K. A. Barbarick

Selenium adsorption to aluminum-based water treatment residuals

Aluminum-based water treatment residuals (WTR) can adsorb water- and soil-borne P, As(V), As(III), and perchlorate, and may be able to adsorb excess environmental selenium. WTR, clay minerals, and amorphous aluminum hydroxide were shaken for 24 h in selenate or selenite solutions at pH values of 5-9, and then analyzed for selenium content. Selenate and selenite adsorption edges were unaffected across the pH range studied. Selenate adsorbed on to WTR, reference mineral phases, and amorphous aluminum hydroxide occurred as outer sphere complexes (relatively loosely bound), while selenite adsorption was identified as inner-sphere complexation (relatively tightly bound). Selenite sorption to WTR in an anoxic environment reduced Se(IV) to Se(0), and oxidation of Se(0) or Se(IV) appeared irreversible once sorbed to WTR. Al-based WTR could play a favorable role in sequestering excess Se in affected water sources.

Soil nitrate analysis by cadmium reduction 1

Abstract The purpose of this research was to determine the feasibility of cadmium reduction analysis of soil nitrate as a teaching method and also as a general soil nitrate analysis method. Sixteen soil samples were analyzed for nitrate using cadmium reduction, phenoldisulfonic acid and steam distillation methods. The soil pH levels ranged from 6.3 to 8.4. The nitrate levels ranged from 1 ppm to 62 ppm while the soil nitrite levels fell between 0.3 ppm to 2.6 ppm. Correlation coefficients between the three methods were found to be highly significant. The analysis means were found to be statistically the same between the cadmium reduction method and steam distillation methods. The analysis of soil nitrate by cadmium reduction was found to be acceptable for the determination of soil nitrate levels.

Biosolids effects on microbial activity in shrubland and grassland soils

Natural ecosystems in the western United States provide potential locations for recycling sewage biosolids. However, little is known about how this practice would affect soil microbial activity. Our objective was to determine whether one-time surface biosolids applications at 0 and 40 Mg ha −1 to a shrubland site and 0 and 30 Mg ha −1 to a grassland site would affect various types of microbial activity 6 years after treatment. Compared with the untreated control, biosolids addition increased microbial respiration by factors of 2.3 and 1.7 at the shrubland and grassland sites, respectively, and nitrogen mineralization increased by factors of 5.4 and 3.6 at the shrubland and grassland sites, respectively. Biosolids application enhanced the colonization of arbuscular mycorrhizal (AM) fungi on root samples of western wheatgrass (Pascopyrum smithii (Rydb.) A. Love) by 33% at the shrubland site and of blue grama (Bouteloua gracilis (H.B.K.) Lag. ex steud) by 23% at the rangeland site 6 years after treatment. Microbial biomass (SIR-Cmicro) increased by at least 11% in the biosolids-amended plots at both sites. Biosolids did not affect the basal respiration rate (BRR) or the metabolic quotient (qCO2) at either site. We conclude that one-time biosolids addition in a shrubland and a grassland ecosystem 6 years after biosolids application enhances micro-bialactivity.

Infrequent composted biosolids applications affect semi-arid grassland soils and vegetation.

Monitoring of repeated composted biosolids applications is necessary for improving beneficial reuse program management strategies, because materials will likely be reapplied to the same site at a future point in time. A field trial evaluated a single and a repeated composted biosolids application in terms of long-term (13-14 years) and short-term (2-3 years) effects, respectively, on soil chemistry and plant community in a Colorado semi-arid grassland. Six composted biosolids rates (0, 2.5, 5, 10, 21, 30 Mg ha(-1)) were surface applied in a split-plot design study with treatment (increasing compost rates) as the main factor and co-application time (1991, or 1991 and 2002) as the split factor applications. Short- and long-term treatment effects were evident in 2004 and 2005 for soil 0-8 cm depth pH, EC, NO(3)-N, NH(4)-N, total N, and AB-DTPA soil Cd, Cu, Mo, Zn, P, and Ba. Soil organic matter increases were still evident 13 and 14 years following composted biosolids application. The repeated composted biosolids application increased soil NO(3)-N and NH(4)-N and decreased AB-DTPA extractable Ba as compared to the single composted biosolids application in 2004; differences between short- and long-term applications were less evident in 2005. Increasing biosolids rates resulted in increased native perennial grass cover in 2005. Plant tissue Cu, Mo, Zn, and P concentrations increased, while Ba content decreased depending on specific plant species and year. Overall, the lack of many significant negative effects suggests that short- or long-term composted biosolids application at the rates studied did not adversely affect this semi-arid grassland ecosystem.

