Showing papers in "Journal of Environmental Quality in 1994"

Managing Agricultural Phosphorus for Protection of Surface Waters: Issues and Options

Abstract: The accelerated eutrophication of most freshwaters is limited by P inputs. Nonpoint sources of P in agricultural runoff now contribute a greater portion of freshwater inputs, due to easier identification and recent control of point sources. Although P management is an integral part of profitable agrisystems, continued inputs of fertilizer and manure P in excess of crop requirements have led to a build-up of soil P levels, which are of environmental rather than agronomic concern, particularly in areas of intensive crop and livestock production. Thus, the main issues facing the establishment of economically and environmentally sound P management systems are the identification of soil P levels that are of environmental concern; targeting specific controls for different water quality objectives within watersheds; and balancing economic with environmental values. In developing effective options, we have brought together agricultural and limnological expertise to prioritize watershed management practices and remedial strategies to mitigate nonpoint-source impacts of agricultural P. Options include runoff and erosion control and P-source management, based on eutrophic rather than agronomic considerations. Current soil test P methods may screen soils on which the aquatic bioavailability of P should be estimated. Landowner options to more efficiently utilize manure P include basing application rates on soil vulnerability to P loss in runoff, manure analysis, and programs encouraging manure movement to a greater hectareage. Targeting source areas may be achieved by use of indices to rank soil vulnerability to P loss in runoff and lake sensitivity to P inputs.

Sequential Fractionation of Copper, Lead, Cadmium and Zinc in Soils from or near Doñana National Park

Abstract: A knowledge of the total amount of truce metals is not enough to assess the environmental impact of polluted soils. For this reason, the determination of metal species in solution is important to evaluate their behavior in the environment and their mobilization capacity. Soils contaminated by Cu, Pb, Cd, and Zn found at Donana National Park (Spain) were examined for total content. Sequential extraction schemes were used to determine the degree of pollution and to partition the trace elements in soils. The three areas studied (marshes, stabilized sand, and mine) have different contamination levels. The northern-most marshes of Donana National Park have the highest total levels of the four metals due to the influence of a mine located 40 km away

Phytoremediation Potential of Thlaspi caerulescens and Bladder Campion for Zinc- and Cadmium-Contaminated Soil

Abstract: Metal-tolerant hyperaccumulator plants may be useful to phytoremediate contaminated soils. To evaluate agronomic management practices to maximize phytoremediation, two metallophytes, Thlaspi caerulescens J. and C. Presl (Zn hyperaccumulator) and bladder campion [Silene vulgaris (Moench) Garcke L.] (an indicator) were compared to ‘Rutgers’ tomato (Lycopersicon esculentum L.) in a pot study to assess Zn and Cd uptake patterns in relation to soil pH. Soils used for the study were gathered at three different sites in the vicinity of an old Zn smelter in Palmerton, PA, and contained 48 000, 4100, and 2100 mg kg⁻¹ Zn and 1020, 37.4, and 35.2 mg kg⁻¹ Cd, respectively. Each soil was adjusted to three pH levels ranging from 5.06 to 7.04. Thlaspi caerulescens showed much greater tolerance to the metals than the other plants (up to 18 455 mg kg⁻¹ Zn and 1020 mg kg⁻¹ Cd dry shoots without yield reduction) with metal stress apparent only in the low pH treatments of the two most contaminated soils. In all treatments except for the farm Soil (least contaminated) at pH 5.06, T. caerulescens had higher concentrations of both Zn and Cd than bladder campion and tomato. Thlaspi caerulescens was also more effective at translocating both Zn and Cd from soil to plant shoots. A variety of soil extractions were used to evaluate the correlation of shoot metal concentrations with quantitative measures of “available” soil metals. Concentrations of Cd measured in several common extractants (DTPA, water, 0.01 M Ca(NO₃)₂, and 1.0 M NH₄NO₃) were significantly correlated with Cd concentrations in tissue of each plant. Shoot Zn concentrations of bladder campion and tomato were significantly correlated with Zn extracted by the neutral salt extractants for all soils. For T. caerulescens, the neutral salt extractable Zn was significantly correlated with shoot Zn only in the two more contaminated soils. No extractant predicted shoot Zn concentration for T. caerulescens in the least contaminated soil.

