Measuring Surface Chemical Properties of Soil Using Flow Calorimetry

Flow calorimetry, which is ideally suited for measuring reactions occurring at the liquid/solid interface, has been used to study the surface chemistry of many types of solids, but little use of it has been made in the study of surface reactions of soils. The purpose of this study was to demonstrate the application of flow calorimetry to the study of two fundamental soil chemical processes, namely cation exchange and phosphate sorption. Surface horizon samples of a Typic Acrorthox and a Typic Tropohumult from Puerto Rico, a strong acid cation exchange resin (Dowex 50W-8), and an amorphous Al(OH)3 were used. Heats for K/Ca exchange on the Dowex resin and the Oxisol, and K/Na exchange on the Ultisol, were consistent with literature values that were obtained using conventional batch calorimetry or derived from the temperature dependence of the exchange constant. Although peak areas associated with a given pair of exchange reactions were equal, peak shapes were generally not equivalent, indicating differences in the rate at which the two reactions occurred. For example, Ca displacing exchangeable K occurred more rapidly than the reverse reaction on the Dowex resin. The reaction of phosphate with the Ultisol and amorphous Al(OH)3 was exothermic. Exposure of the soil to several cycles of phosphate was sufficient to saturate the sorption sites, as evidenced by the loss of a detectable heat signal. However, phosphate reactive sites were regenerated by flushing the column with a salt solution at pH 10. Precipitation of Al-phosphate was shown to be endothermic, confirming that precipitation was not the primary mechanism for phosphate sorption in this study. The results of this study show that flow calorimetry can provide valuable information about surface chemical reactions in soils that cannot be obtained readily by other methods

Heats of K/Ca And K/Pb Exchange in Two Tropical Soils as Measured By Flow Calorimetry

Flow calorimetry can provide useful information about surface chemical reactions in soils that cannot be obtained readily by other methods. When flow calorimetry is conducted over a range of surface coverages, different sorption heats can be calculated to yield information about how binding energies vary with coverage, i.e., surface heterogeneity. The purpose of this study was to determine heats of exchange for K/Ca and K/Pb systems using flow calorimetry and to evaluate the degree of surface heterogeneity with respect to cation exchange. Surface horizon samples from a Typic Acrorthox and Typic Tropohumult from Puerto Rico were used. Lead was adsorbed specifically in both soils, but no adsorption heat was detected for this reaction in either soil. However, heats associated with reversible cation exchange between K and Pb were observed. Heats for K/Ca exchange were greater than those generated for K/Pb exchange in both soils. Heats of exchange were greater in the Ultisol than in the Oxisol. The differential heats of exchange were independent of exchange composition for both K/Pb and K/Ca exchange in the Oxisol, indicating that all cation exchange sites were similar energetically. In the Ultisol, the differential heats of exchange increased as exchangeable K decreased, indicating that the exchange sites were not similar energetically. These differences were attributed to the presence of smectite in the Ultisol, which was able, in part, to collapse when saturated with K

Point Of Zero Charge Determination in Soils and Minerals via Traditional Methods and Detection of Electroacoustic Mobility

Points of zero charge were determined on two highly weathered surface soils from Puerto Rico, an Oxisol and Ultisol, as well as mineral-standard kaolinite and synthetic goethite using three methods: (1) potentiometric titration measuring the adsorption of H+ and OH− on amphoteric surfaces in solutions of varying ionic strength (I) (point of zero salt effect), (2) direct assessment of surface charges via non-specific ion adsorption as a function of pH and I (point of zero net charge), and (3) electroacoustic mobility of reversible particles as it varies with pH and I (isoelectric point). The first two methods yielded points of zero charge for kaolinite (2.7–3.2) and synthetic goethite (7.4–8.2) comparable to those reported previously, indicating the reliability of these analyses. The soil values ranged from 3.9 to 4.4 for the Oxisol and 2.3 to 3.7 for the Ultisol. Electroacoustic mobility, as measured by the AcoustoSizer™, is a parameter that has yet to be thoroughly tested for mineral or soil systems as a viable alternative to PZC assessment. The points of zero charge from electroacoustic mobility of kaolinite (3.8–4.1) and synthetic goethite (8.1–8.2) were similar to values obtained by electrophoretic mobility. Furthermore, the values found for the Oxisol (3.4–3.5) and Ultisol (2.6–2.7) were in the range expected for these soils

