10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Towards Properly Decoding Trends in Wet Deposition of Inorganic Ions Related to Emissions and Climate Drivers
Xiaohong Yao, LEIMING ZHANG, Environment and Climate Change Canada
Abstract Number: 16 Working Group: Remote/Regional Atmospheric Aerosol
Abstract A new approach was developed to preprocess monitored wet deposition data of inorganic ions for generating their decadal trends. Differing from traditional approaches which directly apply annual or seasonal averaged data to trend analysis tools, the proposed new approach makes use of slopes of regression equations between a series of study years and a climatology (base) year in terms of monthly averaged data. This approach was applied to the wet deposition data of SO42-, NO3- and NH4+ at Canadian rural sites where with more than two-decade data, and the extracted decadal trends were properly linked to major driving forces such as emission reduction and climate anomaly. The decreasing trends in SO42- and NO3- wet deposition were clearly observed, accompanied by increasing trends in the equivalent ratios of NH4+/(NO3-+SO42-) and NH4+/NO3-, as a result of sharp decreases in SO2 and NOx emissions in recent years in Canada and the US. Some inconsistencies among wet deposition, equivalent ratio and emission were also seen mostly before 2000, which were identified to be caused either by climate anomaly or errors in estimated emissions. Long-term variations in NH4+ wet deposition were complicated and could not be simply attributed to known dominant factors; thus we confirm no cause-effect relationship was identified between emission and wet deposition for NH4+. The new approach proposed in this study yields more robust results than the traditional ones and stimulates towards properly decoding the trends in wet deposition.