bluuebunny/crossref_metadata_2025 huggingface dataset:
Precipitation Chemistry along an Inland Transect on the Olympic Peninsula, Washington
Authors: Blew Roger D. , Edmonds Robert L.
Published: July 2010

The objective of this study was to examine oceanic influences, seasonal variation, and effect of distance from the ocean on the chemistry of bulk precipitation falling on the Pacific coast of Washington State. Bulk precipitation was collected at Sites 4, 13, 24, and 31 km inland from the Pacific Ocean. Mean electrical conductivity of precipitation ranged from 0.47 to 1.02 mS m−1 and mean pH ranged from 5.3 to 5.6. Annual precipitation increased from 2780 mm at 4 km to approximately 3500 mm at 13 km from the coast and remained constant through 31 km inland. Precipitation was highest in the late fall and winter months and lowest during the summer. Rates of ion deposition had a similar seasonal pattern to that of precipitation. Concentrations of Cl, SO4, Mg, Na, and excess Ca (Ca in excess of expected sea salt levels) were highest nearest to the coast and were reflected in higher electrical conductivity in precipitation falling closest to the coast. Much of the change in precipitation chemistry occurred between 4 and 13 km from the coast. This corresponds to the change in precipitation and suggests that the changes in chemistry are dilution effects due to increased rainfall. Annual deposition of Na, K, Mg, Ca, excess Ca, NO3, and Cl were lower at the collection site farthest from the ocean. Sulfate deposition remained relatively unchanged with increased distance from the ocean; however, excess SO4 (SO4 in excess of expected sea salt levels) deposition increased and deposition of SO4 from sea salt (total minus excess) decreased with increasing distance from the ocean.
Utility and Railway Rights‐of‐Way Contaminants: Dioxins and Furans
Authors: Wan Michael T. , Van Oostdam J.
Published: July 2010

Utility and railway right‐of‐way (ROW) ditches flowing into salmon (Oncorhynchus spp.) streams in the Lower Mainland of British Columbia were sampled in 1990 and 1991 to determine the occurrence and concentrations of selected chlorinated dibenzo‐p‐dioxins (CD) and chlorinated dibenzofurans (CF). Parkland and farmland ditches were also sampled to establish the background concentrations of these chemicals. As well, treated wood utility pole and railway tie samples were collected to confirm the source of CD and CF. Treated wood utility poles contained about 76 700 µg/kg CD and 18 700 µg/kg CF. In railway ties, 13 500 µg/kg CD and 2290 µg/kg CF were found. Although CD and CF were not found in parkland waterways, they were detected in farmland, utility, and railway ROW ditches. Varying mean concentrations of CD (2.2–13 100 ng/L) and CF (0.40–3180 ng/L) were detected in ditch water. In ditch sediments of the same sites, the average CD and CF concentrations ranged from 3.7 to 2580 µg/kg and 0.7 to 1280 µg/kg, respectively. Representative tetra‐, penta‐, hexa‐, hepta‐, and octa‐CD and CF homologs were also detected in ditch water and sediments. Tetra‐CD and tetra‐CF levels found in ditch water adjacent to treated poles did not exceed the 96‐h LC50 (lethal concentration of a chemical to 50% of test organisms) of salmonids and aquatic invertebrate. The biological/toxicological implications to these organisms of high levels of dioxins and furans other than tetra‐CD/CF in sediments and water are discussed.
Plant Litter Decomposition in Wetlands Receiving Acid Mine Drainage
Authors: Kittle D. L. , McGraw J. B. , Garbutt K.
Published: July 2010

The impact of acid mine drainage on the decomposition of wetland plant species of northern West Virginia was studied to determine if the potential exists for nutrient cycling to be altered in systems used to treat this drainage. There were two objectives of this study. First, decomposition of aboveground plant material was measured to determine species decomposition patterns as a function of pH. Second, decomposition of litter from various pH environments was compared to assess whether litter origin affects decomposition rates. Species differences were detected throughout the study. Decomposition rates of woolgrass [Scirpus cyperinus (L.) Kunth] and common rush (Juncus effusus L.) were significantly lower than those of calamus (Acorus calamus L.) and rice cutgrass (Leersia oryzoides L.). Differences among species explained a large proportion of the variation in percentage of biomass remaining. Thus, differences in litter quality among species was important in determining the rate of decomposition. In general, significantly more decomposition occurred for all species in high pH environments, indicating impeded decomposition at low pH. While decomposition of some species litter differed depending on its origin, other species showed no effect. Cattail (Typha latifolia L.), in particular, was found to have lower decomposition rates occurring with material grown at low pH. Lower decomposition rates could result in lower nutrient availability leading to further reduction of productivity under low pH conditions.
Contemporary Groundwater Methane Production from Pleistocene Carbon
Authors: Parkin T. B. , Simpkins W. W.
Published: July 2010

