bluuebunny/crossref_metadata_2025 huggingface dataset:
Can Planted Forests Counteract Increasing Atmospheric Carbon Dioxide?
Authors: Vitousek Peter M.
Published: July 2010

Establishing new forests has been widely suggested as a means to prevent, reduce, or delay fossil fuel‐driven increases in CO2 concentrations in the atmosphere. This analysis examines the potential magnitude of C storage in biomass, emphasizing the amount of land area that could be planted to trees, the rates of C storage in developing forest plantations, and the fate of material harvested from forests. I conclude that while converting old‐growth forests to plantations is a losing proposition, there may be sufficient formerly forested land and the possibility of sufficiently high rates of C storage in young tree plantations that reforestation could remove substantial quantifies of C from the atmosphere (≥1 Pg yr−1). However, rapid net C storage is a short‐lived phenomenon, and it is unlikely that a substantial fraction of material harvested from plantations can go into long‐term storage on land. Therefore, new tree plantations designed to store C can at best cause a brief delay in the accumulation of CO2 in the atmosphere. Forest plantations designed to produce energy from biomass would represent a longer‐term contribution to reducing rates of CO2 accumulation—as long as they replaced fossil fuel‐derived energy.
Effects of Foliar and Soil Acidity on the Rhizosphere pH of Alfalfa, Corn, and Soybean
Authors: Conkling B. L. , Blanchar R. W. , Niblack T. L.
Published: July 2010

The acidity of ambient rainfall and its effect on soil and plants is a growing concern. Glass microelectrodes were constructed and used to investigate the effect of soil pH and foliar application of acid rain on the rhizosphere pH of alfalfa (Medicago sativa L. cv. Arrow), corn (Zea mays L. cv. B73 × MO17), and soybean [Glycine max (L.) Merr. cv. Williams 82]. Plant roots were grown in minirhizotrons containing a reformed sample of Seymour (fine, montmorillonitic, mesic Aquic Argiudoll) silt loam A horizon over a silty clay loam Bt horizon. Low and high pH levels of 4.9 and 6.2 in the A horizon and 4.0 and 5.7 in the Bt horizon were established using dilute sulfuric acid or calcium oxide, respectively. Plants received daily applications of simulated rain, which was either acid (pH 3.1) or nonacid (pH 5.6). After 5, 6, or 15 d of foliar applications to corn, soybean, or alfalfa, respectively, the rhizosphere pH was measured using a glass microelectrode. The pH values for corn and soybean increased with distance from the root while the pH values for alfalfa decreased with distance. As the soil pH increased from 4 to near 6, the difference between the pH at the root surface and the bulk soil increased from 0 to near 1. A trend for lateral root pH values at all distances to be slightly higher than main roots was observed. Increasing the pH of the A horizon had no significant effect on the rhizosphere pH of corn roots growing into the Bt horizon, but significantly increased soybean rhizosphere pH in the Bt horizon. Acid rain applications caused foliar damage, and tended to decrease rhizosphere pH, but few effects were significant. The data emphasize the effect of roots on the heterogeneity of soil pH and show that reliable rhizosphere pH measurements of in situ roots can be made using glass microelectrodes.
Chemical Fractionation and Plant Uptake of Heavy Metals in Soils Amended with Co‐Composted Sewage Sludge
Authors: Sims J. T. , Kline J. S.
Published: July 2010

A sequential extraction method (KNO3, H2O, NaOH, Na2‐EDTA, HNO3) was used to determine the soil fractions and plant availability of Cd, Cr, Cu, Ni, Pb, and Zn in three Atlantic coastal plain soils amended with four rates of Co‐composted sewage sludge (CCSS:0, 11, 22, and 44 Mg/ha), limed to four pH values (pH 5.3–7.2) used to grow wheat (Triticum aestivum L.) and soybean (Glycine max L.) under greenhouse conditions. The average (across soils) increases in total soil Cd, Cr, Cu, Ni, Pb, and Zn, at the highest rate of CCSS were 0.1, 2, 7, 5, 14, and 14 mg/kg, respectively. Distribution of all metals, except Cd, differed in CCSS‐amended soils, with greater percentages found in the NaOH and EDTA fractions and less in the HNO3 form than in unamended soils. The more labile fractions (KNO3, H2O) of Cu, Ni, Pb, and Zn, but not Cd and Cr, increased slightly (<1 mg/kg) when CCSS was added. Liming usually resulted in minor (<5%) changes in the distribution of Cd, Cr, Ni, and Pb among soil fractions. However, liming consistently decreased NaOH extractable Cu and (KNO3 + H2O) extractable Zn, and increased the percentage of these metals in the EDTA and HNO3 fractions. Amendment with CCSS reduced wheat dry matter production in all soils, probably from decreased N availability caused by the high C/N ratio (52:1) of the compost, and slightly increased soybean growth (6–12%). The CCSS had little effect on concentrations of Cd, Cr, or Pb in either crop, but consistently increased Cu, Ni, and Zn in vegetative tissues of wheat and soybean, and Ni and Zn in soybean grain. Liming decreased Mn and Zn in wheat and soybean, and Ni in soybean grain, but rarely affected plant Cd, Cr, Cu, or Pb. With the exception of Zn, consistent correlations between total soil metal content or individual metal fractions and plant metal concentrations or uptake were not observed. However, significant multiple regression models between soil metal fractions and pH and metal concentrations in wheat and soybean were obtained for Ni (R2 = 0.42***–0.86***), Cu (R2 = 0.37**–0.57***), and Zn (R2 = 0.62***–0.82***) with all three soils.
Phosphorus Loads from Selected Watersheds in the Drainage Area of the Northern Adriatic Sea
Authors: Vighi M. , Soprani S. , Puzzarini P. , Menghi G.
Published: July 2010

