bluuebunny/crossref_metadata_2025 huggingface dataset:
Observed and Simulated Transport of a Conservative Tracer under Line‐Source Irrigation
Authors: Comfort S. D. , Inskeep W. P. , Lockerman R. H.
Published: July 2010

Although a number of solute transport models are currently available to predict the transport of agrichemicals in the vadose zone, validation of these models under field conditions has been limited. This study monitored the transport of a conservative tracer (Br−) under three water regimes (high, medium, and low) imposed by a line‐source irrigation system and tested the validity of the simulation model, LEACHM, to predict Br− transport. In July 1990, RbBr was surface applied to 12 uncropped columns at 56 kg Br− ha−1. Four columns (0.203‐m diam., 1.2‐m length) were positioned in each water regime and equipped with soil solution samplers at 0.36‐, 0.66‐, and 0.96‐m depths. Soil solution samples were taken 20 times over 80 d to monitor Br− transport. Cumulative water applied to each water regime, by irrigation and precipitation, ranged between 251 and 458 mm. Results indicated dramatic differences in Br− transport among water regimes. Complete Br− breakthrough curves (with apex concentrations of approximately 60 mg Br− L−1) were observed under high water regime at all depths whereas the majority of Br− applied to the low water regime remained at or near the 0.36‐m depth. Inputs used to predict Br− transport in LEACHM simulations were either measured directly or estimated from experimental conditions. To simulate Br− transport for each water regime, we used three LEACHM input files, which reflected the variability of the soil profile water release retention coefficients. Results indicated that LEACHM's predictions of Br− concentration (at all depths and under all water regimes) differed from observed means by an average (n = 180) of 9.0 to 9.4 mg Br− L−1 (approximately 15–16% of the average apex concentrations). These results indicate that under the experimental system studied, LEACHM adequately predicted the transport of a conservative tracer in the vadose zone.
Cotton Yield Losses and Ambient Ozone Concentrations in California's San Joaquin Valley
Authors: Olszyk D. , Bytnerowicz A. , Kats G. , Reagan C. , Hake S. , Kerby T. , Millhouse D. , Roberts B. , Anderson C. , Lee H.
Published: July 2010

Based on controlled experiments and simulation modeling, ozone (O3) has been estimated to cause significant yield losses to cotton. The study reported here was conducted to verify losses for ‘Acala’ cotton (Gossypium hirsutum L. ‘SJ2’) along a gradient of ambient O3 concentrations across the San Joaquin Valley in California. Cotton was grown in nonfiltered (NF) and charcoal‐filtered (CF) open‐top chambers, and ambient air (AA) at four sites during the 1988 and 1989 summer growing seasons. Cotton yields (weights of mature bolls m−2) were reduced in NF compared with CF air in general proportion to O3 concentrations across all sites and years. Greatest cotton yield losses were as Shafter in the southern part of the San Joaquin Valley (20% in 1989), and lowest losses were at Five Points in the western part of the valley (none in 1989). Ozone injury symptoms on cotton were most noticeable in areas with greatest yield losses. Linear O3 exposure vs. predicted relative yield loss models using four common exposure indices were constructed for each site and year based on the NF, CF, and AA data. All models except the second highest daily maximum concentration (2ndHDM, the current ambient air quality standard for O3) predicted yield losses comparable to those predicted with previously published models for cotton in the San Joaquin Valley. Ozone exposure indices giving more weight to higher O3 concentrations or the 7‐h daytime mean better predicted cotton yield responses over the growing season than 2ndHDM.
Sewage Sludge Proteins: II. Extract Characterization
Authors: Lerch R. N. , Azari P. , Barbarick K. A. , Sommers L. E. , Westfall D. G.
Published: July 2010

The characterization of sewage sludge proteins is necessary to better understand their degradation by microbial populations when sludges are utilized for land application. The objective of this study was to characterize the molecular weights of extractable sewage sludge proteins by dialysis partitioning and polyacrylamide gel electrophoretic (PAGE) separation. Sewage sludges obtained from seven municipalities were extracted using H2O and 1 M NaOH followed by purification and concentration to facilitate molecular weight determinations. Dialysis partitioning of proteins showed that the majority of these compounds had molecular weights < 14 000 (i.e., they were not retained by dialysis membrane). The separation of proteins by PAGE also showed that the bulk of H2O and 1 M NaOH soluble proteins were of low molecular weight (< 17 000). This indicated considerable proteolysis during waste treatment processing. Thus, the extractable sludge proteins appeared to be primarily poly‐ and oligopeptides rather than intact proteins. Based on these findings, sludge proteinaceous materials would be expected to degrade rapidly in soil due to the many soil microorganisms capable of utilizing protein degradation products.
Estimating Daily Nutrient Fluxes to a Large Piedmont Reservoir from Limited Tributary Data
Authors: Nearing M. A. , Risse R. M. , Rogers L. F.
Published: July 2010

