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Atrazine is the most widely used herbicide in the U.S. and has been detected in surface water and groundwater. Technologies are needed for onsite and in situ remediation of water and soil containing atrazine. We investigated the potential of using fine-grained, zero-valent iron (Fe0) to remove atrazine and promote its degradation in contaminated water and soil. Atrazine loss from aqueous solution increased with increasing Fe0concentration (w/v). Agitating 20 μg14C-ring-labeled atrazine L−1with 10% Fe0(w/v) removed 92% of the14C from solution within 48 h. Only about 4% of the14C lost from solution was extractable from the iron with 3 mM CaCl2(readily available pool), 81% was extractable with CH3CN (potentially available pool), and 11% was unextractable residues. A companion experiment indicated that most of the14C extracted from the iron with 3 mM CaCl2after the 48-h Fe0treatment was unaltered atrazine, while the CH3CN extract contained approximately 33% atrazine and 48% was unidentified atrazine transformation products. Treating a highly contaminated solution (20 mg atrazine L−1) with 20% Fe0(w/v) removed 88% of the14C (added as14C-ring-labeled atrazine) from solution within 48 h. Deethylatrazine was the main atrazine transformation product detected in solution after treatment, but small amounts of deisopropylatrazine, didealkylatrazine, and hydroxyatrazine were also found. Treating Sharpsburg surface soil containing 1 mg atrazine kg−1with Fe0(2%, w/w) increased atrazine mineralization from 4.1 to 11.2% after 120 d. Pyrite (4% FeS2, w/w) also increased atrazine mineralization in surface soil, but was less effective in the presence of NO3−or SO42−(100 mg kg−1soil). Adding 2% Fe0(w/w) and 100 mg NO3−kg−1to contaminated subsurface soil increased atrazine mineralization from 0.4 to 8.2% within 120 d, and unextractable residues increased from 4.6 to 9.8%. These results indicate iron can sorb atrazine and promote its transformation in water and soil.

The dissipation and movement of carbaryl within soils of wet and dry sites in boreal (south central Alaska), temperate (north western North Carolina) and Mediterranean (east central California) ecosystems was determined by high-pressure liquid chromatography analyses at 1, 30, 60, 90, 365, and 485 d after applications of aqueous 2% to forest soils. Highest levels of carbaryl occurred within the uppermost soil layers of each site. The greatest carbaryl persistence was within the North Carolina dry site. All sites, with the exceptions of Alaska dry and North Carolina wet, had carbaryl levels exceeding 20 ppm in the upper layer of soil at 90 d. The decreasing order of carbaryl persistence was North Carolina dry > California wet > California dry> Alaska wet> North Carolina wet > Alaska dry. Only twice were replicated amounts of carbaryl found in the lowest soil layer (North Carolina dry, 60 d, Alaska wet, 1 d ) and these levels were only 5.6 and 5.1 ppm, respectively.

Soil surveys can be used to group soils according to taxonomic classification and potential for pesticide transport, but estimation of pesticide mobility may be limited by inclusions of dissimilar soils within map units. Estimation of pesticide mobility may also be affected by the level of detail of soil maps as dictated by the needs and purposes of the soil survey. The objective of this research was to determine the most appropriate level of soil map detail for predicting pesticide mobility in terrace soils. Soil cores were collected on river terrace landscape positions in southwestern, south-central, and southeastern Nebraska. Soil thin-layer chromotography was used to measure the relative mobility (R f ) of benchmark pesticides (alachlor, atrazine, carbofuran, and dicamba) in samples from each core. Composite R f values were calculated for each soil pedon to compare pesticide mobility among map units and sample areas. Mobility was affected more by pesticide solubility and K 0C , and by the general physical and chemical properties of parent materials at the sample sites, than by specific soil type. The research suggests that soil association maps, comprised of map units that are groupings of soil series associated geographically in a repeating pattern, may be the most appropriate for predicting pesticide mobility in terrace soils.

The size and activity of atrazine-degrading populations are among the factors controlling atrazine persistence in soil. Populations of atrazine-degrading microorganisms in surface and subsurface soils were enumerated by the 14C-most-probable-number (14C-MPN) technique using [14C-ethyl]-atrazine or [U-14C-ring]-atrazine in C- or N-limited media. The [14C-ethyl] atrazine served as a potential carbon source for a larger number of microorganisms than [U-14C-ring]-atrazine. Populations of atrazine-degrading microorganisms using [14C-ethyl]-atrazine as a carbon source ranged from 4670 to 31,930 cells g−1 of surface soil, but were 1050 cells g−1 in a subsurface sediment. The size of these [14C-ethyl]-atrazine-degrading microbial populations were positively correlated (r2=0.81) to mineralization of [14C-ethyl]-atrazine added to soil, which suggests that atrazine-degrading populations may serve as an indicator of atrazine persistence in the soil environment. Populations degrading [U-14C-ring]-atrazine ranged from 130 to 1630 cells g−1 soil in C-limited media and from 19 to 10,530 cells g−1 soil in N-limited media. Population size and mineralization activity were generally increased by the frequency of atrazine use, suggesting that long-term exposure encourages microbial adaptation and growth.

The capacity of UV-catalyzed Fenton oxidation to destroy mono-, di- and trinitrotoluenes (MNT, DNT, TNT) in aqueous solution was evaluated. Mononitrotoluenes were rapidly destroyed by Fenton oxidation in the dark at pH 3.0 or by UV/Fenton oxidation without pH adjustment. UV/Fenton oxidation at pH 3.0 was most effective for DNT and TNT destruction. The number and position of nitro substitutions influenced oxidation rate: 2-nitrotoluene > 4-nitrotoluene > 2,4-dinitrotoluene > 2,6-dinitrotoluene > 2,4,6-trinitrotoluene. UV/Fenton oxidation mineralized more than 95% of the TNT in aqueous extracts of contaminated soil. While dissolved humic and fulvic acids differentially influenced destruction rate, total TNT destroyed after 4 h was not greatly affected. Our results demonstrated that UV-catalyzed Fenton oxidation effectively destroyed nitrotoluenes in water and aqueous extracts of contaminated soil.