Wetland and Stream Buffer Size Requirements—A Review

Abstract: Upland vegetated buffers are widely regarded as being necessary to protect wetlands, streams, and other aquatic resources Buffer size requirements, however, have typically been established by political acceptability, not scientific merit This often leads to insufficiently buffered aquatic resources In order to assist public agencies in formulating appropriate buffer standards, we conducted a literature search of the scientific functions of buffers The literature search reconfirmed the need for buffers and emphasized the importance of considering specific buffer functions A range of buffer widths from 3 m to 200 m was found to be effective, depending on site-specific conditions; a buffer of at least 15 m was found to be necessary to protect wetlands and streams under most conditions

Impact of long-term land application of broiler litter on environmentally related soil properties

Abstract: The largest portion of Alabama`s rapidly growing poultry industry is geographically concentrated in the Sand Mountain region of northern Alabama. The result is that large amounts of waste are applied to relatively small areas of agricultural soils. A study was conducted to determine the effects of long-term broiler waste (litter) application on environmentally related soil conditions in the region. The region has an average annual rainfall of 1325 mm, which is evenly distributed throughout the year, a thermic temperature regime, and soils in the region are of the Ultisol order. In each of four major broiler-producing counties, three pairs of sites consisting of long-term (15-28 yr) littered and nonlittered fields on matching soil series and maintained under perennial tall fescue (Festuca arundinacea Schreb.) were sampled. Soil cores were taken to 3 m or lithic contact and depth-incremented samples (0-15, 15-30, and each subsequent 30-cm interval) were analyzed for organic C, total N, NO{sub 3}-N, pH, electrical conductivity, and acid-extractable P, K, Ca, Mg, Co, and Zn. Litter application increased organic C and total N to depths of 15 and 30 cm, respectively, as compared with nonlittered soils, whereas pH was 0.5 units higher to a depth of 60 cm undermore » littered soils. Significant accumulation of NO{sub 3}N was found in littered soils to or near bedrock. Extractable P concentrations in littered soils were more than six times greater than in nonlittered soils to a depth of 60 cm. Elevated levels of extractable K, Ca, and Mg to depths greater than 60 cm also were found as a result of long-term litter use. Extractable Cu and Zn had accumulated in littered soils to a depth of 45 cm. These findings indicate that long-term land application of broiler litter, at present rates, has altered soil chemical conditions and has created a potential for adverse environmental impacts in the Sand Mountain region of Alabama. 43 refs., 6 figs., 3 tabs.« less

Trace and Toxic Metals in Wetlands—A Review

Abstract: The mobility and plant availability of many trace and toxic metals in wetland soils is often substantially different from upland soils. Oxidation-reduction (redox) and associated pH changes that occur in soils as a result of flooding or drainage can affect the retention and release of metals by clay minerals, organic matter, iron oxides, and, for coastal wetlands, sulfides. Except where a flooded soil or sediment becomes strongly acid upon drainage and oxidation, as sometimes occurs, the processes immobilizing metals tend to be complimentary such that large-scale metal releases from contaminated soils and sediments do not occur with changing redox conditions. Metals tend to be retained more strongly in wetland soils compared with upland soils. 50 refs., 4 tabs.

The Role of Turfgrasses in Environmental Protection and Their Benefits to Humans

Abstract: Turfgrasses have been utilized by humans to enhance their environment for more than 10 centuries. The complexity and comprehensiveness of these environmental benefits that improve our quality-of-life are just now being quantitatively documented through research. Turfgrass benefits may be divided into (i) functional, (ii) recreational, and (iii) aesthetic components. Specific functional benefits include: excellent soil erosion control and dust stabilization thereby protecting a vital soil resource; improved recharge and quality protection of groundwater, plus flood control; enhanced entrapment and biodegradation of synthetic organic compounds; soil improvement that includes CO2 conversion; accelerated restoration of disturbed soils; substantial urban beat dissipation-temperature moderation; reduced noise, glare, and visual pollution problems; decreased noxious pests and allergy-related pollens; safety in vehicle operation on roadsides and engine longevity on airfields; lowered fire hazard via open, green turfed firebreaks; and improved security of sensitive installations provided by high visibility zones. The recreational benefits include a low-cost surface for outdoor sport and leisure activities enhanced physical health of participants, and a unique lowcost cushion against personal impact injuries. The aesthetic benefits include enhanced beauty and attractiveness; a complimentary relationship to the total landscape ecosystem of flowers, shrubs and trees; improved mental health with a positive therapeutic impact, social harmony and stability; improved work productivity; and an overall better quality-of-life, especially in densely populated urban areas.