Physically based models of lakes require estimates of daily, spatially varied water and nutrient fluxes into the lake from surrounding watersheds. Often, however, only a selected set of streams are periodically (monthly or biweekly) sampled. The objective of this study was to develop and test a method for estimating daily flux of nutrients into a large reservoir using data from sampling of selected watersheds. Flow rate, nitrate (NO3‐N), total nitrogen (TN), soluble reactive phosphorus (SRP), total phosphorus (TP), and chemical oxygen demand (COD) were measured monthly during 1991 for eight watersheds that feed Lake Lanier in northern Georgia. Daily stream flow in the eight streams was correlated to data from nearby USGS gauged stream stations, and daily nutrient concentrations were related to watershed land use and monthly variation in measured concentrations. Fraction of agricultural land in the watershed (AG) was the only land use parameter that correlated to nonpoint‐source loads. Coefficients of determination for linear regressions between AG and NO3‐N, TN, SRP, TP, and COD were 0.74, 0.73, 0.47, 0.84, and 0.52, respectively. The relationships were tested on an independent data set consisting of two samples from 19 additional streams. Coefficients of determination (r2) between measured and predicted data for the independent test data was 0.77, 0.52, 0.66, 0.64, 0.69, and 0.76 for stream flow, NO3‐N, TN, SRP, TP, and COD, respectively. Percentages of nutrient loads attributable to nonpoint‐source loads ranged between 76% for TN to 92% for TP and COD, whereas those attributable to agricultural nonpoint source were about 15% for COD, 28% for TN, 34% for NO3‐N, 40% for TP, and 70% for SRP.
Orthophosphate and Calcium Carbonate Solubilities in the Upper Jordan Watershed Basin
Authors: Salingar Yigal , Geifman Yoel , Aronowich Michael
Published: July 2010

An understanding of the mechanisms controlling the P concentrations in the Upper Jordan River is necessary to develop strategies to avoid eutrophication of Lake Kinneret. This study examines the solubility of orthophosphate and CaCO3 in the calcareous Upper Jordan Basin via a thermodynamic model. The variation in alkalinity, pH, Ca, and phosphate concentrations in the surface waters of the Jordan River are consistent with an equilibrium between the solution and a metastable Ca phosphocarbonate phase with an apparent composition of Ca2(HCO3)2HPO4. This phase, CBP2, has not been observed in sediments or suspended particles. However, it rapidly forms on calcite surfaces in laboratory experiments. The CBP2 is replaced after a few days by a more stable compound, CBP3, with an apparent composition of Ca3(HCO3)3PO4. The apparent solubility product of CBP2 is 10−19.96±0.87. The consistency of the observed water chemistry collected from a variety of stations in the Upper Jordan Watershed over a period of 20 yr with this simple metastable “equilibrium” model suggests that CBP2 is rapidly formed in the Jordan River waters and its tributaries and needs to be considered in models of fluvial P transport.
Erosion Response of a Disturbed Sagebrush Steppe Hillslope
Authors: Goff Bruce F. , Bent Gardner C. , Hart George E.
Published: July 2010

Land management activities that disrupt surface vegetation cover pose a serious threat to the long‐term stability of buried‐waste sites located within the semiarid sagebrush (Artemisia tridentata Nutt.) steppe region of the northwestern USA. In this study, we evaluated the erosion response of a sagebrush hillslope subjected to three vegetation cover treatments: natural (undisturbed), bare (plant canopy and litter cover removed), and clipped (canopy removed). A rotating boom rainfall simulator was used to apply rain at 60 or 120 mm/h intensities to runoff plots (3.0 m by 10.7 m) with dry, wet, and very wet antecedent moisture conditions, and during two late and one early summer seasons. Supplemental overland flow was added at the upper end of each plot to simulate increased slope length during very wet runs. Maximum soil loss rates on the natural, clipped, and bare treatments were, respectively, 1, 5, and 216 mg/m2 per s during the 60 mm/h rainfall intensity, and 13, 79, and 1473 mg/m2 per s during the 120 mm/h rainfall intensity. Cumulative soil loss was typically 100 to 1000 times greater on the bare treatment than on the natural or clipped treatments. Increases in simulated slope length produced a near linear increase in soil loss from the bare treatment plots (about 0.02 g/m2 per s soil loss per m of slope length) until 30 m, after which the effect of slope length declined. Surface crust development and mound‐intermound microtopography played important roles in governing soil detachment and transport on the hillslope. Despite high rainfall intensity and surface runoff rates, rill erosion was negligible on both the undisturbed and disturbed portions of the hillslope.
Adsorption and Mobility of Cadmium in Natural, Uncultivated Soils
Authors: Sánchez‐Martín M. J. , Sánchez‐Camazano M.
Published: July 2010

The influence of soil properties on the adsorption and mobility of Cd was studied in 22 natural, uncultivated soils from Salamanca province to understand the environmental characteristics of Cd as a pollutant. Cadmium adsorption was studied by means of adsorption isotherms, using low Cd concentrations that were similar to those potentially found in polluted soils, and Cd mobility was investigated by using soil thin layer chromatography. The Freundlich adsorption constant (K) was not found to be related to any soil properties studied. In contrast, the distribution coefficients (Kd) at 15 and 30 µg L−1 equilibrium concentrations were found to be related to the cation exchange capacity (CEC) of the soil (r = 0.43 and r = 0.44, respectively, p < 0.05). The adsorption (Q), amount adsorbed at high concentrations (Ci = 1000/µg L−1), was found to be significantly related to the CEC, the exchangeable Ca2+ content and the sum of bases. In addition, Rf values, which are indicative of the Cd mobility in soil, bore a highly significant (p < 0.001) negative correlation with some soil parameters such as pH, the exchangeable Ca2+ and Mg2+ contents and the sum of bases, as well as a less significant (p < 0.05), negative correlation with the CEC and clay content of the soil, but no correlation whatsoever with the adsorption constants. The type of organic matter present in the soil must be more influential on Cd mobility than was its content. The above results confirm that a CEC of a soil is highly influential on Cd adsorption and mobility.
Bromide in the Natural Environment: Occurrence and Toxicity
Authors: Flury Markus , Papritz Andreas
Published: July 2010

