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Predicting level of dissolved reactive phosphate in the Lafayette River, Virginia, from information on tide, wind, temperature, and sewage discharge
Author(s) -
Montgomery John R.
Publication year - 1979
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/wr015i005p01207
Subject(s) - environmental science , estuary , hydrology (agriculture) , sewage , effluent , salinity , dilution , phosphate , oceanography , chemistry , environmental engineering , geology , geotechnical engineering , organic chemistry , physics , thermodynamics
The Lafayette River in Norfolk, Virginia, is a shallow, turbid, urban estuary, polluted with primary treated sewage. The river was sampled monthly from October 1970 to January 1972. Oxygen, temperature, and salinity values are vertically and laterally homogeneous in the Lafayette River. The mean values of dissolved reactive phosphate (DRP) in the Lafayette River for the winter (1970–1971 and 1972) ranged from 2.2 to 5.8 microgram‐atoms per liter (μg‐at/1) and for the summer of 1971, 7.6 μg‐at/l. Multiple linear regression models were prepared to relate the daily changes in phosphate to tide stage, wind component and rate of phosphate discharge (kg/hr) from the Lamberts Point sewage treatment plant. The equations for the August 1971 sample show that the effect of the tide stage is 3 times as important in the determination of the levels of DRP as the rate of flow of DRP from the sewage effluent on the ebbing tide and is equally as important as the rate of flow of DRP from the sewage effluent on the flooding tide. The daily variations in DRP are more noticeable in the summer because of the higher concentrations of phosphate in the Lafayette River during this season. The increase of phosphate on the ebb tide and the decrease on the flood tide over a daily cycle was attributed to a dilution of the waters of the Lafayette River by the water from Hampton Roads. The direct relation of water temperature to the concentration of DRP for the seasonal model was attributed to the increased biochemical activities of the micro‐organisms in the sediment‐water system.