It is estimated that explosives contaminate approximately 0.82 million cubic metres of soil at former military installations throughout the US; major contaminants often include 2,4,6-trinitrotoluene (TNT) and its degradation products. At some sites, phytoremediation may be a viable option to incineration or other costly remediation treatments. Grasses may be particularly suited for remediation because of their growth habit and adaptability to a wide range of soil and climate conditions. We characterized the effects of TNT on germination and early seedling development of switchgrass and smooth bromegrass to evaluate their potential use on contaminated sites. Switchgrass and smooth bromegrass seeds were germinated in nutrient-free agar containing 0 to 60 mg TNT litre(-1). Smooth bromegrass germination decreased as TNT concentration increased, while switchgrass germination was unaffected by TNT. Concentrations up to 15 mg TNT litre(-1) did not affect switchgrass root growth rate, but bromegrass root growth was reduced at TNT concentrations above 7.5 mg litre(-1). At 7.5 mg TNT litre(-1), however, shoot growth rate was reduced in both species. Examination at 20-fold magnification revealed switchgrass radicles were unaffected by TNT, while smooth bromegrass radicles appeared slightly swollen. Results indicate switchgrass is more tolerant of TNT than smooth bromegrass, but the establishment of both species may be limited to soil containing less than 50 mg kg(-1) of extractable TNT.

Soils surrounding former munitions production facilities are highly contaminated with 2,4,6-trinitrotoluene (TNT). Long-term availability and fate of TNT and its transformation products must be understood to predict environmental impact and develop appropriate remediation strategies. Sorption and transport in surface soil containing solidphase TNT are particularly critical, since nonlinear sorption isotherms indicate greater TNT availability for transport at high concentrations. Our objectives were to determine long-term sorption and bound residue formation in surface and subsurface Sharpsburg soil (Typic Argiudoll). Prolonged equilibration of ¹⁴C-TNT with the soil revealed a gradual increase in amount sorbed and formation of unextractable (bound) ¹⁴C residues. The presence of solid-phase TNT did not initially affect the amount of ¹⁴C sorbed during a 168-d equilibration. After 168 d, 93% of the added ¹⁴C was sorbed by uncontaminated soil, while 79% was sorbed by soil containing solid-phase TNT. In the absence of solid phase, pools of readily available (extractable with 3 mM CaCl₂) and potentially available (CH₃CN-extractable) sorbed TNT decreased rapidly with time and coincided with increased ¹⁴C in soil organic matter. More ¹⁴C was found in fulvic acid than in the humic acid fraction when no solid-phase TNT was present. After sequential extractions, including strong alkali and acid, 32 to 40% of the sorbed ¹⁴C was irreversibly bound (unextractable) in Sharpsburg surface and subsurface soil. Results provide strong evidence for humification of TNT in soil. This process may represent a significant route for detoxification in the soil-water environment. Publication no. 11551, Agric. Res. Div., Univ. of Nebraska — Lincoln, Lincoln, NE 68583-0915.

Past disposal practices at munitions production facilities have generated numerous acres of 2,4,6-trinitrotoluene (TNT)-contaminated soil. We determined the potential of the Fenton reagent (Fe{sup 2+} and H{sub 2}O{sub 2}) to remediate TNT contamination in water, aqueous extracts of contaminated soil, and soil-water slurries. The effects of H{sub 2}O{sub 2} and Fe{sup 2+} concentrations, solution pH, temperature, and initial TNT concentration on transformation and mineralization rates were evaluated. Treating an aqueous TNT solution (70 mg TNT L{sup -1}) with Fenton reagent (1% H{sub 2}O{sub 2}, 80 mg Fe{sup 2+} L{sup -1}) in the dark resulted in 100% destruction of TNT within 24 h. This coincided with 40% mineralization. Subsequent exposure to light resulted in >90% mineralization. We observed generation of 2,4,6-trinitrobenzoic acid and 1,3,5-trinitrobenzene within 15 min following Fenton oxidation of TNT. This indicates that initial TNT destruction likely occurs by methyl group oxidation and decarboxylation. Subsequent transformations involve nitro moiety removal with ring hydroxylation and cleavage, as evidenced by the stoichiometric recovery of TNT-nitrogen as NO{sub 3}{sup -} and production of oxalic acid as the primary C-containing end product. Upon exposure to light, Fe(II) was regenerated and the oxalate produced from 14C-TNT oxidation disappeared; this coincided with a decrease inmore » solution {sup 14}C activity. Similar observations were made when {sup 14}C-oxalic acid was the starting substrate. Fenton oxidation was also effective in destroying TNT in aqueous extracts of contaminated soil and soil-water slurries. Experimental data provide evidence that the Fenton reagent can effectively remediate TNT-contaminated water and soil. 39 refs., 8 figs., 1 tab.« less

Contaminated water and soil at active or abandoned munitions plants is a serious problem since these compounds pose risks to human health and can be toxic to aquatic and terrestrial life. Our objective was to determine if zero-valent iron (Fe(0)) could be used to promote remediation of water and soil contaminated with 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). As little as 1% Fe(0) (w/v) removed 70 mg TNT litre(-1) from aqueous solution within 8 h and removed 32 mg RDX litre(-1) within 96 h. Treating slurries (1:5 soil:water) of highly contaminated soil (5200 mg TNT and 6400 mg RDX kg(-1) soil) from the former Nebraska Ordnance Plant (NOP) with 10% Fe(0) (w/w soil) reduced CH(3)CN-extractable TNT and RDX concentrations below USEPA remediation goals (17.2 mg TNT and 5.8 mg RDX kg(-1)). Sequential treatment of a TNT-contaminated solution (70 mg TNT litre(-1) spiked with (14)C-TNT) with Fe(0) (5% w/v) followed by H(2)O(2) (1% v/v) completely destroyed TNT and removed about 94% of the (14)C from solution, 48% of which was mineralized to (14)CO(2) within 8 h. Fe(0)-treated TNT also was more susceptible to biological mineralization. Our observations indicate that Fe(0) alone, Fe(0) followed by H(2)O(2), or Fe(0) in combination with biotic treatment can be used for effective remediation of munitions-contaminated water and soil.

Nitrate and atrazine (ATR) occur in combination in some drinking-water supplies and might react to form N-nitrosoatrazine (NNAT), which is reportedly more toxic than nitrate, nitrite, or ATR. Current evidence from population-based studies indicates that exposure to nitrate, nitrite, and nitrosatable compounds increases the risk of congenital defects and/or rate of embryo lethality. To test the hypothesis that NNAT induces malformations during embryogenesis, chicken embryos were examined for lethality and developmental abnormalities after treating fertilized eggs with 0.06-3.63 μg NNAT. After 5 d of incubation (Hamburger and Hamilton stage 27), 90% of embryos in NNAT-treated eggs were alive, of which 23% were malformed. Malformations included heart and neural-tube defects, caudal regression, gastroschisis, microphthalmia, anophthalmia, and craniofacial hypoplasia. The findings from this investigation suggest further studies are needed to determine the mechanisms underlying NNAT-induced embryotoxicity.