Bromide ion is widely used as a tracer to study water and solute transport because it does not adsorb to negatively charged soil minerals. Therefore is moves approximately as fast as water in soil. This property and the small natural background concentration make Br− an ideal tracer. It is much better than Cl−, which behaves similarly, but which is ubiquitous in the environment. Since Cl− is a component of several fertilizers, it usually is found in agricultural soils in concentrations too high to allow its use. When using chemicals in the environment, one must consider their fate and toxicity. This review summarizes data on the occurrence of Br− in the environment and its toxicology. Since Br− has low toxicity in mammals, most freshwater organisms, and most plants, its use in small‐scale field studies should not endanger the biota. However, its application on a larger scale requires a careful evaluation of the concentration to be expected in ground and surface water. Based on the toxicity data, a quality criterion for groundwater of 1 mg Br− L−1 was established in the literature. To avoid the risk of chronic toxicity, the concentration of Br− water should not exceed the proposed criterion.
In Vitro Pollen Responses of Two Birch Species to Acidity and Temperature
Authors: Hughes R. N. , Cox R. M.
Published: July 2010

Paper birch (Betula papyrifera Marsh.) and mountain paper birch (Betula cordifolia Regel) near the Bay of Fundy coast frequently intercept acidic advection marine fogs. Chemical deposition by these fogs is thought to be a factor contributing to the observed foliar browning symptoms associated with a marked deterioration of these trees in the area. In vitro experiments were performed to test whether pollen germination in these two birch species would be affected by acidity at levels routinely found in the fog. The combined effect of temperature with acidity was also examined. Pollen germination in both species was inhibited below pH 5.6 (P < 0.0001) and the effect of incubation temperature was also significant (P < 0.01) in both species. There was no difference in in vitro pollen germination between species (P > 0.05) in response to acidity, based on combined data from 12 trees of each; the optimum germination temperature was 22 °C for B. papyrifera and 21 °C for B. cordifolia.
Growth and Trace Element Concentrations of Five Plant Species Grown in a Highly Saline Soil
Authors: Retana J. , Parker D. R. , Amrhein C. , Page A. L.
Published: July 2010

Kesterson Reservoir and other impoundments in the San Joaquin Valley, California, have received large volumes of saline irrigation drainage water that is enriched with trace elements, including As, B, Mo, Se, U, and V. When these ponds are allowed to dry and revert to terrestrial ecosystems, careful soil water and vegetation management may be needed to prevent toxicological hazards to wildlife and/or livestock. We conducted a 248‐d column study in the greenhouse using a soil from Kesterson to assess the growth of salt‐ and B‐tolerant genotypes, and to determine the uptake of As, B, Mo, Se, U, and V by these genotypes. Electrical conductivity decreased with soil depth, from 14 to 5 dS m−1, with B, Mo, Se, and U concentrations paralleling the soil salinity, whereas As and V were higher in the subsoil. Three grasses, alkali sacaton [Sporobolus airoides (Torr.) Torr.], tall wheatgrass [Elytrigia pontica (Podp.) Holub], Indian ricegrass [Oryzopsis hymenoides (Roem & Schult.)], and two Se‐accumulators, Astragalus bisulcatus (Hook.) and A. racemosus Pursh., were successfully established after a preplanting leaching treatment to reduce salts in the seed zone. Three cuttings of alkali sacaton and tall wheatgrass resulted in total shoot yields of 11.1 and 7.6 g per column, respectively, but only 0.8 for a single cutting to the less salt‐ and B‐tolerant Indian ricegrass. The slower‐growing A. bisulcatus and A. racemosus yielded 3.8 and 4.4 g per column, respectively. Shoot concentrations of As, U, and V were low (<3 mg kg−1) in all genotypes, and do not seem to pose food‐chain transfer hazards at this site. Molybdenum and Se shoot concentrations of all genotypes exceeded the upper safe limits for consumption by ruminants, and shoot B concentrations were also high (>60 mg kg−1). Despite high soil solution SO4 concentrations, both Astragalus species accumulated Se to high concentrations in the shoots (ca. 650 mg kg−1), and shoot harvest removed the equivalent of 2 to 3.5 kg Se ha−1. Growth of these Se‐accumulating species shows promise as a means of direct removal of Se from Se‐contaminated sites and could become a component of effective remediation strategies.
Atrazine, Alachlor, and Metolachlor Mobility through Two Sandy Wisconsin Soils
Authors: Wietersen R. C. , Daniel T. C. , Fermanich K. J. , Girard B. D. , McSweeney K. , Lowery B.
Published: July 2010