The Po Valley is one of the most productive agricultural areas in Europe and P losses from fertilizers are often accused of being among the main factors responsible for eutrophication of the Northern Adriatic Sea. To quantify nonpoint phosphorus loads in this area, 15 small watersheds were studied. Thirteen watersheds were in the intensive agricultural area near the coast and two watersheds were in the forested mountains. Land use in the watersheds was carefully examined and P loads from various sources were theoretically evaluated and experimentally measured. The results indicate fertilization does not increase the losses of P through leaching from the coastal soils, where the measured release were in the range 0.03 to 0.21 kg P/ha per year with a mean value of about 0.1 kg P/ha per year. There is, however, a greater loss of P through soil erosion from the mountain watersheds (0.6 kg/ha per year). It can be concluded that the control of point sources must take priority over nonpoint sources in efforts to reduce accelerated eutrophication of the Northern Adriatic Sea.
Reduction of Dissolved Oxygen Concentration in Wisconsin Streams during Summer Runoff
Authors: Graczyk David J. , Sonzogni William C.
Published: July 2010

It is commonly believed that runoff from heavy rainfall is not detrimental to the O content of rural streams free from industrial and municipal discharges. However, evidence is presented of low dissolved O (DO) concentrations during high flows (caused by agricultural runoff during summer rainstorms) in southern Wisconsin streams. Continuous monitoring of streams with in situ oxygen meters indicated a rapid decrease in dissolved oxygen with a rise in the hydrograph. The cause of the oxygen reduction may be due to one or more factors such as (i) inflow of large volumes of runoff with low DO concentrations, (ii) the influx or resuspension of O demanding materials as a result of the storm water input, (iii) decreased O solubility caused by increased water temperature, and (iv) possible reduced photosynthetic productivity. Loss of DO is important because it appears to be associated with fish kills and declining sport fish populations in streams in the region.
Spatial Variations of Sapwood Chemistry with Soil Acidity in Appalachian Forests
Authors: DeWalle David R. , Swistock Bryan R. , Sayre Roger G. , Sharpe William E.
Published: July 2010

Studies were conducted at five Appalachian sites to determine if chemical element concentrations in sapwood tree rings from six tree species varied with soil and soil leachate acidity. The most recent 5‐yr‐growth increment was extracted from 10 tree boles of each species at each site and analyzed for chemical content using plasma emission spectroscopy. Sapwood tree rings generally showed higher concentrations of Mn and lower concentrations of Sr at sites with lower soil pH. Differences in tree‐ring concentrations for Ca and Mn among sites were also found in soil water samples at these sites. Significant differences in soil leachate Al between sites were not duplicated in tree rings. Sapwood tree‐ring chemistry in red oak (Quercus rubra L.), black cherry (Prunus serotina Ehrh.), eastern white pine (Pinus strobus L.) and eastern hemlock (Tsuga canadensis [L.] Carr.) was generally responsive to differences in soil chemistry between sites. Chestnut oak (Q. prinus L.) and pignut hickory (Carya glabra [Mill.] Sweet) were the least responsive species tested. Overall, results show that several common tree species and selected elements are potentially useful for studying historic soil acidification trends at these study sites.
Trace Element Contamination of Soils in the Indiana Dunes
Authors: Esser K. B. , Helmke P. A. , Bockheim J. G.
Published: July 2010

Potential soil contamination by aerosol fallout and rainout and subsequent surface accumulation of trace elements in four soils in the Indiana Dunes have been evaluated based on chemical analyses using XRF and NAA and data from the literature. Among the studied elements, Se, Sb, Zn, and As show highest concentrations in aerosols relative to the soils. The surface accumulation of trace elements in the soil is a function of the proximity to the pollution sources, vegetation, and the organic matter content of the surface horizon. In the studied soils, presence of humus is essential for the retention of trace elements added by aerosols. Enrichment in the Ah horizon compared to the B horizon is, in decreasing order, evident for Mn, Sb, Zn, As, Cs, Se, Cr, Fe, and Co. Contaminant Mn, Sb, As, Se, and possibly Zn have migrated into the E horizon. Bioaccumulation of trace elements has been insignificant in view of apparent input of the elements by deposition, possibly with the exception of Se.
The Mobile Anion Concept—Time for a Reappraisal?
Authors: Hendershot W. H. , Warfvinge P. , Courchesne F. , Sverdrup H.U.
Published: July 2010

The mobile anion concept has been used to support the argument that acid precipitation, containing elevated concentrations of nitrate and sulfate, is acidifying soils and surface waters. We believe that so much attention has been focused on the behavior of the strong acid anions that the effect of other important processes has, in some cases, been obscured. The emphasis, we believe, should be placed on processes that regulate H+ in solution. Thus, we propose that the mobile anion concept (as an explanation of how acid precipitation degrades soils and surface waters) be replaced with descriptions of the mechanisms believed to control the movement of both anions and cations through ecosystems.
Transformation and Sorption of 1,2‐Dibromo‐3‐Chloropropane in Subsurface Samples Collected at Fresno, California
Authors: Deeley George M. , Reinhard Martin , Stearns Stephen M.
Published: July 2010

