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Numerous drinking water plants and agricultural wastewaters generate water treatment residuals (WTR) during coagulation processes. These WTRs may be effective at reducing nutrients entering waterways, thereby decreasing the potential formation of algal blooms. Of the WTRs used in this study, Al-based WTR (Al-WTR) was the most effective achieving a 20 °C cumulative adsorbed concentrations (q e ) after 28 days of desorption of 63-76 mg PO 4 /kg Al-WTR depending on the initial spiked concentration. When the isotherm temperature was 5 °C, Al-WTR effectiveness decreased. Ferric chloride WTR (Fe-WTR) was only effective when 0.6 mg/L of PO 4 was spiked to surface water with 0.01 mg/PO 4 stored at 20 °C yielding a 28 day cumulative q e 5.67 mg PO4/kg Fe-WTR. At 5 °C, the cumulative q e after extended desorption was 1-4.63 mg/kg Fe-WTR. Ferrous sulfate based WTR (Fe2-WTR) was not capable of adsorbing any additional PO 4 regardless of the spiked concentration or temperature., (© 2020 The Author(s).)

Coal mine derived acid mine drainage (AMD) is formed when oxygenated water infiltrates mine voids and oxidizes FeS phases, generating acidic fluid rich in heavy metals, polluting thousands of miles of streams. Existing remediation options are cost-prohibitive and difficult to sustain. In some cases, AMD flows over previously pristine soil in thin sheets over terrestrial surface, enhancing AMD aeration and Fe(II) oxidizing activities, leading to oxidative Fe(II) precipitation from AMD, without any human intervention. Since robust Fe(II) biooxidation occurs in the mixture of intruding AMD and pristine soil, understanding the effects of chemically variant AMD can be exploited for effective Fe(II) removal. We hypothesized that chemistry and microbiology of AMD intruding pristine soil on surface would influence the development of Fe(II) oxidizing capabilities. Therefore, to investigate the response of pristine soil to the addition of AMD varying in chemical and microbial characteristics, we mixed soil with a near-neutral and moderately acidic AMD, in separate incubations. Incubations with near-neutral AMD developed microbial Fe(II) oxidation activities after 10 days. However, Fe(II) oxidation in moderately acidic AMD incubations was mostly abiotic. 16S rRNA gene sequences and metabolic functional prediction (Tax4Fun) analysis of near-neutral AMD and soil mixture indicated development of taxonomically different communities capable of activities similar to microorganisms in a mine void. In conclusion, results indicate that AMD chemistry and microbiology affects development of Fe(II) biooxidation. Therefore, understanding of the effect of AMD chemistry on the development of FeOB activities in soil can be exploited to design site-specific and sustainable solutions., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Phragmites australis has been used to treat acid mine drainage (AMD)-contaminated soil. However, the mechanism about metal translocation in reeds was not widely reported. This study investigated metal (Fe, Al, and Mn) storage location in reeds grown in five different sampling sites of an AMD field. As expected, the more metals in soil, the more metals entered the belowground organs of plants. Reeds grown in soils with the highest levels of metals accumulated 0.16 ± 0.04 mg/g Mn, 16.29 ± 4.15 mg/g Fe, and 1.31 ± 0.22 mg/g Al in roots. Most of the iron was sequestered in the roots, while Al was transferred to the shoots. Histological staining found that most of the iron was sequestered in the exodermis, while Al extended the endodermis of roots. Al even entered the stele of roots grown in soil with higher Al levels. The epidermis, cortex, and central cylinder of rhizomes were the main tissues for Fe and Al storage. The more metals in rhizomes, the stronger intensity of the staining was observed around the vascular systems of rhizomes. No structural difference was observed among reeds collected from different sites. Further studies may be needed to enhance the transfer of metals in reeds and increase the phytoremediation efficiency.

Wetland plants such as Phragmites australis has been used to treat acid mine drainage (AMD) contaminated soil which is a serious environmental issue worldwide. This project investigated metal plaque content(s) and metal uptake in reeds grown in an AMD field in winter and spring. The results indicated that the level of Fe plaque was much higher than Mn and Al plaque as the soil contained more Fe than Al and Mn. The amounts of Mn and Al plaque formed on reeds in spring were not significantly different from that in winter (p > .05). However, more Fe plaque was formed on reeds collected in spring. The concentrations of metals in underground organs were positively related to the metal levels in soils. More Mn and Al transferred to the aboveground tissues of reeds during the spring while the Fe levels in reeds did not significantly vary with seasons. Roots and rhizomes were the main organs for Fe sequestration (16.3 ± 4.15 mg/g in roots in spring) while most Al was sequestered in the shoots of reeds (2.05 ± 0.09 mg/g in shoots in spring). Further research may be needed to enhance the translocation of metals in reeds and increase the phytoremediation efficiency.