Riparian wetlands and water quality

Abstract: Because of wet soils adjacent to the streams, riparian buffers are frequently present between farming and urban activities on the uplands and small streams. These riparian areas have been shown to be very valuable for the removal of nonpoint-source pollution from drainage water. Several researchers have measured >90% reductions in sediment and nitrate concentrations in water flowing through the riparian areas. The riparian buffers are less effective for P removal but may retain 50% of the surface-water P entering them. I consider riparian buffers to be the most important factor influencing nonpoint-source pollutants entering surface water in many areas of the USA and the most important wetlands for surface water quality protection.

A mimicked in-situ remediation study of metal-contaminated soils with emphasis on cadmium and lead

Abstract: The capacity of several additives, i.e., lime, Thomas phosphate baric slag (TBS), hydrous iron oxides (HFO), hydrous manganese oxides (HMO), and Beringite, added to soil to Fix Cd or Pb, was evaluated using two pot experiments in tandem with soil extractions. Three soils from France with metal contents ranging from 0.17 to 108 mg Cd kg -1 soil dry weight (DW) and 47 to 1112 mg Pb kg -1 soil DW were studied. Metal sources were: sludge-borne metals (Soil A), fallout from a smelter (Soil B), and emission from a tetraethyl Pb production facility (Soil C). Ryegrass (Lolium spp.) or tobacco (Nicotiana tabacum L.) shoots were harvested

Decreasing Phosphorus Solubility in Poultry Litter with Aluminum, Calcium, and Iron Amendments

Abstract: Arkansas produces approximately one billion broilers (Gallus gallus domesticus) each year Phosphorous runoff from fields receiving poultry litter is believed to be one of the primary factor affecting water quality in northwest Arkansas Poultry litter contains ≃20 g P kg -1 , of which ≃2 g P kg -1 is water soluble The objective of this study was to determine if soluble P levels could be reduced in poultry litter with Al, Ca and/or Fe amendements Poultry litter was amended with alum, sodium aluminate, quick lime, slake lime, calcitic limestone, dolomitic limestone, gypsum, ferrous chloride, ferric chloride, ferrous sulfate, and ferric sulfate, and incubated in the dark at 25 o C for 1 wk

Passive Treatment of Acid Mine Drainage with Limestone

Abstract: The water treatment performances of two anoxic limestone drains (ALDs) were evaluated Anoxic limestone drains are buried beds of limestone that are intended to add bicarbonate alkalinity to flow-through acid mine drainage Both ALDs received mine water contaminated with Fe²⁺ (216–279 mg L⁻¹) and Mn (41–51 mg L⁻¹) Flow through the Howe Bridge ALD increased alkalinity by an average 128 mg L⁻¹ (CaCO₃ equivalent) and Ca by 52 mg L⁻¹, while concentrations of Fe, K, Mg, Mn, Na, and SO²⁻₄ were unchanged The Morrison ALD increased alkalinity by an average 248 mg L⁻¹ and Ca by 111 mg L⁻¹ Concentrations of K, Mg, Mn, and SO²⁻₄ all decreased by an average 17%, an effect attributed to dilution with uncontaminated water Iron, which decreased by 30%, was partially retained within the Morrison ALD Calcite dissolution was enhanced at both sites by high PCO₂ Untreated mine waters at the Howe Bridge and Morrison sites had average calculated PCO₂ values of 639 kPa (10⁻¹²⁰ atm) and 924 kPa (10⁻¹⁰⁴ atm), respectively At both sites, concentrations of bicarbonate alkalinity stabilized at undersaturated values (SICₐₗcᵢₜₑ = 10⁻¹² at Howe Bridge and 10⁻⁰⁸ at Morrison) after flowing through approximately half of the limestone beds Flow through the second half of each ALD had little additional effect on mine water chemistry At the current rates of calcite solubilization, 179 kg d⁻¹ CaCO₃ at Howe Bridge and 27 kg d⁻¹ CaCO₃ at Morrison, the ALDs have theoretical effective lifetimes in excess of 20 yr By significantly increasing alkalinity concentrations in the mine waters, both ALDs increased metal removal in downstream constructed wetlands