The transformation rate of 1,2‐dibromo‐3‐chloropropane (DBCP) was determined in phosphate buffer solution, in groundwater, and in groundwater/aquifer solid slurries from ambient temperatures to 72 °C. From the disappearance data, the apparent Arrhenius constants for DBCP transformation were calculated and found to decrease in Ea with temperature from 19.2 (±2.4) kcal mol−1 in the 55 to 72 °C range to 12.5 (±1.8) kcal mol−1 in the 21 to 55 °C range. Low sorption values were an indication that sorption does not play a major role in the aquifer being studied. No significant difference in the disappearance rates was observed in the buffer solution (corrected for buffer effects) and in groundwater with and without solids added. However, in the phosphate buffer solution, dehydrohalogenation appeared to be the favored transformation process in contrast to the groundwater systems where hydrolysis seemed to predominate. This apparent influence of dissolved constituents or temperature on transformation mechanism or rate may restrain the use of direct extrapolation of data between systems. Applying the transformation data from this study to median field parameters, a DBCP half‐life of 6.1 yr was calculated for typical groundwater conditions in California (pH 7.8 and 21.1 °C).
Sorption of Polychlorobiphenyl (PCB) Congeners by Residual PCB‐Oil Phases in Soils
Authors: Sun Shaobai , Boyd Stephen A.
Published: July 2010

In this report we show that residual polychlorobiphenyl (PCB) oil present in soils heavily contaminated with PCB mixtures (Aroclors) functions as a highly effective partitioning medium accounting for the sorptive uptake of 2‐chlorobiphenyl from water. A PCB‐oil normalized partition coefficient (KPCB) was evaluated from the experimental sorption data of 2‐chlorobiphenyl onto four PCB‐oil contaminated soils which had PCB‐oil contents ranging from 2.17 g/kg to 7.67 g/kg (2170 ppm‐7670 ppm). This KPCB value (114 000) indicates that the residual PCB‐oil phase in soils, as a partitioning medium for 2‐chlorobiphenyl, is approximately 67 times more effective per unit mass than natural soil organic matter (KOM = 1700) and 3.5 times more effective than octanol (KOW = 32 400). Our results suggest a threshold PCB concentration in soil of about 0.1% (w/w), above which the PCB mixture forms a separate sorptive phase. The threshold concentration may correspond to the solubility of the liquid PCB mixture in natural soil organic matter. Because of its greater surptive effectiveness, the PCB‐oil phase, once formed, will primarily determine the soil‐water distribution of individual PCB congeners. Accurate prediction of the soil‐water distribution of PCB congeners in such soils can be obtained by considering the additive sorptive effects of the anthropogenic and natural organic matter phases.
Design and Performance of Branch Chambers Suitable for Long‐Term Ozone Fumigation of Foliage in Large Trees
Authors: Teskey R. O. , Dougherty P. M. , Wiselogel A. E.
Published: July 2010

Fumigation chambers for exposing branches of mature trees to ozone (O3) were developed and used in a 2‐yr field study. The performance compared very favorably with that of open‐top chambers. The branch chambers were cylindrical, with dimensions of 1.5 by 0.5 m. To examine the effects that the chamber alone might have on branch or foliage physiology and phenology, six chambers were placed on the branches of trees that had no additional treatments (i.e., no charcoal filtration or O3 amendments). These chambers produced no significant effects on the growth of the branches or foliage within them, as compared with adjacent, nonchambered branches. Hourly net photosynthetic rates were also very similar. The air in the chambers was exchanged 10 times per minute, which resulted in nearly identical air temperatures, relative humidities, and CO2 concentrations inside and outside the chambers. Only light levels were significantly lower within the chambers, which was due primarily to the light transmission properties of the PVC plastic covering the chambers. This approach allows long‐term fumigations to be made on mature tissue of large trees, providing an alternative to the use of seedlings in studies of the effects of O3 or other gases on forest species.
Sorbed Chemical Transport in Overland Flow: I. A Nutrient and Pesticide Enrichment Mechanism
Authors: Ghadiri H. , Rose C. W.
Published: July 2010

Mechanisms of sediment detachment by rainfall and transport by runoff were studied to seek explanation for the enrichment of sorbed chemicals in eroded sediment compared with the original soil. Experiments were carried out in which the outer coats of structurally stable aggregates were peeled away and the peeled material and inner core analyzed separately for chemical concentrations. Results showed that the material removed from the outer layers of the aggregate had higher concentrations than the inner core of organic matter, N, and six different sorbed pesticides. Aggregates of the same soil were exposed in a flume to constant‐rate simulated rainfall for two periods of 30 and 50 min. As a result of such exposure, the concentration of N, organic matter, and pesticides decreased for large aggregates and increased for finer particles. It appears that upon impact, raindrops not capable of totally breaking down stable aggregates remove their outer coat, converting it into fine particles that are richer in sorbed chemicals than any size fraction, including those of similar size in the original soil. This generation of fine particles by the peeling action of raindrops yields eroded sediment with finer size characteristics than the original soil. Thus, the hypothesis examined in this article is that the differential concentration of sorbed chemicals within the soil aggregate, coupled with the peeling action of raindrops, is one reason why eroded sediment is finer and richer in sorbed chemicals than the soil from which it originates. This hypothesis was supported by the results of both peeling and flume experiments carried out in this study. Provided raindrop impact does not lead to the total collapse of aggregates, stripping by raindrops can be the major cause of chemical enrichment in the eroded sediment.
Development of a Database and Model Parameter Analysis System for Agricultural Soils
Authors: Carsel Robert F. , Imhoff John C. , Kittle John L. , Hummel Paul R.
Published: July 2010

An interactive computer program was developed for obtaining soils data for geographic analyses and estimation of soil water retention data for simplistic and classical water flow models. The soils data base contains 8080 soil series identified from the USDA‐SCS. The data are organized in sequential files that contain textural, morphological, crop support, and geographical location (at a county level) and density (ha/county). The computer program allows the exploration of the database, clarifying the impact of data on modeled processes, screening geographically based data to identify potential sits for model application or testing, and developing initial guidance on alternative water quality management strategies. The program allows the display of data in the form of generated reports and production of geographic maps and plots of soil water functional reintionships. Indirect methods are used in the program for estimating soil water retention characteristics using textural information from the soil data base. Estimates of variability can be developed within a soil series or among series by using reported ranges for textural information on each series contained in the soil database.
Soil Microbial Activity at High Levels of Carbon Monoxide
Authors: Hendrickson O. Q. , Kubiseski T.
Published: July 2010