Studies were conducted to investigate the interactions among rhizosphere microorganisms, plaque formation, and metal accumulation in reeds [ (Cav.) Trin. ex Steud.] grown in an acid mine drainage-contaminated field. We found that Fe(II)-oxidizing bacteria (Fe(II)OB] played a key role in Fe plaque formation and pH decrease. The kinetics of Fe plaque formation were related to the abundance of rhizosphere Fe(II)OB, which mediated 66.0 to 93.3% Fe(II) oxidation. The Fe(II) concentration decreased from 14.24 to 0.94 mg L in nonsterile samples, with the most abundant Fe(II)OB activity (5.64 ± 3.83 × 10 colony-forming units g) after 2 d, and pH decreased from 2.91 to 2.50. The amount of metal plaque was also positively correlated with metal levels in soil. No significant correlations were found between Fe, Mn, and Al concentration in the plaque. Reeds sequestered Al in the aboveground tissues, and Mn and Al were stored in the roots and rhizomes. Metal plaque did not affect the Mn uptake but inhibited the translocation of Fe and Al in reeds. To increase the phytoremediation efficiency of Fe, Mn, and Al from the acid mine drainage-contaminated site, further research may be needed to inhibit the Fe(II)OB growth and reduce the metal plaque formation, thereby increasing the metal accumulation in reeds., (Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.)

The effect of citric acid (CA), rhizosphere acidophilic heterotrophs and/or Fe(II) oxidizing bacteria (Fe(II)OB) on plaque formation and metal accumulation in Phragmites australis L. (common reed) from acid mine drainage (AMD) solution were investigated. Reeds were grown in different hydroponic solutions that contained AMD, CA and/or rhizosphere bacteria for three months. Triplicate experiments were conducted for each experimental condition. Fe(II)OB enhanced the formation of Fe plaque which decreased Fe and Mn uptake in reeds, while it had no significant influence on Al accumulation. CA inhibited the growth of Fe(II)OB, decreased the formation of metal plaque and increased Fe and Mn accumulation in reeds. Acidophilic heterotrophs consumed CA and made the environment more suitable for the growth of Fe(II)OB. Reeds are a good candidate for phytoextraction while CA is a useful chelator to enhance metal uptake in plants. More research may be needed to investigate the influence of CA on microbial community. Further investigations are required to study the effect of CA on phytoremediation of AMD contaminated fields., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane(4,4'-DDT) is a pesticide well-known for its negative health and environmental effects. Despite being banned by a majority of world countries more than 30 years ago, its persistence in the environment is a continuing problem even today. The objective of the study was the investigation of sorption/desorption behavior of 4,4'-DDT in sandy loam soil. The impact of contaminant concentration and age was observed with three different experiments. The sorption percentages at the end of the short time step (8 h) were 50 and 92 %, for initial concentrations 2.26 and 5.28 mg/L, respectively. When freshly spiked soil was subjected to a conventional sorption study, 82 to 99.6 % of the initial aqueous DDT concentrations were sorbed within 24 h. When modeled with a Freundlich isotherm, the log K f was found to be 3.62. After six consecutive 24 h desorption steps, 33 to 96.6 % still remained in the soil. This was more pronounced for soils that had been aged for 60 days. After seven consecutive 24 h desorption steps of aged soil, the percent remaining sorbed to the soil were 44, 64, and 77 %, for 25, 250, and 500 mg/kg, respectively. All results show that 4,4-DDT has a tendency of sorbing to the soil rapidly and showing resistance to desorption. When comparing desorption values, aged soils were seen to desorb less than non-aged soils. This result was attributed to stronger binding to soil with increased contact time.

Acid mine drainage (AMD) adversely impacts many regions in the world. The interactions among citric acid (CA), rhizosphere bacteria and metal uptake in different types of Phragmites australis cultured in spiked AMD contaminated soil were investigated. Compared with non-contaminated reeds cultured under the same conditions, wild reeds harvested from a contaminated site accumulated more metals into tissues. Rhizosphere iron oxidizing bacteria (Fe(II)OB) enhanced the development of Fe plaque but had no significant impact on the formation of Mn and Al plaque on the root surface of either reeds. Plaque may restrain the accumulation of Fe and Mn into tissues of reeds. CA inhibited the growth of Fe(II)OB, reduced the formation of metal plaque and significantly elevated metal accumulations into both underground and aboveground biomass of reeds. The concentrations of Fe, Al and Mn were higher in belowground organs than aboveground tissues. The roots contained 0.28±0.01 mg/g Mn, 3.09±0.51 mg/g Al, 94.47±5.75 mg/g Fe, while the stems accumulated 0.19±0.01 mg/g Mn, 1.34±0.02 mg/g Al, 10.32±0.60 mg/g Fe in wild reeds cultured in soil added with 33,616 ppm CA. Further field investigations may be required to study the effect of CA to enhance phytoremediation of metals from real AMD contaminated sites.

