences. Psychology; General aspects; Households; Indonesia; Leaching; Morning; Nutrients; Oxygen; Oxygen - analysis; oxygen production; peat soils; photosynthesis; Pollution; Reduction; river water; Rivers; Rivers - chemistry; Siak River; Soil - analysis; Soils; Sumatra; Time Factors; Tropical Climate; Tropical zones; Waste Disposal, Fluid - methods; Waste management; Waste water; Wastewater; Wastewaters; Water management; Water Pollutants, Chemical - analysis; Water pollution; Water treatment and pollution
• ISSN: 0301-4797; 1095-8630; 1095-8630
• DOI: 10.1016/j.jenvman.2010.03.009

The Siak is a typical, nutrient-poor, well-mixed, black water river in central Sumatra, Indonesia, which owes its brown color to dissolved organic matter (DOM) leached from surrounding, heavily disturbed peat soils. We measured dissolved organic carbon (DOC) and oxygen concentrations along the river, carried out a 36-h experiment in the province capital Pekanbaru and quantified organic matter and nutrient inputs from urban wastewater channels into the Siak. In order to consider the complex dynamic of oxygen in rivers, a box-diffusion model was used to interpret the measured data. The results suggest that the decomposition of soil derived DOM was the main factor influencing the oxygen concentration in the Siak which varied between ∼100 and 140 μmol l −1. Additional DOM input caused by wastewater discharges appeared to reduce the oxygen concentrations by ∼20 μmol l −1 during the peak-time in household water use in the early morning and in the early evening. Associated enhanced nutrient inputs appear to reduce the impact of the anthropogenic DOM by favoring the photosynthetic production of oxygen in the morning. A reduction of 20 μmol l −1, which although perhaps not of great significance in Pekanbaru, has strong implications for wastewater management in the fast developing areas downstream Pekanbaru where oxygen concentrations rarely exceed 20 μmol l −1.