Impact of land use activities on fine sediment-associated contaminants, Quesnel River Basin, British Columbia, Canada

摘要

The impact of various land use activities (forestry, mining, and agriculture) on the quality of finegrained sediment (<63 μm) was investigated in the Quesnel River Basin (approx. 12 000 km~2) in British Columbia, Canada. Samples of fine-grained sediment were collected monthly during the snow-free season in 2008 using time-integrated isokinetic samplers at sites representative of forestry, mining, and agricultural activities in the basin. Samples were also collected from replicate control sites that had undergone limited or no disturbance in recent years, and also from the main stem of the Quesnel River. Generally, metal and nutrient concentrations for "impacted" sites were greater than for control sites. Concentrations of As (mining sites), Cu (forestry sites) and Zn (forestry sites) were close to or exceeded upper Sediment Quality Guideline (SQG) thresholds, while Se concentrations for mining sites were elevated and within the range cited for contaminated environments. Phosphorus values were generally <1000 μg g~(-1) for all land use activities and below available SQGs. Values for individual samples were, however, greater than upper SQG levels, such as 22.7 μg g~(-1) (As), 801 μg g~(-1) (Cu), 5.0 μg g~(-1) (Se) and 2192 μg g~(-1) (P). These preliminary results suggest that metal mining and forest harvesting are having a greater influence on the concentration of sediment-associated metals and nutrients in the Quesnel basin, than agricultural activities.