RATES/KINETICS: - Do I have access on pH in the BASIC? If not - how can I realize this, I need this examination of pH-value. I think it would be very important to implement the access of pH in RATES. In Basic, you can calculate pH with the following statement: pH = -LA("H+") - How often will carry out the loop in RATES? I build a little inputfile to test this but the results shown after, don't give any hint. Is it controled by TIME ? For a specified time step, defined in one of the following, TRANSPORT, ADVECTION, or KINETICS, the RATES data block will be evaluated 1 to many times. The program automatically adjusts subtime steps to achieve a tolerance (either default or defined in KINETICS) in the rate integration. Normally, RATES are evaluated 6 times per time step. If the error estimate from the integration from these 6 evaluations is not smaller than the tolerance, a smaller subtime step is set and the integration begins again and will require at least 2 6-evaluation integrations (but likely more) to integrate over the original time step. If the moles calculated by all RATE equations are 0, then the RATE program is only evaluated once. - If I use the parameter ALK with the command If ALK < 0.0 Then .... the value of ALK itself was changed The value of ALK can not be changed within the Basic program, but it may be changed by the reaction that the KINETICS data block adds as a result of the evaluation of the RATE program. - see input-files above: LoII_MIX129_RATES2 gives pH=5.52 LoII_MIX129_RATES gives pH=6.52 - with the same input!? Your Basic programs are pretty jumbled. The two programs probably do not calculate the same amounts of Ca(OH)2. - Your proposal (email 14/11/01) to rate with M=-ALK*0.5 doesn't work in Phreeqci 2.5; in Phreeqci RC1 I'm not sure. PhreeqcI RC1 uses Phreeqc 2.5 to do the calculations, so the two programs will give the same result. I don't remember what I proposed, but I'd say you must find suitable rate equations for your problem. In general: - In a very great MIX-file I've print out all values of N and see that the values of N = N(5), what is N in SOLUTION_MASTER_SPECIES N NO3- 0.0 N 14.0067 N(+5) NO3- 0.0 N N(+3) NO2- 0.0 N N(0) N2 0.0 N N(-3) NH4+ 0.0 N N is the element nitrogen, which can exist as NO3- [N(5)], NO2- [N(3)], dissolved N2 [N(0)], or ammonia species NH3 and NH4+ [N(-3)]. - If one set the Redox-condition: redox Fe(2)/Fe(3) in the solutions and then call up many MIX commands in the kind: MIX 121 1 0.00208268 2 0.00000000 3 0.01971970 1120 0.97819763 USE equilibrium_phases 2 SAVE solution 1121 END will then the Redox-condition be current/valid for all the following MIXings? "redox Fe(2)/Fe(3" only affects the initial solution calculation for a solution. A pe calculated from Fe(2) and Fe(3) will be calculated and used to speciate any redox elements for which a total concentration is given (so unless you define total Mn, As, or some other redox element, it has no effect). During batch reaction calculations like the one above (MIX 121), the redox definition no longer has any effect. - If I use the same MIX - number several times, does it have any consequences ? The latest definition will overwrite the previous definition. The only effect is that you can no longer "USE" the previous definition. David David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225
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