Dissolution of phosphate in a phosphorus-enriched ultisol as affected by microbial reduction

Phosphorus dissolution often increases as soils become more reduced, but the mechanisms are not fully understood. The objectives of this research were to determine rates and mechanisms of P dissolution during microbial reduction of a surface soil from the North Carolina Coastal Plain. Duplicate suspensions of silt + clay fractions from a Cape Fear sandy clay loam (fine, mixed, semiactive, thermic Typic Umbraquult) were reduced in a continuously stirred redox reactor for 40 d. We studied the effects of three treatments on P dissolution: (i) 2 g dextrose kg(-1) solids added as a microbial carbon source at time 0 d; (ii) 2 g dextrose kg(-1) solids split into three additions at 0, 12, and 26 d; and (iii) no added dextrose. After 40 d of reduction, concentrations of dissolved reactive phosphorus (DRP) were similar for all treatments and increased up to sevenfold from 1.5 to 10 mg L(-1). The initial rate of reduction and dissolution of DRP was significantly greater for the 0-d treatment. A linear relationship (R(2) = 0.79) was found between DRP and dissolved organic carbon (DOC). Dissolved Fe and Al and pH increased, suggesting the formation of aqueous Fe- and Al-organic matter complexes. Separate batch experiments were performed to study the effects of increasing pH and citrate additions on PO(4) dissolution under aerobic conditions. Increasing additions of citrate increased concentrations of DRP, Fe, and Al, while increasing pH had no effect. Results indicated that increased dissolved organic matter (DOM) during soil reduction contributed to the increase in DRP, perhaps by competitive adsorption or formation of aqueous ternary DOM-Fe-PO(4) or DOM-Al-PO(4) complexes.     

ESTIMATED CONSUMPTIVE LOSS FROM MAN-MADE SNOW1

ABSTRACT: Consumptive loss of water attributable to man-made snowmaking was estimated using an energy balance model and a mass balance procedure. Data from nine field experiments at Colorado ski areas were collected and used in these models. The mean consumptive loss using the energy balance model for the nine experiments was 6.0 percent and 5.8 percent for the mass balance model A thermodynamic relationship and a regression equation were developed to provide a procedure to estimate consumptive loss as a linear function of atmospheric temperature.     

Comparing geographic boundaries in songbird demography data with vegetation boundaries: a new approach to evaluating habitat quality

To plan for the habitat needs of forest songbirds of conservation concern, managers need to understand how spatial heterogeneity in forest conditions influences habitat quality. I used difference boundary detection (wombling) and spatially constrained clustering to delineate boundaries in various combinations of four forest vegetation variables (understory height, understory density, percent deciduous vs. conifer understory, and percent canopy closure) in two Michigan northern hardwood forests. My goal was to identify vegetation boundaries that corresponded with boundaries in an understory-dependent songbird’s distribution, and with boundaries in demographic measures for this songbird that indicate habitat quality (e.g., occupancy by older vs. yearling males, reproductive success). Both forests were actively-managed, mature stands: The first site (78 ha) was heavily deer-browsed (HB), with many browse-resistant conifers in the understory, and the second (62 ha) was less-browsed (LB), with deciduous-dominated understory. I compared the vegetation difference and cluster boundaries to difference boundaries based on 6 years of distribution and demographic data for black-throated blue warblers (Dendroica caerulescens). At the HB site, warbler boundaries overlapped strongly with vegetation boundaries that included all four variables, and clustering effectively divided the habitat into areas with different warbler occupancy and demographic characteristics. At the LB site, warbler distribution showed high overlap with difference and cluster boundaries based on just the height and density of understory vegetation, and cluster boundaries again effectively partitioned the study area into sites that varied in habitat quality. Thus, geographic boundary analysis is likely to be a useful tool for identifying key vegetation variables for management, and for delineating clusters (habitat patches) within sites that capture differences in habitat quality.

Ex‐situ efficacy analysis of brine remediation products in clay loam soil

This study evaluated the effectiveness of gypsum and three proprietary products to remediate brine‐contaminated soil. The research objective was to determine if additives could increase plant cover germination in soils without costly prior soil‐washing or dilution techniques. The soil was shredded using a soil shredder equipped with a spray bar to apply the individual treatments of DeSalt Plus, SoilTech, Chlor*rid, and calcium sulfate (gypsum). Treatments were placed in 40‐mm high‐density polyethylene cells and small drainage systems were installed to allow removal of excess water. An initial 10‐point soil composite was taken from bulk untreated soils at a depth of more than 2.5 cm. Five‐point composite samples were collected from the same depth at weekly intervals and analyzed for: electrical conductivity, sodium adsorption ratio, cation exchange capacity, sodium, calcium, magnesium, potassium, chlorides, and pH. The Gapon selectivity coefficient was calculated and utilized to quantify the affinity for binding between ionic alkali salt constituent groups Na⁺, Ca ⁺⁺, and Mg ^++. Soil analysis indicated product‐related improvements in and bioavailability of salts. The nature of the products requires some prior treatment such as soil washing or dilution using clean soil to lower electroconductivity levels and allow the site to vegetate.     