Phenol and heavy metals in petroleum waste are environmental and human health concerns, but physicochemical removal is often cost-prohibitive and can produce toxic secondary products and treatment residues. An environmentally benign alternative combines corn cob silica with alginate and immobilized bacteria into beads for treating contaminated water. The concentration of phenol was decreased >92% by Pseudomonas putida YNS1 on aliginate-silica beads (2%, w/v) after equilibrating for 96h with water containing 214mg phenol/L. GC-MS analysis indicated formation of benzoquinone and other polar products. Beads containing corn cob silica decreased Cu concentrations by 84-88% and Cd by 83-87% within 24h. In a mixture of 114mg phenol, 43mg Cu and 51mg Cd/L, phenol removal (93% within 96h) only occurred with beads containing the silica and bacterial strain. Beads containing corn cob silica removed >97% of the Cu and >99% of the Cd, critical for reducing toxicity to the bacteria. Beads with the immobilized strain removed phenol when zeolite was used instead of corn cob silica, but beads with silica were more effective for Cu and Cd removal. Results show the potential of corn cob silica combined with alginate and immobilized bacteria for removing phenol and heavy metals from contaminated water.

Energetics such as RDX, HMX, and CL-20 exhibit low sorption and natural degradation, resulting in widespread groundwater contamination. Alternatively, TNT exhibits strong sorption and degrades to toxic recalcitrant intermediates. Field scale abiotic, biotic, and coupled abiotic/bioremediation can be more cost effective than pump and treat or sediment removal, but rates of processes in relevant insitu conditions need to be understood.

A heavy metal-tolerant fungus, Trichoderma virens PDR-28, was isolated from rhizosphere soil and evaluated for use in remediating mine tailing soil and for plant biomass production. PDR-28 exhibited plant growth-promoting traits, including 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, acid phosphatase and phytase activity, siderophore production, and P solubilization. HMs were more available in mine tailing soil inoculated soil with PDR-28 than in uninoculated soil; the order of HM bioleaching was Cd > As > Zn > Pb > Cu. PDR-28 effectively removed HMs in the order of Pb > Cd > As > Zn > Cu from liquid media containing 100 mg HM L−1. Inoculating HM-contaminated mine tailing soil with the fungus significantly increased the dry biomass of maize roots (64%) and shoots (56%). Chlorophyll, total soluble sugars (reducible and nonreducible), starch, and protein contents increased by 46%, 28%, 30%, and 29%, respectively, compared to plants grown in uninoculated soil. Inoculation increased heavy metal concentrations in maize roots by 25% (Cu) to 62% (Cd) and in shoots by 35% (Cu) to 64% (Pb) compared to uninoculated plants. Results suggest that PDR-28 would be beneficial for phytostabilization and plant biomass production as a potential source of biofuel in the quest for renewable energy.

The degradation and vertical movement of pendimethalin, chlorpyrifos, isazofos, and metalaxyl were monitored in Kentucky bluegrass (Poa pratensis L.) turf managed as a golf course fairway. Intact turf-soil cores from Mead, NE, on a Sharpsburg soil (fine montmorillonitic, mesic Typic Argiudoll) and Gilbert, IA, on a Nicollet loam (fine-loamy, mixed, mesic Aquic Hapludoll) planted to Kentucky bluegrass were periodically removed to 60-cm depth through 113 d after pesticide application. Cores were sectioned into verdure, thatch, and multiple soil depths. While verdure contained high pesticide concentrations after application, precipitation, and clipping, and degradation reduced the amount in plant tissue with time. Thatch was highly retentive of the pesticides, generally containing the most residue throughout the monitoring period. Pesticide residues tended to be lower in soil at the Iowa site where more thatch was present. Little chlorpyrifos or pendimethalin moved through the thatch to the underlying soil. Isazofos was more mobile and metalaxyl moved through the entire soil column. Soil contained an average of 58% less pesticide than thatch over all sampling times, and concentrations in soil were highest at the 0- to 5- and 5- to 10-cm depths. Average time for 50% dissipation in the turf-soil profile (DT 50 ) was 16, 12, 10, and 7 d for metalaxyl, pendimethalin, chlorpyrifos, and isazofos, respectively. The pesticides appeared to degrade more rapidly in the turfgrass environment than typically reported for other agronomic cropping systems. Variability in pesticide residue concentrations for each soil depth among the turf-soil cores indicated non-uniform dissipation in the field.

Degradation reduces ground water contamination from soil-mobile herbicides, but degradation rates vary among soils and with depth. Alachlor and atrazine degradation were determined in Hord silt loam (fine-silty, mixed, mesic Pachic Haplustolls) surface soil (0-15 cm), subsurface soil (45-120 cm), and underlying sediment (150-240 cm) from a terrace of the Platte River near Shelton, Nebraska. Herbicide solution containing 14 C-ring-labeled alachlor or atrazine was added at 100 or 1000 ng g -1 to soil adjusted to -50 kPa water content and incubated at 22°C up to 200 days. 14 CO 2 evolution was monitored to determine mineralization with time, and soil was extracted and combusted to determine residual 14 C-labeled herbicide and bound residue formation. Respective first-order half-lives of alachlor and atrazine ranged from 8 and 11 days in surface soil to 49 and 248 days in deep soil. Soil-bound (unextractable) residue from alachlor and atrazine typically increased with time and ranged from 54 and 46% of applied 14 C in surface soil to 2 and 3% of 14 C applied in deep soil. Stepwise regression indicated that rate of degradation of both herbicides in these soils could be estimated from sorption, NH 4 + Or NO 3 - + NO 2 - , and orthophosphate content. Although atrazine is usually persistent, with little or no mineralization of the s-triazine ring, enhanced degradation was observed in two of the surface soils, where more than 60% of the herbicide was mineralized in 28 days. Lower deethylatrazine concentrations in soil exhibiting enhanced atrazine degradation suggested transformation to more labile polar degradates. A decrease in the polar degradation products and bound residue fractions as mineralization increased indicated their utilization during atrazine degradation in soil.