Experiments were conducted to assess the impact of citric acid (CA) and rhizosphere bacteria on metal uptake in Phragmites australis cultured in a spiked acid mine drainage (AMD) soil. Rhizosphere iron-oxidizing bacteria (Fe(II)OB) enhanced the formation of Fe plaque on roots, which decreased the uptake of Fe and Mn. CA inhibited the growth of Fe(II)OB, decreased the formation of metal plaque, raised the metal mobility in soil, and increased the accumulation of metals in all tissues of the reeds. The higher the CA dosage, the more metals accumulated into reeds. The total amount of metals in reeds increased from 7.8 ± 0.5 × 10(-6) mol plant(-1) (Mn), 1.4 ± 0.1 × 10(-3) mol plant(-1) (Fe), and 1.0 ± 0.1 × 10(-4) mol plant(-1) (Al) in spiked soil without CA to 22.2 ± 0.5 × 10(-6) mol plant(-1) (Mn), 3.5 ± 0.06 × 10(-3) mol plant(-1) (Fe), and 5.0 ± 0.2 × 10(-4) mol plant(-1) (Al) in soil added with 33.616 g C6H8O7·H2O for per kilogram soil. CA could be effective at enhancing the phytoremediation of metals from AMD-contaminated soil.

Many of regions in the world have been affected by acid mine drainage (AMD). The study assessed the effect of rhizosphere bacteria and citric acid (CA) on the metal plaque formation and heavy metal uptake in Phragmites australis cultured in synthetic AMD solution. Mn and Al plaque were not formed, but Fe plaque which was mediated by rhizosphere iron oxidizing bacteria (Fe(II)OB) was observed on the root system of reeds. Fe plaque did not significantly influence the uptake of Fe, Al and Mn into tissues of reeds. CA significantly (p<0.01) inhibited the growth of Fe(II)OB and decreased the formation of Fe plaque. CA also significantly improved (p<0.05) the accumulation of Fe, Mn and Al in all the tissues of reeds. Roots and rhizomes were the main organs to store metals. The roots contained 0.08±0.01mg/g Mn, 2.39±0.26mg/g Fe and 0.19±0.02mg/g Al, while the shoots accumulated 0.04±0.00mg/g Mn, 0.20±0.01mg/g Fe, 0.11±0.00mg/g Al in reeds cultured in solution amended with 2.101g/l CA and without inoculation of rhizosphere bacteria., (Copyright © 2014 Elsevier Inc. All rights reserved.)

To assess the microbiological changes that occur during the maturation of overburden that has been disturbed by surface mining of coal, a surface mining-disturbed overburden unit in southeastern Ohio, USA was characterized. Overburden from the same unit that had been disturbed for 37 and 16 years were compared to undisturbed soil from the same region. Overburden and soil samples were collected as shallow subsurface cores from each subregion of the mined area (i.e., land 16 years and 37 years post-mining, and unmined land). Chemical and mineralogical characteristics of overburden samples were determined, as were microbial respiration rates. The composition of microbial communities associated with overburden and soil were determined using culture-independent, nucleic acid-based approaches. Chemical and mineralogical evaluation of overburden suggested that weathering of disturbed overburden gave rise to a setting with lower pH and more oxidized chemical constituents. Overburden-associated microbial biomass and respiration rates increased with time after overburden disturbance. Evaluation of 16S rRNA gene libraries that were produced by "next-generation" sequencing technology revealed that recently disturbed overburden contained an abundance of phylotypes attributable to sulfur-oxidizing Limnobacter spp., but with increasing time post-disturbance, overburden-associated microbial communities developed a structure similar to that of undisturbed soil, but retained characteristics of more recently disturbed overburden. Our results indicate that over time, the biogeochemical weathering of disturbed overburden leads to the development of geochemical conditions and microbial communities that approximate those of undisturbed soil, but that this transition is incomplete after 37 years of overburden maturation.