Pesticide mobility through Sparta sand from the Lower Wisconsin River Valley (LWRV) and Plainfield sand from the Central Sands (CS) of Wisconsin was examined to interpret results from state‐sponsored groundwater monitoring programs and to identify fundamental mechanisms important in pesticide transport through the unsaturated zone. The mobility of 14C‐labeled atrazine [2‐chloro‐(4‐ethylamino)‐6‐(isopropylamino)‐s‐triazine], alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxym ethyl) acetamide], and metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide] was monitored through replicated intact soil column‐microlysimeters. Soil columns of Sparta sand (sandy, mixed, mesic Entic Hapludolls) from the LWRV and Plainfield sand (sandy, mixed, mesic Typic Udipsamments) from the CS were instrumented in the greenhouse to simulate field conditions. All pesticides were shown to be much more mobile through the Sparta sand as compared to Plainfield sand. Peak atrazine concentration was 15 times greater in the leachate from the Sparta soil than from the Plainfield sand. Percentage loss of applied pesticide was four times greater in the leachate from the Sparta soil than from the Plainfield sand. Similar results were found for metolachlor and alachlor. The relative order of mobility for each soil was found to be atrazine > metolachlor > alachlor. Factors found to contribute to increased mobility of pesticides through the Sparta sand include higher hydraulic conductivity, smaller water‐holding capacity, and less atrazine adsorption due to less organic C and clay content. The hydraulic conductivity (Ksat) of the upper motzone (0–20 cm) of the Sparta soil is five times faster than the Plainfield soil. The waterholding capacity and the atrazine adsorption coefficient (Kd) of the Plainfield sand were measured to be 1.6 and 1.8 times greater, respectively, than those of the Sparta soil.
Nitrate Movement after Anhydrous Ammonia Application in a Ridge Tillage System
Authors: Clay D. E. , Clay S. A. , Brix‐Davis K. , Scholes K. A.
Published: July 2010

Ridge application of N fertilizer has been promoted as a management tool to reduce nitrate movement. However, anhydrous ammonia applicator knives produce slots, which may impact water and nitrate movement. The objective of this study was to determine the effects of N fertilizer placement by an anhydrous ammonia applicator on nitrate movement within a ridge tillage system. Anhydrous ammonia was applied in a subsurface band to the ridge or valley areas of a ridge tillage system at the rates of 0 or 200 kg N ha−1. Rainfall (17 cm) was applied with a drop‐type artificial rainfall simulator 3, 10, and 24 d after fertilizer application in a fallowed field. Percolating water was collected in grid lysimeters (15 by 15 cm) located 75 cm below the soil surface of a Brandt silty clay loam (fine‐silty over sandy or sandy skeletal mixed Pachic Udic Haploboroll). Rainfall timing and N fertilizer placement influenced N fertilizer loss. The percentage of applied fertilizer collected in lysimeters when rainfall occurred 3 and 10 d after fertilizer application was 0 and 15%, respectively. When rainfall occurred 24 d after application, 49 and 73% of the applied N was leached through the profile from valley and ridge treatments, respectively. Increased N loss in the ridge treatment may have resulted from the fertilizer slot remaining open during the rainfall, while in the valley treatment the slot closed.
Estimation of Sorption Coefficients for Fungicides in Soil and Turfgrass Thatch
Authors: Dell C. J. , Throssell C. S. , Bischoff M. , Turco R. F.
Published: July 2010

Environmental fates of turf‐applied fungicides are not well understood. The role of thatch as a sorptive surface for fungicides has not been evaluated. Thatch may decrease mobility of fungicides and decrease their potential to be transported off‐site. Batch type sorption studies were conducted to determine sorption coefficients (Kf) for the fungicides triadimefon, [1‐(4‐chlorophenoxy)‐3,3‐dimethyl 1‐1‐(1H‐1,2,4‐triazol‐1‐g‐1) butanone], vinclozolin [3‐(3,5‐dichlorophenyl)‐5‐methyl‐5‐vinyl‐1,3‐oxazolidine‐2,4‐dione], and chloroneb (1,4‐dichloro‐2,5‐dimethoxybenzone) in thatch and in the underlying soil. The Kf values also were derived from octanol/water partitioning coefficients (Kow) for these and five other compounds. All Kow values were determined with reverse‐phase high pressure liquid chromatography (HPLC) and calculated from physical properties of the fungicides. The Kf values [µmol(l‐n) Ln kg−1] determined from isotherm data for thatch and soil (respectively) were 90 and 10 for triadimefon, 163 and 21 for chloroneb, and 431 and 47 for vinclozolin. When Kf values were adjusted for organic C content of the sample, the resulting Kow values were similar for thatch and soil. The Koc values estimated from HPLC‐derived Kow values were consistently less than those obtained using batch isotherm methods. The Kow values calculated from physical properties of the fungicides were poorly correlated with measured values. The HPLC method appears to be useful for determining sorption coefficients. Results indicate that thatch substantially increases fungicide sorption, which, in turn, decreases the potential for these compounds to migrate off site.
Permethrin and Sulprofos Washoff from Cotton Plants as a Function of Time between Application and Initial Rainfall
Authors: Willis G. H. , McDowell L. L. , Smith S. , Southwick L. M.
Published: July 2010

Understanding pesticide foliar washoff is important in environmental modeling, pest management, and development of integrated management systems. This study was conducted to determine the effect of elapsed time between spray application and initial rainfall on insecticide washoff from foliage. Permethrin [(3‐phenoxyphenyl)‐methyl(1K,S)‐cis,trans‐3‐(2,2‐dichloroethenyl)2,2‐dimethylcyclopropanecarboxylate] and sulprofos [O‐ethyl O‐(4‐methylthiophenyl)‐S‐propyl phosphorodithioate] were applied to mature cotton (Gossypium hirsutum L.) plants as tank‐mixed emulsifiable concentrates with a water carrier. Simulated rain (51 mm in 1 h) was applied to the cotton plants at different times after insecticide application to determine washoff characteristics for both compounds. Residues of both insecticides became increasingly resistant to washoff with increasing time interval between insecticide application and initial rainfall. The mean amounts of both insecticides washed from the plants were related to the mean insecticide loads on the plants and decreased with time. On the average, the first 2 to 3 mm of rain removed 50% of the total amounts of insecticide washed from the plants by the 51‐mm storm.
Use of Cellulosic Substrates for the Microbial Treatment of Acid Mine Drainage
Authors: Béchard Geneviève , Yamazaki Hiroshi , Gould W. Douglas , Bédard Pierre
Published: July 2010

