Manganese inhibition of microbial iron reduction in anaerobic sediments

Potential mechanisms for the lack of Fe(II) accumulation in Mn(IV)‐con‐taining anaerobic sediments were investigated. The addition of Mn(IV) to sediments in which Fe(III) reduction was the terminal electron‐accepting process removed all the pore‐water Fe(II), completely inhibited net Fe(III) reduction, and stimulated Mn(IV) reduction. In a solution buffered at pH 7, Mn(IV) oxidized Fe(II) to amorphic Fe(III) oxide. Mn(IV) naturally present in oxic freshwater sediments also rapidly oxidized Fe(II). A pure culture of a dissimilatory FE(III)‐ and Mn(FV)‐reducing organism isolated from the sediments reduced Fe(III) to Fe(II) in the presence of Mn(IV) when ferrozine was present to trap Fe(II) before Mn(IV) oxidized it. Depth profiles of dissolved iron and manganese reported in previous studies suggest that Fe(II) diffusing up from the zone of Fe(III) reduction is consumed within the Mn(IV)‐reducing zone. These results demonstrate that preferential reduction of Mn(IV) by Fe(III)‐reducing bacteria cannot completely explain the lack of Fe(II) accumulation in anaerobic, Mn(IV)‐containing sedments, and indicate that Mn(IV) oxidation of Fe(II) is the mechanism that ultimately prevents Fe(II) accumulation.     

Human Health Risk Assessment of Non-Regulated Xenobiotics in Recycled Water: A Review

Water suppliers face increased pressure to explain the relative health risks from non-regulated xenobiotics that may be present in recycled water, including pharmaceuticals and personal care products (PPCPs) and endocrine disrupting compounds. This report reviews their occurrence, fate, and recent human health risk assessments for potable and non-potable water reuse. The most effective advanced treatment for PPCPs is reverse osmosis (RO) followed by advanced oxidation. During soil aquifer treatment, the majority of PPCPs are attenuated relatively quickly (within 100 days), yet some are persistent and can migrate to the underlying groundwater at low concentrations. Recently, several investigations have assessed the potential human health risks associated with xenobiotics in recycled water, focusing on exposure from drinking water (e.g., planned and unplanned indirect potable reuse) and non-potable reuse (e.g., exposure via recreational, occupational, and irrigation-related activities at sites utilizing recycled water). Risk assessments conducted over the last 10 years have found no adverse human health effects or significant risks. Though advanced treatment of wastewater that is discharged or recycled may not be required to protect public health, it may be necessary to prevent potential effects on exposed biota and to address, to some degree, the public's perception of water reuse.     

Phosphorus dynamics within agricultural drainage ditches in the lower Mississippi Alluvial Valley

Excessive phosphorus loading from fertilizers in agriculture results in enriched runoff and downstream aquatic system eutrophication. This study evaluated phosphorus dynamics in agricultural drainage ditches across eight sites within the Lower Mississippi Alluvial Valley (LMAV). The objective of the study was to examine the capacity of drainage ditches across the LMAV to sorb P. Spatially and temporally, all drainage ditch sediments had very low immediately bioavailable phosphorus (P_w), and a very low degree of phosphorus saturation (DPS < 20%) throughout the LMAV. Phosphorus binding energy (K) (0.34-0.60 L/mg) and P sorption maxima (17.8-26.6 L/mg) were low, with very little variation in space and time. Using these metrics, drainage ditches sampled within the LMAV could be described as P sinks, capable of sorbing varying degrees of P seasonally as a result to changes in the Fe-P pool. Sorption, however, will likely be low due to low P sorption maxima and low binding energies. These results will help in P management within primary aquatic systems (such as drainage ditches) within the agricultural landscape and enhance P mitigation strategies at the source, prior to runoff reaching downstream aquatic systems.     

Bacillus polymyxa stimulates increased Rhizobium etli populations and nodulation when co-resident in the rhizosphere of Phaseolus vulgaris

Abstract A Gram-negative sporulating thermophilic anaerobe, designated AB11Ad, was isolated from the heated waters of the Great Artesian Basin of Australia. It grew on a variety of carbohydrates including glucose, starch, and dextran and produced a thermostable and thermoactive extracellular endo-dextranase. The enzyme was produced more actively under pH controlled continuous culture conditions than under batch conditions. Ammonium sulfate precipitated crude dextranase exhibited a temperature optimum of 70 °C and a pH optimum between 5 and 6. The half life was ~ 6.5 h at 75 °C and 2 h at 80 °C at pH 5.0 and in the absence of added dextran. 16S rRNA sequence analysis indicated that isolate AB1 lAd was a member of the genus Thermoanaerobacter .     