In the medical field, attached bacteria can cause infections associated with catheters, incisions, burns, and medical implants especially in immunocompromised patients. The problem is exacerbated by the fact that attached bacteria are ∼1000 times more resistant to antibiotics than planktonic cells. The rapid spread of antibiotic resistance in these and other organisms has led to a significant need to find new methods for preventing bacterial attachment. The goal of this research was to evaluate the effectiveness of novel polymer coatings to prevent the attachment of three medically relevant bacteria. Tests were conducted with Pseudomonas aeruginosa, Staphylococcus epidermidis, and Staphylococcus aureus for oligomers derived from modifications of natural rubber (cis 1,4-polyisoprene). The different oligomers were: PP04, with no quaternary ammonium (QA); MV067, one QA; PP06, three QA groups. In almost all experiments, cell attachment was inhibited to various extents as long as the oligomers were used. PP06 was the most effective as it decreased the planktonic cell numbers by at least 50% for all bacteria. Differences between species sensitivity were also observed. P. aeruginosa was the most resistant bacteria tested, S. aureus, the most sensitive. Further experiments are required to understand the full extent and mode of the antimicrobial properties of these surfaces., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The concentration and impact of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)-ethane (DDT) and its metabolites (DDE: 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene) on the environment was expected to decrease after its ban in the mid-1980s. Unfortunately, DDT contamination via its presence as an impurity in dicofol (2,2,2-trichloro-1,1-bis(4-chlorophenyl)ethanol) has led to a new source of contamination. This is particularly true especially in cotton production in Söke Plain, Turkey, where difocol-based pesticides are being used. The aim of this research was to investigate the extent and source of DDT contamination in cotton soils. Söke Plain soil samples were collected from 0-30, 30-60, and 60-90-cm depth and analyzed by GC/MS/MS. o,p'-DDT and p, p'-DDE were detected at 16.2 % and 17.6 % of the sites in the 0-30-cm depth of soils. In the 30-60 cm, p, p'-DDT (14.9 %), o, p'-DDE (8.1 %) and p, p'-DDE (2.7 %) were found in soil samples, and p, p'-DDT was the most prevalent with 9.5 % of the sampling sites. The dominant source of DDT particularly in the 60-90-cm depth was due to historic use of DDT. The presence of p, p'-DDE, o, p'-DDE and p,p'-DDT in the topsoil was attributed to recent dicofol applications.

The effectiveness of zosteric acid, a natural antifoulant from the marine seagrass Zostera marina, in preventing the attachment of quagga mussels, a biofouling bivalve, was investigated. Animals were exposed to water containing zosteric acid ranging from 0 to 1000 ppm, and their attachment to the container glass walls was tracked with time. 500 ppm zosteric acid was not effective at detaching animals that had already attached, but was able to prevent the attachment of most unattached animals for two days. The anti-fouling effect increased with higher concentration. Low concentrations (250 ppm and below) were not effective at preventing attachment; however, 1000 ppm zosteric acid prevented attachment of mussels for the first three days of zosteric acid exposure, and only 20% of the mussels were attached by day 4. In contrast, animals in control (no zosteric acid) solutions began to attach within one day. In conclusion, zosteric acid is an effective natural product deterrent of attachment of a biofouling bivalve.

Dilek National Park in Western Turkey is a protected habitat for several endangered and threatened species. In an attempt to protect the endangered species, the park was classified as a World Heritage Preserve. Even with this change, the animal and flora variety are still at risk from previous metal contamination. Water samples were collected 10 cm below the water surface and sediment from 0-30 and 30-60 cm depth. Inorganic elements were found in all sediment samples. Sodium had the highest aqueous concentration (10,312 mg/L), while Cu, Fe, Mn, and Zn were present at levels significantly lower than the chronic exposure criteria. Zn was the least prevalent (0.4 mg/kg) compound found in the sediment. The highest toxic contaminant concentration was Mg at an average of 1,100 mg/kg. The main contamination source of that seems to be Great Meandrous River. More studies are needed to develop a protection and remediation strategy for Dilek National Park.

Turkey is one of the world's largest producers and exporters of table grapes. Growing social concerns over excessive pesticide use have led to farming to move from conventional to organic practices. Table grapes were collected from 99 different farms in three Aegean regions. Pesticide residues were only detected in farms using conventional agriculture practices while no pesticides were detected in grapes from farms using organic or integrated pest management. A risk assessment model indicated that lambda-cyhalothrin posed the most significant risk at conventional farms.