Sequential Sorption of Lead and Cadmium in Three Tropical Soils

It is important to examine mechanisms of Pb and Cd sorption in soils to understand their bioavailability. The ability of three tropical soils to retain Pb, Cd, and Ca was evaluated. The objectives of this study were to (1) determine the extent to which soil sorption sites are metal specific, (2) investigate the nature of reactions between metals and soil surfaces, and (3) identify how metals compete for sorption sites when they are introduced to soils sequentially or concurrently. Lead was shown to be much less exchangeable than Cd and inhibited Cd sorption. Cadmium had little effect on Pb sorption, though both Ca and Cd inhibited the adsorption of Pb at exchange sites. Lead appears to more readily undergo inner-sphere surface complexation with soil surface functional groups than either Cd or Ca. Thus, regardless of when Pb is introduced to a soil, it should be less labile than Cd. The sorption and desorption of Pb and Cd in tropical soils is strongly influenced by the order in which these metals enter the soil environment

Mechanisms of Lead, Copper, and Zinc Retention by Phosphate Rock

The solid–liquid interface reaction between phosphate rock (PR) and metals (Pb, Cu, and Zn) was studied. Phosphate rock has the highest affinity for Pb, followed by Cu and Zn, with sorption capacities of 138, 114, and 83.2 mmol/kg PR, respectively. In the Pb–Cu–Zn ternary system, competitive metal sorption occurred with sorption capacity reduction of 15.2%, 48.3%, and 75.6% for Pb, Cu, and Zn, respectively compared to the mono-metal systems. A fractional factorial design showed the interfering effect in the order of Pb \u3e Cu \u3e Zn. Desorption of Cu and Zn was sensitive to pH change, increasing with pH decline, whereas Pb desorption was decreased with a strongly acidic TCLP extracting solution (pH=2.93). The greatest stability of Pb retention by PR can be attributed to the formation of insoluble fluoropyromorphite [Pb10(PO4)6F2], which was primarily responsible for Pb immobilization (up to 78.3%), with less contribution from the surface adsorption or complexation (21.7%), compared to 74.5% for Cu and 95.7% for Zn. Solution pH reduction during metal retention and flow calorimetry analysis both supported the hypothesis of retention of Pb, Cu, and Zn by surface adsorption or complexation. Flow calorimetry indicated that Pb and Cu adsorption onto PR was exothermic, while Zn sorption was endothermic. Our research demonstrated that PR can effectively remove Pb from solutions, even in the presence of other heavy metals (e.g. Cu, Zn). ‘‘Capsule’’: Phosphate-induced formation of fluoropyromorphite is primarily responsible for Pb immobilization by phosphate rock, whereas Cu and Zn retention is mainly attributable to the surface adsorption or complexation

Mechanisms of lead, copper, and zinc retention by phosphate rock

Mitteilungen des Förderkreises Archive und Bibliotheken zur Geschichte der Arbeiterbewegung, Nr. 37 / März 2010. Ausführliche Rezension hier in der Tageszeitung junge welt vom Montag 29. März 2010

Vine age affects vine performance, grape and wine chemical and sensory composition of cv. Zinfandel from California

The wine industry regards old vines as nonpareil because of the vine’s decreased capacity to set and mature fruit, which results in superior wine quality. Here we report the viticultural, chemical, and sensory effects of vine age in Vitis vinifera L. cv. Zinfandel. Three treatments, Young vines (five to 12 years old), Control (repre sentative proportion of young to old vines in the block), and Old vines (40 to 60 years old) were established at an interplanted, dry farmed, Zinfandel vineyard block under consistent, industry standard, management practices in California over two consecutive vintages. Old vines produced, on average, 3.7 kg more fruit and more clusters per vine than Young vines (13.37 tons/ha and 6.52 tons/ha, respectively). While no differences in root distribution or architecture were found, Old vines displayed greater rooting depths (1.52 to 1.73 + m) than Young vines (1.40 to 1.52 + m). Wines from Young vines had lower pH, titratable acidity, and tannins than wines from Old vines, which in turn displayed a wider array and intensity of more complex aromas relative to Young vine wines. Overall, it is concluded that there is a potential for greater yield, rooting depths, and wine quality when extending the longevity of Zinfandel vineyards. These findings support maintaining old vine vineyards to increase tonnage without sacrific ing wine quality.EEA MendozaFil: Riffle, Vegas L. California Polytechnic State University. Wine and Viticulture Department; Estados UnidosFil: Alvarez Arredondo, Jocelyn. California Polytechnic State University. Wine and Viticulture Department; Estados UnidosFil: LoMonaco, Isabelle. California Polytechnic State University. Wine and Viticulture Department; Estados UnidosFil: Appel, Chip. California Polytechnic State University. Natural Resources Management and Environmental Sciences; Estados UnidosFil: Catania, Anibal Alejandro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; ArgentinaFil: Dodson Peterson, Jean Catherine. California Polytechnic State University. Wine and Viticulture Department; Estados UnidosFil: Dodson Peterson, Jean Catherine. California Polytechnic State University. Horticulture and Crop Science Department; Estados UnidosFil: Dodson Peterson, Jean Catherine. Washington State University. Department of Viticulture and Enology. Wine Science Center; Estados UnidosFil: Casassa, Luis Federico. California Polytechnic State University. Wine and Viticulture Department; Estados Unido