Past disposal practices at munitions production plants have contaminated terrestrial and aquatk ecosystems with 2,4,6-trinitrotoluene (TNT). We determined TNT transport, degradation, and long-term sorption characteristics in soil. Transport experiments were conducted with repacked, unsaturated soil columns containing uncontaminated soil or layers of contaminated and uncontaminated soil. Uncontaminated soil columns received multiple pore volumes (22-50) of a TNT-{sup 3}H{sub 2}O pulse, containing 70 or 6.3 mg TNT L{sup -1} at a constant pore water velocity. TNT breakthrough curves (BTCs) never reached initial solute pulse concentrations. Apex concentrations (C/C{sub o}) were between 0.6 and 0.8 for an initial pulse of 70 mg TNT L{sup -1} and 0.2 to 0.3 for the 6.3 mg TNT L{sup -1} pulse. Earlier TNT breakthrough was observed at the higher pulse concentration. This mobility difference was predicted from the nonlinear adsorption isotherm determined for TNT sorption. In all experiments, a significant fraction of added TNT was recovered as amino degradates of TNT. Mass balance estimates indicated 81% of the added TNT was recovered (as TNT and amino degradates) from columns receiving the 70 mg TNT L{sup -1} pulse compared to 35% from columns receiving the 6.3 mg TNT L{sup -1} pulse. Most of the unaccountable TNT wasmore » hypothesized to be unextractable. This was supported by a 168-d sorption experiment, which found that within 14d, 80% of {sup 14}C activity (added as {sup 14}C-TNT) was adsorbed and roughly 40% unextractable. Our observations illustrate that TNT sorption and degradation are concentration-dependent and the assumptions of linear adsorption and adsorption-desorption singularity commonly used in transport modeling, may not be valid for predicting TNT transport in munitions-contaminated soils. 29 refs., 6 figs., 7 tabs.« less

A fo ur-year fi eld experiment was conducted near Scotts­ bluff, NE to compare degradation of ethalfluralin, pen­ dimethalin, and trifl uralin in soil. Dinitroaniline herbicides were applied at rates of0.56, 1.12, and 2.24 kg/ha preplant incorporated before planting dry edible bean. Herbicide degradation was monitored by chemical extraction and gas chromatography. Sugarbeet followed dry edible bean in the crop rotation and crop growth was related to dinitroaniline herbicide concentrations in soil. Moldboard plowing of the soil before sugarbeet planting reduced dinitroaniline her­ bicide concentration in the upper 0 to 8 cm of the soil pro: file by 39 and 76010 in 1990 and 1992, respectively. Plowing increased the concentration of herbicide in the 15 to 30 cm zone of the soil profile. Ethalfluralin degraded more rapid~ Iy than pendimethalin or trifluralin. Eleven months after herbicide application, residues of 0.07 mg/kg or greater of pendimethaJin or trifluralin in the upper 0 to 8 cm of the profile reduced sugarbeet growth and stand.

Efficacy, movement, and degradation of dithiopyr and pendimethalin were monitored after application to perennial ryegrass turf in 1990 and 1991. Dithiopyr at 0.6 kg ai ha−1reduced large crabgrass infestation by ≥ 90% up to 87 DAT in both years, while pendimethalin at 1.7 kg ai ha−1provided similar control up to 59 DAT in 1 of 2 yr. Turf thinning due to disease and insect damage in 1990 allowed more herbicide to reach the thatch, mat, and underlying soil in 1991. In both years, more pendimethalin but less dithiopyr was found in thatch 7 DAT than 1 DAT, suggesting greater pendimethalin retention in verdure and thatch. Precipitation was greater after herbicide application in the second year, and concentration in the mat layer reached a maximum by 7 DAT compared to 14 DAT in 1990. Maximum concentrations of dithiopyr and pendimethalin in soil at 0 to 5 cm deep were 20 and 56 μg kg−1, respectively, measured 7 DAT in 1991. Herbicide concentration 5 to 10 cm deep was ≤ 5 μg kg−1at all sampling dates in 1990. In 1991, dithiopyr and pendimethalin concentrations 5 to 10 cm deep did not exceed 4 and 20 μg kg−1, respectively, measured within 1 DAT. Neither herbicide was detected 10 to 20 cm deep, nor in samples collected 30 cm outside of the experimental plots in either year. At 126 DAT (final sampling date), little herbicide was detected in verdure, but residues were found in most thatch and all mat samples. The estimated time for a 50% reduction in detectable residues (DT50) of dithiopyr and pendimethalin from the sampling zone was 35 and 23 days, respectively.

Simulation of field conditions is important when conducting solute movement research in the greenhouse. A study was initiated to develop and test a solute movement system with intact turf-soil columns subjected to suction approximating field capacity and typical irrigations. Intact soil columns from a Sharpsburg soil (fine montmorillonitic, mesic Typic Argiudoll) planted to Kentucky bluegrass (Poa pratensis L.) were encased in concrete, excavated, and brought to the greenhouse. Porous ceramic plates were attached to some column bottoms and suction (50 kPa) was applied to simulate soil water matric potentials at held water capacity and eliminate perched water tables

An indirect enzyme-linked immunosorbent assay (ELISA) for EPTC was developed that may be useful for predicting enhanced carbamothioate herbicide degradation in adapted soils. A modified radioimmunoassay (RIA) procedure was used to detect antibodies specific for EPTC and establish antibody dilutions for optimum ELISA sensitivity. Antibodies were obtained from a rabbit injected with a butylate-analog protein conjugate. An indirect ELISA subsequently was developed for EPTC with a detection range of 10 to 1280 ng ml−1 in a 1:3 aqueous dilution of a 90:10 (v/v) acetonitrile (ACN):water soil extract. EPTC recovery from soil was > 96%, as determined by conventional gas chromatography. Measurement of low concentrations of residual EPTC with the ELISA was less quantitative than by gas chromatography, but the immunoassay provided a rapid, potentially cost-effective method for screening soils to determine enhanced carbamothioate degradation.

A closed incubation system was developed for laboratory simulation of composting conditions at the interior of a large compost pile. A conductive heat flux control system (CHFC) was used to adjust the temperature of the internal wall to that of the compost center and compensate for heat loss. Insulated small vessels (400 cm 3) controlled by the CHFC system were compared with similar vessels maintained at 30°C (mesophilic) and 55°C (thermophilic), and with large vessels (10 000 cm3) with and without the CHFC. Compost temperature rose rapidly to a maximum within 2-4 days, then gradually decreased. In mesophilic treatments (no CHFC), temperature at the matrix center increased to a maximum of 36°C in the small vessel and 50°C in the large vessel, while temperature in both vessels reached 50°C with the CHFC. Microbial activity was maintained by allowing compost to self-heat and controlling temperature externally with the CHFC. Higher temperatures were sustained for longer periods in CHFC vessels than in vessels without the CHFC. Periodic mixing of the compost matrix increased temperature and CO2 evolution. Small vessels were successfully used in laboratory simulation of field-scale composting of a soil/organic matrix containing TNT and RDX munitions. The small vessel system reduced subsample error in compost monitoring from that of the large vessels. The CHFC has particular utility in research requiring expensive chemicals or hazardous substances.

