Low-level soluble chloride extraction in soil


Three methods of extraction of low-level soluble chloride contents from vadose-zone soil were evaluated in this study. Three methods were employed on a silty sand soil using a 2:1 fluid:soil ratio: 1) Method A utilized three successive rinses with deionized water; 2) Method B applied three successive rinses of 0.0001 M and 0.001 M Na2SO4 solution; and 3) Method C passed deionized water through the soil with a pressurized filtration system three times. Method A had lower standard deviation and yielded more consistent soluble chloride contents per rinse than method C; Method B was ruled out because of concerns that the Na2SO4 reagent contained trace amounts of chloride. Method A was applied with a 1:1 fluid:soil ratio in duplicate to 50 samples from a 34-m thick vadose-zone borehole, yielding a mean difference in duplicates of 13.9% and percent total extracted soluble chloride of 62.4 ± 9.9%, 25.2 ± 7.4%, and 12.4 ± 6.6% in each of the three successive rinses. • Three successive rinses of soil with deionized water achieved consistent extraction results. • Multiple rinses are necessary to extract soluble chloride if chloride contents are low. • This method is amenable to analysis of soil in vadose-zone borehole samples.

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