Back to the basics – Estimating the sensitivity of freshwater to acidification using traditional approaches

This study examines the effects of acidifying sulphur emissions on freshwater ecosystems in the traditional territory of Treaty 8 First Nations in British Columbia (BC). Due to the absence of detailed water chemistry data for most lakes in the region, revised empirical methods for estimating freshwater sensitivity to acidification are formulated using linear regression relationships between individual chemical measurements, and critical loads of acidity calculated using the Steady State Water Chemistry (SSWC) model. Lake alkalinity is the most effective chemical indicator of acidification sensitivity in northeast BC. Critical loads of acidity (CL(A)) estimated using alkalinity range from 0.0827 to 9.48 keq ha−1 yr−1. Sulphur deposition estimates range from 0.0113 to 0.303 keq ha−1 yr−1 and do not exceed the estimated CL(A) at any of the study lakes. The spatial situation of both the lakes and the emission sources is responsible for the lack of exceedances, and expanded/continued monitoring is recommended to account for geological variability and source proliferation. Measurements of lake conductivity and alkalinity provide a means of community monitoring for freshwater acidification sensitivity as part of cumulative effects management strategies.