The effect of lindane on numbers and community structure of oribatid mites was studied in northern Montana. Trees on five O.4-haplots were sprayed with lindane at 5.5 kg/ha (AI) in a simulated operational program to protect lodgepole pine from bark beetles. Sprayed plots and paired control plots were sampled before spray application and five times after treatment over a 2-yr period. Numbers of immature specimens changed more than numbers of adults. Both were Significantly depressed 113 after treatment. Two superfamilies were significantly affected after spraying. Of five measures of community structure, none demonstrated an effect; however, the powers of the statistical tests were quite low. The importance of statistical power in studies of effect of pesticides on nontarget species is discussed. Because the observed effects were short-lived and of relatively small amplitude, we conclude it is unlikely there is a lasting effect on the oribatid community.

Coronary spasm, dissection, and localized thrombosis are recognized sources of iatrogenic obstruction during coronary angioplasty. A fourth important cause is reported, namely, guidewire-induced mechanical straightening and shortening of tortuous right coronary artery resulting in the invagination of redundant vascular tissue. Reversal is achieved with guidewire retraction. Recognition of this entity is crucial to avoid unnecessary and potentially harmful intervention. © 1992 Wiley-Liss, Inc.

Mountain pine beetle, Dendroctonusponderosae Hopkins, is the primary pest affecting lodgepole pine, Pinuscontorta var. latifolia Engelm., ecosystems in western North America. In 1988, aerial treatments of the antiaggregation pheromone, verbenone, were applied to lodgepole pine stands infested with mountain pine beetle in northwestern Montana. The pheromone was formulated by PHERO TECH Inc. in controlled-release, cylindrical 5 × 5 mm plastic beads and applied without benefit of a sticker at the rate of 54 g verbenone per hectare. There were significantly fewer successfully attacked trees on the treated plots, as evidenced by (i) a fourfold greater incidence of current-year attacked trees per hectare in the untreated check plots and (ii) the significantly lower (α = 0.05) ratio of 1988:1987 attacked trees in the treated plots. Further, the number of trees per hectare resisting attacks (as reflected by number of trees pitching out bark beetles) was higher (α = 0.05) in the treated plots. More pitch outs occurred in treated plots presumably because avoidance of verbenone by beetles reduced the number of beetles below that needed to overcome the natural resistance of attacked trees.

The watershed provides a physical basis for establishing linkages between aquatic contaminants, environmental health and human health. Current attempts to establish such linkages are limited by environmental and epidemiological constraints. Environmental limitations include difficulties in characterizing the temporal and spatial dynamics of agricultural runoff, in fully understanding the degradation and metabolism of these compounds in the environment, and in understanding complex mixtures. Epidemiological limitations include difficulties associated with the organization of risk factor data and uncertainty about which measurable endpoints are most appropriate for an agricultural setting. Nevertheless, it is our contention that an adoption of the watershed concept can alleviate some of these difficulties. From an environmental perspective, the watershed concept helps identify differences in land use and application of agrichemicals at a level of resolution relevant to human health outcomes. From an epidemiological perspective, the watershed concept places data into a construct with environmental relevance. In this perspectives paper, we discuss how the watershed can provide a conceptual framework for studies in environmental and human health.

Pendimethalin dissipation was studied following annual 1.7 kg ai ha7l applications to 3-yr-old Kentucky bluegrass turf growing on a Sharpsburg silty clay loam soil and an 85/15 by volume sand/Sharpsburg soil mixture in 150-cm-deep rhizotron containers. Plant tissue, thatch, and soil were sampled periodically between application and 168 days after treatment (DAT). Soil and leachate were collected to monitor pendimethalin movement. Most of the herbicide appeared to remain within the turfgrass system. Pendimethalin concentration was highest in plant tissue and thatch. The 4-hydroxymethyl pendimethalin metabolite was detected in turfgrass tissue up to 42 DAT. No pendimethalin was detected at the 30-, 60-, or 120-cm depths in the rhizotron containers. Traces (?0.003 mg kg-1) of pendimethalin detected in rhizotron leachate collected between 6 and 14 days after heavy rainfall (88 and 95 DAT, respectively) were attributed to gravitational displacement of soil colloids containing adsorbed herbi- cide. Pendimethalin application to established turfgrass would not appear to pose a high risk of groundwater contamination. Nomenclature: Pendimethalin, N-(1-ethyl- propyl)-3,4-dimethyl-2,6-dinitrobenzenamine; Kentucky bluegrass, Poa pratensis L. Additional index words. Pendimethalin metabolite, thatch

Two experiments were conducted on the Kenai Peninsula, Alaska, to evaluate the effectiveness of acephate, dimethoate, and carbofuran delivered by Medicap implants in previously unattacked spruce trees [natural hybrids of Sitka (Picea sitchensis) and white spruce (P. glauca)] to prevent tree mortality (preventive treatment); and in successfully attacked spruce trees to kill brood of spruce beetle, Dendroctonus rufipennis, and thereby prevent tree mortality (remedial treatment). Tree mortality ranged from 60% to 93% in the treated trees and were judged as inadequate in preventing tree mortality. There was no evidence of egg, larval, pupae, or adult beetle mortality. Residue analysis of foliages removed from the crown of sample trees ranged from ca. 5 ppm 28-days postspray to ca 23 ppm 128 days postspray showing that acephate moved vertically into the tree crown. Neither carbofuran nor dimethoate were recovered from foliage samples. West. J. Appl. For. 6(1):4-7.

Pectinmethylesterase (PME) activity was found in the salivary glands of nymphs and adults of a leaf-footed bug, Leptoglossus occidentalis Heidemann. Puncture wounds in cone scales resulting from PME activity in the saliva of these bugs were seen by staining with a 0.05% aqueous solution of ruthenium red. This staining technique can be used to estimate feeding damage by L. occidentalis on cones of western white pine (Pinus monticola Dougl.), sugar pine (P. lambertiana Dougl.), and Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco).