Relative to surface systems, microbial activities in groundwater have been poorly studied, especially with regard to methanogenesis. Past studies have reported high concentrations of CH4 in groundwater in the late Wisconsinan till and Wisconsinan loess of central Iowa. The objectives of this work were to assess whether CH4 is presently produced in the till and loess, and, if so, to characterize the spatial variability of CH4 production rates. Groundwater and sediment sampies were collected at several locations within the Des Moines Lobe in central Iowa. Methane concentrations in groundwater ranged from 0.04 µmol L−1 at 1 m to 2600 µmol L−1 at 7 m. Incubations of deep sediment obtained from core samples revealed active CH4 production was occurring, although high variability was observed. Highest specific CH4 production rates were associated with buried particulate C fragments of Wisconsinan age. Results of our study indicate methanogenesis is an active process in the sediments beneath the Des Moines Lobe, that the substrate for methanogenesis is of late Wisconsinan age, and that the high spatial variability of CH4 production is controlled by the heterogeneous distribution of particulate organic C fragments in the glacial sediments.
Fecal Bacteria in Agricultural Waters of the Bluegrass Region of Kentucky
Authors: Howell J. M. , Coyne M. S. , Cornelius P.
Published: July 2010

Agricultural runoff influenced by nonpoint pollution frequently exceeds the USEPA standards for bacterial contamination of primary contact water (200 fecal coliforms/100 mL). Few studies have evaluated the effect of cattle (Bos taurus) grazing on fecal contamination of ground water in the karst topography of central Kentucky. Our objectives were to: (i) observe the extent and pattern of fecal bacteria in agricultural waters from two central Kentucky watersheds; (ii) determine if monthly sampling accurately assessed the extent and variability of fecal contamination; and (iii) assess the fecal coliform/fecal streptococci ratio (FC/FS) as an indicator of fecal bacteria source. Springs, streams, and wells in two agricultural watersheds typical of central Kentucky were monitored for fecal coliform and fecal streptococci from December 1991 to January 1993. Springs and wells exceeded primary contact water standards, between 28 and 74% of the time; streams exceeded water quality standards between 87 and 100% of the time. When fecal bacteria were present, rainfall rapidly moved them from the soil surface into spring and well water. At two springs in Fleming county, only 29% of samples exceeded primary contact standards before cattle were present; 80% exceeded standards after cattle began grazing the surrounding pasture. Monthly sampling adequately reflected the extent of fecal contamination in our study, which had relatively continuous cattle grazing. Although the FC/FS ratio identified domestic animal contamination sources, it did not distinguish between domestic animal and human sources of contamination.
Environmental Impacts of Dryland Residue Management Systems in the Southern High Plains
Authors: Jones O. R. , Smith S. J. , Southwick L. M. , Sharpley A. N.
Published: July 2010

Increased use of agricultural chemicals with no‐tillage (NT) may negatively impact the environment through chemical or nutrient loss in runoff or by leaching below the root zone. We compared environmental impacts of NT and the lower chemical input stubble mulch (SM) management methods for dryland crop production on a clay loam soil in a semiarid environment. We measured runoff volume and sediment, nutrient, and triazine concentrations in runoff for 9 yr from seven field‐sized watersheds (2‐5 ha each) cropped in a dryland winter wheat (Triticum aestivum L.)‐grain sorghum [Sorghum bicolor (L.) Moench]‐fallow sequence with SM or NT management with no N or P fertilizer added. We analyzed soil cores to a 6‐m depth for NO−3‐N and to a 3‐m depth for atrazine and propazine content. Adoption of NT management reduced sediment loss by 54% compared with SM, although annual runoff was 15 mm yr−1 greater from NT. Nutrient concentrations and losses (NO−3‐N, NH+4‐N, TN, soluble P, biologically available P, TP) in runoff were extremely small from both tillage systems (losses <3 kg N and <1 kg P ha−1 yr−1) on these unfertilized watersheds. Atrazine [6‐chloro‐N‐ethyl‐N′‐(1methylethyl)‐1,3,5‐triazine‐2,4‐diamine] did not accumulate in the soil or leach below the root zone. Maximal losses of atrazine and propazine in runoff were 0.26 and 1.5% of total application, respectively. Propazine [6‐chloro‐N,N′‐bis(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], applied to both NT and SM sorghum when runoff is probable, appears to have a greater potential for negatively impacting the environment under semiarid conditions than does atrazine, which is applied when runoff probability is small. Propazine accumulated in the soil profile but was undetected below 0.6 m. Perhaps the most detrimental impact of adopting NT management was increased leaching of NO−3‐N to depths below the plant root zone as a result of wetter soil and improved water conservation with NT in the semiarid environment.
Topographic Influences on Soil Water and Spring Wheat Yields on Reclaimed Mineland
Authors: Schroeder S. A.
Published: July 2010

Topographic positions on undisturbed soils affect available soil water and crop yields. Reclaimed minelands are required by regulation to have productivity levels “equal to or greater than” premine levels. Since a normal reclamation technique is to place uniform depths of topsoil and subsoil across the topography, this technique often changes the topsoil and subsoil depths from the premine condition. The objective of this research was to determine if these changes in topsoil and subsoil depths have resulted in effects on soil water and crop yields unlike those documented for undisturbed soils. This study was initiated on reclaimed mineland in 1986 at two North Dakota coal mines where topographic positions (summit, shoulder, backslope, and footslope) were monitored for 6 yr for available water at planting, spring wheat (Triticum aestivum L.) yields, and soil water recharge from harvesting to planting the following year. Results showed that downslope topographic positions had nearly 300% more available soil water at planting (0‐ to 1.2‐m depth due to greater recharge) and generally significantly greater (P = 0.10) spring wheat yields than upslope positions. Relationships between total water use and wheat yields were similar to those found for undisturbed soils. These results seem to suggest that the uniform depths of replaced topsoil and subsoil have not affected soil water and wheat yields differently on reclaimed minelands than on undisturbed landscapes in a semi‐arid climate.
Soil Ventilation: Effects on Microbial Populations in Gasoline‐Contaminated Subsurface Soils
Authors: Hickey W. J.
Published: July 2010

