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Ecosystem Science Reports
Aquatic Sciences
Project Title: Nutrients, metals, bacteria and organic compounds in groundwater exposed to agricultural activities
in the Lower Fraser Valley, British Columbia.
Completion Date:
March 2004
Investigators:
B. Hii, S. Sylvestre, T. Tuominen, M. Sekela and M. Mazalek, Aquatic and Atmospheric Sciences Division, Environment Canada, Pacific and
Yukon
Region
Study Overview
The effects of agricultural activities on groundwater quality were investigated in 1998 by surveying 16 wells and/or
piezometers (study wells) located in agricultural areas of the Lower Fraser Valley, British Columbia. Four reference wells that were
not exposed to agriculture were also surveyed for comparison. Nutrients (nitrogen and phosphorus), bacteria, metals and organic
contaminant concentrations were measured. Screening tests for the presence of endocrine disrupting substances were also applied.
Key Points for Decision-Makers
- Agricultural activity in the Lower Fraser Valley is causing elevated nitrogen concentrations and bacterial numbers in
groundwater, especially in the shallow unconfined aquifers, at one-quarter of the agricultural sites sampled in this study.
- Nitrate + nitrite concentrations were higher in groundwater samples collected from the Abbotsford/Matsqui areas than those
from the Chilliwack/Vedder areas.
- Pesticide levels in the Lower Fraser Valley groundwater, both in agricultural areas and reference areas, were low; however
there is evidence that small amounts of both in-use (endosulphan, methoxychlor) and historical pesticides or their degradation
products (DDD and DDE) are entering groundwater via agricultural activities in the Lower Fraser Valley.
- The presence of some organic compounds such as polycyclic aromatic hydrocarbons (PAHs) and sterols are ubiquitous suggesting an
association with a broad range of human activities. Higher levels of several sterols at one shallow well in an agricultural area
that also had elevated nitrogen and bacteria indicate that some agricultural activities can introduce these compounds to groundwater.
- Contaminants in the ground water sampled showed no significant endocrine disrupting activity.
Key Scientific Findings
- Groundwater in agricultural areas of the Lower Fraser Valley had higher nitrate + nitrite concentrations, bacterial numbers and
pesticide concentrations than groundwater in reference sites.
- Metals levels in the Lower Fraser Valley groundwaters were mainly within acceptable limits of water quality guidelines.
- A few pesticides and their degradation products (e.g. endosulphan, methoxychlor, DDE and DDD) were detected at low levels at
sites in the agricultural area only.
- PAHs and sterols were detected at both agricultural and reference sites, suggesting that the presence of these compounds in
groundwater is due to general human presence, rather than agriculture, specifically. However, elevated levels of several sterols at
one shallow well at an agricultural site that also had elevated nitrogen and bacteria indicates that agricultural activities can be a
source of sterols to the groundwater.
References
The report is published in electronic form on Environment Canada's Green Lane web site in both official languages. The report may be
downloaded for printing from the Green Lane in Adobe pdf format.
English - http://www.pyr.ec.gc.ca/georgiabasin/reports/lfv_groundwater/summary_e.htm
Français - http://www.pyr.ec.gc.ca/georgiabasin/reports/lfv_groundwater/summary_f.htm
It may also be obtained directly from the author at basil.hii@ec.gc.ca .
The correct citation of the paper is:
Hii, B., S. Sylvestre, T. Tuominen, M. Sekela, and M. Mazalek. 2004.
Nutrients, metals, bacteria and organic compounds in groundwater exposed to agricultural activities in the Lower Fraser Valley, British Columbia. Environment Canada, Georgia Basin Ecosystem Initiatve, Report EC/GB/04/76.
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