Laboratory and greenhouse studies were con- ducted to determine imazaquin and imazethapyr adsorp- tion, mobility, and efficacy in Sharpsburg silty clay loam, Holdrege silt loam, and Tripp sandy loam soils after adjusting pH to 5, 6, and 7. Both herbicides were more strongly absorbed, less mobile, and less efficacious at a lower pH. Observations were attributed to ionic bonding resulting from protonation of basic functional groups on the herbicide molecules as pH decreased. Adsorption was greatest in the silty clay loam and least in the sandy loam soil. Conversely, the herbicides were more efficacious and mobile in the more coarse-textured soils. Imazethapyr was less mobile, more highly adsorbed, and more phytotoxic than imazaquin. Greater adsorption of imazethapyr was attributed to a stronger basic pKa and steric factors. Nomenclature: Imazethapyr, (?)-2-(4,5-dihydro-4-methyl- 4-(1-methylethyl)-5-oxo-lH-imidazol-2-yl)-5-ethyl-3-pyrid- inecarboxylic acid; imazaquin, 2-(4,5-dihydro-4-methyl- 4-(1-methylethyl)-5-oxo-lH-imidazol-2-yl)-3-quinolinecar- boxylic acid. Additional index words. Sorption, leaching, phytotoxicity, AC-252,214, AC-263,499.

This project was initiated by SERDP to quantify processes and determine the effectiveness of abiotic/biotic mineralization of energetics (RDX, HMX, TNT) in aquifer sediments by combinations of biostimulation (carbon, trace nutrient additions) and chemical reduction of sediment to create a reducing environment. Initially it was hypothesized that a balance of chemical reduction of sediment and biostimulation would increase the RDX, HMX, and TNT mineralization rate significantly (by a combination of abiotic and biotic processes) so that this abiotic/biotic treatment may be a more efficient for remediation than biotic treatment alone in some cases. Because both abiotic and biotic processes are involved in energetic mineralization in sediments, it was further hypothesized that consideration for both abiotic reduction and microbial growth was need to optimize the sediment system for the most rapid mineralization rate. Results show that there are separate optimal abiotic/biostimulation aquifer sediment treatments for RDX/HMX and for TNT. Optimal sediment treatment for RDX and HMX (which have chemical similarities and similar degradation pathways) is mainly chemical reduction of sediment, which increased the RDX/HMX mineralization rate 100 to150 times (relative to untreated sediment), with additional carbon or trace nutrient addition, which increased the RDX/HMX mineralization rate an additional 3 to 4 more » times. In contrast, the optimal aquifer sediment treatment for TNT involves mainly biostimulation (glucose addition), which stimulates a TNT/glucose cometabolic degradation pathway (6.8 times more rapid than untreated sediment), degrading TNT to amino-intermediates that irreversibly sorb (i.e., end product is not CO2). The TNT mass migration risk is minimized by these transformation reactions, as the triaminotoluene and 2,4- and 2,6-diaminonitrotoluene products that irreversibly sorb are no longer mobile in the subsurface environment. These transformation rates are increased 13 times further by chemical reduction of sediment. Dithionite reduction alone is not an effective treatment for TNT (intermediates that irreversibly sorb are not produced), even though the TNT degradation rate (to 2- or 4-aminodinitrotoluene) increases. « less

Reductive dehalogenation of chlorinated compounds is the most important process occurring within the zerovalent iron (Fe0) barrier. The relative reaction rates of individual halocarbons with Fe0 can vary considerably. This variability has been the stimulus for using various chemical descriptors for a priori predictions of transformation rates via linear free-energy relationships (LFERs). Our objective was to determine the efficacy of four molecular descriptors to describe the transformation rates of three chloromethanes, three chloroethanes, and six chloropropanes by Fe0. This was accomplished by generating an internally consistent set of rate constants under controlled environmental conditions (16 degrees C, anaerobic) and regressing the surface-area normalized rate constants (k(SA)) against (i) energy of the lowest unoccupied molecular orbital (E(LUMO)); (ii) vertical attachment energies (VAE); (iii) thermal electron attachment rate constants; and (iv) the molar response from a commercial electron capture detector (ECD). Results showed good correlations between k(SA)'s and all four descriptors (r2: 0.72-1.0), but a separate trend line was required for the chloromethanes and the chloro- ethanes/ propanes. Given the availability and ease with which ECD response can be obtained, this physical measurement may provide a practical means of determining relative rates of reactivity of various halocarbons in permeable reactive iron barriers.

The use of activated carbon may help overcome the toxicity of organic pollutants to microbes and plants during soil bioremediation. Experiments were conducted with 3,4-dichloroaniline (DCA), 2,4,6-trinitrotoluene (TNT), and polychlorinated biphenyls (PCB) to demonstrate that activated carbon (AC) can reduce the toxicity of readily available chemicals in soil by transferring them to a less toxic soil fraction. This process results in accelerated biodegradation of DCA by inoculated chloroaniline-degrading strains. In the case of TNT, the AC promotes strong binding through accelerated microbial reduction of its nitro groups and catalytic chemical oxidation of the methyl group and polymerization or binding of the products formed. Degradation of PCB in soil is rather slow. However, amendment with AC leads to a sharp reduction of extractable PCB, mostly due to strong binding to the adsorbent. The introduced AC was shown to maintain a low content of toxicants in soil solution, creating favorable conditions for plant growth, while in the unamended soils plants die or are highly inhibited. Biotests with Daphnia magna also demonstrated a sharp reduction of the toxicity of these contaminated soils in the presence of AC.

The wide use of cadmium (Cd) in batteries and semiconductors poses human and environmental health hazards when these materials are disposed. Citrobacter sp. JH 11-2, isolated from soil at an abandoned mining site, shows potential for use as a biosorbent for Cd removal from aqueous solution. A minimal inhibitory concentration of 300 mg L−1 indicated high tolerance of the strain to Cd. The strain effectively removed 47.7% of the Cd from a 100 mg L−1 solution within 160 h. Cell fractioning revealed that most of the Cd (43.5%) was in the membrane fraction, while 38.5% was in the peptidoglycan layer and 18.0% was in the cytoplasmic fraction. Fourier transform infrared spectroscopy (FTIR) confirmed the presence of functional groups on dried Citrobacter sp. JH 11-2 cells that can adsorb or complex Cd ions. A Langmuir model provided a good fit to Cd removal by the cells, which followed pseudo-second-order kinetics. Results support further development of Citrobacter sp. JH 11-2 as a biosorbent for Cd removal.

Electron capture detectors (ECDs) are widely used in gas chromatography to detect electronegative compounds. In this work, we examine the connections between the ECD response and the cross sections for dissociative electron attachment (DEA) determined from low energy electron beam studies in the chloroalkane family, stressing in particular the role of temporary anion state energies. We show that attachment rate coefficients computed from these cross sections are well correlated with ECD response, and that the latter decreases exponentially with increasing energies of the lowest anion states. ECD measurements are also carried out in monochloroalkanes substituted with unsaturated ethenyl and phenyl moieties, and the response is shown to depend strongly on the mixing between the unsaturated pi* and the C-Cl sigma* temporary anions as exhibited by the vertical attachment energies (VAEs) of these states. The results show good correlations between the chloroalkene and phenyl chloride ECD responses and the VAEs for the mixed states.