Short‐ and long‐term effects of vapor extraction (VE) in an unsaturated subsurface soil and in situ biodegradation of gasoline were evaluated in a field study. Subsurface temperature, moisture, solid‐ and gas‐phase contaminant levels, atmospheric gases, nutrient levels, and microbial population densities were measured during and after soil VE for 462 d. Microbial activity, based on in situ O2 consumption rates, measured 7 d after VE started averaged 3.8% O2 d−1; by Day 62 these rates dropped to 0.2% O2 d−1. Soil VE was stopped on Day 180 and about 70 d elapsed before renewed, low‐level (0.05% O2 d−1) activity was detectable. Following a second round of VE, average O2 consumption rates increased to 0.11% O2 d−1. Microbial population densities did not consistently reflect activity changes measured by O2 consumption. Activity increases in the latter part of the study were not adequately accounted for by changes in subsurface moisture levels, temperature, or contaminant vapor concentrations. At the study's completion, 400 kg of gasoline was volatilized from the soil and another 139 kg estimated to be biodegraded in situ. A two‐phase process is proposed to account for the effects of VE on microbial activity. The initial phase is characterized by declining microbial activity levels in response to substrate reduction. Microbial activity slowly increases as a result of interactions between gasoline vapor concentrations and possibly changes in degradative activities of the microbial population. More work is needed to identify the gasoline constituents serving as substrates for microbial populations before and after ventilation.
Minesoil Properties of 15 Abandoned Mine Land Sites in West Virginia
Authors: Johnson C. D. , Skousen J. G.
Published: July 2010

The characteristics of minesoils on abandoned mine land (AML) often dictate which plant species will invade and establish from nearby undisturbed areas. This study measured physical and chemical minesoil properties on 15 AML sites in northern West Virginia and matched these properties to vegetation cover. Fifteen sites ranging in age from 13 to 35 yr old were selected from three surface‐mined coal beds (Pittsburgh, Freeport, and Kittanning). On each site, three 1 m‐deep pits were dug and minesoil samples were extracted from two horizons, and vegetation was sampled in three 100‐m2 plots near the pits. Minesoils on Freeport sites had more rock fragments and sand than either Pittsburgh or Kittanning sites. No particle‐size changes with depth or age were evident between horizons in any minesoil. Acidity increased and pH decreased with minesoil age on Pittsburgh and Kittanning minesoils due to the oxidation of pyritic materials near the soil surface. A cluster analysis distinguished three minesoil types on these sites. Minesoil type A had low acidity and high CEC. Minesoil type B had high acidity and moderate CEC. Minesoil type C had high rock fragment content, low to moderate acidity, and low CEC. Minesoil type A was completely covered by herbaceous plants and trees, while minesoil types B and C were generally covered by trees. Based on our minesoil analyses and other studies, barren AML sites may not require complete redisturbance for revegetation but may be revegetated by adjacent plant species if surface amendments are applied.
Test of the LEACHP Model for Predicting Atrazine Movement in Three Minnesota Soils
Authors: Khakural B. R. , Robert P. C. , Koskinen W. C. , Sorenson B. A. , Buhler D. D. , Wyse D. L.
Published: July 2010

Leaching Estimation and Chemistry Model‐pesticide (LEACHP) was evaluated for predicting atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) movement in sandy loam (sandy, Typic Hapludoll), silt loam (fine‐silty, Typic Hapludoll), and clay loam (fine‐loamy, Typic Haplaquoll) soils under moldboard and chisel plow tillage practices. Atrazine distribution in the root zone was measured by analyzing soil cores. Model predictions were compared with observed atrazine concentrations in the soil profiles on various dates after application (two to three growing seasons). Model performance was evaluated by testing whether model predictions fall within a specified factor of true values and using Goodness‐of‐Fit tests (maximum error, root mean squared error, coefficient of determination, modelling efficiency, coefficient of residual mass). LEACHP predicted depth of peak atrazine concentration in the soil profile accurately in all three soils (under both moldboard [MB] and chisel plow [CP] treatments and at all sampling dates). It predicted depth of atrazine movement and atrazine concentrations in the soil profile reasonably well in the Estherville soil (sandy, mixed, mesic Typic Hapludoll) except some disparities between measured and predicted concentrations in 1988 because of the difficulty in recovering representative samples. In Port Byron (fine‐silty, mixed, mesic Typic Hapludoll) and Webster soils (fine‐loamy, mixed, mesic Typic Haplaquoll), depth of atrazine movement and atrazine concentrations in the soil profile were predicted reasonably well during relatively dryer years (1988 and 1989). In a relatively wet year (1987), however, the model did not predict significant amounts of atrazine at depths >45 cm, whereas, 2.5 to 27.5 µg kg−1 of atrazine were detected in soil samples during earlier sampling dates (43, 73 DAA in Port Byron and 14, 43 DAA in Webster soils). Overall performance of the model was similar in both tillage treatments (MP or CP). Considering the broad range in soil properties and climatic conditions used in testing, the model performed well.
Effects of Ozone and Water Deficit on Field‐Grown Soybean: I. Leaf Gas Exchange
Authors: Vozzo Steven F. , Miller Joseph E. , Pursley Walter A. , Heagle Allen S.
Published: July 2010

