EVALUATION OF THE CAPABILITIES OF DEPOSITION NETWORKS TO RESOLVE REGIONAL TRENDS AND SPATIAL PATTERNS

Sulfur emission control programs are being implemented in North Americ a at the same time as budgetary pressures are leading to reduced numbe rs of stations in acid deposition monitoring networks. In order to ass ess the effectiveness of emission control programs,it is essential tha t deposition monitoring networks continue to fulfill their principal g oals of detecting and quantifying temporal changes in deposition, and of describing changes in spatial deposition patterns. A set of statist ical techniques has been developed and applied to assess the capabilit ies of the Canadian Air and Precipitation Monitoring Network (CAPMoN) in southeastern Canada according to two performance criteria: (1) the ability of CAPMoN to detect and quantify projected regional trends in precipitation sulfate in a timely fashion, and (2) the ability of CAPM oN to delineate both present and projected future spatial patterns of wet sulfate deposition. In the area of southern Canada now receiving i n excess of 20 kg ha(-1) yr(-1) wet sulfate deposition, the seven CAPM oN stations alone would be able to detect and quantify projected regio nal trends within one year of the 41 stations now operating in the are a. However, in the regions now receiving less than 20 kg ha(-1) yr(-1) wet sulfate deposition, CAPMoN would require 4-8 yr longer than the l arger set of currently available stations to detect projected reductio ns. The current configuration of CAPMoN is adequate to monitor some ar eas with sulfate deposition exceeding 20 kg ha(-1) yr(-1) until deposi tion goes below this value, but not those areas situated in extreme so uthwestern and southeastern Ontario, southern Quebec, and the Bay of F undy region. In comparison to using all currently operating monitoring stations, using only CAPMoN stations underestimates the area in which wet sulfate deposition exceeds 20 kg ha(-1) yr(-1). Copyright (C) 199 6 Elsevier Science Ltd.