Units
 PROPERTIES & UNITS   Hydrolysis constant (KH)          -d(RX)/dt=KH[RX], where KH = 0.693/half-life of substrate (days) Photolysis constant (Kp)          -d(RX)/dt = K p[RX], where K p= 0.693/half-life of substrate (days) Vapor Pressure mPa = milliPascals [1 mm Hg=133,000 mPa] Solubility ppm = part per million = ug g -1 (or ug ml -1 in water) Henry's Law constant - air-water partioning coefficient (Hc) Hc = p/c, where p = pesticide vapor pressure (Pa) c = solubility in water (mol m-3 )         Hc=Pa/moles M-3=Pa M3/moles Hc=P1 x MW x 10-3/c1                   Hc=mPa x MW x 10-3/PPM where p' = pesticide vapor pressure (mPa) mw = Molecular weight of pesticide c' = solubility in water (ppm) Acid Dissociation constant (pKa, shown as pKa in database) RH =R- + H+ K = [R-] [H+]/[RH] pKa=-log10 Ka   Octanol-water partition coefficient (Kow and pKow, shown as log Kow in database) Kow = C octanol/Cwater, where C = molar concentration pKow =-log10 Kow   Sorption coefficient (KD, shown as Kd in database) KD=C ' soil /C ' water, where C ' = concentration (ppm)   Organic carbon sorption coefficient ( shown as Koc in database) Koc = KD x 100 / % oc, where % oc = percent organic carbon in the soil = % organic matter/1.72         Field dissipation half-life (days) Measure of overall rate of disappearance of pesticide from soil-includes leaching, runoff, hydrolysis, photolysis, microbial degradation, vaporization function of pesticide, site, climate, soil. Related to"Persistence" is equivalent to about 4 half-lives, and is the time taken forabout 90% of the pesticide to dissipate.   Soil half-life (days) Microbiological (aerobic and anaerobic) degradation in the soil. It is afunction of pesticide, soil, soil temperature, soil water content andmicro-organisms present.