Ozone (O3) and water deficit can suppress net carbon exchange rate (NCER) of plant tissues, but little is known concerning their combined effects on NCER of field‐grown plants. Soybean [Glycine max (L.) Merr. ‘Young’] plants were exposed to two soil moisture regimes (providing well‐watered and periodically water‐deficient conditions) and three levels of O3 in open‐top field chambers throughout the growing season. Seasonal (12 h d−1) mean O3 concentrations were 0.018, 0.059, or 0.085 µL L−1. Measurements of NCER, transpiration (Tn), and stomatal resistance (Rs) were conducted periodically on center leaflet of the fifth or sixth trifoliolate from the apex. During vegetative and early reproductive growth, less visible foliar injury due to O3 occurred on water‐deficient plants. Ozone usually suppressed leaflet NCER and leaflet WUE (NCER/Tn). Leaflet NCER was usually suppressed and WUE increased in water‐deficient treatments during water deficit episodes. Diurnal measurements illustrated that leaflet NCER was limited in water‐deficient plants when leaf water potential fell to about −1.1 MPa. On two occasions under low photosynthetically active radiation, NCER was greater for leaflets in water‐deficient treatments than in well‐watered treatments. Significant O3 × H2O interactions for NCER were infrequent on individual days, although water deficit suppressed response to O3 when data were analyzed over the season.
Leaching of Nitrate, Atrazine, and Metribuzin from Sugarcane in Southern Louisiana
Authors: Southwick L. M. , Willis G. H. , Johnson D. C. , Selim H. M.
Published: July 2010

We have studied the leaching losses of NO3, atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], and metribuzin [4‐amino‐6‐(1,1‐dimethylethyl)‐3‐(methylthio)‐1,2,4‐triazine‐5(4H)‐one] applied to sugarcane (Saccharum officinarum L.) planted in Mississippi River alluvial soil in southern Louisiana. Nitrogen (122 kg/ha) and atrazine (2.24 kg/ha) were applied in June, and atrazine (2.24 kg/ha) and metribuzin (1.12 kg/ha) were applied in December; losses through a Sharkey clay (very fine, montmorillonitic, nonacid, thermic Vertic Haplaquepts) into subsurface drains (5.5‐ and 10.9‐m spacing) were measured for about 100 d in both seasons. Five days after application NO3‐N appeared in its highest concentrations (5–11 mg/L) in the drain water; after this first event, concentrations remained below 10 mg/L throughout the summer season. After application in the summer atrazine appeared in the subsurface drains at its highest seasonal concentrations (114–144 µg/L) on the day of application; after 4 to 7 wk these concentrations remained below 3.0 µg/L. Total losses in the summer amounted to 3 to 8% of the NO3 application and 0.6 to 1.2% of the atrazine application. Almost 50% of the NO3 leaching into the subsurface drains occurred after Day 76, whereas 82% of the atrazine leached into the drains by Day 8. After the winter application, high concentrations of atrazine (67–81 µg/L) and metribuzin (52–94 µg/L) were measured within 8 d. Similarly, large concentrations of atrazine occurred in the drain water throughout the winter season. The much higher concentrations of atrazine during the winter study, compared with the summer, coincided with soil surface concentrations that were 3 to 10 times those of the summer. Total losses during the winter were 0.4 to 2.0% (atrazine) and 0.4 to 1.7% (metribuzin) of the applications. Evidence for preferential flow into the drains of the NO3 and the herbicides is presented.
Effects of Diet on Ungulate Excretion of Enterococcus spp., Streptococcus bovis, and Streptococcus equinus in Feces
Authors: Darby Neal W. , Mosley Jeffrey C. , Davitt Bruce B. , Bohach Gregory A.
Published: July 2010

We compared fecal streptococci (FS) quantities and species composition excreted by native and domestic ungulates that were consuming various feed rations. Group 1 was comprised of elk (Cervus elaphus), white‐tailed deer (Odocoileus virginianus), and bighorn sheep (Ovis canadensis) fed alfalfa (Medicago sativa) hay. Group 2 consisted of elk, cattle (Bos spp.), mule deer (Odocoileus hemionus), domestic sheep (Ovis aries), and horses (Equus caballus) grazing separate grass paddocks of similar botanical composition. Group 3 had four subgroups of cattle each fed a different feed ration: (1) grain and silage; (2) hay, grain, and silage; (3) hay; and pasture. The FS were isolated from ungulate species in each group using the membrane filter technique. Filters were placed on KF streptococcus agar and all pink to red colonies were counted. The FS composition was determined by randomly selecting 20 colonies from each filter and then identified by using growth characteristics and C source utilization. Forage samples were analyzed for crude protein (CP) and neutral detergent fiber (NDF). Ungulates did exhibit some differences in FS quantities and composition, however, all FS species were present in most all ungulates and occurrences were highly variable. Nutritive quality of ungulate diets on grazed forage did not greatly affect the quantities and composition of FS excreted, but trends were difficult to discern because of the high variability of FS samples. Botanical composition of ungulate diets altered both FS quantities and composition. The FS quantities from cattle were greatest when cattle were fed grain rations and smallest when cattle consumed hay or pasture forage. Streptococcus bovis proliferated in feces of cattle fed grain and silage rations while S. equinus and Enterococcus durans dominated on pasture and hay diets. We concluded that the use of FS as indicators of fecal pollution from specific ungulates is unreliable in most cases because of the effects of forage nutritive quality and botanical composition.
Chlorimuron Adsorption, Desorption, and Degradation in Soils from Conventional Tillage and No‐Tillage Systems
Authors: Reddy Krishna N. , Zablotowicz Robert M. , Locke Martin A.
Published: July 2010