A mixed aerobic‐anaerobic microbial treatment process was developed previously for acid mine drainage (AMD) using straw as a substrate. The process was effective only if AMD was supplemented with sucrose. The present study was conducted to determine which, if any, of three cellulosic materials could sustain the microbial treatment of AMD without the addition of a sucrose amendment and to determine the effect of the retention time on the performance of the reactors. The performance of small reactors that treated simulated AMD in the continuous mode was evaluated using alfalfa (Medicago sativa L.) hay, timothy (Phleum pratense L.) hay, and straw with a 5‐d retention time. Parameters measured were pH, Fe, Al, sulfate, and ammonium. Timothy hay and straw sustained AMD mitigation for 3 wk, and thereafter all activity ceased. After the reactors ceased treating AMD, the mitigative activities were reinitiated by the addition of sucrose, but not by urea. Alfalfa sustained AMD mitigation for a longer time period than either straw or timothy. The effect of three retention times, 3.5, 7, and 35 d, was then investigated for reactors containing fresh alfalfa. Increasing the retention time resulted in better metal removal and a greater pH increase. With a 7‐d retention time, 75 L of simulated AMD were neutralized from a pH of 3.5 to a pH value greater than 6.5. Reactors operating with a 3.5‐d retention time treated only 58.3 L of simulated AMD before failing. Ammonium was detected in effluents of active reactors. The results of this study indicate that a low maintenance microbial treatment system can be developed with alfalfa as a substrate without the addition of a sucrose amendment.
Nutrient Leaching following Land Application of Aerobically Digested Municipal Sewage Sludge in a Northern Hardwood Forest
Authors: Medalie L. , Bowden W. B. , Smith C. T.
Published: July 2010

Concentrations of selected cations and anions were determined in soil solutions from a forested site in southern New Hampshire during the first growing season after surface application of an aerobically‐digested, limed, liquid municipal sludge. Sludge was applied in June 1989 at 0, 3.3, 6.9, and 14.5 Mg ha−1, which corresponded to 199, 396, and 740 kg N ha−1 as total Kjeldahl N (TKN). Porous, suction‐cup lysimeters were used to sample soil solutions below the rooting zone (≈60cm) within subplots designed to include (untrenched) exclude (trenched) uptake by vegetation. Following sludge application, measured solute concentrations remained low until September 1989, when NO3, Cl, Ca, Mg, Na, and K in trenched subplots increased simultaneously to maximum values in October or November 1989, just before the soil froze for the winter. Nitrate was the dominant anion in soil solutions from trenched subplots and averaged in excess of 0.71 mmol L−1 (10 mg L−1 NO3‐N) at all loading rates. Highest concentrations of NO3 occurred on subplots with the highest sludge application rates. In the untrenched areas, NO3 concentrations rarely exceeded 0.001 mmol L−1; Cl increased in treated areas and was the dominant anion by the end of the season. Soil solution NH4, PO4, SO4, K, and pH did not change significantly for any sludge application rate. Comparison of results from trenched and untrenched areas suggests that, at application rates of up to 14.5 Mg ha−1 (799 kg TKN ha−1), a combination of physical, chemical, and biological factors (most likely plant uptake) limited the movement of sludge or sludge‐derived constituents from the sites of application.
Foliar Amino Acid Accumulation as an Indicator of Ecosystem Stress for First‐Year Sugar Maple Seedlings
Authors: McLaughlin James W. , Reed David D. , Bagley Susan T. , Jurgensen Martin F. , Mroz Glenn D.
Published: July 2010

Accumulation of certain plant foliar amino acids (arginine, glutamine, and proline) can be used as indicators of anthropogenic and natural stressors, such as atmospheric deposition and mineral nutritional imbalances, which result in decreased plant growth. In this study a number of factors were evaluated to assess the use of foliar amino acid accumulation as indicators of sugar maple seedling stress at two sugar maple dominated forests in Michigan. These factors were: (i) first‐year sugar maple (Acer saccharum Marshall) seedling growth, (ii) N and P nutrition, (iii) soluble foliar and root total amino acid concentrations, and (iv) concentrations of foliar arginine, glutamine, and proline. The most southern site (Wellston), which was exposed to high atmospheric deposition and had high available soil P and seedling foliar P, had greater seedling growth. Foliar glutamine, arginine, and proline were greater at the most northern site (Alberta), which received lesser amounts of atmospheric deposition, but also had lower levels of available soil phosphorus, seedling foliar phosphorus, less seedling growth, and greater canopy closure. These results suggest that since atmospheric deposition is high in nitrogen, even the low levels of deposition at Alberta may be interacting with ecological variables such as, available soil phosphorus, light, or moisture to result in N/P imbalances and consequently higher arginine and glutamine concentrations in seedling foliage.
Analysis of Volatile‐Phase Transport in Soils Using Natural Radon Gas as a Tracer
Authors: Chen C. , Thomas D. M.
Published: July 2010

