Location: Water Reuse and Remediation Research2009 Annual Report
1a. Objectives (from AD-416)
Water quality criteria were initially developed to protect irrigated soils from possible adverse soil structural changes (such as reduced infiltration) and avoid reductions in crop yield due to salinity. Increased demands on our limited water resources necessitates that we more accurately determine these criteria since many waters deemed unsuitable can be used under specified conditions. Application of these criteria and application of recycled irrigation drainage water and treated municipal waste water will reduce the margin of error and require that we carefully monitor changes in soil properties, and thus develop improved monitoring protocols and practices. Based on these needs the research project is focused under two objectives: Objective 1: Develop new knowledge and guidelines related to major ion, B, and Mo concentrations for the sustained use of degraded waters including drainage waters and municipal waste waters. Objective 2: Evaluate the use of geophysical and geographic information system technology to monitor spatio-temporal changes of soil properties, salinity, trace elements and N. Both of these objectives are necessary for effective and protective implementation of irrigation with impaired waters. Although the stated objectives can be achieved by pursuing parallel lines of research, they will be combined in development of management practices. The monitoring technology objective is also essential to future field evaluation of the criteria and predictions made relative to objective one.
1b. Approach (from AD-416)
1:The adsorption behavior of B and Mo will be studied as a function of solution pH, solution anion concentration, electrolyte composition, and competing anion concentration in batch systems on soils chosen to represent a variety of soil orders. The adsorption behavior will be described using a chemical surface complexation model, allowing for development of improved management of degraded waters high in B and Mo. The desorption behavior of both native soil B and recently added B will be characterized in batch systems to determine the extent of desorption hysteresis in the presence and absence of competing ions. If desorption hysteresis is found, mathematical equations will be developed to describe the B desorption process in batch systems. Data will be analyzed, and B movement predicted using initial soil characteristics, ET calculations, and water composition using the UNSATCHEM model. New B transport routines will be developed if needed. Waters of varying composition including salinity, SAR, pH, alkalinity, and Ca/Mg ratio, will be applied to soils in outdoor containers with measurement of the water infiltration rate for both irrigation water and alternate application of rain using a rainfall simulator. The results of these experiments will be incorporated into predicted routines in UNSATCHEM and in guidelines for use of impaired waters. We will evaluate the impact of use of degraded water on soil quality, productivity and forage quality of a marginally productive saline-sodic soil. Characterization of soil spatial variability will utilize ECa measured by electromagnetic induction equipment, where each site is geo-referenced using GPS. 2: Validation of use of ECa-directed sampling to spatially characterize soil properties (salinity, texture, water content) will be made at a drainage water reuse site. ECa measurements will be used to determine 40 site locations from a response surface sampling design algorithm. Additional sites will be randomly selected for a validation data set. Correlating properties will be predicted from spatial regression models and compared to randomly chosen positions where validation sample data have been collected with development of a protocol for model validation of directed sampling techniques. A site in semi-arid CO under no-till will be used to evaluate ECa-delineated zones as a framework for site-specific N management in winter wheat and for field-scale monitoring of soil quality response and identification of soil quality trends. To evaluate site specific management, using ECa zones, 3 years of yield, ECa zone, and N-treatment maps will be compared with geo-referenced soil sample analyses for N-use efficiency and optimal N rates for each ECa zone. A phenomenological model of salinity development will be formulated based on spatial data of potential soil salinization factors (e.g., soil type, poor drainage areas, topography, leaching fraction, depth to groundwater, groundwater quality, etc.) for the Red River Valley basin of North Dakota and Minnesota. The phenomenological model will be used to create an inventory map of salinity for the entire Red River Valley. Formerly 5310-5310-61000-012-00D.