Rates of lateral channel migration along the Mala Panew River (southern Poland) based on dating riparian trees and Coarse Woody Debris

Two methods of estimating the lateral migration of a river channel have been proposed. The first method is based on Coarse Woody Debris (CWD) dating. The terraces of the Mala Panew River are mainly covered with plantations of Pinus sylvestris where individual trees grow at equal distances to each other. During times of high discharges trees fall onto the riverbed providing information on the extent of flood plain erosion. The ages of CWD and the surface of the eroded flood plain provide an estimation of the rate of lateral migration. The erosion rates measured at two sites in the Mala Panew River were between 0.24 and 0.36 m/year.Another way of reconstructing the rate of lateral migration is by dating trees growing on different-aged sandy meander bars. These levels are primarily covered with Alnus glutinosa and Alnus incana. The oldest trees growing on each level give information about the minimum age of that level, which allows us to reconstruct the rate of lateral migration. The lateral migration of the channel has also been estimated dating the oldest trees growing on mid-channel islands separated from the lateral banks. The values obtained for 10 sites of the Mala Panew channel oscillate between 0.07 and 1.83 m/year.Tree ring analyses also allow us to determine the impact of individual high discharges on the lateral migration rate of the Mała Panew channel. The lateral migration of the channel was most rapid in the years 1953–57 and 1966–68 as well as during the extraordinary flood in 1997.     

Landscape and Vegetation Effects on Avian Reproduction on Bottomland Forest Restorations

ABSTRACT Forest restoration has been undertaken on >200,000 ha of agricultural land in the Mississippi Alluvial Valley, USA, during the past few decades. Decisions on where and how to restore bottomland forests are complex and dependent upon landowner objectives, but for conservation of silvicolous (forest-dwelling) birds, ecologists have espoused restoration through planting a diverse mix of densely spaced seedlings that includes fast-growing species. Application of this planting strategy on agricultural tracts that are adjacent to extant forest or within landscapes that are predominately forested has been advocated to increase forest area and enhance forested landscapes, thereby benefiting area-sensitive, silvicolous birds. We measured support for these hypothesized benefits through assessments of densities of breeding birds and reproductive success of 9 species on 36 bottomland forest restoration sites. Densities of thamnic (shrub-scrub dwelling) and silvicolous birds, such as yellow-breasted chat (Icteria virens), indigo bunting (Passerina cyanea), and white-eyed vireo (Vireo griseus) were positively associated with 1) taller trees, 2) greater stem densities, and 3) a greater proportion of forest within the landscape, whereas densities of birds associated with grasslands, such as dickcissel (Spiza americana) and red-winged blackbird (Agelaius phoeniceus), were negatively associated with these variables. Vegetation structure, habitat edge, and temporal effects had greater influence on nest success than did landscape effects. Taller trees, increased density of woody stems, greater vegetation density, and more forest within the landscape were often associated with greater nest success. Nest success of grassland birds was positively related to distance from forest edge but, for thamnic birds, success was greater near edges. Moreover, nest success and estimated fecundity of thamnic species suggested their populations are self-sustaining on forest restoration sites, whereas these sites are likely population sinks for grassland and open-woodland species. We recommend restoration strategies that promote rapid development of dense forest stands within largely forested landscapes to recruit breeding populations of thamnic and silvicolous birds that have reproductive success sufficient to sustain their populations.     

Determination of total copper and zinc contents of Egyptian soils using three different methods

Summary To compare chemical methods for determining total contents of Cu and Zn in Egyptian soils, surface samples of two groups of soils from Egypt namely the alluvial and the calcareous were chosen. The samples were analyzed for the total Cu and Zn using three chemical methods namely, aqua regia, hydrofluoric acid and fusion methods. The mean values of total Cu determined by aqua regia, hydrofluoric acid and fusion methods were 58.7, 69.2, 69.4 ppm for the alluvial soils and 11.8, 13.0, 12.8 ppm for the calcareous soils respectively. The corresponding values of Zn were 138.6, 189.4, 189.8 ppm for the alluvial soils and 58.6, 89.7, 90.3 ppm for the calcareous soils. The Cu and Zn contents in the alluvial and calcareous soils, determined by the aqua regia method was lower as compared with those determined by the fusion or hydrofluoric methods.An attempt was made to use the etching of soil with aqua regia and the linear relationship, to quantitavely evaluate the total content of Cu and Zn determined with hydrofluoric acid or fusion methods.     

Winter Avian Community and Sparrow Response to Field Border Width

Abstract: Transformations of agricultural practices in the southeastern United States have drastically reduced preexisting quantities of strip-cover habitat along field margins. The National Conservation Buffer Initiative has promoted the establishment of herbaceous field borders to restore wildlife benefits once provided by such habitat. We evaluated effects of native warm-season grass field border establishment and width on winter bird response. Narrow (approx. 8-m) field borders represented a marginal improvement to non-bordered margins that were cropped ditch to ditch, whereas wide (approx. 30-m) borders significantly enhanced total avian conservation value, abundance, species richness, and sparrow abundance compared to non- or narrow borders. Furthermore, presence of wide borders altered bird use of row-crop fields. We observed increased sparrow (Emberizidae) abundances in agricultural fields adjacent to wide borders, which likely resulted from enhanced waste grain foraging opportunities. Given these benefits to wintering farmland birds, we advocate the integration of herbaceous field border habitat in agricultural landscapes, particularly borders of enhanced width.