Soils are an important sink for atmospheric carbon monoxide (CO) via microbial uptake. In this study, the disappearance of CO during a 24‐h period was used to quantify potential CO uptake rates (Vmax) for various soils and treatments. When 2.0 kPa CO was added to the gas phase above forest soil, amounts of this gas declined linearly for 24 h, suggesting a zero‐order or saturated reaction. Amounts of CO remained constant over autoclaved soil. Rates for forest, lawn, and garden soils ranged from 0.56 to 7.41, 0.39 to 0.80, and 0.17 to 0.19 mg CO‐C kg−1 dry soil h−1, respectively. Ability of roadside soil to consume CO was significantly reduced by a 19‐d incubation at ambient CO levels, but was increased tenfold by repeated exposures to 2 kPa CO. This positive effect of long‐term CO exposure indicated that autotrophic organisms (carboxydobacteria) were active in roadside soil, but did not exclude the presence of heterotrophic organisms, which oxidize CO by cometabolic processes. A strong relationship between CO consumption and soil organic matter content or soil respiration suggested that high potential rates of soil CO consumption in unpolluted environments may reflect microbial exposure to endogenous CO arising from abiotic oxidation of soil C compounds. Forest soils with intact surface organic horizons may be particularly active CO sinks.
Reclamation Effects on Mycorrhizae and Productive Capacity of Flue Gas Desulfurization Sludge
Authors: Wilson G. W. T. , Hetrick B. A. D. , Schwab A. P.
Published: July 2010

Ten years after portions of a dewatered flue‐gas desulfurization sludge pond has been reclaimed by seeding and fertilizing, the productive capacity of reclaimed sites was higher than abandoned sites. Mycorrhizal symbiosis may be partly responsible for the increased productive capacity of the reclaimed sites, as indicated by the observation that the reclaimed sites had 2.4 times the number of mycorrhizal spores, 5.1 times the root colonization, and 2.2 to 28 times the inoculum potential of the abandoned sludge. In reclaimed sludge, 82 to 100% of all plants became mycorrhizal compared with 30 to 67% of plants in abandoned sludge. Through regression analysis, it was predicted that the reclaimed sludge sites would have a greater productive capacity than the abandoned sludge sites, even if all plants were mycorrhizal. To determine whether these differences in productive capacity were caused by differences in inoculum level, ecotypic variation in inocula, or host plant adaptation to the indigenous inoculum, inocula from an undisturbed soil, pot culture, and the sludges were compared on five host plants grown in the sludges and a prairie soil. While host, soil, and mycorrhizal status (with or withouot mycorrhizae) did affect herbage yield, inoculum source did not. In undisturbed soil, reclaimed sludge, and abandoned sludge, mycorrhizal C3 plants were 7, 71, and 90% larger, and C4 plants were 1300, 1100, and 600%6 larger than nonmycorrhizal plants, respectively. These studies demonstrate that reclamatio6n efforts stimulate recovery and productive capacity of disturbed sites, and that mycorrhizal symbiosis is an integral component in site recovery from disturbance.
Influence of pH, Sodium Adsorption Ratio, and Salt Concentration on Settling Kinetics of Suspended Solids in Coal‐Mine Ponds
Authors: Evangelou V. P. , Karathanasis A.D.
Published: July 2010

Colloidal particle‐settling experiments were conducted in the laboratory to test the influence of pH and dissolved solids on the kinetics of settling of suspended solids in a coal‐mine spoil sample obtained from western Kentucky. Potentiometric titrations suggested that the pH range of colloid coflocculation for the sample tested was around 4.2. Repulsive diffuse double layers at pH above 4.2 appeared to control‐suspended solid behavior. The rate of settling of suspended solids decreased as the pH of the suspension increased. This rate was highly influenced by the ionic strength, sodium adsorption ratio (SAR) and type of divalent cation (Ca or Mg). With Ca as the saturating cation and SAR values below 1, the suspended solids dropped below the required 35 mg/L limit within a 2–h period. At SAR values above 4 and pH near and/or above 7 suspended solids exceeded those required by law. When the divalent cation was Mg, the coal‐mine spoil solids appeared to be less dispersive. For sedimentation ponds neutralized with NaOH, this type of kinetic information is necessary to improve sediment trapping efficiency and design ponds with appropriate water detention times.
Acid‐Base Chemistry of Dissolved Organic Matter in Aqueous Leaf Extracts: Application to Organic Acids in Throughfall
Authors: Brown Aaron D. , Sposito Garrison
Published: July 2010

Elemental composition data were obtained for bulk precipitation and throughfall samples and for aqueous extracts of the leaves 6of three woody plant species common in the subalpine Sierra Nevada range, California: chinquapin (Chrysolepis sempervirens Hjelmqvist), western white pine (Pinus monticola Dougl.), and willow (Salix orestera Schneider). The acid‐base equilibria of the extracts were characterized by potentiometric titration and proton formation functions were computed. The latter then were modeled assuming four classes of quasiparticle acidic functional groups, yielding negative logarithms of conditional protonation constants in the range 4.8 to 5.0, 6.1 to 6.6, 7.4 to 7.7, and 9.1 to 9.4. The relative concentration of a given acidic functional group class varied markedly among the three woody species, but the conditional protonation constants were very similar. The model parameters, along with dissolved organic C concentration and pH values, were used to estimate net anion deficits in throughfall samples collected from the same sites as the leaf samples. On average, the calculated charge concentration of free organic anions in the western white pine extract matched the throughfall anion deficit, whereas the deficits in the chinquapin and willow throughfall samples were not accounted for by free anion concentrations. Metal complexation and in situ, species‐dependent leaf surface processes may account for these latter differences. In general, the anion deficit and, therefore, organic acids were an important component of rainfall and throughfall charge balance.
Microbial Populations in an Agronomically Managed Mollisol Treated with Simulated Acid Rain
Authors: Miller Kathleen W. , Cole Michael A. , Banwart Wayne L.
Published: July 2010

