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The imprints of fireworks displays on the adjacent water body were investigated from the perspective of cogeneration of black carbon, metals and perchlorate (ClO4−). In particular, the mixing and dissipation of ClO4− were studied at Oak Lake, Lincoln, Nebraska, following fireworks displays in 2015 and 2016. Following the display, ClO4− concentration in the water increased up to 4.3 μg/L and 4.0 μg/L in 2015 and 2016, respectively. A first-order model generally provided a good fit to the measured perchlorate concentrations from which the rate of dissipation was estimated as 0.07 d−1 in 2015 and 0.43 d−1 in 2016. SEM images show imprints of soot and metal particles in aerosol samples. EDS analysis of the lake sediment confirmed the presence of Si, K, Ca, Zn and Ba, most of which are components of fireworks. The δ13C range of −7.55‰ to −9.19‰ in the lake water system closely resembles fire-generated carbon. Cogeneration of black carbon and metal with perchlorate was established, indicating that ClO4− is an excellent marker of fireworks or a burning event over all other analyzed parameters. Future microcosmic, aggregation and column-based transport studies on black carbon in the presence of perchlorate and metals under different environmental conditions will help in developing transport and fate models for perchlorate and black carbon particles.

Island populations are rarely studied for risk of arsenic (As) poisoning. As poisoning, multimetal contamination and people's perceptions of health risks were assessed on India's Majuli Island, the largest inhabited river island in the world. This holistic approach illustrated the association of groundwater contamination status with consequent health risk by measuring levels of inorganic arsenic (iAs) in groundwater, borehole sediment and biological samples (hair, nails and urine). Piper and Gibbs's plots discerned the underlying hydrogeochemical processes in the aquifer. Demographic data and qualitative factors were evaluated to assess the risks and uncertainties of exposure. The results exhibited significant enrichment of groundwater with As, Mn and Fe along with significant body burden. Maximum Hazard Index values indicated severe non-carcinogenic health impacts as well as a significantly elevated risk of cancer for both adults and children. Most (99%) of the locally affected population did not know about the adverse health impacts of metal contamination, and only 15% understood bodily ailments and health issues. Various aspects of the island environment were used to elucidate the status of contamination and future risk of disease. A projection showed adverse health outcomes rising significantly, especially among the young population of Majuli, due to overexposure to not only As but also Ba, Mn and Fe.

by Jaehong Shim, Manish Kumar, Ritusmita Goswami,Payal Mazumder, Byung-Taek Oh and Patrick J. Shea

Light and bacteria can be used in combination to enhance secondary metabolite production during fermentation. Red yeast rice powder (RYRP) was inoculated with Bacillus subtilis (B2) isolated from freshwater seafood and incubated under light-emitting diodes (LEDs) of different colors (blue, green, red, white), fluorescent white light, and in darkness. Blue LED-mediated fermentation with B2 significantly enhanced production of phenolic compounds (68.4 ± 1 mg GAE/g DW) and flavonoids (51.7 ± 1 mg QE/g DW) compared to white light and darkness. Total antioxidant activity of RYRP extract after fermentation with B2 was > 77%; hydroxyl radical and superoxide scavenging were > 66%. DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) and ABTS (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid)) radical scavenging activities were 51% and > 67%, respectively. Reducing power was approximately twice that of extract from RYRP without B2. FTIR analysis showed a high content of hydroxyl, nitrile and carboxylic groups in the extract. Derivatives of cinnamic, benzoic and phophinodithioic acid, and quinazolinone were identified by GC–MS. Findings show that fermenting RYRP with B. subtilis B2 under blue LEDs enhances production of secondary metabolites, which should have applications in industrial fermentation processes.

Bacillus bacteria have major utility in large-scale production of industrial enzymes, among which proteases have particular importance. B. subtilis B22, an aerobic and chemotrophic strain, was isolated from kimchi and identified by 16S rRNA gene sequencing. Extracellular protease production was determined in basic medium, with 1% (w/v) casein as substrate, by submerged fermentation at 37 °C under blue, green, red and white light-emitting diodes (LEDs), white fluorescent light and darkness. Fermentation under blue LEDs maximized protease production (110.79 ± 1.8 U/mL at 24 h). Various agricultural waste products enhanced production and groundnut oil cake yielded the most protease (334 ± 1.8 U/mL at 72 h). Activity and stability of the purified protease were optimum at pH 7–10 and 20–60 °C. Activity increased in the presence of Ca2+, Mg2+ and Mn2+, while Fe2+, Zn2+, Co2+ and Cu2+ moderated activity, and Ni2+ and Hg2+ inhibited activity. Activity was high (98%) in the presence of ethylenediaminetetraacetic acid (EDTA) but inhibited by phenylmethanesulfonyl fluoride (PMSF). The protease was unaffected by nonionic surfactants, tolerated an anionic surfactant and oxidizing agents, and was compatible with multiple organic solvents. These properties suggest utility of protease produced by B. subtilis B22 under blue LEDs for industrial applications.

