Nutrients, Metals, Bacteria and Organic Compounds in Groundwater Exposed to Agricultural Activities in the Lower Fraser Valley , B.C.

Full Report in Adobe portable document format (876 kb)

Executive Summary

As part of the Georgia Basin Ecosystem Initiative, Environment Canada conducted a survey of groundwater quality in 1998 at selected Lower Fraser Valley (LFV) sites. The survey included areas of intensive agricultural use (impacted sites) as well as those with no known agricultural activities (reference sites). Twenty sites (16 impacted and 4 reference) in several LFV aquifers were sampled for nutrients, bacteriological parameters, metals, organic contaminants, and estrogen/androgen screening tests.

Nitrate + nitrite concentrations were elevated at four impacted sites; two were over 3 milligrams nitrogen per litre (mg N/l) and another two also exceeded the 10 mg N/l Canadian Water Quality Guideline for Drinking Water. The nitrate + nitrite concentrations at reference sites were all less than 1 mg N/l. Total and fecal coliform and Escherichia coli counts were zero at reference sites and positive at four impacted sites, with total coliform counts ranging from 2 to 1300 colonies per 100 ml. Many trace metals concentrations were within the acceptable limits of the Canadian Council for Ministers of the Environment (CCME) guidelines for drinking, irrigation, protection of fresh water aquatic life and livestock watering. Other trace metals like copper, iron and manganese exceeded some of these guidelines. Not all the organic compounds analyzed were detected in the survey. All the detected organic compounds had concentrations below CCME guidelines, where they have been established, for drinking or protection of freshwater life. Few pesticides were detected in groundwater however endosulphan was detected at several impacted sites but at none of the reference sites. Organic compounds not necessarily associated with agriculture such as PAHs and some sterols (cholesterol and β-sitosterol) were detected at many of the impacted and reference sites. Two screening tests were used to detect substances in the water that mimic estrogen or androgen hormones. The results showed no significant estrogenic or androgenic activity.

This survey of groundwater quality in the Lower Fraser Valley showed that agricultural activities can result in an increase in bacterial, nutrient, and pesticide levels and possibly sterol levels (in shallow wells). However, groundwater in the Lower Fraser Valley is affected by more than just agricultural land activity; it is affected also by other activities and land uses related to general human presence.