No‐tillage (NT) and other conservation management practices designed to enhance plant residue accumulation can affect the herbicides fate in soil. This study was designed to evaluate adsorption, desorption, and degradation of chlorimuron {ethyl 2‐[[[[(4‐chloro‐6‐methoxy‐2‐pyrimidinyl)amino]carbonyl]amino] sulfonyl]benzoic acid} in soils collected from long‐term conventional tillage (CT) and NT plots. Soils were Miami silt loam (fine‐silty, mixed, mesic, Typic Hapludalf) and Drummer silty clay loam (fine‐silty, mixed, mesic, Typic Endoaquoll) from Illinois, and Dundee silt loam (fine‐silty, mixed, thermic Aeric Ochraqualf) from Mississippi. Adsorption was determined on five concentrations of 14C‐chlorimuron (0.22–12.26 µmol kg−1) equilibrated for 72 h. Desorption in four cycles (1, 24, 24, and 24 h) was measured for samples initially sorbed at 2.60 µmol kg−1. Adsorption Kf values ranged from 0.56 to 6.53 and were higher in NT compared with CT soils. The N values were less than unity in all soils. Desorption was hysteretic and the total amount desorbed in four desorptions ranged from 18 to 51% of that sorbed. Desorption Kf values ranged from 0.60 to 2.74 and were higher in NT compared with CT soils. After 63 d incubation of 14C‐chlorimuron, 44 to 54% of applied remained as extractable chlorimuron and 10 to 16% of applied mineralized to 14CO2 among the soils. Half‐life of over 2 mo and relatively low mineralization suggests poor adaptability of native microbial populations to chiorimuron as substrate. Differences in the chlorimuron degradation pattern were minor between NT and CT soils, despite NT soils in general having greater organic C, microbial populations, and soil enzyme activity compared with CT soils.
Shoot and Root Development of Tall and Hard Fescues in Two Different Soils
Authors: Brar G. S. , Palazzo A. J.
Published: July 2010

Tall (Festuca arundinacea Schreb.) and hard fescue [Festuca ovina var. longifolia (L.) Koch] are among the most widely sown grasses used to stabilize disturbed soils in both the cool‐humid and transition climatic zones of the USA. Our objective was to evaluate the root and shoot development of two turfgrasses grown in sand and silt loam soils. Significant differences in leaf area, plant height, shoot and root dry matter, root depth (RD), root branching (RB), and root length (RL) were recorded with tall fescue compared with hard fescue. Greater leaf area, leaf number, plant height, shoot and root dry matter, and RL were observed when the grasses were grown in a silt loam soil. Greater RD and root/shoot ratio were recorded in sandy soil. Both turfgrass species and soil texture affected leaf area, leaf number, plant height, shoot dry matter, RD, RL, RB, root dry matter, and the root/shoot ratio. Significant correlations were obtained for shoot dry matter with root dry matter and RL; leaf area with shoot dry matter and root dry matter; root dry matter with TRL and RB; RD with root/shoot ratio; RL with leaf area; and RB with TRL and RD. Turfgrasses and soil types had an significant impact on shoot and root development. A greater understanding of early root development for these grasses will assist in developing techniques for establishment and persistence under disturbed soils and adverse climatic conditions.
Biodegradation of Phenol, 2,4‐DCP, 2,4‐D, and 2,4,5‐T in Field‐Collected Rhizosphere and Nonrhizosphere Soils
Authors: Boyle Jay J. , Shann Jodi R.
Published: July 2010

This study investigated xenobiotic biodegradation in rhizosphere soil collected from field‐grown plants, grouped for analysis as monocots or dicots. Microbial activity was highest in monocot rhizosphere soils, followed by dicot rhizosphere soils and, finally, nonrhizosphere soils. No differences were seen between these soils in the mineralization of phenol or 2,4‐dichloropbenol (2,4‐DCP), but there were differences in 2,4‐dichlorophenoxyacetic acid (2,4‐D) and 2,4,5‐trichlorophenoxyacetic acid (2,4,5‐T) mineralization. The rate constants for 2,4‐D or 2,4,5‐T mineralization in nonrhizosphere soil were lower than those for either rhizosphere soil. Monocot rhizosphere soil mineralized these compounds faster than dicot rhizosphere soil. Thus, soils that had a prior association with a plant showed significantly increased rates of mineralization for the more recalcitrant compounds tested. In addition, this enhanced mineralization in the rhizosphere appeared to be dependent on the type of plant involved.
Analysis of Cobalt(II)EDTA and Cobalt(III)EDTA in Pore Water by Ion Chromatography
Authors: Taylor D. L. , Jardine P. M.
Published: July 2010