Seasonal variation in methane emission from stored slurry and solid manures

Abstract: Methane (CH{sub 4}) is an important greenhouse gas and recent inventories have suggested that livestock manure makes a significant contribution to global CH{sub 4} emissions. The emission of CH{sub 4} from stored pig slurry, cattle slurry, pig solid manure, and cattle solid manure was followed during a 1-yr period. Methane emission was determined by dynamic chambers. Emission rates followed a ln-normal distribution for all four manures, Indicating large spatial and seasonal variation& Monthly geometric means for pig slurry, cattle slurry, pig solid manure, and cattle solid manure varied from 0.4 to 35.8, 0.0 to 34.5, 0.4 to 142.1, and 0.1 to 42.7 g CH{sub 4} m{sup -3} d{sup -1}, respectively. For slurries CH{sub 4} emission rates increased significantly with storage temperatures, the Q{sub 10} value ranging from 14 to 5.7 depending on slurry type. The presence of a natural surface crust reduced CH{sub 4} emission from slurry by a factor of 11 to 12. Surface crust effects declined with increasing slurry temperature. Solid manures stored in dungheaps showed significant heat production. Pig solid manure temperatures were maintained at 30 to 60{degrees}C throughout most of the year, while cattle solid manure temperatures were close to ambient levels until late spring, whenmore » heat production was initiated. Methanogenesis in solid manure also increased with increasing temperatures. For pig solid manure, CH{sub 4} emission rates peaked at 35 to 45{degrees}C. No distinct temperature optimum could be detected for cattle solid manure, however, temperatures rarely exceeded 45{degrees}C. The Q{sub 10} values for dungheaps ranged from 2.7 to 10.3 depending on-manure type and Q{sub 10} temperature interval. Annual CH{sub 4} emissions from pig slurry, cattle slurry, pig solid manure, and cattle solid manure were estimated at 8.9, 15.5, 27.3, and 5.3 kg animal{sup -1} yr{sup -1}, respectively. 27 refs., 6 figs., 2 tabs.« less

Increased Soil Salinity Causes Elevated Cadmium Concentrations in Field-Grown Potato Tubers

Abstract: Elevated Cd concentrations have been observed in potato (Solanum tuberosum L.) tubers from commercial crops in certain regions of southern Australia. Reasons for enhanced Cd uptake by tubers were investigated by a survey of commercial crops and associated soils. Eighty-nine sites were selected and paired tuber and soil samples taken. Concentration of Cd in tubers was compared to potato variety, tuber elemental composition, and chemical-physical characteristics of topsoil (0-150) and subsoil (150-300 mm). Tuber Cd concentrations were positively related to soil electrical conductivity (EC) and extractable Cl (R{sup 2} = 0.62, P < 0.001) in the topsoil, with extractable Cl accounting for more variation than EC. Tuber Cd concentrations were not strongly related (R{sup 2} = 0.23, P < 0.05) to potato variety alone. However, inclusion of variety and EDTA-extractable Zn with water-extractable Cl in a multivariate model resulted in a small but significant improvement in the variance accounted for by the model (R{sup 2} = 0.73, p < 0.001). Tuber Cd was unrelated to tuber concentrations of P or tuber but was positively related to concentrations of major cations in the tuber particularly Na. Soil pH, total C, EDTA-extractable Cd, or particle-size distribution were not correlated to tuber Cdmore » concentrations, either singly or after inclusion in a multivariate model with soil Cl concentrations. As Cl is known to mobilize soil Cd and increase its phytoavailability, elevated Cd concentrations in potato tubers in southern Australia appear to be largely a result of the use of saline irrigation waters. 41 refs., 5 figs., 4 tabs.« less

Oxygen Respirometry to Assess Stability and Maturity of Composted Municipal Solid Waste