National parks are used worldwide as a means to protect the ecological integrity of unique ecosystems. Dilek National Park in western Turkey is a protected habitat for several endangered and severely threatened species. Thirty-seven water and 59 sediment samples were collected and analyzed for pesticides at two different sampling depths. The park is contaminated with 16 different organochlorine pesticides, with more pesticides detected in sediments than in water. The most prevalent pesticides in the 30-60-cm depth were DDT (69.5% of the samples), heptachlor (62.3%), a-endosulfan (55% of samples), and endrin (37%). Lindane isomers were present, but at <30% of the sediment samples. These pesticides could be a long-term contamination source that enters the food web used by the very species the park is trying to protect.

Dried grapes make the ideal low-calorie snack. The formation of gray mold during the drying of the grapes can severely decrease production. Pesticides and fungicides are applied to prevent losses due to pests and mold. Dried grapes from 99 farms in the Aegean region were sampled for pesticide residues. Of the 26 pesticides analyzed for, chlorpyrifos methyl, chlorpyrifos ethyl, deltamethrin, lambda-cyolathrin, dichlofluanid, iprodione, and procymidone were detected in the dried grapes. Only seven samples contained residues above the maximum residue limit. It is important to note that pesticide residues were only present in samples originating from vineyards using conventional farming practices.

Background, Aim, and Scope: Dicofol is widely used as a pesticide in agriculture applications. Since dicofol is mainly synthesized from dichlorodiphenyltrichlorethane (DDT), it contains DDT as an impurity. The European Community has forced Prohibition Directive 79/117/EEC to reduce DDT in dicofol formulations. Specifically, DDT content in a dicofol formulation cannot exceed 0.1%. The goal of this project was to determine the DDT content in dicofol formulations used in Turkey., Materials and Methods: Samples of all the dicofol formulations in Turkey were collected to quantify DDT and DDT-related compounds. Four replicates were used for each sample. GC/MS/MS was used to analyze p,p' and o,p' isomers of DDT, DDD, and DDE. A HPLC was used to determine p,p'-Cl-DDT concentrations., Results: The total DDT content of the formulated dicofol was found between 0.3% and 14.3%. The concentration of p,p'-DDE ranged from 167 to 1,042 mg kg(-1) in dicofol samples. p,p'-DDT concentrations were found to be 32 to 183 mg kg(-1). The o,p'-DDT level ranged from 2 to 34 mg kg(-1) in the dicofol formulations analyzed., Discussion: It was estimated that 617.8 kg of DDT was released from dicofol. The main impurity was identified as p,p-Cl-DDT. Based on these results, dicofol serves as a continuing source of DDT contamination., Conclusions: All DDT concentrations in dicofol samples analyzed were higher than the permitted 0.1% level of Prohibition Directive 79/117/EEC. The reduction of dicofol is critical since it serves as a continual source of DDT contamination., Recommendations and Perspectives: DDT has been found in soil, water, and air samples. Dicofol has been identified as a contributor to continued DDT contamination in soil and water. More studies are needed to ascertain the source of DDT in the air.

Sundance sunflowers were subjected to contaminated solutions containing 3, 4, or 5 heavy metals, with and without EDTA. The sunflowers exhibited a metal uptake preference of Cd=Cr>Ni, Cr>Cd>Ni>As and Fe>>As>Cd>Ni>Cr without EDTA and Cr>Cd>Ni, Fe>>As>Cd>Cr>Ni with EDTA. As uptake was not affected by other metals, but it decreased Cd and Ni concentration in the stems. The presence of Fe improved the translocation of the other metals regardless of whether EDTA was present. In general, EDTA served as a hindrance to metal uptake. For the experiment with all five heavy metals, EDTA decreased Cd in the roots and stems from 2.11 to 1.36 and from 2.83 to 2.3 2mg g(-1) biomass, respectively. For the same conditions, Ni in the stems decreased from 1.98 to 0.94 mg g(-1) total metal uptake decreased from 14.95 mg to 13.89 mg, and total biomass decreased from 2.38 g to 1.99 g. These results showed an overall negative effect in addition of EDTA. However it is unknown whether the negative effect was due to toxicity posed by EDTA or the breaking of phytochelatin-metal bonds. The most important finding was the ability of Sundance sunflowers to achieve hyperaccumulator status for both As and Cd under all conditions studied. Ni hyperaccumulator status was only achieved in the presence of three metals without EDTA.