We have conducted a field study of soil gas transport processes using radon gas as a naturally occurring tracer. The experiment monitored soil gas radon activity, soil moisture, and soil temperature at depth; barometric pressure, rainfall, and wind speed were monitored at the soil surface. Linear and multiple regression analysis under natural environmental conditions are influenced by soil moisture content, barometric pressure variations, soil temperature, and soil structure. The effect of wind speed on subsurface radon activities under our field conditions has not been observed.
Nitrate Leaching in a Udic Haploboroll as Influenced by Fertilization and Legumes
Authors: Campbell C. A. , Lafond G. P. , Zentner R. P. , Jame Y. W.
Published: July 2010

An ongoing 34‐yr crop rotation experiment being conducted on a heavy clay at Indian Head, SK, allowed a snap‐shot assessment to be made of the influence of fertilization, legume green manure and legume‐grass hay crops, and frequency of cropping to monoculture hard red spring wheat (Triticum aestivum L.) on deep leaching of soil nitrate (NO3). The results showed that NO3 leaching was greatest when summer fallowing was most frequently employed. Although N fertilization may increase No3‐N leached, using a soil test as a guide to choosing fertilizer application rates and cropping annually will minimize NO3 leaching. Further, we found that, although deep‐rooted forage crops such as alfalfa (Medicago sativa L.) remove NO3 and water to a depth of 2.4 m, and because legumes increase the N supplying power of the soil, considerable NO3 leaching can still occur under these systems. This is especially true if legume plowdown is followed by a fallow period, because during the fallow period, copious net N mineralization may occur together with increased soil moisture storage. These results do not imply that NO3 leaching is pervasive on the Canadian Prairies, but they do confirm certain well‐known principles: viz., that NO3 leaching can be expected whenever conditions favor NO3 accumulation and water buildup in soil. Consequently, it is important to keep the land cropped for a large proportion of the time and to use fertilizers at moderate rates based on soil tests.
Hydraulic Conductivity of an Allophanic Andisol as Affected by Solution pH
Authors: Nakagawa T. , Ishiguro M.
Published: July 2010

Recently, acid precipitation problems have become serious in many regions of the world. The adverse effects of acid precipitation on soils are also feared. In this study, our objective was to determine the effect of inflowing solution pH on saturated hydraulic conductivity (K). The K values were determined at a constant hydraulic gradient in columns packed at a dry bulk density of 0.51 Mg m−3. Influent solutions with the same electrolyte level (1 molc m−3) were prepared at pH 3, 4.2, 5.7, 10, and 11, respectively. The K values decreased when the influent solutions were pH 3 and 11. The K values at 38 pore volumes of an effluent decreased to ≈0.067 of the initial K0 at pH 3, and ≈0.25 of the initial K0 at pH 11, respectively. Measurements of dispersion by optical absorbance method were also carried out. Clay dispersed at low pH (pH < 4.5) and high pH (pH > 10). The structure of the soil columns when K was reduced were visually inspected after K measurements. Those aggregates at the upper portion (≈1 mm thickness) of the soil column seemed to be destroyed by dispersion of clay. It became clear that acidic or alkaline solution decreased permeability of the allophanic andisol. Such a reduction of permeability may significantly change the water balance in a field.
Phosphorus Nutrition of Arsenate‐Tolerant and Nontolerant Phenotypes of Velvetgrass
Authors: Meharg A. A. , Naylor J. , Macnair M. R.
Published: July 2010

Velvetgrass (Holcus lanatus L.), also known as Yorkshire fog grass, has evolved tolerance to high levels of arsenate, and this adaptation involves reduced accumulation of arsenate through the suppression of the high affinity phosphate‐arsenate uptake system. To determine the role of P nutrition in arsenate tolerance, inhibition kinetics of arsenate influx by phosphate were determined. The concentration of inhibitor required to reduce maximum influx (Vmax) by 50%, K1, of phosphate inhibition of arsenate influx was 0.02 mol m−3 in both tolerant and nontolerant clones. This was compared with the concentration where influx is 50% of maximum, a Km, for arsenate influx of 0.6 mol m−3 for tolerants and 0.025 mol m−3 for nontolerants and, therefore, phosphate was much more effective at inhibiting arsenate influx in tolerant genotypes. The high affinity phosphate uptake system is inducible under low plant phosphate status, this increasing plant phosphate status should increase tolerance by decreasing arsenate influx. Root extension in arsenate solutions of tolerant and nontolerant tillers grown under differing phosphate nutritional regimes showed that indeed, increased plant P status increased the tolerance to arsenate of both tolerant and nontolerant clones. That plant P status increased tolerance again argues that P nutrition has a critical role in arsenate tolerance. To determine if short term flux and solution culture studies were relevant to As and P accumulation in soils, soil and plant material from a range of As contaminated sites were analyzed. As predicted from the short‐term competition studies, P was accumulated preferentially to As in arsenate tolerant clones growing on mine spoil soils even when acid extractable arsenate in the soils was much greater than acid extractable phosphate. Though phosphate was much more efficient at competing with arsenate for uptake, plants growing on arsenate contaminated land still accumulated considerable amounts of As. Plants from the differing habitats showed large variation in plant phosphate status, pasture plants having much higher P levels than plants growing on the most contaminated mine spoil soils. The selectivity of the phosphate‐arsenate uptake system for phosphate compared with arsenate, coupled with the suppression of this uptake system enabled tolerant clones of the grass velvetgrass to grow on soils that were highly contaminated with arsenate and deficient in phosphate.
Monitoring for Selected Degradation Products following a Spill of VAPAM into the Sacramento River
Authors: del Rosario Aurora , Remoy John , Soliman Violeta , Dhaliwal Joginder , Dhoot Jagdev , Perera Kusum
Published: July 2010