Here, metal oxides/hydroxide (MO = (PdO)n·[Pd(OH)2]m, Co(OH)2, and (PdO)n·[Pd(OH)2]m/CoO, n > m) clusters were successfully co-loaded on the surface of acid-treated molten salt fluxed TiO2 nanorods (ATO-NRs) via conventional wet impregnation. The synergistic effect of palladium oxide/palladium hydroxide and cobalt oxide [((PdO)n·[Pd(OH)2]m/CoO)] co-loading on ATO-NR demonstrated by the photocatalytic degradation of Orange II dye, bisphenol A and S. typhimurium inactivation under mimicked and unfiltered solar light (Xe arc lamp) radiation. Optimum [((PdO)n·[Pd(OH)2]m/CoO)] co-loaded ATO-NRs exhibited significantly higher degradation efficiency (Orange II (91%) and BPA (97%) within 30 min of treatment) over (PdO)n·[Pd(OH)2]m (n > m) and CoO/ATO-NRs under Xe arc lamp light radiation. Also, optimal sample showed higher inactivation efficiency for S. typhimurium than (PdO)n·[Pd(OH)2]m (n > m)/ATO and CoO/ATO-NRs under UVA light radiation, however, the photocatalytic mechanisms for S. typhimurium inactivation was different than the BPA. Photoelectrochemical analyses demonstrated that the significantly accelerated charge-transfer process in metal oxides/hydroxide cluster [(PdO)n·[Pd(OH)2]m/CoO] co-loaded ATO-NRs leading to higher degradation efficiency than other studied samples. Radical trapping supports h+ and O2 − as major reactive species, with OH playing a secondary role in Orange II and BPA degradation. Cell membrane interruption by reactive oxygen species (ROS) and reactions of photocatalyst with the –NH and –COOH group of protein and metalloproteins, nucleic acid in bacterial cells could be the main cause in S. typhimurium disinfection. Plausible charge transport pathways were proposed for photocatalytic degradation of organic pollutants and bacterial inactivation over the (PdO)n·[Pd(OH)2]m/CoO/ATO-NR’s.

The Barney M. Davis Power Plant in Corpus Christi, Texas, withdraws large quantities of water from the Laguna Madre for non-contact cooling. As a result, fish and shellfish may be harmed when impinged against screens intended to remove debris and wrack (floating sea grass). To reduce impingement it is important to understand related factors and their interrelationships. Several operational, water quality, and temporal factors were correlated with the total number of impinged organisms when the plant is pumping water. In this study, operational factors included hourly average flow and the number of screens in operation during sampling. Water quality factors included temperature, dissolved oxygen, pH, conductivity and salinity. Temporal factors included month and time of day of impingement sampling. Over the course of a year, fish and shellfish impinged on Passavant traveling drum screens were collected, classified, and counted. Multiple regression analyses were conducted and the number of organisms impinged was the response variable. Total impingement was most associated with dissolved oxygen concentration, sampling month and sampling time. For fish, sampling month and dissolved oxygen were most associated with impingement, while for shellfish, sampling month and sampling time were most important. Hourly flow and number of operating screens were not significant predictors of impingement.

A hydrothermally synthesized rhodium/antimony co-doped TiO2 nanorod and titanate nanotube (RS-TONR/TNT) composite was prepared for removal of heavy metals and organic pollutants from water under visible light irradiation. The composite provides the dual function of simultaneous adsorption of heavy metal ions and enhanced degradation of dissolved organic compounds. Acid treatment transformed titanate nanotubes to irregular tubular structures distributed homogeneously over untransformed RS/TONRs. Synergistic removal and degradation was studied with various heavy metals, Orange (II) dye, and Bisphenol A. The adsorption capacity of the composite for heavy metal ions was Pb(II) > Cd(II) > Cu(II) > Zn(II). The adsorbed metals enhanced photocatalytic degradation of the organic pollutants, but Cu was most effective, with degradation exceeding 70% for the dye and 80% for Bisphenol A after 5 h of treatment. Photocatalytic activity was enhanced more by adsorption than photodeposition of Cu ions. A decrease in XRD rutile peak intensity with adsorbed metal indicates a change in crystallinity which may enhance photocatalytic activity. Thick and bulging nanostructures in FE-SEM images signify ion adsorption within titanate pores. BET analysis indicated titanate nanotubes with adsorbed metal are mesoporous but their tubular structure persists. XPS showed more active Cu 2p3/2 states under light, supporting an active role of Cu+ in photocatalytic ROS generation. Detection of ROS and Cu species using methanol, EDTA, pCBA, and benzoic acid probes provided strong evidence for degradation via a charge transfer mechanism. Findings demonstrate the potential of the RS-TONR/TNT composite for simultaneous removal of heavy metals and degradation of organic pollutants.

For sustainable production, there is an urgent need to minimize the adverse environmental impacts of swine farming, which is a major contributor of the pollutants p-cresol and tylosin. Novel reactive composite alginate beads (CAB-MOACs) were fabricated by combining alginate with activated carbon (AC) and MnO

Arsenic (As) and fluoride (F−) in groundwater are increasing global water quality and public health concerns. The present study provides a deeper understanding of the impact of seasonal change on the co-occurrence of As and F−, as both contaminants vary with climatic patterns. Groundwater samples were collected in pre- and post-monsoon seasons (n = 40 in each season) from the Brahmaputra flood plains (BFP) in northeast India to study the effect of season on As and F− levels. Weathering is a key hydrogeochemical process in the BFP and both silicate and carbonate weathering are enhanced in the post-monsoon season. The increase in carbonate weathering is linked to an elevation in pH during the post-monsoon season. A Piper diagram revealed that bicarbonate-type water, with Na+, K+, Ca2+, and Mg2+ cations, is common in both seasons. Correlation between Cl− and NO3 − (r = 0.74, p = 0.01) in the post-monsoon indicates mobilization of anthropogenic deposits during the rainy season. As was within the 10 µg L−1 WHO limit for drinking water and F− was under the 1.5 mg L−1 limit. A negative correlation between oxidation reduction potential and groundwater As in both seasons (r = −0.26 and −0.49, respectively, for pre-monsoon and post-monsoon, p = 0.05) indicates enhanced As levels due to prevailing reducing conditions. Reductive hydrolysis of Fe (hydr)oxides appears to be the predominant process of As release, consistent with a positive correlation between As and Fe in both seasons (r = 0.75 and 0.73 for pre- and post-monsoon seasons, respectively, at p = 0.01). Principal component analysis and hierarchical cluster analysis revealed grouping of Fe and As in both seasons. F− and sulfate were also clustered during the pre-monsoon season, which could be due to their similar interactions with Fe (hydr)oxides. Higher As levels in the post-monsoon appears driven by the influx of water into the aquifer, which drives out oxygen and creates a more reducing condition suitable for reductive dissolution of Fe (hydr)oxides. An increase in pH promotes desorption of As oxyanions AsO4 3− (arsenate) and AsO3 3− (arsenite) from Fe (hydr)oxide surfaces. Fluoride appears mainly released from F−-bearing minerals, but Fe (hydr)oxides can be a secondary source of F−, as suggested by the positive correlation between As and F− in the pre-monsoon season.

