sResin pre-treatment
For the extraction of Ca, Na, Mg, Al, Fe, Mn, P, and S, resins were a
mixed-bed cation/anion resin combination of Amberlite IRA-400 and
IR-120 combined at a 1:1 milliequivalent ratio. For the extraction of
DOC, resins used were Lewatit S 5128. Amberlite resins were pretreated
with 2 M KCl (3:1 solution-to-resin weight ratio)
and Lewatit resins were pretreated with 2 M NaCl
(12:1 ratio) and shaken for two hours. The supernatant was decanted,
and resins were rinsed with DI. Approximately 90 mg of resin was
assembled into resin packs, which were encased in nylon wrapped around
two rubber washers along a CPVC pipe and sealed with electrical tape.
Undeployed resin was reserved and kept at 4°C to use as blanks to test
resins for any background contributions from resin degradation.
Deployment
Resin packs were pushed to the bottom of screened wells that were
installed to either the B-C soil horizon interface, or on top of
bedrock if the C horizon did not exist. Resin packs were exchanged out
four consecutive times, with deployment periods ranging from 2-4
months each for a total of one year integration from August 2019-2020.
Resin post-deployment
Resins in each resin pack were weighed for total weight, and
subsampled to 20g three times. Subsamples were extracted with 2
M KCl following similar protocols to
pretreatment, using a 3:1 solution-to-resin ratio and shaken for 2
hours. Subsamples underwent two subsequent extractions (volume: 240 L)
and diluted by 200 for ICP-MS analysis.
Final calculations: Mass of ion extracted per resin
pack
Ion mass extraction (mg) = (Ion in extract (mg/L) * extractant vol (L)
* dilution factor) – (Ion in blank extract (mg/L) * blank extractant
vol (L) * blank dilution factor)
Ion mass of subsample (mg) = Ion mass extraction 1 (mg) + extraction 2
(mg)
Weight scaler = total resin weight (g) / resin subsample weight (20 g
* 3 subsamples)
Ion mass per resin pack (mg) = (ion mass of subsample 1 (mg) +
subsample 2 (mg) + subsample 3 (mg)) * Weight scaler