Goal, Scope and Background: Pentachlorophenol (PCP) is the second highest volume pesticide used in the United States. It is a mutagenic compound whose exposure poses significant health effects, One of the most desirable, environmentally friendly treatment methods is bioremediation. For soil-based contamination, the effectiveness of bioremediation will also be affected by the presence of an active indigenous population, sorption of the contaminant onto the soil, and environmental parameters., Methods: Two pure strains and their mixed culture were used to evaluate PCP biodegradation in two different field soils, Columbia (CO) and New Mexico (NM). Biostimulation of the indigenous microbes was evaluated by adding nutrients. The efficiency of adding bacteria strains (bioaugmentation) for degrading PCP was determined with Arthrobacter sp., Flavobacterium sp. and a 50:50 mixture of the two bacteria strains., Results: In CO soil, only 24%, 12% and 25% of the initial PCP concentration were degraded by Flavobacterium sp., Arthrobacter sp. and mixed culture, respectively. Arthrobacter sp. was used in NM soil with two initial concentrations and achieved degradation efficiencies of 57% and 61% for 361 and 95 mg kg- concentrations, respectively. Discussion. Analysis via statistical methods showed that the bacteria had different efficiencies on PCP degradation in each soil. 2, Conclusions: All bacteria catalyzed a higher PCP degradation when present in NM soil. Second, Flavobacterium sp. degraded more PCP than Arthrobacter sp. in CO soil. The mixed culture achieved the highest degradation efficiency regardless of the initial concentration or soil origin., Recommendations and Perspectives: The effect of the soil properties, such as the soil organic matter (SOM) on PCP biodegradation should be investigated. Future work can also investigate the effect of aging time on biodegradation.

Response surface methodology (RSM) was used to evaluate the effect of additives for enhancing the aerobic biodegradation of trichloroethylene (TCE). The parameters investigated include the initial TCE concentration, addition of extra bacteria, use of toluene as an inducer and hydrogen peroxide as terminal electron acceptor (TEA). Without additive, degradation efficiencies of >or=80% were obtained for TCE concentrations<700 mg/L. According to the second-order polynomial RSM and biodegradation results, the use of toluene to induce enzyme production inhibited degradation at TCE concentrations<300 mg/L. The addition of hydrogen peroxide did improve the overall degradation efficiency but decreased the degradation rate. The RSM model for toluene, extra bacteria and TEA predicted that the best approach to optimize degradation of high TCE concentrations is to ensure adequate population in conjunction with supplemental TEA.

Pentachlorophenol (PCP) contamination is a severe environmental problem due to its widespread occurrence, toxicity and recalcitrance. In order to gain a better understanding of the fate of PCP in soils, the role of the soil organic matter (SOM) and clay minerals in the PCP sorption-desorption was studied on two bulk field soils, two subsoils (i.e., SOM or clay-removed soil) and two artificial soils. The two field soils used were a silty loam from New Mexico (NM) containing 10% clay and a sandy-clay-loam from Colombia (CO) South America comprised of 18% clay minerals. The bulk CO soil containing kaolinite sorbed significantly less PCP than the NM soil. All soils depicted an apparent hysteresis during sorption. The CO bulk and subsoils desorbed 14-20% and 15-26% of the sorbed PCP respectively whereas the NM bulk and subsoils desorbed only 4-12% and 5-16%, respectively. Experiments conducted with pure clay and artificial soils indicated that the expandable clay minerals were key sorbent material. Additional studies to investigate the interaction between SOM and clay minerals are needed to fully understand sorptive phenomena.

The use of two EDTA concentrations for enhancing the bioavailability of cadmium, chromium, and nickel in three natural soils (Ohio, New Mexico and Colombia) was investigated. The resulting uptake, translocation and selectivity with Helianthus annuus after mobilization were also examined. In general, plants grown in the sandy-loam Ohio soil had a higher uptake that resulted in a selectivity and total metal content of Cd>Cr>>Ni and 0.73 mg and Cr>Cd>>Ni and 0.32 mg for 0.1 and 0.3 g kg-1 EDTA, respectively. With the silty-loam New Mexico soil, although the total metal uptake was not statistically different the EDTA level did alter the selectivity; Cd>Cr>>Ni (0.1 g kg-1 EDTA) and Cd>>Cr>Ni (0.3 g kg-1 EDTA). Conversely, with the Colombian (sandy clay loam) soil increasing the EDTA level resulted in a higher total metal uptake (0.62 mg) than the 0.1 g kg-1 (0.59 mg) treatment. For all three soils, the translocation of Cd was limited. Evaluating the mobile metal fraction with and without EDTA determined that the chelator was capable of overcoming mass transfer limitations associated with the expandable clay fraction in the soils. Root wash results and root biomass concentrations indicated that Cd sorption was occurring. Therefore limited Cd translocation was attributed to insufficient phytochelatin levels.