Bacillus sp. strain JH 2-2, isolated from the rhizosphere of plants at a multi-metal contaminated mine site, has the potential to reduce Cr(VI) to Cr(III) and promote plant growth by reducing Cr toxicity and producing IAA. The minimum inhibitory concentration of Cr(VI) to Bacillus sp. JH 2-2 was 1000 mg L(-1) and the strain reduced 99% of 10 mg Cr(VI) L(-1) to Cr(IV) within 24 h. Lower Cr(VI) stress (10 mg L(-1) ) stimulated IAA production, but much less IAA was produced at 30 or 50 mg Cr(VI) L(-1) . Inoculation with Bacillus sp. JH 2-2 increased the length of Brassica juncea L. roots by 364% and stems by 735% in the presence of 10 mg Cr(VI) L(-1) from those of uninoculated control plants. These findings suggest potential use of Bacillus sp. JH 2-2 to promote phytoremediation of soil contaminated with Cr(VI).

Fungi can facilitate phytoremediation of mine tailing soil containing heavy metal(loid)s (HMs). Penicillium aculeatum PDR-4 and Trichoderma sp. PDR-16, isolated from the rhizosphere of Pinus koraiensis in mine tailing soil, exhibited high HM tolerance and plant growth-promoting characteristics. The isolates increased available P in a 1:1 (w/w) mixture of soil and liquid media by 14–43% and the bioavailability of As, Cu, Pb and Zn was also increased. Both isolates exhibited phosphatase, phytase and siderophore activity. ACC deaminase activity was greater in PDR-16 than in PDR-4; IAA was produced by PDR-4 but not by PDR-16. Sorghum-sudangrass (Sorghum bicolor × sudanense) produced 37–95% more aboveground dry biomass and contained 74–128% more chlorophyll in inoculated soil. In soil inoculated with both isolates, HM concentrations increased in roots by 109% (As), 39% (Cu), 50% (Pb) and 38% (Zn), and in shoots by 72% (As), 69% (Pb) and 82% (Zn) compared to those of control plants (Cu concentration did not increase in shoots). HM bioavailability and available soil P, as well as plant biomass, chlorophyll content and plant As, Pb and Zn concentrations were highest in soil inoculated with both fungi. Results suggest that inoculating soil with P. aculeatum PDR-4 and Trichoderma sp. PDR-16 will be beneficial for phytoremediation and production of sorghum-sudangrass as a bioenergy crop in HM-contaminated soils.

Vegetation is critical to stabilize and remediate mine tailing sites, but plant growth is often poor due to toxicity from heavy metal(loid)s (HMs). A non-symbiotic endophytic fungus, Trichoderma sp. PDR1-7, isolated from Pb-contaminated mine tailing soil, exhibited both high tolerance to HMs and desirable plant growth-promoting characteristics. PDR1-7 promoted HM solubilization in mine tailing soil and removed significant amounts of Pb and other HMs from liquid media containing single and multiple metals. Pb removal efficiency increased with initial pH from 4 to 6 and with Pb concentration from 100 to 125 mg L− 1. Inoculating soil with PDR1-7 significantly increased nutrient availability and seedling growth, chlorophyll and protein contents, as well as antioxidative enzyme (superoxide dismutase) activity. A decrease in malondialdehyde indicated less oxidative stress. HM concentrations were much higher in Pinus sylvestris roots when PDR1-7 was present. These observations suggest the utility of Trichoderma sp. PDR1-7 for pine reforestation and phytoremediation of Pb-contaminated mine soil.

The effectiveness of nanoscale zero-valent iron (nZVI) to remove heavy metals from water is reduced by its low durability, poor mechanical strength, and tendency to form aggregates. A composite of zeolite and nanoscale zero-valent iron (Z–nZVI) overcomes these problems and shows good potential to remove Pb from water. FTIR spectra support nZVI loading onto the zeolite and reduced Fe 0 oxidation in the Z–nZVI composite. Scanning electron micrographs show aggregation was eliminated and transmission electron micrographs show well-dispersed nZVI in chain-like structures within the zeolite matrix. The mean surface area of the composite was 80.37 m 2 /g, much greater than zeolite (1.03 m 2 /g) or nZVI (12.25 m 2 /g) alone, as determined by BET-N 2 measurement. More than 96% of the Pb(II) was removed from 100 mL of solution containing 100 mg Pb(II)/L within 140 min of mixing with 0.1 g Z–nZVI. Tests with solution containing 1000 mg Pb(II)/L suggested that the capacity of the Z–nZVI is about 806 mg Pb(II)/g. Energy-dispersive X-ray spectroscopy showed the presence of Fe in the composite; X-ray diffraction confirmed formation and immobilization of Fe 0 and subsequent sorption and reduction of some of the Pb(II) to Pb 0 . The low quantity of Pb(II) recovered in water-soluble and Ca(NO 3 ) 2 -extractable fractions indicate low bioavailability of the Pb(II) removed by the composite. Results support the potential use of the Z–nZVI composite in permeable reactive barriers.