A fertile well‐buffered mollisol (Flanagan silt loam, fine montmorillonitic mesic Aquic Argiudoll) under cultivation with corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] was subjected to simulated rain of pH 5.6, 4.2, and 3.0, while moisture‐activated rain exclusion shelters provided protection from ambient rain. Soil was sampled to a depth of 3 cm on four dates throughout the 1985 growing season. The following microorganisms were enumerated by plate counts or most probable number: general heterotrophic bacteria, general soil fungi, free‐living N‐fixing bacteria, fluorescent pseudomonads, autotrophic ammonium‐oxidizing, nitrite‐oxidizing, and thiosulfate‐oxidizing bacteria. The ANOVA was used to determine the combined and individual effects of rain treatments, crop field, and sampling date. Crop field and sampling date affected microbial numbers more than rain treatments. Overall, rain treatment effects were limited to nitrite‐oxidizing bacteria; lower numbers occurred in the corn field in subplots treated with rain of pH 4.2 and 3.0, and in the soybean field treated with rain of pH 3.0. The trend was strongest in June and July. In the corn field in subplots treated with rain of pH 3.0, numbers of thiosulfate‐oxidizing bacteria were higher and numbers of general heterotrophic bacteria were lower; however, these trends were comparatively weak. Rain treatments caused essentially no decrease in soil pH, suggesting that acid rain constituents affect certain microbial populations without causing overt changes in pH. Because they appear to be unusually sensitive, nitrite‐oxidizing bacteria could be used as experimental indicators of changes in soil microbial communities subjected to acid rain.
Phosphorus and Nitrogen Export from Forested Stream Catchments in Central Ontario
Authors: Dillon P. J. , Molot L. A. , Scheider W. A.
Published: July 2010

The ability to predict export of algal nutrients from forested stream catchments is essential to estimate background levels of nutrients in lakes and therefore gauge the effects of anthropogenic activities on the trophic status of Ontario lakes. Data from 32 forested stream catchments in the Muskoka‐Haliburton area of central Ontario collected during the 8‐yr period 1976–1977 to 1983–1984 were used to develop empirical regression models of long‐term average NH4, NO–3, TON, and TP export employing mathematical transformations of geology, physiography, hydrology, and annual meteorological data. At least 6 consecutive years of sampling were necessary to avoid poor fits due to anomalous years and to produce regression models able to make reliable (R2 > 0.70) long‐term average predictions of TP export. Atmospheric deposition of algal nutrients typically exceeded catchment export. Total annual phosphorus (TP) export was variable with outputs from two catchments exceeding atmospheric inputs. Total organic nitrogen (TON) export was also variable with annual export from 22 catchments exceeding atmospheric inputs, although total N (TN) export never exceeded input. Peat deposits or beaver (Castor canadensis Kuhl) ponds in most of these catchments were the likely sources of the high TP and TON export. Nitrate retention (defined as the fraction of annual deposition retained by the catchment) was high in most catchments, exceeding 0.74 in 26 of the 32 catchments. Low NO–3 retention was observed primarily in those catchments with steep grades (>5.9%). Ammonium retention was very high (>0.87) in all catchments.
Phosphorus Geochemistry in the Sediment‐Water Column of a Hypereutrophic Lake
Authors: Moore P. A. , Reddy K. R. , Graetz D.A.
Published: July 2010

The role of sediment biogeochemistry on diffusive flux of inorganic P was examined under laboratory conditions using intact sediment cores obtained from a subtropical hypereutrophic lake. The effect of light and dark conditions in the water column on soluble P flux from sediments was measured over a period of 1 yr. Soluble reactive P (SRP) level in the overlying water column was low (<0.01 mg P L–1) under light conditions, while values under dark conditions steadily increased. This suggests algal uptake under light conditions. Diffusive flux of soluble P from sediments as calculated by measuring the increase in concentration of the overlying water in the dark was 2.71 mg P m–2 d–1. Flux of this magnitude could increase lake water SRP levels by approximately 0.5 mg P L–1 yr–1. Soluble reactive P concentrations were roughly equivalent to dissolved P concentrations, both for the water column and for the sediment porewater. Porewater SRP increased with depth to a maximum of 6.0 mg P L–1 at 40 cm. Phosphorus flux as calculated from prewater SRP gradients averaged 1.69 mg P m–2 d–1. Sediment P fractionation indicated that water soluble P, KCl extractable P, and Fe and Al‐bound P decreased with depth, whereas the amount of Ca‐bound P increased. Calcium‐bound P was the dominant fraction, comprising over 50% of the total P content. Ion activity products (IAP) calculated using GEOCHEM indicated that the sediments were supersaturated with respect to apatite, beta tricalcium phosphate and whitlockite, with the latter expected to be the phase controlling PO–34 activities.
The Transport of Bioavailable Phosphorus in Agricultural Runoff
Authors: Sharpley Andrew N. , Smith S.J. , Jones O.R. , Berg W.A. , Coleman G.A.
Published: July 2010