Abstract: The stability and maturity of compost prepared from municipal solid waste (MSW) at a full-scale composting plant was assessed through chemical, physical, and biological assays. Respiration bioassays used to determine stability (O{sub 2} and CO{sub 2} respirometry) were sensitive to process control problems at the composting plant and indicated increasing stability with time. Radish (Raphanus sativus L.) and ryegrass (Lolium perenne L.) growth bioassays revealed that immature compost samples inhibited growth. Growth of ryegrass in potting mix prepared with cured compost not amended with fertilizer was enhanced as compared to a pest control. Garden cress (Lepidium sativum L.) seed germination, used as an indicator of phytotoxicity, revealed inhibition of germination at all compost maturity levels. The phytotoxicity was though to be salt-related. Spearman rank-order correlations demonstrated that O{sub 2} respirometry, water-soluble organic C, and the water extract organic C to organic N ratio, significantly correlated with compost age and best indicated an acceptable level of stability. Oxygen respirometry also best predicted the potential for ryegrass growth, and an acceptable level of compost maturity. 31 refs., 4 figs., 5 tabs.

Brilliant Blue FCF as a Dye Tracer for Solute Transport Studies—A Toxicological Overview

Abstract: Brilliant Blue FCF (C.I. 42090) was found to be a useful dye tracer to stain the flow paths of water in soil media. Being neutral or anionic, it is not strongly adsorbed by negatively charged soil constituents. The dye is used in food because its general toxicity is low. However, to stain the flow paths of water in soil, fairly large concentrations are required to ensure good visibility of the tracer. Therefore, toxic effects cannot be entirely excluded, and assessing the environmental risk is a necessity, especially when field research is conducted in an environmental context. A literature review was carried out to compile data on Brilliant Blue FCF toxicity. The literature suggests that there is no carcinogenicity or mutagenicity to rodents. Brilliant Blue FCF does not accumulate in plants or animals, but degrades slowly in the environment. From the toxicological point of view the dye can be considered as a suitable and environmentally acceptable tracer for studying solute transport in soil, especially in the field.

Denitrification in Riparian Wetlands Receiving High and Low Groundwater Nitrate Inputs

Abstract: Wetlands potentially remove a high percentage of the groundwaterborne nitrate (NO~) that moves from upland environments before it reaches streams. It is important to determine how much of the NO~ that enters wetlands is actually removed from the ecosystem by denitrifleation (conversion of NO~into N2 gas) rather than cycled between plants and soil. We measured denitrifieation in riparian forests with upland to wetland transition zones (moderately well drained and somewhat poorly drained soils) and red maple (Acer rubrum L.) swamps (poorly and very poorly drained soils) on two sides of a stream. Soils on the two sides were similar, but the upland land use on one side was a high density, unsewered residential development (enriched site), while the upland on the other side was undeveloped (control site). Denitrification was measured using an acetylene-based intact core (0-15 cm) technique under unnmended, water amended, and water plus nitrate-amended conditions. Denitrification (both unamended and amended rates) and soil and groundwater NO~ levels were consistently higher in soils on the enriched site. Estimates of annual denitrifieation ranged from <5 kg N ha-1 yr-~ on the moderately well drained control site soil to nearly 40 kg N ha-~ yr-t on the very poorly drained enriched site soil. Stimulation of surface soil denitrification by subsurface NO~ enrichment requires a complex interaction between hydrology, plant uptake of NO~-, and movement of plant N into soil NO~ pools through iitterfail, mineralization, and nitrification. Comparison of measured enitrification rates with estimates of groundwater NO~ loading suggested that denitrification may have removed up to 50% of the groundwater NO~ that entered the

The effects of zinc fertilization on cadmium concentration in wheat grain

Abstract: Although the effect of Zn in soil on Cd uptake by plants has been studied extensively there appears to be no consensus in the literature about the interactions. Furthermore, the majority of investigations have studied soils containing elevated concentrations of Cd or Zn as a result of pollution, e.g., the application of sewage sludge to the soil. The accumulation of Cd by wheat (Triticum aestivum L.) grain grown at nine sites across South Australia was investigated. Applications of low rates of Zn fertilizer (up to 5.0 kg Zn ha{sup -1}) were found to markedly decrease the Cd concentration in wheat grain grown in areas of marginal to severe Zn deficiency. No further significant decreases in Cd concentration in grain occurred at higher rates of applied Zn. Effectiveness of applied Zn on grain Cd concentration decreased with time since application. Grain Cd concentrations decreased with fresh and residual applications of Zn fertilizer (up to 5.0 kg Zn ha{sup -1}). Soil tests may provide useful guides to situations where Cd concentrations in grain may be beneficially decreased by Zn applications. 25 refs., 4 figs., 4 tabs.

