Premium
Ion Activity Products of Calcium Carbonate in Waters Below the Root Zone
Author(s) -
Suarez Donald L.
Publication year - 1977
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1977.03615995004100020027x
Subject(s) - calcite , lysimeter , precipitation , carbonate , calcium carbonate , chemistry , residence time (fluid dynamics) , supersaturation , soil water , environmental chemistry , mineralogy , soil science , hydrology (agriculture) , environmental science , geology , physics , geotechnical engineering , organic chemistry , meteorology
The pH, Ca 2+ , and HCO 3 ‐ relations were investigated in 28 well waters obtained from beneath irrigated fields in Arizona. The mean [Ca] [CO 3 ] ion activity product (IAP) was 11.3 × 10 −9 (pIAP = 7.95) with a standard error of 0.7 × 10 −9 based on field measurements of pH. As indicated by ionic strength the residence time of the waters in the soil vary widely. The lack of a trend in pIAP vs. ionic strength indicates the kinetics of calcite equilibration (from supersaturation) is quite slow in soil‐water systems. This conclusion was supported by an average pIAP of 7.97 calculated from 35 water analyses obtained from wells in the Grand Valley of Colorado and by a pIAP value of 7.96 obtained from a soil water sample in a lysimeter study. Since these pIAP values are quite consistent and were obtained under a wide variety of conditions, a pIAP value of 7.95 is recommended for use in predictive models when CaCO 3 precipitation occurs.