Following a rail accident that spilled the soil fumigant VAPAM into the Sacramento River on 14 July 1991, a special study was carried out to assess the extent of contamination in Lake Shasta. A total of 32 river water samples collected on 18 July and another 316 samples collected from 22 July through 30 August were analyzed. Data obtained clearly showed the presence of the degradation products of Metham, namely, methyl isothiocyanate, carbonyl sulfide, methyl sulfide, and traces of methylamine. However, due to the emergency nature of the incident that required quick analytical turnaround times, as well as the unavailability of a satisfactory analytical method, the presence of Metham could not be demonstrated with certainty initially. Nonetheless, the laboratory's timely response to the crisis assisted public health officials in assessing the extent of the contamination and assuring the community‐at‐large that their drinking water was safe to consume. None of the degradation products analyzed were detected 1 wk after the spill.
Effect of Formulation and Tillage Practice on Volatilization of Atrazine and Alachlor
Authors: Wienhold Brian J. , Gish Timothy J.
Published: July 2010

Conservation tillage practices are being implemented by many farmers to conserve water and soil resources. These practices may modify the soil surface in ways that differentially effect dissipation of pesticide when compared to conventionally tilled fields. We measured volatilization of atrazine [2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine] and alachlor [2‐chloro‐2′‐6′‐diethyl‐n‐(methoxymethyl) acetanilide] applied as either an experimental starch‐encapsulated formulation or as a commercial formulation, containing atrazine as a wettable powder and microencapsulated alachlor, to adjacent no‐till and conventionally tilled corn fields in Maryland. Both formulations were applied at the same rate; 1.7 kg ha−1 for atrazine and 2.8 kg ha−1 for alachlor. After 35 d, cumulative volatilization of alachlor from conventionally tilled fields was 14% of that applied for both formulations. Cumulative volatilization of alachlor was less from no‐till fields with 9% of the commercial formulation and 4% of the starch‐encapsulated formulation being lost. After 35 d, cumulative volatilization of the commercial formulation of atrazine from the conventionally tilled field was 9% of that applied compared with 4% of that applied to the no‐till field. Starch encapsulation reduced volatilization losses of atrazine to <2% of that applied for both tillage practices. Starch encapsulation appears to be a viable formulation modification for reducing volatilization losses of herbicides, especially from no‐till fields.
Comparing Microbial Parameters in Natural and Constructed Wetlands
Authors: Duncan Colin P. , Groffman Peter M.
Published: July 2010

Microbial biomass C, soil respiration, denitrification enzyme activity (DEA), and potential net N mineralization and nitrification were compared in two constructed and three natural wetlands in Massachusetts and Rhode Island. The constructed wetlands studied had marsh and wet meadow vegetation and received storm water discharge directly from a large shopping mall and its associated parking lots. The natural sites encompassed three soil drainage classes (moderately well drained, poorly drained, and very poorly drained) across an upland to wetland transition zone with red maple (Acer rubrum L.) swamps and mixed oak (Quercus sp.) forests in the transition zone. Our objective was to determine if microbial biomass and activity were similar in the constructed wetlands and the most common type of natural wetland in our area. Microbial biomass C, DEA, and potential net N mineralization and nitrification were similar among the constructed and natural wetland sites. In all cases, levels of these parameters in the constructed wetlands fell within the range of variability observed in the natural wetlands. Denitrification enzyme activity was higher (p < 0.05) in the constructed wetlands than in the moderately well drained soils at the natural sites. Soil respiration was generally lower (p < 0.05) in the constructed wetlands than in the natural wetlands. The results suggest that the constructed wetlands have a significant and active microbial community that facilitates nutrient cycling and water quality maintenance functions similar to natural wetlands. The successful development of the microbial community in these wetlands was likely due to the use of organic substrates and aggressive establishment of the plant community during wetland construction.
Fertilizer Management Effects on Leaching of Labeled Nitrogen for No‐Till Corn in Field Lysimeters
Authors: Baker J. L. , Timmons D. R.
Published: July 2010

The fate of labeled N fertilizer applied to no‐till corn (Zea mays L.) grown in nonweighing lysimeters was determined for 3 yr after application to evaluate NO3‐N leaching losses from point‐injection and conventional N management systems. In 1984, 15N‐enriched double‐labeled urea‐ammonium nitrate solution (UAN) at 200 kg N ha−1 was either surface‐banded or knifed‐in at the VI growth state. It was also point‐injected at either 200 or 125 kg N ha−1 in split applications at the V1, V5, and V9 growth stages. Labeled N as NO3‐N was detected in drainage from the bottom of the lysimeters (1.37 m deep) with the first significant rain (54 mm) 7 d after application for all treatments. Greatest labeled NO3‐N concentrations, however, occurred with drainage in the fall after harvest and in the spring of 1985, the year after application. In 1985, when unlabeled N was applied using the same four systems, average labeled NO3‐N concentrations and annual losses were the greatest and ranged from 1.0 to 5.1 mg L−1 and from 1.7 to 6.8 kg ha−1, respectively; the ratio of labeled NO3‐N to total NO3‐N ranged from 0.08 to 0.25. Labeled NO3‐N concentrations, losses, and ratios were smallest for the 125 kg ha−1 point injected‐split system for each of 3 yr. For all systems, about one‐fourth of the applied labeled N remained in the soil profile at the end of the study. Total recovery (77%) and recovery in grain (48% in 1984) were also greatest for the 125 kg ha−1 point‐injected system and least for the surface‐banded system (64 and 30%, respectively). Unrecovered N was believed lost through denitrification and ammonia volatilization from soil or aboveground vegetation.
Characterizing Chemical Transport Variability Due to Natural Weather Sequences
Authors: Haan C. T. , Nofziger D. L. , Ahmed F. K.
Published: July 2010