The traditional solution for preventing organisms from attaching to submerged surfaces is to apply antifouling coatings or biocides. Based on the varied defence mechanisms exhibited by biofilms, the antifoulant needs to prevent bacterial attachment during the early stages of biofilm formation. The potential of benzoic acid and sodium benzoate (NaB) as antifoulants for deterring freshwater bacterial attachment was evaluated with the antifoulants dispersed in solution or entrapped in silicone coatings. Effectiveness was based on the decrease in microbial attachment, limited toxicity, and minimum alteration of the properties of the coatings. The optimal NaB concentration when dispersed in solution, 700 mg l-1, resulted in a biofilm surface coverage of only 3.34% after four weeks. The model silicone, Sylgard 184, demonstrated a better overall performance than the commercial coating, RTV11. Sylgard 184 containing sodium benzoate had 41-52% less biofilm in comparison to the control Sylgard 184, whereas both the control and NaB-entrapped RTV11 coatings had significant biofilm coverage.

Trichloroethylene (TCE) and perchloroethylene (PCE) are two of the most frequently detected chlorinated organics found in groundwater. Biodegradation with a new aerobic consortium was used to ascertain the viability of bioremediation for waste minimization applications. After 1 week of treatment, the degradation rate constants, k, were between 0.004 and 0.012 d(-1) for initial concentrations of 54-664 microM TCE. When PCE was used as the sole contaminant, the k values were approximately 0.01 d(-1) regardless of the initial concentration. The addition of 0.2 microM toluene or phenol as an inducer dramatically increased TCE degradation. For instance, at 200 microM TCE the k value when toluene was added (0.03 d(-1)) was 2.2 times higher than without inducers (0.009 d(-1)). The addition of 0.2 microM phenol increased the rate constant by 58%. However, PCE degradation rates were not changed significantly.

The possibility to clean heavy metal contaminated soils with hyperaccumulator plants has shown great potential. One of the most recently studied species used in phytoremediation applications are sunflowers. In this study, two cultivars of Helianthus annuus were used in conjunction with ethylene diamine tetracetic acid (EDTA) and citric acid (CA) as chelators. Two different concentrations of the chelators were studied for enhancing the uptake and translocation of Cd, Cr, and Ni from a silty-clay loam soil. When 1.0 g/kg CA was used, the highest total metal uptake was only 0.65 mg. Increasing the CA concentration posed a severe phytotoxicity to both cultivars as evidenced by stunted growth and diminished uptake rates. Decreasing the CA concentration to 0.1 and 0.3 g/kg yielded results that were not statistically different from the control. EDTA at a concentration of 0.1 g/kg yielded the best results for both cultivars achieving a total metal uptake of approximately 0.73 mg compared to approximately 0.40 mg when EDTA was present at 0.3 g/kg.

This study was conducted to evaluate the influence of sorbent modification by synthetic, chemical/thermal weathering on the sorptive behavior of polycyclic aromatic hydrocarbons (PAHs). A clean sandy-clay-loam soil was subjected to Soxhlet extraction and PAH sorptive phenomena were evaluated based on quantity and quality changes in soil organic matter (SOM) and clay minerals. Critical changes in sorption capacity were found to depend on the initial PAH concentrations. Above 7 mg/l, weathering increased the PAH in comparison to that of unmodified soil, whereas it decreased when applied below this concentration. Similarly, less PAH was desorbed from the altered soil when PAH was applied above 7 mg/l. Therefore, when PAH was applied below 7 mg/l, quantitative reduction of sorbent amount (i.e., SOM and clay minerals) by soil weathering governed PAH sorptive behavior. However, when the PAH was applied above the critical limit, qualitative modifications in the sorbents facilitated an opposite trend. Sorbent swelling, removal of competing compounds, and possible changes in surface characteristics by Soxhlet extraction, together with increased concentration gradient effects were factors that resulted in dissimilar PAH sorptive phenomena, pivoting at the critical concentration.

