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Soil acidification threatens dryland crop production in the inland Pacific Northwest (IPNW). Our objective was to assess the efficacy of lime to lower soil acidity, alter M chemistry, and increase crop yield in a direct-seeded system. Treatments of subsurface banded fertilizer (120-168 kg N [ha.sup.-1][ yr.sup.-1]) alone or with subsurface banded lime (224 kg [ha.sup.-1][ yr.sup.-1]), or a one-time broadcast application of lime (7000 kg [ha.sup.-1] or elemental S (1000 kg [ha.sup.-1]) were initiated in spring 2002. Grain yield was measured annually from 2002 to 2005 in a spring barley (Hordeum vulgare L.) -spring wheat (Triticum aestivum L.)--winter wheat rotation. Soil was sampled in spring 2004 to assess pH and model Al speciation. Low pH was evident at the depth of fertilizer placement (5-10 cm). Broadcast lime increased pH in the surface 15 cm, although reductions in [Al.sup.3+] activity [([Al.sup.3+])] occurred only in the 0- to 5-cm layer. Relative to banded N, there was no increase in pH at the 5- to 10-cm depth where banded lime was placed. At the 0- to 5-cm depth, lower pHs were observed with broadcast S (4.6) compared with the banded N control (5.1) or banded lime (5.0). There was no effect of treatment on yield. Modeling suggests that soluble Al is dominated by organic matter--Al complexes (fulvic acid, FA; [FA.sub.2] [Al.sup.+] and [FA.sub.2] [AlO[H.sup.0]). Solid- and solution-phase organic complexes may control ([Al.sup.3+]) at pH Abbreviations: CT, conventionally tilled; DS, direct seeded; FA, fulvic acid; IPNW, inland Pacific Northwest; NT, no-till.

Physical and chemical weathering processes in the rhizosphere may lead to the generation of a greater density of Cs-selective frayed edge sites (FES) on rhizosphere soil as compared with bulk soil. This study was undertaken to determine if there are significant differences between bulk and rhizosphere soils from the Idaho National Laboratory (INL) with respect to their ability to bind Cs. The capacity of FES on bulk and rhizosphere soil materials and conditional Cs/K selectivity of FES ([[sup.K].sup.FES.sub.ex]) were determined as a function of both soil type and initial exchanger composition. The FES capacity was significantly higher in untreated, Ca-saturated, and K-saturated rhizosphere soil materials as compared with bulk soil materials. Sorption-desorption isotherms were obtained at Cs concentrations between 5 x [10.sup.9] and 5 x [10.sup.-6] M. No difference in Cs sorption was observed between bulk and rhizosphere soil materials. The composition of the exchanging solution had the greatest effect on the magnitude of Cs desorption; significantly more Cs was desorbed in the presence of KCl than in either Ca[Cl.sub.2] or a mixed-cation soil solution. In addition, Cs desorption was greater from rhizosphere soil materials relative to bulk soil materials. Cesium selectivity with respect to both Ca and K was significantly suppressed by weathering in the rhizosphere. We conclude that enhanced weathering in the rhizosphere increased the Cs sorptiun capacity of FES, but also reduced Cs selectivity on these sites. Enhanced Cs desorption from rhizosphere INL soils is likely in the presence of actively growing plants and associated microorganisms.

Buried waste storage tanks at the USDOE Hanford Reservation in Washington State have released solutions containing high concentrations of Na, OH, N[O.sub.3], and Al into the vadose zone. When such solutions contact vadose zone sediments, mineral transformations will change the sediment matrix. We hypothesized that Si, dissolved from primary and secondary minerals, will combine with AI from the tank waste to form crystalline or poorly crystalline network silicates such as zeolites and feldspathoids. In this study, we characterized the colloidal (

Pretreatment of soils to enable physical separation and purification of minerals may alter their structural or chemical composition and preclude meaningful surface charge characterization. A natural imogolite and allophane, a synthetic imogolite (Al/Si = 2.01) and allophane (Al/Si = 1.64), and clays from the Bs and BC horizons of a Spodosol containing imogolite were subjected to standard [H.sub.2][O.sub.2] treatments before and after extraction with buffered dithionite-citrate-bicarbonate (DCB) to determine if effects on their surface charge characteristics and bulk composition were reversible. The [H.sub.2][O.sub.2] slightly shifted the point of zero charge (PZC) determined by electrophoretic mobility (EM) of natural imogolite and allophane toward more positive values, probably by the partial oxidation of retained organics, whereas it had no effect on the PZC values of soil clays. Five DCB extractions removed the most Al and Si from the synthetic allophane and the least Al from the synthetic, imogolite. More Si than Al was removed from the synthetic imogolite by five DCB extractions. Citrate retained on allophane and soil clays after DCB extraction was probably partially transformed to oxalate by subsequent [H.sub.2][O.sub.2] treatment. The EM in synthetic allophane could not be restored by oxidation of retained citrate following DCB treatment. Synthetic imogolite, after five DCB extractions, had only positive mobility up to pH 11.8. The DCB extraction, commonly used to remove Fe oxide from imogolite and allophane samples isolated front soils, irreversibly altered mineral surfaces and modified surface charge characteristics.

