Acidez titulable del suelo a pH = 7, al filtrar el extracto y controlar el pH con electrodo

Abstract

Whwn measuring the titratable acidity to pH=7 (AT_pH7) the soil is placed down with a buffer solution of pH=7 and the amount of acidity released is quantified with alkali. There is no comparative information about different analytical methods used in Uruguay. The AT_pH7 was measured by three methods: a) the mixture calcium acetate:soil was stirred and allowed a 16 hours rest, the extraction was filtered, and titration at pH = 7 was controlled by electrode (AT_pH7_fil); b) the same as the previous method, but after a 16 hours rest the supernatant was titrated unfiltered (AT_pH7_sob); c) four successive extractions with barium acetate buffered to pH = 7 were done, the extract was filtered and titrated to pH = 7 using phenolphthalein (AT_pH7fen) as an indicator. The AT_pH7fen values were considered as reference. When comparing AT_pH7_sob with AT_pH7_fil the first were considered as reference values. The fit between AT_pH7_fil and AT_pH7_sob was satisfactory. The average difference was 0.36 meq.100g-1 but differences from-1.00 to 1.70 meq.100g-1 were observed. There was no bias in the differences. Some sources of acidity may have remained in the sediment and were not evaluated when titrating the supernatant. The AT_pH_fil overestimated the average AT_pHfen values in 0.73 meq.100g 1. The average values of AT_pH_sob and AT_pHfen did not differ. The samples had the same classification according to their base saturation regardless of the method used. Neither the measurement of pH = 7 with electrode instead of phenolphthalein, nor the longest extraction time, or the use of calcium acetate as extractant introduced significant errors of interpretation. The AT_pH_fil method had acceptable precision and accuracy.

Proposal of an Initial Environmental Management and Land Use for Critical Cemeteries in Central Ecuador

“…All the soil samples analyzed presented electrical conductivity values within the established range of the Ecuadorian [66] and Canadian environmental regulations [62]. The soils have characteristics between light and moderately saline soil [55], which could affect the presence of sensitive vegetation [69].…”