Data collected from the IMPROVE program are used to calculate aerosol particle mass and visibility parameters. IMPROVE Reconstructed Fine Mass (RCFM) is the sum of ammonium sulfate, ammonium nitrate, particulate organic mass, elemental carbon, soil, and sea salt. The algorithm for RCFM has the following form, with concentrations in μg m-3:
[RCFM] = ammonium sulfate + ammonium nitrate + organic mass + elemental carbon + fine soil + sea salt
Each of these components is derived from IMPROVE measurements, with concentrations designated in square brackets, where:
Ammonium Nitrate = 1.29*[ NO3-];
Ammonium Sulfate = 4.125*[S];
Fine Soil = 2.2*[Al]+2.49*[Si]+1.63*[Ca]+2.42*[Fe]+1.94*[Ti];
Organic Mass by Carbon = 1.8*([OC1]+[OC2]+[OC3]+[OC4]+[OP]);
Elemental = [EC1]+[EC2]+[EC3]-[OP];
Sea Salt = 1.8 * [Cl-];
In these calculation, OC1, OC2, OC3,and OC4 designate organic carbon fractions; EC1, EC2 and EC3 designate elemental carbon fractions; and OP designates pyrolized organic carbon; all are determined from the TOR method.
Key assumptions on which this model is based include:
- All aerosol sulfur is in the form of (NH4)2SO4;
- All aerosol nitrate is in the form of NH4NO3;
- All Al, Ca, Si, Fe, and Ti are of crustal source;
- All crustal material is made up of the same basic oxides;
- The A, B, and C modules all have cut points of 2.5 μm.