Evaluating Agricultural Nonpoint-Source Pollution Using Integrated Geographic Information Systems and Hydrologic/Water Quality Model

Abstract: Considerable progress has been made in developing physically based, distributed parameter, hydrologic/wwater quality (H/WQ) models forplanning and control of nonpoint-source pollution. The widespread use of these models is often constrained by the excessive and time-consuming input data demands and the lack of computing efficiencies necessary for iterative simulation of alternative management strategies. Recent developments in geographic information systems (GIS) provide techniques for handling large amounts of spatial data for modeling nonpoint-source pollution problems. Because a GIS can be used to combine information from several sources to form an array of model input data and to examine any combinations of spatial inputs output data, it represents a highly effective tool for H/WQ modeling

Phosphorus Nutrition of Arsenate-Tolerant and Nontolerant Phenotypes of Velvetgrass

Abstract: 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.

Plant and Soil Relationships of Uranium and Thorium Decay Series Radionuclides—A Review

Abstract: The behavior of radionuclides of the uranium (U) and thorium (Th) decay series in terrestrial systems is of interest because of environmental effects of mining and disposal activities related to nuclear power plant fuels. The soil-plant relationships of U, Th, and polonium (Pb), and some other daughter radionuclides, notably radium ({sup 226}Ra), are not well understood. Most studies have been concerned with relative uptake of these radionuclides by various plant species. Plant concentrations have been related to total contents of these radionuclides in the soil as a plant/soil concentration ratio (CR), even though the fraction of these radionuclides, which may be available to plants, is not well known. These CR values have been used to predict transport of radionuclides and other elements of interest through the food chain as well as for other purpose including biogeochemical exploration for U. Little information is available on uptake and transport mechanisms of radionuclides in plants. However, the mechanisms relating to Ca uptake and translocation in plants may be similar to those of some radionuclides, especially {sup 226}Ra. Son chemical reactions of these radionuclides also have not been studied as well as those of plant nutrients, although knowledge of the effects of soil pH,more » soil texture, and organic matter content on uptake, as well as mobility in soil of these radionuclides, has been gained in recent years. 45 refs., 13 tabs.« less

Hycrest Crested Wheatgrass Accelerates the Degradation of Pentachlorophenol in Soil

Abstract: We investigated the effects of vegetation on the fate of pentachlorophenol (PCP) in soil using a novel high-flow sealed test system. Pentachlorophenol has been widely used as a wood preservative, and this highly toxic biocide contaminates soil and ground water at many sites. Although plants are known to accelerate the rates of degradation of certain soil contaminants, this approach has not been thoroughly investigated for PCP. The fate of [14C]PCP, added to soil at a concentration of 100 mg/kg, was compared in three unplanted and three planted systems. The plant used was Hycrest, a perennial, drought-tolerant cultivar of crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes]. The flow-through test system allowed us to maintain a budget for 14C-label as well as monitor mineralization (breakdown to 14CO2) and volatilization of the test compound in a 155-d trial. In the unplanted systems, an average of 88% of the total radiolabel remained in the soil and leachate and only 6% was mineralized. In the planted system, 33% of the radiolabel remained in the soil plus leachate, 22% was mineralized, and 36% was associated with plant tissue (21% with the root fraction and 15% with shoots). Mineralization rates were 23.1 mg PCP mineralized kg-1 soil in 20 wk in the planted system, and for the unplanted system 6.6 mg PCP kg-1 soil for the same time period. Similar amounts of volatile organic material were generated in the two systems (1.5%). Results indicated that establishing crested wheatgrass on PCP-contaminated surface soils may accelerate the removal of the contaminant.