Monitoring and restoration activities at contaminated waste facilities throughout the USA have identified complicated mixtures of organic and inorganic contaminants in soil and groundwater. Inorganic contaminants are sometimes associated with various chelating agents (termed co‐contaminants), which alter the geochemical behavior of the contaminants in subsurface environments. Until recently, the significance of the chelating agents was usually dismissed, and they were not routinely measured as part of environmental compliance programs. A method is presented for separating and quantifying the common subsurface co‐contaminant species of CoEDTA in aqueous solution. Cobalt(II)EDTA and Co(III)EDTA are separated by an ion chromatograph using a carbonate, bicarbonate eluant, and quantified in the presence of common pore‐water inorganic anions using electrical conductivity and visible light detectors. The chromatograph detects Co(II)‐EDTA to 0.6 µmol L−1 with a linear range >4000 µmol L−1. Cobalt‐(III)EDTA is detected to 1.8 µmol L−1 with a linear range >860 µmol L−1. The method has application in basic scientific research and environmental restoration activities.
Soil Erosion Contribution to Pesticide Transport by Furrow Irrigation
Authors: Agassi M. , Letey J. , Farmer W. J. , Clark P.
Published: July 2010

Movement of pesticides from fields in runoff water and on sediment can degrade surface waters. Research typically found that because of the high water‐to‐sediment ratio, the total amount of pesticide in water greatly exceeded that associated with sediment. These observations suggested that erosion control would have little effect in reducing pesticide transport from the field. A laboratory study was conducted in a miniature furrow system to determine whether reduction in erosion would contribute to a reduction of napropamide [2‐α‐naphthoxy)‐N,N‐diethylpropionamide] transport. Variable erosion was created by polymer addition to the water combined with using variable water flow rates. Bromide was used as a nonsorbing independent tracer. Napropamide transport was linearly related to the amount of fine soil particulates eroded. Bromide transport was independent of the amount of erosion, and the percentage of the applied Br− removed in the runoff was less than that of napropamide. The results indicate that reduction in erosion of fine particulates will result in reduced transport of sorbed pesticides from the field.
Dissolved Organic Carbon In Northern Hardwood Stands With Differing Acidic Inputs and Temperature Regimes
Authors: Liechty Hal O. , Kuuseoks Eimar , Mroz Glenn D.
Published: July 2010

We monitored concentrations and fluxes of dissolved organic carbon (DOC) in throughfall and forest floor solutions in two northern hardwood stands located at the northern and southern end of a latitudinal acidic deposition and air temperature gradient in the Great Lakes Region to determine if DOC levels are altered by regional and temporal variation in acidic inputs and temperature. Amounts of precipitation received at the two sites were similar, but precipitation pH and air temperature, respectively, averaged 4.83 and 13.9°C at the northern gradient site and 4.29 and 15.1°C at the southern gradient site. Volume weighted DOC concentrations in throughfall were significantly greater at the northern (20.5 mg L−1) than the southern (15.9 mg L−1) site, but these differences in DOC levels were caused by the differing amounts of throughfall passing through the canopy of the two sites rather than levels of precipitation acidity or air temperature. Temporal variation in the levels of DOC in throughfall was not related to the variation in either precipitation acidity or air temperature. Like throughfall, levels of DOC in forest floor solutions were not found to be altered by acidic inputs. However, DOC in these solutions increased with seasonal increases in soil temperature. A regression equation relating seasonal variation in soil temperature and forest floor concentrations of DOC estimated that an observed 2.1°C difference in soil temperature at the two sites during the growing season could represent as much as 3.7 mg L−1 difference in forest floor solution concentrations of DOC.
Simulating Saline Water Management Strategies with Application to Arid‐Region Agroforestry
Authors: Letey J. , Knapp Keith C.
Published: July 2010

Irrigation projects have greatly increased agricultural productivity in arid and semiarid regions, but they frequently contribute as well to saline high water tables, which must be mitigated by a drainage system. Drainage waters, sometimes contaminated by toxic elements, can lead to environmental degradation if not properly managed. One option is to irrigate salt‐tolerant plants with drainage water to further increase the salt concentration while reducing the volume that would ultimately require treatment or disposal. Transient and steady‐state models were used to simulate the consequences of applying saline drainage water to eucalyptus trees (Eucalyptus camaldulensis) under conditions typical to the San Joaquin Valley of California. Simulated results agreed well with limited field data. High evapotranspiration and large tree growth require application of large amounts of water, leading to large, deep percolation volumes. Degradation of soil physical properties by saline water could reduce the transmission of water through soil. This limits the quantities of irrigation water that can be applied, with consequent poor tree growth and low evapotranspiration.
Occurrence of Nitrite in the Lough Neagh River System
Authors: Smith R. V. , Foy R. H. , Lennox S. D. , Jordan C. , Burns L. C. , Cooper J. E. , Stevens R. J.
Published: July 2010

The Lough Neagh catchment area covers about one‐third of the land area of Northern Ireland. This report documents NO2− concentrations in the major rivers entering Lough Neagh, which are frequently in the range of 100 to 150 μg N L−1 and exceed the European Community (EC) water quality guide values. The contribution of land drainage to NO2− loads carried by these rivers was estimated to be about 40%. The remaining 60% of NO2− appears to originate from N transformations at the sediment‐water interface of the river system. The available evidence suggests that NH+4 originating from agricultural pollution provides the N substrate for nitrification by Nitrosomonas to NO2−. What is anomalous is why this NO2− is not further oxidized rapidly to NO−3 by Nitrobacter. A possible mechanism is that the Nitrobacter is retarded by the presence of free ammonia concentrations that can be predicted to be present in the range of 65 to 76 μg N L−1.
Leaching of Bromacil and Norflurazon as Affected by Herbicide Mixture
Authors: Tan S. , Singh M.
Published: July 2010