The hypothesis evaluated was that sorption/desorption experiments conducted under nonequilibrium conditions would sorb/desorb smaller amounts of polycyclic aromatic hydrocarbons (PAHs) in comparison to those conducted under an equilibrium condition. The magnitude of phenanthrene's (PHEs) sorption coefficient was approximately the same for both equilibrium and nonequilibrium conditions. However, when the initial PHE concentrations were varied, sorption nonequilibrium resulted in a 1.4-4.8% decrease in the actual PHE sorbed than those obtained under equilibrium conditions. Similarly, thermodynamic nonequilibrium led to a smaller pyrene (PYR) desorption. For example, when PYR was initially spiked at 10 mg/L, a total of 3.1 mg PYR/kg was desorbed under desorption nonequilibrium, whereas 3.6 mg/kg when equilibrium had been achieved. Mechanistic analysis of sorptive phenomena with respect to soil organic matter (SOM), clay minerals, and dissolved organic matter (DOM) demonstrated that both expandable clays and aliphatic SOM served as main sorbents for PAH sorption/desorption; that DOM was not a primary desorptive factor; and the interaction with clay minerals were stronger than that with SOM.

Desorption and biodegradation of pyrene (PYR) were investigated and their relationships to soil characteristics were addressed. The results indicated that maximum achievable desorption was 30.2, 10.4, and 1.0 mg/kg for soils that had 1.7, 2.2, and 4.4 wt.% of expandable clays (smectite and vermiculite), respectively. Neither dissolved organic matter (DOM) nor total clay amounts made a good prediction of the desorption trend. Subsequently, the ease of desorption facilitated a faster aqueous biodegradation rate. The slowest aqueous biodegradation rate, 0.02 l/h, was achieved for the soil system that had the greatest amount of expandable clays, whereas the soil containing 1.7% expandable clays only achieved 0.73 l/h. The soil with 2.2% expandable clays depicted 0.41 l/h of aqueous biodegradation rate. A good linear correlation was obtained between maximum achievable desorption and aqueous biodegradation rate (R(2)=0.92). Soil analysis revealed that the total (soil+water) biodegradation reached was 65%, 78.3%, and 81.8% of the initial concentration (100 mg/kg) for the sandy clay loam (Colombian), sandy loam (Ohio), and silty loam (New Mexico) soils, respectively. This biodegradation extent was also in good agreement of expandable clay amount. Although aqueous PYR bioavailability was limited due to the strong association with the expandable clays, microbial movement and adhesion to those clays seemed to result in a great extent of the soil-phase biodegradation.

Background: Capsaicin, a non-toxic natural product antifoulant, is an attractive alternative to the currently used toxic metal-based antifoulants for protecting the submerged surfaces. The problem associated with conducting capsaicin experiments is its limited aqueous solubility., Methods: A procedure was developed to obtain the maximum capsaicin concentration in water. Capsaicin was first dissolved in one of the three organic solvents, methanol, ethanol, and acetone. The organic solvent was replaced by gradually adding distilled water and evaporating the organic solvent., Results: The best solvent for obtaining highest concentration of capsaicin in water was ethanol. A maximum capsaicin in water 6400 ppm was achieved by using 16 mg capsaicin dissolved in 0.8 ml ethanol followed with the addition of 2.5 ml distilled water in 0.2 ml increments and then slow evaporation of the solvent., Conclusion: The concentration obtained using our approach is well above the threshold concentration of capsaicin in deterring the marine organism attachments.

Degradation with an aerobic consortium was used to evaluate the bioremediation trichloroethylene (TCE) as a model substrate. After one week, 228-1186 mg TCE l(-1) was degraded at rates of 20-50 microg TCE l(-1) h(-1). The introduction of 10 mg toluene l(-1) enhanced the degradation rates for TCE when greater than 600 mg l(-1). Using isolated enzymes, a TCE degradation intermediate(s) appears inhibitory to the oxygenase enzymes thereby diminishing the overall degradation.

Pyrene and phenanthrene degradation was examined in both single and binary slurry systems for three different natural soils. It was found that the amount of total expandable clays (smectite and vermiculite) was in a good agreement with the achieved rate and extent of biodegradation. For instance, the intrinsic phenanthrene biodegradation rate was 626 microg/L/day for the soil with the largest expandable clay and 3203 microg/L/day for the soil with the least. Similarly, the smallest total pyrene biodegradation (65%) was found for the soil rich in expandable clays, compared to an 82% pyrene reduction in the soil that had the lowest amount. Mass transfer limitation after compound sorption to the clays was more pronounced for the more hydrophobic pyrene. In the presence of phenanthrene, total pyrene biodegradation increased by 2 to 7% due to cometabolism, while the total phenanthrene biodegradation was only enhanced by 0.5 to 5% in the binary system. This research demonstrated that expandable clays might govern the substrate availability to microorganisms and microbial accessibility to substrates. Therefore, the contribution of organic matter and expandable clays to sorption, desorption and biodegradation should be taken equally into account in order to better understand complex bioremediation issues.