The presence of mixed contaminants, such as BTEX (benzene, toluene, ethylbenzene and xylene isomers) can affect the biodegradation, fate and environmental impacts of each compound. To understand the influence of interactions among BTEX compounds on their biodegradation, four bacteria were isolated from oil-contaminated soil and assayed for BTEX biodegradation in vitro. The isolate exhibiting maximum biodegradation was identified as Pseudomonas putida based on the 16S rDNA sequence. The biodegradation of the BTEX compounds was greatly influenced by pH, temperature, and salinity. Substrate mixture studies (binary, tertiary and quaternary) revealed that the presence of toluene increased the biodegradation rate of benzene, ethylbenzene, and xylene.

Natural pigments are an important alternative to potentially harmful synthetic dyes. We investigated the feasibility of corn cob powder as a substrate for production of pigments by Monascus purpureus KACC 42430 in solid-state fermentation. A pigment yield of 25.42 OD Units/gram of dry fermented substrate was achieved with corn cob powder and optimized process parameters, including 60% (w/w) initial moisture content, incubation at 30°C, inoculation with 4mL of spores/gram of dry substrate, and an incubation period of 7 days. Pigment yield using corn cobs greatly exceeded those of most other agricultural waste substrates. The pigments were stable at acidic pH, high temperatures, and in salt solutions; all important considerations for industrial applications. Our results indicate the viability of corn cob substrate in combination with M. purpureus for industrial applications.

Zerovalent iron barriers have become a viable treatment for field-scale cleanup of various ground water contaminants. While contact with the iron surface is important for contaminant destruction, the interstitial pore water within and near the iron barrier will be laden with aqueous, adsorbed and precipitated Fe(II) phases. These freshly precipitated iron minerals could play an important role in transforming high explosives (HE). Our objective was to determine the transformation of RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), and TNT (2,4,6-trinitrotoluene) by freshly precipitated iron Fe(II)/Fe(III) minerals. This was accomplished by quantifying the effects of initial Fe(II) concentration, pH, and the presence of aquifer solids (Fe(III) phases) on HE transformation rates. Results showed that at pH 8.2, freshly precipitated iron minerals transformed RDX, HMX, and TNT with reaction rates increasing with increasing Fe(II) concentrations. RDX and HMX transformations in these solutions also increased with increasing pH (5.8-8.55). By contrast, TNT transformation was not influenced by pH (6.85-8.55) except at pH values6.35. Transformations observed via LC/MS included a variety of nitroso products (RDX, HMX) and amino degradation products (TNT). XRD analysis identified green rust and magnetite as the dominant iron solid phases that precipitated from the aqueous Fe(II) during HE treatment under anaerobic conditions. Geochemical modeling also predicted Fe(II) activity would likely be controlled by green rust and magnetite. These results illustrate the important role freshly precipitated Fe(II)/Fe(III) minerals in aqueous Fe(II) solutions play in the transformation of high explosives.

Activated carbon (AC) can help overcome toxicity of pollutants to microbes and facilitate soil bioremediation. We used this approach to treat a Histosol and an Alluvial soil historically contaminated with PCB (4190 and 1585 mg kg(-1), respectively; primarily tri-, tetra- and pentachlorinated congeners). Results confirmed PCB persistence; reductions in PCB extractable from control and AC-amended soils were mostly due to a decrease in tri- and to some extent tetrachlorinated congeners as well as formation of a bound fraction. Mechanisms of PCB binding by soil and AC were different. In addition to microbial degradation of less chlorinated congeners, we postulate AC catalyzed dechlorination of higher chlorinated congeners. A large decrease in bioavailable PCB in AC-amended soils was demonstrated by greater clover germination and biomass. Phytotoxicity was low in treated soils but remained high in untreated soils for the duration of a 39-month experiment. These observations indicate the utility of AC for remediation of soils historically contaminated with PCB.

AES, XPS and SIMS analyses were used to characterize the surface of Pantex aquifer sediment under pretreatment conditions previously shown to activate the sediment for remediation of the explosives-contaminated aquifer. The untreated sediment contains detectable concentrations of iron, but the composition is heterogeneous and the nature of the iron at the surface is poorly defined. Treatment with dithionite (Na2S2O4) produced Fe3O4-like material, as evidenced by characteristic Fe 2p XPS structure. Sediment treated with buffered dithionite (pH = 8.8) shows a higher Fe2+/Fe3+ ratio and retains strongly adsorbed FeS-like surface species even after copious washing with deionized water. The negative SIMS data indicate that, in the absence of the K2CO3 buffer, the dithionite treatment places relatively little sulfur onto the surface, but requires the higher buffered pH to form sulfide and sulfates. Detection of Fe3O4 and FeS on the sediment surface after dithionite treatment supports the effectiveness of this treatment in remediating contaminated aquifer sediment. SIMS and XPS indicate that treating with buffered dithionite also results in some loss of iron from the sediment surface. Copyright © 2009 John Wiley & Sons, Ltd.

Agrichemical spills and discharges to soil can cause point-source contamination of surface and ground waters. When high contaminant concentrations inhibit natural attenuation in soils, chemical treatments can be used to promote degradation and allow application of treated soils to agricultural lands. This approach was used to remediate soil containing >650 mg atrazine, >170 mg metolachlor and >18,000 mg nitrate kg−1. Results indicated a decrease in metolachlor concentration to 150 mg atrazine and >7000 mg nitrate kg−1 remained. Laboratory experiments confirmed that subsequent additions of sucrose (table sugar) to the chemically pretreated soil promoted further reductions in atrazine and nitrate concentrations. Field-scale results showed that adding 5% (w/w) sucrose to windrowed and pretreated soil significantly reduced atrazine (

Zerovalent iron (Fe 0 , ZVI) has drawn great interest as an inexpensive and effective material to promote the degradation of environmental contaminants. A focus of ZVI research is to increase degradation kinetics and overcome passivation for long-term remediation. Halide ions promote corrosion, which can increase and sustain ZVI reactivity. Adding chloride or bromide salts with Fe 0 (1% w/v) greatly enhanced TNT, RDX, and HMX degradation rates in aqueous solution. Adding Cl or Br salts after 24 h also restored ZVI reactivity, resulting in complete degradation within 8 h. These observations may be attributed to removal of the passivating oxide layer and pitting corrosion of the iron. While the relative increase in degradation rate by Cl − and Br − was similar, TNT degraded faster than RDX and HMX. HMX was most difficult to remove using ZVI alone but ZVI remained effective after five HMX reseeding cycles when Br − was present in solution.

