Arsenic adsorption
Arsenic adsorption
(OP)
Hello all
A site which used to be an old orchard is producing soil samples with 100 ppm arsenic concentrations. Let us assume this is "available" arsenic, as in, if possible it will enter water solution.
What would be an effective calculation method to show this "available" arsenic's solubility in groundwater?
Thank you for your time.
A site which used to be an old orchard is producing soil samples with 100 ppm arsenic concentrations. Let us assume this is "available" arsenic, as in, if possible it will enter water solution.
What would be an effective calculation method to show this "available" arsenic's solubility in groundwater?
Thank you for your time.





RE: Arsenic adsorption
Or are you concerned with runoff, rather than groundwater impact?
RE: Arsenic adsorption
Basically a proof of the amount of arsenic not bound to soil (available) 100ppm which "would" enter solution.
RE: Arsenic adsorption
My problem is that a general solubility calculation is required for this situation, provided only with an available arsenic conc of 100 ppm for an old orchard soil.
I am not sure what form of arsenic to use or how to structure this calculation.
Any suggestions on how to look at this are appreciated.
RE: Arsenic adsorption
Using the TCLP (toxicity characteristic leaching proceedure), the maximum level would be 1/20th of the total concentration of ANY total metal concentration. Add to this the soil's natural CEC (cation exchange capacity) and you have too may unanswered variables to provide anything meaningful.
As a relavent aside, do you have any idea of natural background arsenic levels in the area? Here in Central Virginia, natural arsenic levels can often be elevated owing to the parent rock mineralogy (i.e., the arsenic is so locked into the soil minerology that it never went anywhere).
Good luck, just trying to help.
f-d
¡papá gordo ain't no madre flaca!
RE: Arsenic adsorption
RE: Arsenic adsorption
RE: Arsenic adsorption
Lead Arsenate was a popular insecticide during the first half of the 20th century because of its low toxicity to plants and great effectiveness for controlling insect pests. The most common use was for control of codling moth on commercial apple orchards. (THIS IS MY CASE) Repeated applications of lead arsenate over time cause lead and arsenic to accumulate in soil. Soil lead and arsenic concentrations vary considerably in former orchard sites because applicators using hand-held sprayers applied lead arsenate individually to trees. Higher concentrations appear between the former tree sites. Lead arsenate was banned on most food crops in the U.S. in 1988 and all food crops in 1991.
RE: Arsenic adsorption
If you have a 1-in rain event and you get 1/3-in runoff how would you determine the arsenic flux? No clue. Afterall, there have likely been many 1-in rain events and some level of arsenic (potentially mobile forms) remain.
Not sure if I'm helping, but I do appreciate the problem you are facing. . .
f-d
¡papá gordo ain't no madre flaca!
RE: Arsenic adsorption
I tabulated these and showed how much in ppm of each would dissolve in a litre of water ie mg/L
This is the best I could come up with. eg calcium magnesium lead and iron 3 arsenates.
RE: Arsenic adsorption
¡papá gordo ain't no madre flaca!
RE: Arsenic adsorption
This is all I could come up with to produce a bracket of values which inspectors could use. Is this method totally ludicrous? Like you I am questioning this entire undertaking but Im sure you would understand that town simply wants to know.
RE: Arsenic adsorption
Not trying to be blunt, but this is the peril of being too conservative.
f-d
¡papá gordo ain't no madre flaca!
RE: Arsenic adsorption
RE: Arsenic adsorption
For surface water flow, the contact time would have to be something less than the time of concentration (that is if you are only considering surface water adsorption).
Just something to think about.
f-d
¡papá gordo ain't no madre flaca!
RE: Arsenic adsorption
The term "i" is a function of the time of concentration. "c" is a direct chart take-off. Please look at my link, go to hydrology and click on the link for the "rational method" If you print it out, you'll have something to go on. Sorry for the oversight. Maybe I posted too late, sigh. . .
f-d
¡papá gordo ain't no madre flaca!
RE: Arsenic adsorption