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Changes in Inorganic Nitrogenous Compounds from Septic Tank Effluent in a Soil with a Fluctuating Water Table
Author(s) -
Reneau R. B.
Publication year - 1977
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1977.00472425000600020015x
Subject(s) - nitrification , water table , denitrification , soil water , environmental science , ammonium , nitrate , environmental chemistry , nitrite , hydrology (agriculture) , horizon , soil science , groundwater , chemistry , nitrogen , geology , mathematics , geotechnical engineering , geometry , organic chemistry
Changes in NH 4 + , NO 2 − , and NO 3 − were monitored in situ during 1972, 1973, 1974, and 1975 in a Virginia Coastal Plain soil with a fluctuating water table. Samples of soil solution above and in a very slowly permeable plinthic horizon were analyzed for the above‐mentioned inorganic N fractions. Ammonium‐N in solution above the plinthic horizon decreased with increased distance from the drainfield in the direction of ground water flow. This decrease ranged from 23 to 4 µ g/ml at 0.15 and 12.0 m from the drainfield, respectively. Decreased NH 4 + was attributed to the processes of adsorption and nitrification. Nitrite and NO 3 − concentrations did not change significantly with distance above the plinthic horizon, but did accumulate in the plinthic material beginning at a 1.27‐m distance from the drainfield. Nitrification adjacent to the drainfield was possibly inhibited by the high oxygen demand, high NH 4 + content, and general anaerobic conditions present. Nitrification above the plinthic horizon was apparently related to distance from the drainfield and fluctuations in the water table level. In this zone nitrification appeared to be followed by denitrification when NO 3 − moved into a more anaerobic zone or when higher water table levels resulted in inundation of the original zone of nitrification. Areas where denitrification was postulated to occur had redox potentials of approximately +200 mV (adjusted to 25C and pH 7.0). Nitrite and NO 3 − that moved into the plinthic horizon apparently did not undergo denitrification since conditions in this horizon are unfavorable for the biological denitrification process.