It is a common practice to apply herbicides as mixtures of two or more products; however, no information is available about the effect of the mixture on leaching of each herbicide in soils. This study was designed to evaluate the effect of tank mixed herbicide combinations on the leaching potential of bromacil (5‐Bromo‐3‐sec‐butyl‐6‐methyluracil) and norflurazon [4‐chloro‐5‐(methylamino)‐2‐(a,a,a‐trifluoro‐m‐tolyl)‐3(2H)‐pyridazinone]. Leaching bromacil or norflurazon in soil columns under different increments of water application was measured using a radioactive tracer method. Metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide] and terbacil (3‐tert‐Butyl‐5‐chloro‐6‐methyluracil) significantly decreased the leaching of norflurazon when the amount of water application was equivalent to two or more pore volumes. Oxadiazon [2‐tert‐butyl‐4‐(2,4‐dichloro‐5‐isopropoxyphenyl)‐Δ2‐1,3,4‐oxadiazolin‐5‐one] and simazine [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine] significantly reduced the leaching of norflurazon when three and four pore volumes of water were applied. Trifluralin (α,α,α‐Trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) significantly decreased the leaching of norflurazon when two or three pore volumes of water were applied. The combining herbicides with bromacil had no effect on bromacil leaching except for diuron 4L formulation and napropamide, which decreased bromacil leaching under certain levels of water application. None of the herbicides tested significantly increased the leaching of bromacil or norflurazon.
Spatial and Seasonal Nitrous Oxide and Methane Fluxes in Danish Forest‐, Grassland‐, and Agroecosystems
Authors: Ambus Per , Christensen Søren
Published: July 2010

Fluxes of N2O and CH4 were measured monthly from 1990 through 1992 along a topogradient in a spruce forest (Picea abies L.), beech forest (Fagus silvatica L.), riparian grassland, coastal grassland, abandoned farmland, upland arable soil, and drained arable soil in Denmark. Spatial coefficints of variation (CV) in N2O emissions ranged between 106 and 617%. A consistent spatial pattern occurred across a temporary flood water boundary in the coastal grassland. Although inorganic N levels were low at this site, N2O emission rates compared with those at the N‐fertilized sites. Maximum N2O emission generally occured in the spring and autumn. Spatial CVs in CH4 fluxes ranged between 166 and 1787%, and consistent spatial patterns were found at the riparian and coastal grassland sites where CH4 was produced in temporarily flooded areas at rates of 7877 and 112 mg C m−2 yr−1, respectively. Uptake, as well as emission of CH4, reached maximum rates when soils dried up, presumably because CH4 diffusion became unconstrained. Annual site means of N2O emission were inversely correlated with CH4 uptake, and were 77 and 91 mg N and C m−2 in the spruce forest, 80 and 37 mg N and C m−2 in the beech forest, 66 and 69 mg N and C m−2 in the riparian, 124 and 7 mg N and C m−2 in the coastal grassland, 26 and 80 mg N and C m−2 in the abandoned farmland, 361 and 22 mg N and C m−2 in the upland arable, and 467 and 11 mg N and C m−2 in the drained arable. In this study, spatial variability in trace‐gas fluxes was high and poorly explained at all sites. The results suggest large‐scale integrative measurement techniques are necessary to obtain accurate flux estimates of N2O and CH4 from these ecosystems.
Sampling Mast for Measuring Volatile Organic Compounds in the Near‐Surface Atmosphere
Authors: Yates S. R. , Ernst F. F. , Gan J. , Spencer W. F.
Published: July 2010

Accurate measurement of the atmospheric concentration of volatile organic compounds is essential when estimating the emission rate from the soil surface or in studies relating to worker exposure to volatile compounds. For estimating the surface flux, many methods are available which, in general, require profiles of the concentration during the experimental period. For example, the aerodynamic and the integrated horizontal flux methods require precise determination of the atmospheric concentration so that either the concentration gradients or the concentration profiles can be obtained. The accuracy of this information has a direct effect on the accuracy of the flux measurements. The proposed air sampling device provides a suitable method for measuring the atmospheric concentration of volatile compounds. Two designs are illustrated along with a description of their construction and operation. Their use is illustrated with concentration profiles observed in the field.
Off‐Site Movement of Pesticide‐Contaminated Fill from Agrichemical Facilities during the 1993 Flooding in Illinois
Authors: Roy W. R. , Chou S.‐F. J. , Krapac I. G.
Published: July 2010

Twenty retail agrichemical facilities were flooded. There was a concern that pesticide‐contaminated road fill at these facilities had been transported into residential areas by the flooding. Forty fill and flood‐related sediment samples were collected at six facilities. No significant accumulation of sediments was present at any of the six facilities. At five of the six facilities, it did not appear that road fill had been transported off‐site. Pesticides were detected in sediment samples collected off‐site adjacent to five of the facilities. Of the 21 samples collected off‐site, atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazide) and metolachlor (2‐chloro‐6′‐ethyl‐N‐(2‐methoxy‐1‐methylethyl)acet‐o‐toluidine) were detected in 86 and 81% of the samples, respectively. When compared with on‐site concentrations, off‐site pesticide concentrations were either at similar levels, or were as much as three orders of magnitude less. The interpretation of the pesticide data was difficult and often inconclusive, because there were no background data on the occurrence and distribution of pesticides at each site before flooding.
Effects of Pocket Gopher Burrowing on Cesium‐133 Distribution on Engineered Test Plots
Authors: Gonzales G. J. , Saladen M. T. , Hakonson T. E.
Published: July 2010