Distribution of Copper and Cadmium Fractions in Two Forest Soils

Abstract: Pollution of soil by Cu and Cd seems to be increasing in Switzerland. To know the background concentration in low polluted soil we have measured their concentrations in every horizon and calculated the total amounts. The concentrations were low: the largest concentrations of Cu and Cd occurred in the top soil of a Typic Dystrochrept (acid brown soil) (13.5 mg kg {sup -1}Cu and 437 {mu}g kg {sup -1}Cd) and in the Oi-Oa-Al and Bh horizons of a Typic Haplorthod (podzol) (up to 16 mg kg {sup -1}Cu and 460 {mu}g kg {sup -1}Cd in Oi), though when corrected by density, concentrations were higher in A1 horizon of the Haplorthod and A1 and BC of the Dystrochrept. The Dystrochrept was found to contain more of the metals than the Haplorthod. The soil is the main storage compartment of both ecosystems. A six step sequential extraction was applied to evaluate the affinity of metals for the soil constituents and the binding strength to the solid matrix. Water, 0.1 M NaNO{sub 3}, 0.1 M hydroxylamine, 1 M hydroxylamine plus acetic acid, H{sub 2}O{sub 2} and aqua regia were used as successive reagents. Patterns of Cu and Cd distribution in a given soilmore » are different and, to a lesser extent, for a given element the distribution patterns depend on the soil type. Organic matter of Fe and Mn oxides seem to immobilize Cu whereas Cd is associated mainly with Fe and Mn oxides. If the sequential extraction is considered as succession of reagents of increasing strength, then Cd seems to be less strongly bound to soil than Cu and thus more readily solubilized and translocated within soil. The results show the limitations of multistep sequential extraction as a technique for studying metal fractions. 87 refs., 3 figs., 7 tabs.« less

Ferric complexes as catalysts for fenton degradation of 2,4-D and metolachlor in soil

Abstract: Fenton-type reactions of hydrogen peroxide with Fe compounds generate bydroxyl radical (OH{center_dot}) 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 tigand) as catalysts for degradation of herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and metolachlor (2-chloro-N-[2-ethyl 6-methylphenyl]-N-[2-methoxy-l-methylethyl]acetamide) Reactions were carried out in 1:1 aqueous suspensions of a topsoil (157 g kg{sup -1} organic C) at the natural pH of 57 with herbicides at concentrations representative of a spill (2-3 g kg{sup -1} about 001 mol kg{sup -1}) The two herbicides had contrasting sorption behavior in that 2,4-D was mostly in solution, whereas metotachlor was mostly sorbed The best results were obtained using Fe-nitrilotriscetate (NTA) or Fe-hydroxyethyleniminodiacetate (HEIDA) at 001 mol kg-{sup -1} and [H{sub 2}O{sub 2}]{ge} 05 mol kg{sup -1} The gallic acid complex was less effective In 3 h,{sup 14}C-labeled 2,4-D was quantitatively dechlorinated and partially (15-30%) converted to {sup 14}CO{sub 2}: metolachlor was 93% transformed and 29% dechlorinated Controls using free ligand plus peroxide or peroxide alone gave little or no reaction Fe-L + H{sub 2}O{sub 2} was superior to the Fentonmore » reagent itself (Fe{sup 2+} + H{sub 2}O{sub 2}) The results of this study demonstrate that relatively mild chemical oxidation can be effective for remediation of certain contaminants in soil 23 refs, 2 figs, 6 tabs« less

Phosphorus Retention by Wetland Soils used for Treated Wastewater Disposal

Abstract: Wetlands function as buffers for nutrients loaded from terrestrial ecosystems through drainage and surface discharges. The objectives of our study were to (1) determine the P retention capacity of representative wetland soils being used for disposal of treated wastewater and (2) relate P retention characteristics to selected physicochemical properties to evaluate likely mechanisms of P removal to the solls. Intact soil cores (0-40cm) and bulk soil samples (0-15 cm) were collected from a system of natural and constructed wetlands currently being used for disposal of treated wastewater. Floodwater P concentrations of the intact soil cores were monitored over time to determine the rate of P removal. Batch experiments were conducted to deternime maximum P retention capacity of the soils. Soil samples were analyzed for inorganic P pool sizes, and selected physicochemical properties. During a 21 d hydraulic retention time, the constructed wetlands (sandy, low organic matter solls) retained 52 to 66% of added P, as compared with 46 to 47% retained by the natural wetlands (high organic matter soils). The P retention maximum, as estimated using the Langmuir model, ranged from 196 to 1821 mg P kg{sup -1} (aerobic incubations) and from 32 to 1415 mg P kg{sup -1} (anaerobicmore » incubations). The P sorption maximum for these soils could be predicted by batch equilibration with a single high P solution. Anaerobic conditions increased P solubility Organic P pools and the Fe-Al-bound fraction seemed to control P chemistry in these natural and constructed wetland. 38 refs., 4 figs., 8 tabs.« less