3. Progress Report
We investigated anion adsorption on an aluminum oxide, gibbsite, as a function of solution pH (3-11) and solution Mo (3.13, 31.3, or 313 µM), P (96.9 µM), or suphate (156 µM) concentration. Adsorption of all three anions decreased with increasing pH. Electrophoretic mobility measurements were consistent with an inner-sphere adsorption mechanism for all three anions. The constant capacitance model having an inner-sphere adsorption mechanism was able to describe Mo and P adsorption; while the triple layer model with an outer-sphere adsorption mechanism was used to describe sulfate adsorption. Competitive adsorption experiments showed no reduction at a Mo:S ratio of 1:52 and 1:520, concentrations that are realistic for natural systems. The constant capacitance model was able to predict the competitive effect of P on Mo adsorption semi-quantitatively. The adsorption behavior of B was studied as a function of solution pH and major cation concentration on five arid zone soils from California. Boron adsorption in the presence of divalent cations was comparable to that in the presence of the monovalent cation. This result indicated that adsorption of B-divalent cation ion pairs did not provide a significant contribution to B adsorption, contrary to what had been previously indicated in the literature. Sustainability of Drainage Water Reuse as Evaluated with ECa-directed Soil Sampling: The 5-year sustainability of drainage water reuse on a saline-sodic soil was demonstrated from the interpretation of field-scale spatio-temporal data of soil chemical properties collected using ECa-directed sampling. Use of Geophysical Techniques to Map and Monitor Saline-Sodic Soils at Field Scales during Remediation: A statistical analysis of spatial data was completed confirming the validity of the response surface sampling design approach for characterizing soil spatial variability with ECa-directed sampling. Guidelines and Protocols for Regional-scale Salinity Assessment of the Red River Valley: Analysis of soil samples was completed for the second (Walsh County) of three counties used to formulate and calibrate the regional-scale salinity development model for the Red River Valley. A salinity development model was developed for Kittson County. We conducted infiltration studies using a noncalcareous soil in the presence and absence of rain, examining the interaction of irrigation water pH and SAR. The pH, ranged from 5.5 to 9 and SAR, ranged from 0 to 10. We collected data on each rain or infiltration event over a one year cycle. The pH and SAR hazard increased in the presence of rain and the detrimental effects of high pH and SAR increased through the irrigation season, indicating that short term experiments underestimate these impacts on infiltration. We conducted long term large scale column experiments, adding a high B irrigation water to a clay soil, and examining the adsorption and transport of B. The results will be compared to predictions using the UNSATCHEM model.
1. Predicting perchlorate concentration in vegetables. Perchlorate contamination of waters used for irrigation is of concern as, it may have detrimental effects on humans (thyoid function) and has been detected in lettuce and other vegetables grown with Colorado River water. ARS scientists at Riverside, CA examined the factors that affect perchlorate uptake by lettuce and spinach grown under controlled greenhouse conditions and developed predictive equations describing perchlorate uptake as related to perchlorate, chloride and nitrate in the soil solution. Perchlorate uptake was suppressed by increasing chloride or nitrate and was considerably higher in the outer leaves of lettuce, indicating that removal of the outer leaves is sufficient to greatly decrease perchlorate in the market product. We also determined that the potential for spinach contamination with perchlorate was much greater than for lettuce as it is a much stronger accumulator of perchlorate. This information is useful to growers seeking reduce the perchlorate concentration of their produce.
2. Salt tolerance and chloride toxicity of strawberries. Strawberry is an extremely salt sensitive, high value crop grown in coastal regions of California that are experiencing increased salinity and chlorine(Cl) concentrations in the irrigation water. ARS scientists in Riverside, CA determined that strawberry has a specific toxicity to chloride ions, as well as being sensitve to salinity in general. Based on both sandtank and field experiments we have determined that Cl concentrations at or above 115 mg/L in the irrigation water adversely affect yield for Camarosa cv as well as Ventana cv, while Ventana appeared more salt tolerant when irrigated with high sulfate, low chloride water. These results indicate that for strawberry, characterization of salt tolerance is not sufficient to describe yield loss and that specific ion composition must also be considered. This information will assist producers, irrigation water specialists and regulatory agencies in determining water quality suitability for strawberry production.
3. Predicting molybdenum adsorption in soils. Molybdenum (Mo) is a potentially toxic element to livestock and is present in high concentrations in some agricultural drainage waters. Understanding its movement in soil is essential to maintaining concentrations below toxic levels. The adsorption behavior of Mo was studied by ARS scientists at Riverside, CA as a function of solution pH, solution Mo concentration, salt composition and competing ion concentration on five arid zone soils from California. We determined both Mo adsorption isotherms (amount adsorbed as a function of equilibrium solution Mo concentration) and adsorption envelopes (amount adsorbed as a function of solution pH per fixed total Mo mass). The adsorption behavior was described using a chemical surface complexation model. The model was able to describe Mo adsorption, thus aiding in predicting Mo transport in soils.
Goldberg, S.R., Hyun, S., Lee, L.S. 2008. Chemical modeling of Arsenic(III, V) and Selenium(IV, VI) adsorption by soils surrounding ash disposal facilities. Vadose Zone Journal. 7(4):1231-1238.