title: [Distribution characteristics of dissolved oxygen and mechanism of hypoxia in the upper estuarine zone of the Daliaohe River].
abstract: Based on field surveys in the upper estuarine zone of the Daliaohe River in Spring and Summer of 2009, the spatial and temporal distributions of dissolved oxygen were analyzed and the mechanism of hypoxia were preliminarily discussed. The results indicated that DO concentrations were higher in the river mouth and lower in the upper reaches, higher in surface layers and lower in bottom concerning its spatial distribution. For its temporal distribution, DO concentrations were higher in daytime and lower at night, higher in Spring and lower in Summer. The DO concentrations in the upper estuarine zone of the Daliaohe River in Summer ranged between 1.36-4.77 mg/L with an average of 3.44 mg/L. The concentrations in the lower reaches were higher with an average of 3.94 mg/L. A large hypoxia area was recorded in Summer in the upper reaches of the estuary starting from about 45 km away from the river gate with an average DO concentration of 2.33 mg/L and a minimum of 1.36 mg/L. The correlation analysis showed that DO concentration was significantly correlated with nutrients and permanganate index. Excessive discharge of nutrients and organic pollutants were, therefore, main factors causing hypoxia, and water column stratification due to temperature rise in Summer in surface layers led to further reduction of DO in bottom layers of the water.
authors.affiliation: College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China. yangln-851002@126.com
authors.forename: Li-Na
authors.initials: LN
authors.lastname: Yang
authors.forename: Zheng-Yan
authors.initials: ZY
authors.lastname: Li
authors.forename: Xue-Qing
authors.initials: XQ
authors.lastname: Zhang
mesh_terms: D002681:China; D004784:Environmental Monitoring / Q000379:methods*; D009792:Oceans and Seas; D010100:Oxygen / Q000032:analysis*; D045483:Rivers; D012621:Seasons; D012623:Seawater / Q000737:chemistry*; D012995:Solubility; D014876:Water Pollution / Q000032:analysis*
chemical_list: D010100:Oxygen