The necessity of disinfecting playground soil is an important issue, because pathogenic protozoa, bacteria, and parasite eggs remain viable for several months and can infect children. UV irradiation has been used to decontaminate water but its effectiveness on soil is unclear. We determined the efficacy of UV radiation for inactivation of an indicator bacteria, E. coli (strain ATCC 8739), on playground soil. While 99% inactivation of E. coli in the soil was readily achieved by UV radiation within 55 min at 0.4 mW cm-2, complete inactivation was not achieved, even after prolonged treatment at 4 mW cm-2. This was attributed to the irregular surface of the soil. A small number of E. coli escaped the UV radiation because they were situated in indentations or under small particles on the soil surface. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) confirmed that the surface characteristics of the soil is the major limiting factor in the inactivation of E. coli by UV radiation. Thus UV treatment may not be adequate for disinfecting some soils and should be carefully evaluated before being used on playground soils.

The prevalent use of chloroacetanilide herbicides has resulted in nonpoint contamination of some groundwater and surface water. We determined the efficacy of dithionite-treated sediment and soils to transform chloroacetanilides. When used alone, dithionite rapidly dechlorinates chloroacetanilides in water, with the following order of reactivity: propachloralachloracetochlormetolachlor. Stoichiometric release of chloride occurs during reaction with dithionite, and thiosulfate herbicide derivatives are produced. Treating aquifer sediment with dithionite reduces native Fe(lII), creating a redox barrier of Fe(ll)-bearing minerals and surface-bound Fe(ll). Washing the reduced sediment (buffered with citrate-bicarbonate) with oxygen-free water removed Fe(ll) and excess dithionite and no alachlor transformation was observed. In contrast, a dithionite-treated surface soil, rich in clay and iron, effectively dechlorinated alachlor after washing. Exposing alachlor to aquifer sediment treated with dithionite in potassium carbonate buffer (pH 8.5-9.0) produced dechlorinated alachlor as the major degradation product. Our results provide proof-of-concept that dechlorination of chloroacetanilide herbicides by dithionite and dithionite-treated aquifer sediment and soil is a remediation option in natural environments where iron-bearing minerals are abundant.

Soil properties impact pesticide persistence. Because these characteristics operate together in situ, identification of their clustered associations can help explain pesticide fate. Factor analysis was used to reduce the dimensionality of soil characteristics by grouping them into clustered independent factors, which were then related to the mineralization of atrazine and selected degradation intermediates. A Sharpsburg silty clay loam, Ortello sandy loam, and Hord silt loam were inoculated with a Hord soil that had a high capacity for atrazine mineralization. The soils were spiked with 14C-radiolabeled atrazine, deethylatrazine, hydroxyatrazine, N-isopropylammeline, N-isopropylammelide or cyanuric acid and sampled during incubation for 80 d (atrazine) or 40 d (degradation intermediates) at 22°C. Low mineralization in uninoculated soils demonstrated that the absence of atrazine-mineralizing microorganisms was most limiting. In inoculated soils, regression analysis indicated mineralization of atrazine (R2 ...

Mixtures of energetic compounds pose a remediation problem for munitions-contaminated soil. Although treatment with zerovalent iron (Fe0) can be effective, RDX and TNT are more readily destroyed than HMX. Adding didecyldimethylammonium bromide (didecyl) at 2% w/v with 3% (w/v) Fe0 to a 20% slurry of Los Alamos National Laboratory soil containing solid-phase HMX (45 000 mg/kg) resulted in80% destruction within 6 days. Because the HMX concentration did not increase in solution and the didecyl equilibrium concentration was well below the critical micelle concentration, we conclude thatthe solution primarily contained didecyl monomers. The adsorption isotherm for didecyl on iron is consistent with electrostatic adsorption of monomers and some hydrophobic partitioning at low equilibrium concentrations. Fe0 pretreated with didecyl was superior to Fe0 alone or mixed with didecyl in removing HMX from solution, but it was less effective than Fe0 + didecyl when solid-phase HMX was present. Reseeding HMX to mimic dissolution indicated an initial high reactivity of didecyl-pretreated Fe0, but the reaction slowed with each HMX addition. In contrast, reaction rates were lower but reactivity was maintained when Fe0 and didecyl were added together and didecyl was included in fresh HMX solutions. Destruction of solid-phase HMX requires low didecyl concentrations in solution so that hydrophobic patches are maintained on the iron surface.

We evaluated the effectiveness of 4-allylanisole (4AA) as a protective treatment for loblolly pines threatened by the southern pine beetle, Dendroctonus frontalis Zimmermann. Three products were evaluated in combination with two methods that promoted attack of trees by D. frontalis. One method used attractive semiochemicals and the other decreased host resistance, both of which are important scenarios for implementing protective treatments of individual trees. Each method promoted mass attack of unprotected control trees, thus providing a statistically verifiable challenge to the candidate protectants. In trees with increased susceptibility, mortality ranged from 63% (untreated) to 77% (4AA applied in paintball formulation), and two products appeared to alter the relative composition of scolytid species that attacked at two heights; however, tree mortality was unaffected. In trees challenged with semiochemical attractants, mortality ranged from 54% (4AA released from vials) to 82% (untreated and paintball application of 4AA). Although 4AA consistently reduces catch of D. frontalis in traps, it was not efficacious for protecting individual loblolly pines over a period of 30 or 60 days in this experiment.