Sewage biosolids cumulative effects on extractable-soil and grain elemental concentrations

While land application of sewage biosolids is the most expedient method of recycling plant nutrients, concern over trace element additions resulted in U.S. Environmental Protection Agency (USEPA) beneficial-use regulations. We studied 11-yr biosolids addition effects on ammonium bicarbonate diethylenetriaminepentaacetic acid (AB-DTPA) and 4 M HNO 3 extractable levels of soil Cd, Cu, Mo, Ni, P, Pb, and Zn, and the relationship between the soil-extractable concentrations and grain concentrations. The soils at our four dryland wheat (Triticum aestivum L.) sites were Aridic Paleustolls (Weld and Platner loam). For each application, we used four rates of biosolids (0, 7, 14, and 28 Mg ha -1 ) from the Littleton/Englewood, CO Wastewater Treatment Plant. We tested linear, quadratic, and either exponential-rise (plateau) or exponential-decay models for AB-DTPA- and 4 M HNO 3 -extractable concentrations compared with the cumulative quantity of biosolids-borne element added and with elemental grain concentrations. Models for AB-DTPA-extractable Cu, P, Pb, and Zn and 4 M HNO 3 -extractable Cu and P vs. the cumulative quantity added produced R 2 values ≥ 0.46. For grain concentrations, only the models for AB-DTPA vs. grain Zn produced an R 2 ≥ 0.50. For monitoring soil levels of Cd, Cu, Mo, Ni, P, Pb, and Zn in Paleustolls (common soils in the western Great Plains dryland wheat areas) that continuously receive biosolids, we recommend AB-DTPA over 4 M HNO 3 soil extractions. The AB-DTPA extractions also provide soil fertility information (NO 3 -N and plant available P, K, and micronutrients).

Amendment effects on pH and salt content of bauxite residue

Bauxite residue, a waste product from the refining of bauxite to alumina, contains excessive Na and an elevated pH. We investigated the use of four chemical amendments to reduce bauxite residue pH and Na content and to improve soil characteristics for reclamation purposes. A control (unamended) and treatments of gypsum, acidic gypsum, sulfuric acid, or elemental sulfur were thoroughly mixed with bauxite residue at rates to reduce the exchangeable sodium percentage (ESP) to 5%, with or without an equivalent of 90 Mg ha−1 wood chips for aeration. Materials were placed in separate 32-L PVC containers, leached with water, and 8 separate pore volumes collected. All treatments were replicated three times. Pore volumes 1 through 5 and 8 were analyzed for pH, Na, Ca, Mg, and sodium adsorption ratio (SAR). The acidic gypsum and acidic gypsum + wood chips treatments significantly lowered the pH (<8.5), leached the greatest amount of Na, Ca, and Mg for all pore volumes, and lowered the SAR as compared with other treatments. On completion of the leaching experiment, we analyzed the 0- to 15-cm and 15- to 30-cm depths in the columns for Na, Ca, Mg, SAR, ESP, pH, and electrical conductivity and compared values with unamended treatment. For all treatments, the Na content and ESP were reduced by an order of magnitude, Ca and Mg content increased, pH was reduced, and SAR was reduced by several orders of magnitude as compared with pre-experiment concentrations. Overall, the acidic gypsum and the acidic gypsum + wood waste treatments showed the most promise for reducing bauxite residue pH and Na content.

Combinations of water treatment residuals and biosolids affect two range grasses

The beneficial reuse of water treatment plant residuals (WTR) and biosolids via land co-application is of concern since the WTR is postulated to greatly reduce plant phosphorus (P) availability and, along with biosolids, possibly provide an additional source of trace metals to soil. Potential plant Al toxicity with increasing WTR rates, because of the Al content of WTR [Al2(SO4)3·14H2O], has also been speculated. In a greenhouse study we investigated the efficacy of co-application of WTR and biosolids to the native shortgrass prairie species blue grama (Bouteloua gracilis H.B.K. Lag) and western wheatgrass [Agropyron smithii (Rydb.) A. Love]. Co-application rates were a factorial combination of 0, 2.5, 5, 7.5, and 10 g kg− 1 of WTR and 0, 2.5, 5, 7.5, and 10 g kg− 1 of biosolids. Increasing WTR rate, averaged over biosolids rate, resulted in a decrease (p<0.10) in blue grama P concentration and an increase in Al concentration. Increasing biosolids rate, averaged over WTR rates, significantly affected most constituents. With only WTR addition (no biosolids) to blue grama, we observed an increase in plant Al concentration and uptake, and a decrease in plant Mo concentration. Increasing WTR rate, averaged over biosolids rate, produced a significant decrease in western wheatgrass P and molybdenum (Mo) concentrations. Increasing biosolids rate, averaged over WTR rates, again affected most constituents studied. With only WTR addition (no biosolids) to western wheatgrass, this study observed a decrease in plant Mo concentration and uptake. In both studies no significant WTR-biosolids interactions were observed. These results indicate WTR could reduce P availability even when co-applied with biosolids. Co-application can aid municipalities dealing with excessive biosolids-borne P and Mo application associated with an agronomic (nitrogen) biosolids application rate. However, high application rates of WTR should be avoided due to its adverse effect on P availability to plants, unless a supplemental P source is supplied.