Bioavailable P (BAP) in agricultural runoff represents P potentially available for algal uptake and consists of soluble P (SP) and a variable portion of participate P (PP). Evaluation of the impact of agricultural management on BAP in runoff will aid assessment of the resultant biological productivity of receiving water bodies. Soluble P, PP, and bioavailable PP (BPP) (estimated by NaOH extraction) were determined over a 5‐yr period in runoff from 20 unfertilized and fertilized, grassed, and cropped watersheds in the Southern Plains. Soluble P, BPP, and BAP loss in runoff was reduced by practices minimizing erosion and runoff, with respective mean annual amounts ranging from 237 to 122, 1559 to 54, and 1796 to 176 g P ha−1 yr−1 (for peanut‐sorghum [Arachis hypogaea L.‐Sorghum bicolor (L.) Moench] and native grass watersheds, respectively). However, as vegetative cover improved, BAP (SP plus BPP) comprised a larger portion of total P (TP) loss (29% for peanut‐sorghum and 88% for native grass). This results from an increasing contribution to BAP of SP (13% for peanut‐sorghum and 69% for native grass watersheds) and BPP to PP (26% for peanut‐sorghum and 69% for native grass watersheds). Clearly, P bioavailability is a dynamic function of physiochemical processes controlling erosion, particle size enrichment, P desorption‐dissolution reactions, and plant residue breakdown, in addition to soil and fertilizer P management. Hence, the change in trophic state of a water body may not be adequately reflected by TP inputs only. To more reliably evaluate the biological response of a water body to agricultural P inputs, particularly from conservation tillage practices, it may be necessary to determine BAP in runoff.
Effect of Surface Application of Polyvinyl Alcohol on Phosphorus Losses in Runoff and on Corn Growth
Authors: Marsh M.H. , Groenevelt P.H.
Published: July 2010

Phosphorus loading in surface water bodies due to runoff from cropland is a major concern with respect to water quality. Losses of water, soil, and different forms of P, from five runoff plots treated with polyvinyl alcohol (PVA), were comparet do losses from five untreated plots. The plots were on a loam soil with 6.5 to 9.5% slopes. The effect of a single application of PVA was observed over 2 yr under natural rainfall. During the first year after application of PVA, runoff and soil losses were reduced by 56 and 80%, respectively. Extractable P, total P, and dissolved molybdate‐reactive P (DMRP) losses were reduced by 79, 75, and 64%, respectively. Corn (Zea mays L.) grain yield on the treated plots was 12% higher than on the control plots. All the above differences were statistically significant. During the second year, in which no tillage occurred and no PVA was applied, total P and DMRP losses were reduced by 42 and 40%, respectively, by the PVA treatment of the previous year. Although runoff and soil loss were lower for the treated plots, these differences were not significant at P = 0.05 (P values were 0.11 and 0.10, respectively.
Vegetative Filter Treatment of Dairy Barnyard Runoff in Cold Regions
Authors: Schellinger G. R. , Clausen J. C.
Published: July 2010

A vegetative filter strip was installed to treat barnyard runoff from an active dairy farm in Vermont. Runoff from a concrete surfaced barnyard flowed through a detention pond, then onto a vegetative filter strip measuring 22.9 m by 7.6 m with a 2% slope. The water input and surface and subsurface outputs for the strip were continuously monitored from December 1984 through May 1986. Of the total barnyard runoff entering the strip, 65% left as surface runoff and 27% was measured as subsurface outflow. The average hydraulic loading rate was 14.7 cm wk−1 and the average overland flow detention time was 15 min. The filter strip did not significantly (P < 0.05) reduce solids, P, N and bacteria concentrations in the surface output. Over the period of study the mass retention was 33% total suspended solids, 12% total P and 18% total Kjeldahl N. Mass retention was highest during the growing season and was poorest during snowmelt periods. It was concluded that poor filter strip performance was due to an excessive hydraulic loading rate resulting in an inadequate detention time for proper treatment. A preferential flow path from the level lip spreader to the subsurface drain tiles may have contributed to the poor subsurface treatment performance.
Nitrogen Fixation in Soybean Treated with Nitrogen Dioxide and Molybdenum
Authors: Gupta Gian , Narayanan Radhika
Published: July 2010

Soybean plants were treated with Mo (0.0 or 2.0 mg kg−1, soil dry wt.) and exposed to NO2 (0.0, 0.05, or 0.1 µmol mol−1) at flowering stage. Specific root nodule activity (SNA), chlorophyll‐a (Ch‐a), chlorophyll‐b (Ch‐b), leaf N, number of pods, seeds per pod, weight of seeds, and shoot dry weight were measured. Compared with control, SNA did not change on the addition of 2 mg Mo to the soil, but increased by 65% on exposure to 0.1 µmol mol−1 NO2 and by 106% on treatment with both NO2 and Mo. Both Ch‐a and Ch‐b increased significantly on exposure to 0.1 µmol mol−1 NO2 and the amount of this increase with 0.05 µmol mol−1 NO2 and 2 mg MO was almost the same as with 0.1 µmol mol−1 NO2 alone. Leaf‐N increased by 46% on exposure to NO2 but did not change on the addition of Mo. Pod number, seed number and weight, and shoot dry weights showed significantly higher values on exposure to 0.1 µmol mol−1 NO2 and 2 mg Mo.
Effects of Sewage Sludge Cadmium Concentration on Chemical Extractability and Plant Uptake
Authors: Jing Jung , Logan Terry J.
Published: July 2010