Dicamba (3,6-dichloro-2-methoxybenzoicacid) is a highly mobile pre- and post-emergence herbicide that has been detected in ground water. We determined the potential of zerovalent iron (Fe 0 ) to remediate water contaminated with dicamba and its common biological degradation product, 3,6-dichlorosalicylic acid (DCSA). Mixing an aqueous solution of 100 lM dicamba with 1.5% Fe 0 (w/v) resulted in 80% loss of dicamba within 12 h. Solvent extraction of the Fe 0 revealed that dicamba removal was primarily through adsorption; however when the Fe 0 was augmented with Al or Fe(III) salts, dicamba was dechlorinated to an unidentified degradation product. In contrast to dicamba, Fe 0 treatment of DCSA resulted in removal with some dechlorination observed. When DCSA was treated with Fe 0 plus Al or Fe(III) salts, destruction was 100%. Extracts of this Fe 0 treatment contained the same HPLC degradation peak observed with the Fe 0 + Al or Fe(III) salt treatment of dicamba. Molecular modeling suggests that differences in removal and dechlorination rates between dicamba and DCSA may be related to the type of coordination complex formed on the iron surface. Experiments with 14 C-labeled dicamba confirmed that Fe-adsorbed dicamba residues are available for subsequent biological mineralization (11% after 125 d). These results indicate that Fe 0 could be potentially used to treat dicamba and DCSA-contaminated water. 2003 Elsevier Ltd. All rights reserved.

The use of some adsorbents may decrease the toxicity of organic pollutants to microbes and plants during soil bioremediation. Experiments were conducted with 3,4-dichloroaniline (DCA) and 2,4,6-trinitrotoluene (TNT). Here we demonstrate that activated carbon can reduce the toxicity of readily available chemicals in soil by transferring them to a less available fraction. This process results in accelerated biodegradation of dichloroaniline by the inoculated Paracoccus denitrificans st. 3XA. In the case of TNT, activated carbon promotes strong binding through accelerated microbial reduction of its nitro-groups and catalytic chemical oxidation of the methyl-group and polymerisation or binding of the products formed.

Soils in Technical Area 16 at Los Alamos National Laboratory (LANL) are severely contaminated from past explosives testing and research. Our objective was to conduct laboratory and pilot-scale experiments to determine if zerovalent iron (Fe(0)) could effectively transform RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) in two LANL soils that differed in physicochemical properties (Soils A and B). Laboratory tests indicated that Soil A was highly alkaline and needed to be acidified [with H2SO4, Al2(SO4)3, or CH3COOH] before Fe(0) could transform RDX. Pilot-scale experiments were performed by mixing Fe(0) and contaminated soil (70 kg), and acidifying amendments with a high-speed mixer that was a one-sixth replica of a field-scale unit. Soils were kept unsaturated (soil water content = 0.30-0.34 kg kg(-1)) and sampled with time (0-120 d). While adding CH3COOH improved the effectiveness of Fe(0) to remove RDX in Soil A (98% destruction), CH3COOH had a negative effect in Soil B. We believe that this difference is a result of high concentrations of organic matter and Ba. Adding CH3COOH to Soil B lowered pH and facilitated Ba release from BaSO4 or BaCO3, which decreased Fe(0) performance by promoting flocculation of humic material on the iron. Despite problems encountered with CH3COOH, pilot-scale treatment of Soil B (12 100 mg RDX kg(-1)) with Fe(0) or Fe(0) + Al2(SO4)3 showed high RDX destruction (96-98%). This indicates that RDX-contaminated soil can be remediated at the field scale with Fe(0) and soil-specific problems (i.e., alkalinity, high organic matter or Ba) can be overcome by adjustments to the Fe(0) treatment.

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.

Corn cob silica (CCS), produced via a modification of the sol-gel method, can reduce heavy metal availability and stabilize contaminated soil on abandoned mining sites. Adding 5 % (w/w) CCS to mining site soil increased pH from 4.0 to 7.7, and cation exchange capacity increased from 94.5 to 100.3 cmol+/kg. Sequential extraction showed that adding CCS decreased heavy metal availability in the soil. Mobility factor (MF) values indicated that CCS reduced Pb mobility more than that of Zn or Cu in all fractions. Pb concentrations in leachate from all fractions using the toxicity characteristic leaching procedure (TCLP) were greatly decreased by adding 3 % (w/w) CCS. CCS similarly reduced Zn concentrations in TCLP leachate. CCS addition did not impact Cu concentrations in leachate, likely because concentrations were much lower than those of the other metals. As was generally less mobile than the heavy metals; however, As mobility and leachability tended to increase with CCS addition because its oxyanions arsenite and arsenate have low affinity for negatively charged surfaces on the CCS. Shoot and root growth of Spinacia oleracea L. (spinach) was much greater in CCS-treated soil than in unamended soil. Results demonstrate the utility of CCS to stabilize heavy metals in contaminated mining site soil, but this treatment may not be ideal for As-contaminated soils.

A bacterial strain (JH 70-4) exhibiting plant growth promoting characteristics (indoleacetic acid production and 1-aminocyclopropane-1-carboxylate deaminase activity), as well as heavy metal(loid) (HM) tolerance and Pb precipitation, was isolated from HM-contaminated soil at an abandoned mine site. The bacterium was identified as Pseudomonas fluorescens based on 16S rDNA sequencing. The JH 70-4 strain induced precipitation of Pb as PbS nanoparticles, confirmed by X-ray diffraction. Solution pH, incubation time, and Pb concentration influenced removal and PbS formation. Inoculating contaminated soil with JH 70-4 decreased Pb availability; exchangeable Pb decreased while organic- and sulphide-bound Pb increased. The toxicity characteristic leaching procedure showed a 65% decrease in Pb in leachate 60 d after inoculating soil with JH 70-4. Shoot and root lengths of Sudan grass grown in the inoculated soil were greater than in the uninoculated soil. Findings suggest that microbial Pb fixation is a viable strategy for remediating soil and promoting plant growth for phytostabilization of contaminated sites.