Analysis of Chromium and Nickel in Soil and Plant Tissue Collected from the Experimental Vineyard at California Polytechnic State University, San Luis Obispo, CA

Serpentinitic soils often contain high concentrations of heavy metals, including chromium (Cr) and nickel (Ni). Soils derived from serpentine parent material are used for agricultural purposes throughout San Luis Obispo County, CA. This study was undertaken to determine the amount of total and bioaccessible Cr and Ni in soil and vine tissue from a vineyard planted on soils derived from serpentine geology. Eighteen soil and plant samples were collected from different slope position and vine types (syrah and chardonnay). Soil samples were collected from about 0 to 30 cm at the base of the vines and 15 to 20 leaf with attached petiole samples were collected from one vine at each sample location. Soil and plant samples were extracted with 1:1 HNO3 for total Cr and Ni concentrations using U.S. EPA method 3050a. Bioaccessible Cr and Ni concentrations from soil samples were determined by extracting samples twice with neutral 1 N NH4C2H3O2. Metal concentrations were determined using flame atomic absorption spectroscopy. Mean total Cr and Ni concentrations from all soil samples were 49.26 and 42.43 mg kg-1, respectively. Total mean Cr concentrations in vine tissue samples were below the method detection limit (MDL) for Cr, and total mean Ni concentrations in vine tissue were 2.75 mg kg-1. Bioaccessible Cr and Ni concentrations from soil samples were below MDLs for each metal. The undetectable amounts of bioaccessible Cr and Ni indicate that they are most likely strongly sorbed to soil particles. The low heavy metal bioaccesiblility in this vineyard soil indicates that Cr and Ni poise little risk to vine health for toxicity considerations. Future research will evaluate Cr and Ni concentrations in other local agricultural soils derived from serpentinite

Determination of Total and Bioavailable Soil Lead from a Shooting Range in Central California.

Lead can pose a significant risk to environmental quality at and around shooting ranges due to its use in bullets and shot. The concentrations of Pb in soils, plants and surficial waters from a shooting range were determined in this study. Soil and plant samples were analyzed for total Pb (US EPA method 3050a) to determine the extent of Pb contamination. The toxicity characteristic leach procedure (TCLP; US EPA method 1311) was followed to ascertain bioavailable Pb. Soil samples ranged from 14.71 to 6346.15 mg Pb kg-1 soil with an average value of 1157.43 (±2000.57) mg Pb kg-1 soil across the shooting range. Plant samples ranged from 632.76 to 2896.00 mg Pb kg-1 plant with an average value of 1410.31 (±1287.11) mg Pb kg-1 plant, demonstrating significant Pb uptake. Bioavailable Pb was highest in the berm at 2038.00 mg Pb kg-1 soil. Sampling at depth showed Pb concentrations of 72.92 mg Pb kg-1 soil. When compared to surface samples (897.96 mg Pb kg-1), this shows some Pb is leaching through the profile. High Pb concentrations were detected in soil samples collected from the drainage (457.84 mg Pb kg-1), while low Pb levels were detected in the stormwater retention pond and sediments (0.11 mg Pb L-1 and 39.36 mg Pb kg-1 respectively). This indicates Pb is being transported through erosion of soil colloids. Elevated Pb levels from soil sampled in the drainage indicate most Pb present is attached to soil colloids and not free (Pb+2) to leach or runoff. Higher concentrations of Pb were detected in plant samples than extracted by TCLP bioavailable Pb estimations. This could present a problem for any pastoral activities and should come under further scrutiny