Fate of biosolids trace metals in a dryland wheat agroecosystem

Biosolids land application for beneficial reuse applies varying amounts of trace metals to soils. Measuring plant-available or total soil metals is typically performed to ensure environmental protection, but these techniques do not quantify which soil phases play important roles in terms of metal release or attenuation. This study assessed the distribution of Cd, Cr, Cu, Mo, Ni, Pb, and Zn associated with soluble/exchangeable, specifically adsorbed/carbonate-bound, amorphous Mn hydroxyoxide-bound, amorphous Fe hydroxyoxide-bound, organically complexed, and residual inorganic phases. Biosolids were applied every 2 yr from 1982 to 2002 (except in 1998) at rates of 0, 6.7, 13.4, 26.8, and 40.3 dry Mg biosolids ha(-)(1) to 3.6- by 17.1-m plots. In 2003, 0- to 20-cm and 20- to 60-cm soil depths were collected and subjected to 4 mol L(-1) HNO(3) digestion and sequential extraction. Trace metals were concentrated in the 0- to 20-cm depth, with no significant observable downward movement using 4 mol L(-1) HNO(3) or sequential extraction. The sequential extraction showed nearly all measurable Cd present in relatively mobile forms and Cr, Cu, Mo, Ni, Pb, and Zn present in more resistant phases. Biosolids application did not affect Cd or Cr fractionation but did increase relatively immobile Cu, Mo, and Zn phases and relatively mobile Cu, Ni, and Pb pools. The mobile phases have not contributed to significant downward metal movement. Long-term, repeated biosolids applications at rates considered several times greater than agronomic levels should not significantly contribute to downward metal transport and ground water contamination for soils under similar climatic conditions, agronomic practices, and histories.

Phosphorus Extraction Methods for Water Treatment Residual–Amended Soils

Abstract Water treatment residuals (WTR) can adsorb tremendous amounts of phosphorus (P). A soil that had biosolids applied eight times over 16 years at a rate of 6.7 Mg ha−1 y−1 contained 28 mg kg−1 ammonium–bicarbonate diethylenetriaminepentaacetic acid (AB‐DTPA), 57 mg kg−1 Olsen, 95 mg kg−1 Bray‐1, and 53 mg kg−1 Mehlich‐III extractable P. To 10 g of soil, WTRs were added at rates of 0, 0.1, 1, 2, 4, 6, 8, and 10 g, then 20 mL of distilled deionized H20 (DI) were added and the mixtures were shaken for 1 week, filtered, and analyzed for soluble (ortho‐P) and total soluble P. The soil–WTR mixtures were dried and P extracted using DI, AB‐DTPA, Olsen, Bray‐1, and Mehlich‐III. Results indicated that all methods except AB‐DTPA showed reduced extractable‐P concentrations with increasing WTR. The AB‐DTPA extractable P increased with increasing WTR rate. The water‐extractable method predicted P reduction best, followed by Bray‐1 and Mehlich‐III, and finally Olsen.

Predicting soil-extractable Zn, P, Fe, and Cu in a biosolids-amended dryland wheat agroecosystem

Biosolids Beneficial Use Programs frequently involve multiple applications at agronomic rates, with plant-nutrient availability changing as elements react with soil constituents over time. Consequently, can regression equations reasonably estimate plant availability of Zn, P, Fe, and Cu, where multiple applications of Littleton and Englewood, Colorado Wastewater Treatment Plant biosolids are applied to a dryland wheat (Triticum aestivum L.)-fallow agroecosystem? Before each growing season, we added Littleton and Englewood biosolids at rates of 0 to 11.2 dry Mg ha−1 to plots arranged in randomized complete blocks with four replications per treatment. Soil samples collected after each wheat harvest were analyzed using an NH4HCO3-diethylenetriaminepentaacetic acid extraction. We completed planar (included the number of applications and elemental additions), linear, quadratic, and exponential-rise-to-a-maximum (as a function of elemental additions only) regression analyses for six applications at two sites. We found that the planar regression models provided superior R2 values and SE of the estimate in almost all cases. These results suggest that lability changes as biosolids-borne Zn, P, Fe, and Cu react with the soil over time. Consequently, predictions of nutrient availability involving multiple biosolids applications to dryland wheat-fallow agroecosystems should account for the number of biosolids additions.