Endophytic bacteria have the potential to promote plant growth and heavy metal(loid) (HM) removal from contaminated soil. Pseudomonas koreensis AGB-1, isolated from roots of Miscanthus sinensis growing in mine-tailing soil, exhibited high tolerance to HMs and plant growth promoting traits. Transmission electron microscope (TEM) analysis revealed that AGB-1 sequestered HMs extracellularly and their accumulation was visible as dark metal complexes on bacterial surfaces and outside of the cells. DNA sequencing of HM resistance marker genes indicated high homology to the appropriate regions of the arsB, ACR3(1), aoxB, and bmtA determinants. Inoculating mining site soil with AGB-1 increased M. sinensis biomass by 54%, chlorophyll by 27%, and protein content by 28%. High superoxide dismutase and catalase activities, and the lower malondialdehyde content of plants growing in AGB-1-inoculated soil indicate reduced oxidative stress. Metal(loid) concentrations in roots and shoots of plants grown in inoculated soil were higher than those of the controls in pot trials with mine tailing soil. Results suggest that AGB-1 can be used in association with M. sinensis to promote phytostabilization and remediation of HM-contaminated sites.

Treating mixed contaminants with zerovalent iron (Fe0) for environmental remediation requires a thorough understanding of the competition among electron acceptors. The authors conducted aqueous batch tests to determine competitive reduction of nitrate, nitrite, and nitrobenzene by Fe0 under varying conditions. Results indicate that nitrate reduction by Fe0 was accompanied by substantial Fe0 oxidation by water. Nitrite and nitrobenzene were concomitantly reduced by Fe0, forming a lepidocrocite (γ-FeOOH) coating on the Fe0 grains. When present together, nitrite and nitrobenzene reduction proceeded without apparent interference from nitrate. Nitrate reduction, however, did not occur in the presence of nitrite or nitrobenzene. Adding aqueous Fe(II) facilitated nitrate reduction by Fe0, but not until the lepidocrocite coating on the Fe0 grains was transformed to magnetite (Fe3O4), a process that is significantly accelerated by surface-bound Fe(II). This study illustrates the relative reactivity of Fe0 ...

Bacillus sp. strain JH 2-2, isolated from the rhizosphere of plants at a multi-metal contaminated mine site, has the potential to reduce Cr(VI) to Cr(III) and promote plant growth by reducing Cr toxicity and producing IAA. The minimum inhibitory concentration of Cr(VI) to Bacillus sp. JH 2-2 was 1000 mg L(-1) and the strain reduced 99% of 10 mg Cr(VI) L(-1) to Cr(IV) within 24 h. Lower Cr(VI) stress (10 mg L(-1) ) stimulated IAA production, but much less IAA was produced at 30 or 50 mg Cr(VI) L(-1) . Inoculation with Bacillus sp. JH 2-2 increased the length of Brassica juncea L. roots by 364% and stems by 735% in the presence of 10 mg Cr(VI) L(-1) from those of uninoculated control plants. These findings suggest potential use of Bacillus sp. JH 2-2 to promote phytoremediation of soil contaminated with Cr(VI).

We reviewed the application of carbaryl (1-naphthyl N-methylcarbamate) against bark beetles (Scolytidae) in forest trees (Pinaceae) of North America. Our objective was to encapsulate carbaryl’s 30-yr history of successes and limitations against these beetles and to present appropriate safety and environmental information that relates to this usage.

Microbial degradation and detoxification of TNT (2,4,6-trinitrotoluene) in soils ultimately depends on the presence of effective intracellular or extracellular enzymes. TNT was rapidly degraded by an enzyme obtained from a Pseudomonas aeruginosa strain isolated from TNT-contaminated soil. The nitroreductase enzyme was purified to apparent electrophoretic homogeneity by sequential chromatography on phenyl-sepharose, hydroxyapatite, and ion exchange resins. The TNT-nitroreductase catalyzed reduction of TNT to 4-hydroxylamino-4,6-dinitrotoluene (4HADNT) and 4-amino-2,6-dinitrotoluene (4ADNT). TNT reduction to 4ADNT in cell-free enzyme preparations corresponded to 2ADNT production by intact cells. The enzyme required NADH as a cosubstrate and the optimal pH for the reaction was approximately 6.5. The purified enzyme also exhibited NADH diaphorase activity and its denatured molecular weight was approximately 54 kDa.

Activated carbon can be used to decrease 2,4,6-trinitrotoluene (TNT) toxicity and promote bioremediation of highly contaminated soil. Adding activated carbon at 0.25, 0.75, and 1.0% (w/w) to Sharpsburg soil contaminated with 500, 1,000, and 2,000 mg TNT/kg decreased concentrations of TNT and its transformation products in soil solution to 5 mg/L or less, resulting in low toxicity to corn plants (Zea mays L.) and soil microorganisms. As much as 50% of the added TNT was rapidly bound to the soil-activated carbon matrix. Simultaneous accumulation of 2,4,6-trinitrobenzaldehyde (TNBAld) indicated that the activated carbon promoted oxidation of TNT. Some of the TNBAld was further oxidized to 1,3,5-trinitrobenzene, followed by reduction to 3,5-dinitroaniline. Reversibly bound TNT was gradually transformed to 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene, and both were bound to the soil-activated carbon matrix. The transformation and binding of TNT to soil were further promoted by incorporating shredded corn plants after growing for 52 d in the activated carbon-amended soil. After 120 d, these amendments reduced extractable TNT and transformation products by 91% in soil containing 2,000 mg TNT/kg, compared to 55% in unamended soil. These results demonstrate the potential use of activated carbon in combination with plants to promote in situ bioremediation of soils highly contaminated with explosives.

