TECHNICAL ARTICLEEffect of Dissolved Organic Carbon in Recycled Wastewaters on Boron Adsorption by SoilsGoldberg, Sabine; Suarez, Donald L.Author Information USDA-ARS, US Salinity Laboratory, Riverside, California. Address for correspondence: Dr Sabine Goldberg, USDA-ARS, US Salinity Laboratory, 450 W Big Springs Rd, Riverside, CA 92507. E-mail: [email protected] Financial Disclosures/Conflicts of Interest: None reported. Received September 20, 2016. Accepted for publication April 18, 2017. Supplemental digital contents are available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.soilsci.com). Soil Science: March 2017 - Volume 182 - Issue 3 - p 94-100 doi: 10.1097/SS.0000000000000199 Buy SDC Metrics Abstract In areas of water scarcity, recycled municipal wastewaters are being used as water resources for nonpotable applications, especially for irrigation. Such wastewaters often contain elevated levels of dissolved organic carbon (DOC) and solution boron (B). Boron adsorption was investigated on eight arid-zone soils from California and one from Arizona as a function of equilibrium B concentration (0–100 mg L−1) and solution pH (4–10). The B equilibrating solutions were prepared using either recycled wastewaters or synthetic wastewaters containing DOC up to 10 mg L−1. The synthetic wastewaters were synthesized to have the same chemical composition as the recycled wastewaters but contained no DOC. Boron adsorption on the soils increased with increasing solution pH, reaching an adsorption peak near pH 9, and then decreased with further increases in solution pH. The pH-dependent amounts of B adsorption were not statistically significantly different at the 95% level of confidence for both types of waters. For all soils, B adsorption as a function of solution B concentration conformed to the Langmuir adsorption isotherm equation. Boron adsorption maxima, obtained using the Langmuir isotherm, were not statistically significantly different at the 95% confidence level for both types of waters. The constant capacitance surface complexation model was able to predict B adsorption as a function of solution pH using the soil chemical properties: aluminum oxide, inorganic carbon, organic carbon contents, and surface area. The magnitude of B adsorption as a function of solution pH and equilibrium solution B concentration was unaffected by the presence of DOC in the recycled wastewaters. This result indicates that these treated recycled wastewaters, because of their low DOC contents, will not affect B adsorption behavior of soils when used for irrigation of crops and landscape vegetation. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.