Seventeen anaerobically digested sludges of widely varying total Cd contents were used to test the hypothesis that, at a fixed Cd application rate, plant uptake of the metal is proportional to Cd concentration in the sludge. Proof of this hypothesis would support the concept of a “clean” sludge as a mechanism for reducing risk of food‐chain contamination by sludge Cd. The sludges varied in total Cd content from 0.07 to 2.02 mmol/kg. The sludges were extracted with: (i) 0.05 M Ca(NO3)2: (ii) 0.05 M Ca(NO3)2 plus 50 µM Na‐EDTA (ethylene diamine tetraacetate); and (iii) Chelex 100 resin. Total concentrations of Cd and major cations and anions were determined in the equilibrium salt solutions, and the chemical speciation program GEOCHEM was used to calculate Cd2+ activities. Uptake of Cd by sudax [Sorghum bicolor (L.) Moench], a hybrid of sorghum [Sorghum vulgare (L.) Moench] and sudangrass (Sorghum vulgare var. sudanense), was measured in a pot study at constant Cd application rates of 11 and 22 µmol/kg soil. Sudax was seeded into acid‐washed sand in paper pots with bottoms removed and the sand held in place with cheesecloth. After full root development, the pots were placed on similar containers containing 500 g (oven‐dry basis) of Spinks loamy sand (Typic Udipsamment) and grown for 6 wk. The aboveground biomass was weighed and analyzed for Cd. Total Cd (CdT) and Cd2+ in Ca(NO3)2 and Ca(NO3)/EDTA, and resin‐extractable Cd were all correlated positively with each other and with sludge CdT. Plant uptake of Cd was positively correlated with sludge CdT (R2 = 0.33), Ca(NO3)2‐CdT (R2 = 0.91), Ca(NO3)2‐Cd2+ (0.89), Ca(NO3)/EDTA‐CdT (R2 = 0.94), Ca(NO3)/EDTA‐Cd2+ (0.90), and resin‐Cd (R2 = 0.92) Uptake was better correlated with Cd/P ratios in sludge than with Cd content alone. The results of this study support the hypothesis that plant uptake is controlled, in part, by sludge Cd chemistry, specifically sludge Cd content, and suggests that “clean” sludges pose less of a risk to the food chain than more contaminated sludges at equal sludge application rates.
Lead, Cadmium, and Zinc Contamination of Aspen Garden Soils and Vegetation
Authors: Boon D.Y. , Soltanpour P.N.
Published: July 2010

Samples of old silver mine dump materials, garden soils contaminated with mine dump materials, noncontaminated garden soils, and vegetation grown in these gardens were collected to determine the extent of Pb, Cd, and Zn contamination in Aspen, CO. Total HNO3‐HCIO4‐HF‐soluble and NH4HCO3‐DTPA (AB‐DTPA)‐extractable metals in mine dump materials and soils, respectively, were determined by inductively coupled plasma atomic emission spectrometry (ICPS). Plant samples were diegested with HNO3 and analyzed by ICPS. Total metals ranged from 135 to 21 700 mg kg−1 Pb, from 13.3 to 223 mg kg−1 Cd, and from 144 to 20 000 mg kg−1 Zn in mine dump materials. The AB‐DTPA‐extractable metals ranged from 9.2 to 808 mg kg−1 Pb, from 0.2 to 14.2 mg kg−1 Cd, and from 8.4 to 484 mg kg−1 Zn in garden soils. Many of the mine dump materials and soils contained sufficient quantities of Pb and Cd to pose potential health risks if the contaminated materials were ingested. Plant tissues were sampled from the above gardens. In general, leafy tissue concentrations of Pb, Cd, and Zn were highest. Root and other tuber crops were intermediate, lower than leaves, but higher than fruits. The range of concentrations of metals in the leafy tissues were from <5.0 to 45 mg kg−1 for Pb, from 0.6 to 11.9 mg kg−1 Cd, and from 16 to 444 mg kg−1 for Zn. In the roots, metals ranged from <5.0 to 12 mg kg−1 Pb, from 0.5 to 3.6 mg kg−1 Cd, and from 19 to 150 mg kg−1 Zn. Vegetable fruits contained <5.0 mg kg−1 Pb, from <0.5 to 2.7 mg kg−1 Cd, and from 46 to 107 mg kg−1 Zn. Members of the species Brassica oleracea did not accumulate Pb in leaves, even when grown on highly contaminated soils, but accumated Cd and Zn. It was concluded that old mine dump materials have contaminated garden soils placed on them with Pb, Cd, and Zn. The contaminated material poses a health hazard, especially for children. These potential health risks caused the USEPA to list the site on the National Priority List (Superfund sites). The USEPAh as completed its REMEDIAL INVESTIGATION/FEASIBILITY STUDY of Aspen mine dumps and has scheduled implementation of remedial action (clean up) to begin in 1991.
Remediation of Gasoline‐Contaminated Soil by Passive Volatilization
Authors: Donaldson Susan G. , Miller Glenn C. , Miller W. W.
Published: July 2010

