We previously identified issues with how pH, bicarbonate (HCO3) and carbonate (CO3) samples reported in the Chemical properties of surface water () and Chemical properties of groundwater () data products were being analyzed by the external lab. Hold times regularly exceeded those allowed by the standard method, and sample bottles were opened multiple times prior to analysis. As a result, in 2022 we began recommending that the domain lab pH values be used instead of the external lab pH values, and stopped reporting external lab HCO3 and CO3 values.
Beginning with RELEASE-2025, all historical external lab pH, HCO3 and CO3 samples will be deleted from future releases. Historical samples included in older releases should not be used. HCO3 and CO3 can alternatively be estimated using either external lab dissolved inorganic carbon (DIC) or domain lab alkalinity (ALK) and the corresponding domain lab pH reported in these data products.
For more detailed information please use the Contact Us form. Select DP1.20093.001 in the Data Product dropdown list and include the term 鈥淩ITM0066587鈥� in the body of your request.