The solubility method for determining solid-phase controls on solute activities in aqueous systems is subject to potential sources of misinterpretation. Measurement errors cause deviation of solid-phase solubilities from theoretical values, whereas autocorrelation between dependent and independent variables of a solubility diagram may lead to false interpretation of data points falling on a given solubility line. In this study, a Monte Carlo simulation was performed to determine the influence of measurement errors and autocorrelation on the interpeptation of solubility data. For solid-phase control of Al activity at pH THERMODYNAMICALLY more stable minerals form in soil at the expense of less stable minerals as weathering of minerals proceeds. In the last decade, thermodynamics has been extensively applied to soil systems to obtain a better understanding and a more accurate prediction of soil mineral transformations and change of soil solution chemistry (Rai and Kittrick, 1989). The solubility method is a widely used approach for obtaining thermodynamic data for soil components due to its simplicity and high sensitivity (Rai and Kittrick, 1989). More importantly, the solubility method provides direct information on how close the soil solution approaches equilibrium with soil components under various environmental conditions and at different time intervals. However, two critical problems in the solubility approach need to be addressed. The first problem is related to the ambiguity of the term near equilibrium often used to describe natural systems in the literature. Taking the Al chemistry in acid soil and water as an example, the concentration ([C.sub.Al]) or activity of 'free' [Al.sup.3+] ([a.sub.Al]) in natural samples cannot be measured directly. Instead, the total inorganic monomeric Al concentration ([C.sub.Al(T)]) is Usually determined and [a.sub.Al] Calculated using the

Study on thermodynamic stability of volcanic minerals indicates that the soil solution of Bs and BC horizons in a Spodosol, are in equilibrium with imogolite and interlayer Al(OH)3 phase. The Al(OH)3 phase shows more solubility than crystallized gibbsite. Imogolite is consistent with the previous data of Su and Harsh 1994.

Three different DNA fragments were used to study DNA polydisperse solutions in eight different soils and no corresponding changes between the absorption coefficients (k) and the organic carbon contents, pHs, clay contents and cation exchange capacities were noted. The eight chosen model soils had different physical and chemical properties. The K values ranged from 300 for one soil to 1.1 for acid-washed soil.

An easier technique to define and quantify labile and nonlabile Si species in the presence of Al in acid was examined, and the importance of nonlabile Si species on Si and Al speciation in soil solutions were investigated. Labile Si was found to be identical to dialyzable Si and nonpositively charged Si. The lability of orthosilicic acid when Al is present was reduced when titrated with NaOH. An important factor effecting errors in Al or Si speciation for most acidic solutions is colloidal particles rather than polymeric Al-Si complexes.

The present study quantifies the transport of Escherichia coli pathogenic O157:H7 and nonpathogenic K12 strains in water-saturated Quincy sand (QS) columns amended with oxidized (OX) or unoxidized (UO) pine wood (PW) or pine bark (PB) biochar produced at either 350 or 600 °C. Our results showed that (1) the addition of oxidized biochar into QS columns enhanced the transport of E. coli O157:H7 by 3.1 fold compared to the unoxidized counterparts, likely because of an increase in the repulsive forces due to their higher negative charge densities. (2) The retention of E. coli O157:H7 was 3.3 fold higher than that of E. coli K12 in all biochar-amended sand columns. (3) Increased application rates of unoxidized PW600 biochar from 0 to 20 wt % led to a reduction in the transport of E. coli O157:H7 and K12 from 98 to 10% and from 95 to 70%, respectively. Our data showed that mixing sand with PW350-UO at a 20 wt % application rate almost completely retained the pathogenic E. coli in the subsurface, suggesting that utilizing sand mixed with biochar can act as a promising biofilter capable of protecting natural aquafers from pathogens. [ABSTRACT FROM AUTHOR]