Plants can be used for effective and economical remediation of soil provided they are tolerant or resistant to the contaminants. Greenhouse experiments were conducted to determine the tolerance of the cool-season grasses: smooth bromegrass (Bromus inermus Leyss.) and tall fescue (Festuca arundinaceae Schreb), and the warm-season grasses: big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum L.) to TNT (2,4,6-trinitrotoluene) in soil. TNT-contaminated soil was mixed with uncontaminated soil to obtain water-extractable TNT concentrations ranging from 71 to 435 mg kg-1, corresponding to acetonitrile-extractable concentrations of 278 to 3115 mg kg-1. Germination, shoot and root dry weight, and root area were measured in response to TNT concentrations in the soil mixtures. Germination and height of the warm-season grass species were more sensitive than the cool-season grass species to increasing TNT concentrations in soil. Significant reductions in shoot and root growth were obse...

Bioremediation of munitions-contaminated soil requires effective transformation and detoxification of high concentrations of 2,4,6-trinitrotoluene (TNT). Pseudomonas aeruginosa strain MX, isolated from munitions-contaminated soil, aerobically transformed TNT (100 mg/L) in culture medium within 15 h, causing transient accumulation of hydroxylaminodinitrotoluenes (HADNTs). The predominance of 2-hydroxylamino-4,6-dinitrotoluene (2HADNT), as well as 2-amino-4,6-dinitrotoluene (2ADNT) and 4,4′,6,6′ -tetranitro-2,2′ -azoxytoluene (2,2′AZT), indicated preferential reduction of the TNT ortho nitro group. While only 12% of the TNT was transformed to 2ADNT, up to 65% was transformed to tetranitroazoxytoluenes (AZTs), which accumulated as a precipitate. The precipitate was formed by microscopic particles adhering to bacterial cells, which subsequently formed clusters containing lysed cells. Toxicity toward bacteria was primarily attributed to 2ADNT, because pure AZTs preincubated with sterile medium had little effec...

Soil and water contaminated with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a serious environmental problem at several active and abandoned munitions production facilities. Zero-valent iron (Fe0) can effectively remediate RDX-contaminated soil and water. The objective of this study was to manipulate Eh and pH for enhanced Fe0-mediated destruction of RDX. This was accomplished by monitoring RDX destruction under controlled Eh-pH conditions (Eh: −300 to +150 mV; pH: 2−10). Decreasing Eh and pH increased RDX destruction in aqueous solution. Treating 20 mg of RDX L-1 (90 μM) under a static Eh of −150 mV and pH 7 with 20 g of Fe0 L-1 removed 95% of the RDX within 4 h; no RDX was detected after 8 h. Treating a soil slurry (20% solids; 510 mg RDX kg-1 soil) with 20 g of Fe0 L-1 at an Eh of −150 mV and pH 7 increased RDX destruction by 24% over the unbuffered control and resulted in 99% RDX destruction within 24 h. Adding 4.2 mM sodium sulfide (in lieu of a static Eh) under similar conditions resulted in 9...

Enhanced microbial activity and xenobiotic transformations take place in the rhizosphere. Degradation and binding of 2,4,6-trinitrotoluene (TNT) were determined in two rhizosphere soils (RS) and compared to respective unplanted control soils (CS). The rhizosphere soils were obtained after growing corn for 70 d in soils containing 2.8% (Soil A) or 5.9% (Soil B) organic matter. Aerobically agitated soil slurries (3:1, solution/soil) were prepared from RS and CS and amended with 75 mg TNT L−1 (14C-labeled). TNT degraded more rapidly and formed more un-extractable bound residue in RS than in CS. In Soil A, total extractable TNT decreased from 225 to 1.0 mg kg−1 in RS, whereas 11 mg kg−1 remained in CS after 15 d. Unextractable bound 14C residues accounted for 40% of the added 14C-TNT in RS and 28% in CS. The smaller differences in Soil B were attributed partially to the higher organic matter content. The predominant TNT degradation products were monoaminodinitrotoluenes (ADNT), which accumulated and disappear...

Soil and water contaminated with RDX (hexahydro-1,3,3-trifluoro-1,3,5-triazine) pose a serious threat to the environment and human health. Our objective was to determine the potential for using zero-valent iron (Fe 0 ) to remediate RDX-contaminated water and soil. Mixing an aqueous solution of 32 mg RDX L -1 (spiked with 14 C-labeled RDX) with 10 g Fe 0 L -1 resulted in complete RDX destruction within 72 h. Nitroso derivatives of RDX accounted for approximately 26% of the RDX transformed during the first 24 h; these intermediates disappeared within 96 h and the remaining 14 C products were water soluble and not strongly sorbed by iron surfaces. When RDX-contaminated soil (30 mg RDX kg -1 spiked with 14 C-RDX) was treated with a single amendment of Fe 0 (20 g kg -1 soil) in a static soil microcosm, more than 60% of the initial 14 C-RDX was recovered as 14 CO 2 after 112 d. Treating surface and subsurface soils containing 3600 mg RDX kg -1 with 50 g Fe 0 kg -1 at a constant soil water content (0.35-0.40 kg H 2 O kg -1 soil) resulted in a 52% reduction in extractable RDX following 12 mo of static incubation. A second Fe 0 addition at 12 mo further reduced the initial extractable RDX by 71% after 15 mo. These results support the use of zero-valent iron for in situ remediation of RDX-contaminated soil.