More than thirty percent of the United States is currently in a drought that is expected to have profound social, economic, and environmental impacts. The intensification of drought conditions in southern and western regions of the country has spurred interest in wastewater reuse in agriculture, including in wine production. Presented here is the first data set of its kind to support California growers and vintners in the reuse of treated winery wastewater (WWW). The data provide a detailed description of California WWW, with particular emphasis on salinity, to enable the benefits and risks of land application to be assessed. Monthly samples were obtained over a 20-month period from 18 wineries in Ukiah, Napa, Lodi, King City, and Paso Robles. Samples collected before and after physicochemical and biological treatment were analyzed for pH, electrical conductivity (EC), cation and anion concentrations, specific ultraviolet absorbance (SUVA 254 ), dissolved organic carbon (DOC), and biological oxygen demand (BOD 5 ). The pH of the WWW varied widely (from 3 to 12). Organic parameters (SUVA 254 , DOC, and BOD 5 ) showed that treatment effectively decreased organic carbon to levels that would not have negative effects on plant growth or soil. Cation concentrations (Na) in WWW were not reduced by treatment. These baseline data confirm that dissolved salts pose a challenge to the reuse of WWW. However, total salinity of the WWW was moderate (mean EC of 1.0 dS/m) and usually below risk thresholds for common winegrape rootstocks and soil salinity hazards. The conditions under which WWW could be recommended as a water management option in California are described.

a b s t r a c tThe reuse of winery wastewater (WW) could provide an alternative water source for vineyard irrigation. The shift of many wineries and other food processing industries to K + -based cleaners requires studies on the effects of K + on soil hydraulic conductivity (HC). Depending on clay content and mineral composition, K + additions can affect the HC either positively or negatively. Soil mineralogy was anticipated to exhibit a strong influence on HC responses and, therefore, soils of contrasting mineralogy were evaluated for changes in soil HC resulting from applications of solutions elevated in Na + and K + . To examine the impact of mineral-ion relationships on HC, soils dominant in montmorillonite, vermiculite, or kaolinite from the Napa and Lodi wine regions of California, were packed into soil columns to observe changes in leachate chemistry and HC. Irrigation with Na + -and K + -rich WW was simulated by applying solutions at sodium absorption ratio (SAR) values of 3, 6, and 9 and potassium absorption ratio (PAR) values of 1, 2, 4, and 9. While HC was reduced in the 2:1 clay soils (montmorillonite and vermiculite) for all SAR treatments, the vermiculite and the kaolinite rich soils exhibited equal or greater reductions in HC for PAR treatments, as compared with the SAR treatments. Findings from this evaluation of the interaction of Na + and K + with three different mineral soils suggest that the reuse of WW with increasing PAR are least problematic for montmorillonite dominated soils and most detrimental to the HC of the vermiculite dominated soil. The presence of minerals with a high affinity for K + (e.g., vermiculite, mica) in this soil suggest that the interlayer binding of K + could lead to greater reductions in HC. Full analysis of soil and WW is recommended prior to all land applications.

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Nitrate is often present in surface water, soil solution, and groundwater at undesirable or toxic levels. This study follows development of an in situ nitrate monitoring probe and examines its performance in the presence of potentially interfering ionic species and dissolved organic carbon (DOC). Ultraviolet (UV) absorption spectroscopy measurements of aqueous NO3− were obtained under conditions where prevalent ionic species (i.e., Na+, K+, Ca2+, Mg2+, NH4+, Zn2+, Cu2+, Mn2+, Fe2+, Fe3+, Al3+, Cl−, H2PO4−, HPO42−, SO42−, and HCO3−) and DOC were present at maximum characteristic concentrations for a range of pH levels, allowing UV interference on NO3− concentrations from individual ions to be investigated. While most solutions did not show interference, Fe2+ ions and DOC absorbed ultraviolet light strongly in regions of the spectrum where NO3− also exhibited significant absorption. Natural water samples showed very low concentrations of Fe2+, which do not cause interference with nitrate measurements. A two‐wavelength measurement scheme was adopted to correct for the potential interference of DOC in measurements of aqueous NO3−. A multivariate calibration is presented to account for possible interference from both DOC and other ions in solution. The application of the UV spectroscopy probe is especially useful for deep vadose zone measurements of nitrate, as typically DOC concentrations will exponentially decrease with depth, and ion interference will be low.

Shallow, small-rate releases of ethanol-blended fuels from underground storage tanks (USTs) may be quite common and result in subsurface CH 4 generation. However, vadose zone transport of CH 4 generated from these fuel releases is poorly understood, despite the potential to promote vapor intrusion or create explosion hazards. In this study, we simulated shallow CH 4 generation with a controlled subsurface CH 4 release from July 2014 to February 2015 to characterize subsurface CH 4 migration and surface emissions and to determine environmental controls on CH 4 fate and transport. July 2014 through November 2014 was an extended period of drought followed by precipitation during December 2014. Throughout the experiment, under varied CH 4 injection rates, CH 4 formed a radially symmetrical plume around the injection point. Surface efflux during the drought period of the experiment was relatively high and stable, with approximately 10 to 11 and 34 to 52% of injected CH 4 reaching the ground surface during the low-and high-rate injections, respectively. Following the period of precipitation and increased soil moisture, efflux dropped and stabilized at approximately 1% of injected CH 4 , even as soil moisture began to decrease again. Tracer and inhibitor experiments and estimates of soil diffusivity suggest that microbial CH 4 oxidation was responsible for the observed drop in efflux. The decrease in efflux only after soil moisture increased suggests a strong environmental control over the transport and oxidation of vadose zone CH 4 .