The Sudden Oak Death Second Science Symposium provided a forum for current research on sudden oak death, caused by the exotic, quarantine pathogen, Phytophthora ramorum. Ninety papers and forty-six posters on the following sudden oak death/P. ramorum topics are included: biology, genetics, nursery and wildland management, monitoring, ecology, and diagnostics. Several papers on P. kernoviae and other forest Phytophthora species are also presented.

Finely ground and pretreated iron substrates known as "zerovalent iron" or "Fe0" are used as reductants in the environmental remediation of halogenated hydrocarbons, and the composition of their surfaces significantly affects their reactivity. Samples of unannealed and annealed (heat-treated under H2/N2) zerovalent iron were analyzed using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Surface concentration of the iron and of the impurities observed by XPS and AES, carbon, chlorine, sulfur, and oxygen, were measured before and after soaking in trichloroethylene (TCE) and in water saturated with TCE (H2O/TCE) to simulate chlorocarbon remediation conditions. Samples pretreated by annealing at high temperature under H2 contained less iron carbide. The carbide contaminant was evident in both iron and carbon XPS spectra, with binding energies of 709.0 and 283.3 eV for the Fe 2p3/2 and C 1s, respectively. The annealed Fe0 surface also contained more sulfur. The carbide concentration was essentially unchanged by TCE and H2O/TCE exposure, whereas the sulfur decreased in proportion to chlorine adsorption following the dechlorination reaction. While oxygen concentration is initially lower on the annealed substrate surface, it rapidly increased during the model TCE remediative treatment process and thus does not represent a significant effect of the annealing process on surface reactivity.

Soils contaminated from military operations often contain mixtures of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), and TNT (2,4,6-trinitrotoluene) rather than a single explosive. Differences among explosives in solubility and reactivity make developing a single remediation treatment difficult. When Fe(0) was used to treat a munitions-contaminated soil, we observed high rates of destruction for RDX and TNT (98%) but not HMX. Our objective was to determine if HMX destruction by Fe(0) could be enhanced by increasing HMX solubility by physical (temperature) or chemical (surfactants) means. To determine electron acceptor preference, we treated RDX and HMX with Fe(0) in homogeneous solutions and binary mixtures. Increasing aqueous temperature (20 to 55 degrees C) increased HMX solubility (2 to 22 mg L(-1)) but did not increase destruction by Fe(0) in a contaminated soil slurry that also contained RDX and TNT. Batch experiments using equal molar concentrations of RDX and HMX demonstrated that RDX was preferentially reduced over HMX by Fe(0). By testing various surfactants, we found that the cationic surfactants (HDTMA [hexadecyltrimethylammonium bromide], didecyl, and didodecyl) were most effective in increasing HMX concentration in solution. Didecyl and HDTMA were also found to be highly effective in facilitating the transformation of HMX by Fe(0). Using HDTMA or didecyl solutions (3%, w/v) containing solid-phase HMX, we observed that 100% of the added HMX was transformed by Fe(0) in the didecyl matrix and 60% in the HDTMA matrix. These results indicate that cationic surfactants can increase HMX solubility and facilitate Fe(0)-mediated transformation kinetics but HMX destruction rates will be slowed when RDX is present.

High pesticide concentrations in soil from spills or discharges can result in point-source contamination of ground and surface waters. Cost-effective technologies are needed for on-site treatment that meet clean-up goals and restore soil function. Remediation is particularly challenging when a mixture of pesticides is present. Zerovalent iron (Fe0) has been shown to promote reductive dechlorination and nitro group reduction of a wide range of contaminants in soil and water. We employed Fe0 for on-site treatment of soil containing > 1000 mg metolachlor, > 55 mg alachlor, > 64 mg atrazine, > 35 mg pendimethalin, and > 10 mg chlorpyrifos kg(-1). While concentrations were highly variable within the windrowed soil, treatment with 5% (w/w) Fe0 resulted in > 60% destruction of the five pesticides within 90 d and increased to > 90% when 2% (w/w) Al2(SO4)3 was added to the Fe0. GC/MS analysis confirmed dechlorination of metolachlor and alachlor during treatment. Our observations support the use of Fe0 for ex situ treatment of pesticide-contaminated soil.

Electron transfer from zerovalent iron (Fe0) to targeted contaminants is affected by initial Fe0 composition, the oxides formed during corrosion, and surrounding electrolytes. We previously observed enhanced metolachlor destruction by Fe0 when iron or aluminum salts were present in the aqueous matrix and Eh/pH conditions favored formation of green rusts. To understand these enhanced destruction rates, we characterized changes in Fe0 composition during treatment of metolachlor with and without iron and aluminum salts. Raman microspectroscopy and X-ray diffraction (XRD) indicated that the iron source was initially coated with a thin layer of magnetite (Fe3O4), maghemite (gamma-Fe2O3), and wustite (FeO). Time-resolved analysis indicated that akaganeite (beta-FeOOH) was the dominant oxide formed during Fe0 treatment of metolachlor. Goethite (alpha-FeOOH) and some lepidocrocite (gamma-FeOOH) formed when Al2(SO4)3 was present, while goethite and magnetite (Fe3O4) were identified in Fe0 treatments containing FeSO4. Although conditions favoring formation of sulfate green rust (GR(II); Fe6(OH)12SO4) facilitated Fe0-mediated dechlorination of metolachlor, only adsorption was observed when GR(II) was synthesized (without Fe0) in the presence of metolachlor and Eh/pH changed to favor Fe(III)oxyhydroxide or magnetite formation. In contrast, dechlorination occurred when magnetite or natural goethite was amended with Fe(II) (as FeSO4) at pH 8 and continued as long as additional Fe(II) was provided. While metolachlor was not dechlorinated by GR(II) itself during a 48-h incubation, the GR(II) provided a source of Fe(II) and produced magnetite (and other oxide surfaces) that coordinated Fe(II), which then facilitated dechlorination.

