ch_rtpest Subroutine

subroutine ch_rtpest()

 ~ ~ ~ PURPOSE ~ ~ ~
 this subroutine computes the daily stream pesticide balance
 (soluble and sorbed)

initialize depth of water for pesticide calculations

volume of water entering reach and stored in reach use channel water temperature (inflow + storage weighted) for aquatic/benthic decay pesticide transported into reach during day calculate mass of pesticide in reach calculate mass of pesticide in bed sediment BUG FIX zero outflow/accumulators so values from a previous channel are not forwarded downstream or into basin totals in-stream processes calculate sediment concentration set kd calculate fraction of soluble and sorbed pesticide BUG FIX kd is in mL/g (=L/kg), sedcon in mg/L (=g/m3) Product kdsedcon has units (L/kg)(mg/L) = mg/kg, NOT dimensionless. Need 1.e-6 to convert to (m3/g)*(g/m3) = dimensionless.

CORRECTED Benthic partition: fd2 = pore water fraction in benthic sediment per unit bulk volume: dissolved = porcw; sorbed = ch_bdkdcw fd2 = por / (por + kdch_bd); kd [cm3/g] * ch_bd [g/cm3] = dimensionless CORRECTED

calculate flow duration calculate amount of pesticide that undergoes chemical or biological degradation on day in reach add decay to daughter pesticides BUG FIX: local variable avoids double-counting with multiple parents calculate amount of pesticide that volatilizes from reach calculate amount of pesticide removed from reach by settling calculate resuspension of pesticide in reach calculate diffusion of pesticide between reach and sediment calculate removal of pesticide from active sediment layer by burial verify that water concentration is at or below solubility insignificant flow benthic processes calculate loss of pesticide from bed sediments by reaction add decay to daughter pesticides BUG FIX: local variable avoids double-counting with multiple parents set new pesticide mass of (in + store) after processes calculate outflow and storage in water column

Arguments