A chemical transport model, CMLS, and a weather simulation modal, WGEN, were coupled to investigate the impact of possible and equally likely weather sequences on the travel time and relative amount of various chemicals penetrating given depths into the soil profile. Several combinations of geographical locations and soil chemical properties were investigated. Considerable variability in travel time from one weather sequence to another resulted. This variability is expressed in the form of probability distributions. Implications of this variability in terms of monitoring programs, the interpretation of model studies, and regulations on agricultural chemicals are discussed.
Field‐Scale Mobility and Persistence of Commercial and Starch‐Encapsulated Atrazine and Alachlor
Authors: Gish T. G. , Shirmohammadi A. , Wienhold B. J.
Published: July 2010

Recent laboratory studies have shown that starch‐encapsulation (SE) may reduce leachate losses of certain pesticides. This study compares field‐scale mobility and persistence of SE‐atrazine [2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine] and alachlor [2‐chloro‐N(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide] to that of a commercial formulation (CF) of atrazine and alachlor. The research site consisted of four (0.25 ha) fields. Two fields were under no‐tillage management (NT) and two were under conventional tillage (CT). One field in each tillage system received SE‐formulated atrazine and alachlor, while the others received CF‐atrazine and alachlor. Chemical movement and persistence was determined by analysis of surface samples (≈3 cm) taken immediately after application and 1.1‐m soil cores collected seven times over 2 yr. No significant difference in herbicide residue levels was observed between NT and CT, but there was a herbicide formulation effect. Soil residue analysis suggests that SE‐atrazine was more persistent and less mobile than CF‐atrazine. Starch‐encapsulated‐alachlor was slightly more persistent than CF‐alachlor, but no differences in mobility between formulations was observed. The differential field behavior between SE‐herbicides is attributed to the faster release of alachlor from the starch granules. Increased atrazine persistence was attributed to the reduction of leachate losses. The reduction in atrazine leaching is likely due to the slow release from the starch granules and subsequent diffusion into the soil matrix where it is less subject to preferential flow processes.
Detoxificant Enzymes in Pumpkin Grown in Polluted Ambient Air
Authors: Ranieri Annamaria , Schenone Giorgio , Lencioni Livio , Soldatini Gian Franco
Published: July 2010

Pumpkin [Cucurbita pepo (L.) cv. Ambassador] plants were grown under either nonfiltered or filtered ambient air in open‐top field chambers (OTCs) near the urban area of Milan, Northern Italy. The effects of ambient air pollution on the enzymatic detoxification system of the leaves, both in terms of activity and isoform pattern were investigated. The data on air quality showed that ozone was the main phytotoxic pollutant present in ambient air, reaching a 7 h mean of 63 nL L−1 and a maximum hourly peak of 104 nL L−1. The peroxidase and catalase activities increased fourfold and twofold, respectively in the nonfiltered air plants in comparison to the filtered air ones. The peroxidase patterns were very modified in the polluted plants. In contrast no significant changes were found in the activity and isoenzyme pottern of superoxide dismutase. The data reported here suggest that in field‐grown pumpkin plants exposed to ambient levels of photooxidants, a stimulation of the peroxidase‐catalase detoxification system takes place.
Ferric Complexes as Catalysts for “Fenton” Degradation of 2,4‐D and Metolachlor in Soil
Authors: Pignatello Joseph J. , Baehr Katharina
Published: July 2010

Fenton‐type reactions of hydrogen peroxide with Fe compounds generate hydroxyl radical (OH‐) or other reactive species and are potentially useful for degrading organic contaminants in soil. The use of simple Fe salts is limited, however. This study investigated certain pH 6‐soluble Fe(III) complexes (Fe‐L, where L is an organic ligand) as catalysts for degradation of herbicides 2,4‐dichlorophenoxyacetic acid (2,4‐D) and metolachor (2‐chloro‐N‐[2‐ethyl‐6‐methylphenyl]‐N‐[2‐methoxy‐1‐methylethyl]acetamide). Reactions were carried out in 1:1 aqueous suspensions of a topsoil (15.7 g kg−1 organic C) at the natural pH of 5.7 with herbicides at concentrations representative of a spill (2–3 g kg−1, about 0.01 mol kg−1). The two herbicides had contrasting sorption behavior in that 2,4‐D was mostly in solution, whereas metolachlor was mostly sorbed. The best results were obtained using Fe‐nitrilotriacetate (NTA) or Fehydroxyethyleniminodiacetate (HEIDA) at 0.01 mol kg−1 and [H2O2] ≥ 0.5 mol kg−1. The gallic acid complex was less effective. In 3 h, 14C‐labeled 2,4‐D was quantitatively dechlorinated and partially (15–30%) converted to 14CO2: metolachlor was 93% transformed and 29% dechlorinated. Controls using free ligand plus peroxide or peroxide alone gave little or no reaction. Fe‐L + H2O2 was superior to the Fenton reagent itself (Fe2+ + H2O2). The results of this study demonstrate that relatively mild chemical oxidation can be effective for remediation of certain contaminants in soil.