Successful microbial-mediated remediation requires transformation pathways that maximize metabolism and minimize the accumulation of toxic products. Pseudomonas aeruginosa strain MX, isolated from munitions-contaminated soil, degraded 100 mg TNT L(-1) in culture medium within 10 h under aerobic conditions. The major TNT products were 2-amino-4,6-dinitrotoluene (2ADNT, primarily in the supernatant) and 2,2'-azoxytoluene (2,2'AZT, primarily in the cell fraction), which accumulated as major products via the intermediate 2-hydroxylamino-4,6-dinitrotoluene (2HADNT). The 2HADNT and 2,2'AZT were relatively less toxic to the strain than TNT and 2ADNT. Aminodinitrotoluene (ADNT) production increased when yeast extract was added to the medium. While TNT transformation rate was not affected by pH, more HADNTs accumulated at pH 5.0 than at pH 8.0 and AZTs did not accumulate at the lower pH. The appearance of 2,6-diamino-4-nitrotoluene (2,6DANT) and 2,4-diamino-6-nitrotoluene (2,4DANT); dinitrotoluene (DNT) and nitrotoluene (NT); and 3,5-dinitroaniline (3,5DNA) indicated various routes of TNT metabolism and detoxification by P. aeruginosa strain MX.

Under anoxic conditions, zerovalent iron (Fe(0)) reduces nitrate to ammonium and magnetite (Fe3O4) is produced at near-neutral pH. Nitrate removal was most rapid at low pH (2-4); however, the formation of a black oxide film at pH 5 to 8 temporarily halted or slowed the reaction unless the system was augmented with Fe(2+), Cu(2+), or Al(3+). Bathing the corroding Fe(0) in a Fe(2+) solution greatly enhanced nitrate reduction at near-neutral pH and coincided with the formation of a black precipitate. X-ray diffractometry and scanning electron microscopy confirmed that both the black precipitate and black oxide coating on the iron surface were magnetite. In this system, ferrous iron was determined to be a partial contributor to nitrate removal, but nitrate reduction was not observed in the absence of Fe(0). Nitrate removal was also enhanced by augmenting the Fe(0)-H2O system with Fe(3+), Cu(2+), or Al(3+) but not Ca(2+), Mg(2+), or Zn(2+). Our research indicates that a magnetite coating is not a hindrance to nitrate reduction by Fe(0), provided sufficient aqueous Fe(2+) is present in the system.

Permeable zerovalent iron (Fe°) barriers have become an established technology for remediating contaminated ground water. This same technology may be applicable for treating pesticides amenable to dehalogenation as they move downward in the vadose zone. By conducting miscible displacement experiments in the laboratory with metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide; a chloroacetanilide herbicide] under unsaturated flow, we provide proof-of-concept for such an approach. Transport experiments were conducted in repacked, unsaturated soil columns attached to vacuum chambers and run under constant matrix potential (-30 kPa) and Darcy flux (approximately 2 cm d -1 ). Treatments included soil columns equipped with and without a permeable reactive barrier (PRB) consisting of a Fe 0 -sand (50:50) mixture supplemented with Al 2 (SO 4 ) 3 . A continuous pulse of 14 C-labeled metolachlor (1.45 mM) and tritiated water ( 3 H 2 O) was applied to top of the columns for 10 d. Results indicated complete (100%) metolachlor destruction, with the dehalogenated product observed as the primary degradate in the leachate. Similar results were obtained with a 25:75 Fe 0 -sand barrier but metolachlor destruction was not as efficient when unannealed iron was used or Al 2 (SO 4 ) 3 was omitted from the barrier. A second set of transport experiments used metolachlor-contaminated soil in lieu of a 14 C-metolachlor pulse. Under these conditions, the iron barrier decreased metolachlor concentration in the leachate by approximately 50%. These results provide initial evidence that permeable iron barriers can effectively reduce metolachlor leaching under unsaturated flow.

Activated carbon can remove 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitrobenzene (TNB) from aqueous solution and promote oxidation of TNT. After equilibrating a 0.35 mM TNT solution with activated carbon (0.2-1% w/v), HPLC and GC/MS analysis confirmed the presence of 2,4,6-trinitrobenzaldehyde (TNBAld) and 2,4,6-trinitrobenzene (TNB), and provided strong evidence supporting 2,4,6-trinitrobenzyl alcohol (TNBAlc) as an intermediate of TNT oxidation. After 6 d, TNT and its oxidation products were strongly bound to the activated carbon, while TNB was extractable with acetonitrile. Observations indicate that activated carbon catalyzes TNT oxidation to TNBAlc, which is readily oxidized to TNBAld and TNB in the absence of activated carbon under dark conditions. While adsorbed TNB was extractable with acetonitrile, activated carbon promoted rapid TNT oxidation and formation of unextractable residues. Strong binding is attributed to catalyzed oxidation of the TNT methyl group, probably through a free radical mechanism, and subsequent chemisorption of oligomers and polymerized products that are not desorbed from micropores. Our observations indicate TNT oxidation and bound residue formation after sorption by activated carbon increases the effectiveness of activated carbon to decontaminate water.

Publisher Summary The objective of the research discussed in this chapter is to elucidate the mechanisms of 2,4,6-trinitrotoluene (TNT) transformation and detoxification in soil and to suggest an approach to accelerate this process through the addition of activated carbon. The persistence of TNT in highly contaminated soils can be attributed to toxicity to microorganisms and plants, which decreases the binding of residues. In the research discussed in the chapter, soil amendment with activated carbon accelerated TNT transformation and binding in soil containing 2000 and 1000 mg TNT/kg. Within 6 h after mixing with activated carbon, extractable TNT was reduced by 20 or 40%, compared to less than 10 or 15% decrease in unamended soil. Adding activated carbon to the soil decreased TNT concentrations in soil solution and created favorable conditions for growth of microorganisms and plants. It accelerated binding because the TNT reversibly adsorbed to the activated carbon became gradually available for microbial transformation. Moreover, the activated carbon sharply increased TNT binding through an oxidative mechanism(s). These observations indicate the potential use of activated carbon to minimize toxicity of TNT and its products, thus promoting further TNT transformation and bound residue formation in highly contaminated soils.

A near-field tracer study was conducted to study the movement and dispersion of gas in the lower forest canopy in an attempt to improve guidance for forest managers deploying anti-aggregation pheromone sources to protect high value forest stands. Data are shown from three forest canopies and include over 13000 chemical tracer samples compiled into half hour dispersion fields around a point source. A high frequency sampler was also deployed to ascertain the structure of the gas plumes at 1 Hz. The plumes showed strong Gaussian tendencies in many cases and very high peak-to-mean ratios. Average maximum ÷/Q values were relatively consistent over the canopies studied though high variance in the maximum ÷/Q values was observed.