The effects of hand force variation on shoulder muscle activation during submaximal exertions

Upper limb injuries are highly prevalent in the workplace and new tools are needed to proactively design workstations to reduce injury risk. The objective was to characterize spatial, load and direction dependency of muscle activity for hand exertions in the upper limb workspace. Electromyographic signals were collected from 14 upper limb muscles during exertions for all combinations of 4 submaximal hand forces (20/30/50/60?N) in 6 cardinal (up/down/left/right/forward/backward) directions at 5 hand locations. Linear muscle activity increases accompanied increased hand forces. Total muscle activity increases between 20 and 60?N hand forces ranged by direction from 92% (downward) to 189% (right). Prediction equations for all muscles depended on hand force, and linear, quadratic and interaction permutations of hand location. Muscle activity associated with manual tasks is load, direction and spatially dependent. Equations developed to describe these complex relationships can be used to better design future and evaluate current occupational activities.     

Comparison of Escherichia coli and Campylobacter jejuni transport in saturated porous media

Due to the difficulties in testing for specific pathogens, water samples are tested for the presence of nonpathogenic indicator organisms to determine whether a water supply has been contaminated by fecal material. An implicit assumption in this approach is that where pathogenic microorganisms are present fecal indicator organisms are present as well; yet surprisingly few studies have been conducted that directly compare the transport of indicator organisms with pathogenic organisms in ground water environments. In this study we compared the cell properties and transport of Escherichia coli, a commonly used indicator organism, and Campylobacter jejuni, an important enteropathogen commonly found in agricultural wastes, through saturated porous media. Differences in cell properties were determined by measuring cell geometry, hydrophobicity, and electrophoretic mobility. Transport differences were determined by conducting miscible displacement experiments in laboratory columns. Under the experimental conditions tested, C. jejuni was much more negatively charged and more hydrophobic than E. coli. In addition, C. jejuni cells were slightly longer, narrower, and less spherical than E. coli. The variations in cell properties, primarily surface charge, resulted in significant differences in transport between these two microorganisms, with the transport of C. jejuni exceeding that of E. coli when conditions favored low attachment rates, thus calling into question the usefulness of using E. coli as an indicator organism for this important pathogen.     

Low-wind/high particulate matter episodes in the Calexico/Mexicali region

The U.S. Environmental Protection Agency (EPA) currently classifies Imperial County, CA, as a nonattainment area for PM10 (particulate matter [PM] < or = 10 microm in diameter), and this region suffers from high rates of chronic bronchitis and childhood asthma. Although high annual and daily average PM levels can have negative health and economic effects, recent studies have identified an association between adverse health effects and short-term PM spikes of tens of micrograms per cubic meter. This study identified PM episodes in Calexico/Mexicali that involve PM concentration spikes with concentrations up to 10 times greater than those reported to cause adverse health effects. These episodes appear to be relatively common during the winter months, are associated with wind speeds below 2 m/sec and stable boundary level heights below 500 m, and can comprise a large portion of the 24-hr PM levels. The organic composition of the PM10 samples collected during the low-wind/ high-PM episodes differed from that collected at other times. However, a preliminary source attribution identified only one significant difference between the source classes: agricultural burning accounted for 6.7% of organic-fraction PM10 for low-wind/high-PM episodes versus 0.25% at other times. This preliminary source attribution also revealed that motor vehicles were the most important relative contributor to organic PM10.     

Microbial mineralization of organic nitrogen forms in poultry litters

Ammonia volatilization from the mineralization of uric acid and urea has a major impact on the poultry industry and the environment. Dry acids are commonly used to reduce ammonia emissions from poultry houses; however, little is known about how acidification affects the litter biologically. The goal of this laboratory incubation was to compare the microbiological and physiochemical effects of dry acid amendments (Al+Clear, Poultry Litter Treatment, Poultry Guard) on poultry litter to an untreated control litter and to specifically correlate uric acid and urea contents of these litters to the microbes responsible for their mineralization. Although all three acidifiers eventually produced similar effects within the litter, there was at least a 2-wk delay in the microbiological responses using Poultry Litter Treatment. Acidification of the poultry litter resulted in >3 log increases in total fungal concentrations, with both uricolytic (uric acid degrading) and ureolytic (urea degrading) fungi increasing by >2 logs within the first 2 to 4 wk of the incubation. Conversely, total, uricolytic, and ureolytic bacterial populations all significantly declined during this same time period. While uric acid and urea mineralization occurred within the first 2 wk in the untreated control litter, acidification resulted in delayed mineralization events for both uric acid and urea (2 and 4 wk delay, respectively) once fungal cell concentrations exceeded a threshold level. Therefore, fungi, and especially uricolytic fungi, appear to have a vital role in the mineralization of organic N in low-pH, high-N environments, and the activity of these fungi should be considered in best management practices to reduce ammonia volatilization from acidified poultry litter.