Ground water age and nitrate distribution within a glacial aquifer beneath a thick unsaturated zone

The impact on ground water quality from increasing fertilizer application rates over the past 40 years is evaluated within a glacial aquifer system beneath a thick unsaturated zone. Ground water ages within the aquifer could not be accurately determined from the measured distribution of 3H and as a...

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Bibliographic Details
Published in:Ground water 1998-01, Vol.36 (1), p.171-180
Main Authors: Johnston, C.T. (University of Waterloo, Waterloo, Ontario, Canada.), Cook, P.G, Frape, S.K, Plummer, L.N, Busenberg, E, Blackport, R.J
Format: Article
Language:English
Subjects:
ABONOS NITROGENADOS
AGE DETERMINATION
AGUAS SUBTERRANEAS
Aquifers
CAPA FREATICA
CARACTERISTICAS MORFOLOGICAS SUELO
CHLORIDES
CHLOROFLUOROCARBONS
CHLORURE
CLORUROS
COMPOSE ORGANOHALOGENE
Composition
COMPUESTO ORGANICO HALOGENO
DETERMINACION DE LA EDAD
DETERMINATION DE L'AGE
DISSOLVED OXYGEN
EAU SOUTERRAINE
ENGRAIS AZOTE
Environmental aspects
EPAISSEUR
ESPESOR
Fertilizers
FLUVIOGLACIAL SOILS
GROUNDWATER
GROUNDWATER RECHARGE
GROUNDWATER TABLE
HELIUM
Hydrology
LEACHING
LESSIVAGE DU SOL
LITHOLOGICAL SOIL TYPES
LIXIVIACION
METALLOIDE
NAPPE SOUTERRAINE
Nitrates
NITROGEN FERTILIZERS
NO METALES
NONMETALS
ONTARIO
ORGANIC HALOGEN COMPOUNDS
OXIGENO EN DISOLUCION
OXYGENE EN DISSOLUTION
POLLUTION DE L'EAU
POLUCION DEL AGUA
RECARGA DE AGUAS SUBTERRANEAS
RECHARGE DE LA NAPPE
SOIL MORPHOLOGICAL FEATURES
SURFACE LAYERS
THICKNESS
TIPOS LITOLOGICOS DE SUELO
TRAIT MORPHOLOGIQUE DU SOL
TRITIO
TRITIUM
TYPE DE SOL LITHOLOGIQUE
WATER POLLUTION
Water, Underground
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Summary:The impact on ground water quality from increasing fertilizer application rates over the past 40 years is evaluated within a glacial aquifer system beneath a thick unsaturated zone. Ground water ages within the aquifer could not be accurately determined from the measured distribution of 3H and as a result, chlorofluorocarbon (CFC) and 3H/3He dating techniques were applied. Beneath a 25 m thick unsaturated zone, ground water ages based on CFC-11 concentrations were greater than 3H/3He ground water ages by 6 to 10 years, due to the time lag associated with the diffusion of CFCs through the unsaturated zone. Using the corrected CFC-11 and 3H/3He ground water ages and the estimated travel time of 3H within the unsaturated zone, the approximate position of ground water recharged since the mid-1960s was determined. Nitrate concentrations within post mid-1960s recharge were generally elevated and near or above the drinking water limit of 10 mg-N/L. In comparison, pre mid-1960s recharge had nitrate concentrations 2.5 mg-N/L. The elevated NO3- concentrations in post mid-1960s recharge are attributed mainly to increasing fertilizer application rates between 1970 and the mid- to late 1980s. Anaerobic conditions suitable for denitrification are present within pre mid-1960s recharge indicating that removal of DO is a slow process taking tens of years. Over the next 10 to 20 years, nitrate concentrations at municipal well fields that are currently capturing aerobic ground water recharged near the mid-1960s are expected to increase because of the higher fertilizer application rates beginning in the 1970s and 1980s
ISSN:0017-467X
1745-6584
DOI:10.1111/j.1745-6584.1998.tb01078.x