Very low levels of radionuclides exist on soil surfaces from atmospheric fallout following weapons testing or from stack discharges, and from exposure of some of the older waste storage and disposal sites worldwide. Biological factors including vegetation and animal burrowing can influence the fate of these surface contaminants. Animal burrowing introduces variability in radionuclide migration that confounds estimation of nuclide migration pathways, risk assessment, and assessment of waste burial performance. A field study on the surface and subsurface erosional transport of surface‐applied 133Cs as affected by pocket gopher (Thomomys bottae) burrowing was conducted on simulated waste landfill caps at the Los Alamos National Laboratory in north central New Mexico. Surface loss of Cs, adhered to five soil particle size ranges, was measured several times over an 18‐mo period while simulated rainfalls were in progress. Gophers reduced Cs surface loss by significant amounts, 43%. Cesium surface loss on plots with only gophers was 0.8 kg totalled for the study period. This compared with 1.4 kg for control plots, 0.5 kg for vegetated plots, and 0.2 kg for plots with both gophers and vegetation. The change in Cs surface loss over time was significant (P < 0.01). Relatively little subsurface Cs was measured in plots containing only gophers (0.7 g kg−1). Vegetation‐bearing plots had significantly more total subsurface Cs (µ = 1.7 g kg−1) than plots without vegetation (µ = 0.8 g kg−1). An average of 97% of the subsurface Cs in plots with vegetation was located in the upper 15 cm of soil (SDR1 + SDR2) compared with 67% for plots without vegetation. Vegetation moderated the influence of gopher activity on the transport of Cs to soil subsurfaces, and stabilized subsurface Cs by concentrating it in the rhizosphere. Gopher activity may have caused Cs transport to depths below that sampled, 30 cm. The results provide distribution coefficients for models of contaminant migration where animal burrowing occurs.
Electromagnetic Conductivity Surveys of Dairies for Groundwater Nitrate
Authors: Drommerhausen D. J. , Radcliffe D. E. , Brune D. E. , Gunter H. D.
Published: July 2010

A recent study of dairies in a five‐county area in north Georgia found a high incidence of NO3 contaminated well water. We used a ground electromagnetic conductivity meter to survey eight dairies in the region to determine the source of contamination. Ground conductivities were highest in the loafing areas on most dairies. These are the corrals or small fields near the barn where the milking herd is kept when it is not in the barn or on pasture and other areas near the barn where there is high animal traffic. Conductivities were typically 15 to 20 mS m−1 in these areas, compared with <10 mS m−1 in the pastures away from barns. Water samples from groundwater monitoring wells installed in the loafing areas on three dairies to depths of 7 to 10 m had NO3‐N concentrations between 47 and 135 mg L−1. Shallow ground conductivities in the vicinity of these wells were 10 to 24 mS m−1. There was evidence of seepage at three of the six lagoons we surveyed, but the loafing areas appeared to be a greater threat to drinking water supplies because they were closer to the milking barn where the supply well was located. Stocking rates were probably high enough in the loafing areas to result in excessive N deposition from manure, but not high enough to cause anerobic conditions that would inhibit mineralization or promote denitrification. Best management practices need to be developed that address NO3 leaching from loafing areas.
Distribution and Chemical Characteristics of Cations in Annual Rings of Japanese Cedar
Authors: Momoshima N. , Eto I. , Kofuji H. , Takashima Y. , Koike M. , Imaizumi Y. , Harada T.
Published: July 2010

The objectives of this study were to investigate the distribution and chemical characteristics of cations in annual rings of Japanese cedar (Cryptomeria japonica D. Don) grown in a healthy stand of an unindustrialized region in Japan and discuss the possibility of using cations in tree‐rings as a chronological index of acidic deposition. Radial distributions of some cations and P at different vertical positions of the stem were analyzed for five trees from the same mountain. Each cation and P in all trees showed a specific distribution in its radial pattern but similar distribution trends were observed at all vertical positions. The cations and P were classified into three groups: (I) constant radial concentrations (Ca2+, Sr2+, Na+, and probably Ba2+), (II) high concentrations in the heartwood and low in the sapwood (Mg2+, K+, Rb+, Cs+), and (III) increasing concentrations in the sapwood (P, Mn2+, Cu2+). The total concentration of cations exceeded the calcium‐binding capacity (CBC) of the wood, and the excess was attributed to K+ in a salt form. The CBC increased from the sapwood/heartwood boundary toward the pith in the heartwood but remained constant in the sapwood. The increase of CBC in the heartwood was consistent with the profile of Mg2+, indicating a transfer of Mg2+ into heartwood and fixation on the acquired binding site. The radial distribution of 90Sr was closely related to the cumulative deposition of fallout from the nuclear weapon tests, but that of 137Cs was unrelated. This suggests immobility of Sr2+ and mobility of Cs+ in the horizontal direction of wood. The conservation of the historical 90Sr/Sr2+ change indicated that no influence of heartwood formation on the chemical environment of Sr2+ in cedar xylem and a possibility of using Sr2+ as a chronological index of nutrient availability. A steady‐state in nutrient availability is speculated for trees growing in this mountain because all of the trees analyzed show constant radial distributions of Sr2+ for decades.