Loss of 10 hydrocarbons characteristic of those found in gasoline (benzene; n‐heptane; toluene; m‐xylene; n‐nonane; n‐propylbenzene; 1,2,4‐trimethylbenzene; n‐butylbenzene; 1,2,4,5‐tetramethylbenzene; and n‐dodecane) from 20‐cm soil layers was investigated in several field experiments. Soil was spiked with 50 mg kg−1 of each compound, placed in pans outdoors, and subjected to one of five treatments: dry, unmixed soil; dry soil mixed weekly; soil watered once only; soil watered periodically; and soil watered and mixed periodically. Significantly greater rates of loss occurred from wet soils, with an average of 5.7% remaining in wet and mixed treatments at the 18‐ to 20‐cm depth on Day 32 of the spring experiment, compared with 61% remaining in dry, unmixed soils. Following wetting of the soil by rain, less than 8% overall remained in any soil layer by Day 64. Loss was greatest during the summer experiment. By Day 32, only tetramethylbenzene and dodecane were measurable for the wet treatments, with totals below 5% at the 18‐ to 20‐cm depth. An average of 48.6% remained in the dry soils. The final experiment during fall 1989 demonstrated loss of 500 mg kg−1 of unleaded gasoline from spiked soil. No measurable amounts remained after 8 d in wet and mixed treatments and 16 d in wet, unmixed treatments, but 3.5% remained after 32 d in initially dry soil. These findings indicate that removal of gasoline from contaminated soils can be significantly accelerated by the addition of water.
Nitrate‐Nitrogen and Phosphate‐Phosphorus in Seven Kentucky Streams Draining Small Agricultural Watersheds: Eighteen Years Later
Authors: Thomas Grant W. , Haszler Gerald R. , Crutchfield James D.
Published: July 2010

Seven streams draining agricultural watersheds and representing the agriculturally important physiographic regions of Kentucky were resampled during the months of December 1989 through June 1990. These streams had previously been sampled in 1971–1972. During the intervening 18 yr, the use of fertilizer N in Kentucky has nearly doubled and fertilizer phosphate use has increased slightly. Nevertheless, phosphate contents of these streams averaged somewhat lower than they did 18 yr ago and NO3‐N was almost exactly the same. Only one watershed had changed appreciably in land use; a subdivision had been built and equipped with a sewage plant that drains into one of the creeks. Samples taken above and below the sewage effluent demonstrated the strong effect of the subdivision on both NO3 and PO4 in the water. As indicated 18 yr ago, parent rock of the soils continues to have a greater effect on NO3‐N and PO4 content of streams than does agricultural use.
The Environmental Impact of Bovine Somatotropin Use in Dairy Cattle
Authors: Johnson Donald E. , Ward Gerald M. , Torrent Joan
Published: July 2010

The environmental impact of bovine somatotropin (bST) use in dairy cattle (Bos taurus) was analyzed with the following assumptions: base herd (1989) of 10.1 × 106 cows, milk production 6475 kg of 3.5% fat per 305 d; bST herd of 8.96 × 106 cows, 3.8 kg/d increase during 215 d treatment period; 100% adoption rate, 60 d dry period, 40% replacement rate; all formulated diets from: alfalfa (Medicago sativa L.) hay, corn (Zea mays L.) silage, cracked corn, soybean [Glycine max (L.) Merr.] meal, and supplement to satisfy level of production. Using these assumptions, the analysis indicates that the current U.S. milk supply could be produced by 11% fewer cows fed 9% less feed produced on 6% less land, and soil loss would be 5% less. Fossil fuel requirements would be 6% less and irrigation water use would be reduced by 9%. Output of the greenhouse gas methane would be decreased 9%; manure production and outputs of N and P declined by 10, 8, and 10%, respectively.
Utility and Railway Right‐of‐Way Contaminants in British Columbia: Chlorophenols
Authors: Wan Michael T.
Published: July 2010

Utility and railway right‐of‐way ditches flowing to salmon (Oncorhynchus spp.) streams in the Lower Mainland of British Columbia, Canada, were sampled in 1990 to determine the occurrence and levels of chlorophenols (CP). Ditches of pristine watershed areas, parklands, and agricultural lands were also sampled to establish background/reference levels of CP. While CP were not detected in ditches of pristine watershed areas and parklands, they were found in farmland, utility, and railway right‐of‐way ditches. In utility right‐of‐way ditches, CP in water adjacent to treated poles averaged 1408 µg/L, compared to a mean level of 13.6 µg/L 4 m downstream; in sediments collected from the same sites, the mean concentration of CP was respectively 139 mg/kg and 0.3 mg/kg. For railway right‐of‐way ditches, the mean level of CP in water adjacent to treated poles was 225 µg/L, in contrast to 3.8 µg/L 4 m downstream. Chlorophenol levels in ditch sediments of railway right‐of‐way with treated poles averaged 49.7 mg/kg, compared to 0.4 mg/kg in sediments of railway right‐of‐way ditches without treated poles. Soils at the base of utility poles registered a mean CP concentration of 2168 mg/kg, whereas those from railway ties averaged 38.6 mg/kg of CP. Low CP levels were found only in ditch sediments of farmlands. Although the biological implications of CP‐contaminated ditch sediments are not well known, CP levels found in ditch water adjacent to treated poles exceeded the 96‐h LC50 (lethal concentration of a chemical to 50% of the test fish population) of salmonids, while those found downstream were within the range reported harmful to the fish and aquatic invertebrates.
Leaching, Dissipation, and Efficacy of Metolachlor Applied by Chemigation or Conventional Methods
Authors: Barnes C.J. , Lavy T.L. , Talbert R.E.
Published: July 2010

Field leaching, dissipation, and efficacy of metolachlor (2‐chloro‐N(2‐ethyl‐6‐methylphenyl)‐N‐(methoxy‐1‐methylethyl)acetamide) were evaluated for 8 wk when the herbicide was applied by conventional and chemigation methods to a Taloka silt loam soil (coarse‐silty, mixed, nonacid, thermic Mollic Albaqualf). Laboratory studies were conducted to evaluate adsorption and mobility of the herbicide in five soil depths ranging from 0 to 38 cm. Metolachlor leaching below 30 cm was not observed in either year, regardless of application method. Dissipation rates of metolachlor were not influenced by application method either year. Efficacy of the herbicide was not affected by method of application. Metolachlor sorption was highest in the 0‐ to 8‐cm soil depth of the Taloka silt loam with an organic matter content of 1.1%.