Evidence for exocellular Arsenic in Fronds of Pteris vittata

The arsenic (As) hyperaccumulating fern species Pteris vittata (PV) is capable of accumulating large quantities of As in its aboveground tissues. Transformation to AsIII and vacuolar sequestration is believed to be the As detoxification mechanism in PV. Here we present evidence for a preponderance of exocellular As in fronds of Pteris vittata despite numerous reports of a tolerance mechanism involving intracellular compartmentalization. Results of an extraction experiment show that 43-71% of the As extruded out of the fronds of PV grown in 0.67, 3.3 and 6.7 mM AsV. SEM-EDX analysis showed that As was localized largely on the lower pinna surface, with smaller amounts on the upper surface, as crystalline deposits. X-ray fluorescence imaging of pinna cross-sections revealed preferential localization of As on the pinna surface in the proximity of veins, with the majority localized near the midrib. Majority of the As in the pinnae is contained in the apoplast rather than vacuoles. Our results provide evidence that exocellular sequestration is potentially a mechanism of As detoxification in PV, particularly at higher As concentrations, raising concern about its use for phytoremediation.

Water Treatment Residuals and Scrap Tire Rubber as Green Sorbents for Removal of Stormwater Metals

Bench scale tests were performed to evaluate two recycled wastes, water treatment residuals (WTR) and scrap tire rubber (STR), for adsorption of selected metals from urban stormwater, and assess their release from used sorbents. Aluminum-WTR alone could rapidly and effectively remove Cu, Pb, and Zn, while STR alone continuously released Zn accompanied with Cu and Pb adsorption. Zn leaching from STR was significantly reduced in the presence of WTR. Very little metals released from used combined adsorbents in NaNO3 solution, and only part of them were extracted with EDTA (a strong chelating agent), suggesting that metal release is not a concern in a typical stormwater condition. A combination of WTR and STR is a new, effective method for mitigation of urban stormwater metals-WTR can inhibit the STR leaching, and STR improves the hydraulic permeability of WTR powders, a limiting factor for stormwater flow when WTR is used alone.

Immobilization of tetracyclines in manure and manure-amended soils using aluminum-based drinking water treatment residuals

Veterinary antibiotics (VAs) are emerging contaminants of concern in the environment, mainly due to the potential for development of antibiotic-resistant bacteria and effect on microbiota that could interfere with crucial ecosystem functions such as nutrient cycling and decomposition. High levels of VAs such as tetracyclines (TCs) have been reported in agricultural soils amended with manure, which also has the potential to cause surface and groundwater contamination. Several recent studies have focused on developing methods to immobilize VAs such as composting with straw, hardwood chips, commercial biochar, aeration, mixing, heat treatment, etc. The major shortcomings of these methods include high cost and limited effectiveness. In the current study, we assessed the effectiveness of aluminum-based drinking water treatment residuals (Al-WTR) as a "green" sorbent to immobilize TCs in manure and manure-applied soils with varying physicochemical properties by laboratory incubation study. Results show that Al-WTR is very effective in immobilizing tetracycline (TTC) and oxytetracycline (OTC). The presence of phosphate resulted in significant (p < 0.01) decrease in TTC/OTC sorption by Al-WTR, but the presence of sulfate did not. attenuated total reflection (ATR)-FTIR spectroscopy indicate that TTC and OTC likely forming surface complexes via inner-sphere-type bonds in soils, manure, and manure-applied soils amended with Al-WTR.

Determination of Prometryn in Vetiver Grass and Water Using Gas Chromatography-Nitrogen Chemiluminescence Detection

Nitrogen chemiluminescence detector (NCD) is a nitrogen-specific detector that responds to ammonia, hydrazine, hydrogen cyanide and nitrogen oxide. A method to analyze the herbicide prometryn in plant and water samples was developed using gas chromatograph (GC) coupled with NCD. Extracts from plant (vetiver grass) and water matrices were analyzed for prometryn using an Agilent 7890A GC coupled with an Agilent 255 NCD in a split injection mode with a ratio of 2 : 1. Separation was carried out at 200°C and combustion at 1,018°C with H2 and O2 following optimized method development conditions. The percent recovery of prometryn in the two different matrices tested ranged from 81 to 107%, with relative standard deviations varying from 0.10 to 3.30% for spiked samples. Detection limit of the proposed method was 0.02 µg mL(-1) and the limit of quantification was 0.06 µg mL(-1). The proposed GC-NCD method was successfully applied to determine prometryn extracted from plant and water samples without potential interference of S-triazine, a pesticide from the same group.

Effect of solution properties, competing ligands, and complexing metal on sorption of tetracyclines on Al-based drinking water treatment residuals

In the current batch study, we investigated the effect of solution properties, competing ligands (phosphate (P(V)) and sulfate), and complexing metal (calcium (Ca(2+))) on tetracycline (TTC) and oxytetracycline (OTC) sorption by Al-based drinking water treatment residuals (Al-WTR). The sorption behavior for both TTC and OTC on Al-WTR was pH dependent. The sorption in absence of competing ligands and complexing metal increased with increasing pH up to circum-neutral pH and then decreased at higher pH. The presence of P(V) when added simultaneously had a significant negative effect (p < 0.001) on the sorption of TTC and OTC adsorbed by Al-WTR at higher TTC/OTC:P ratios. However, when P(V) was added after the equilibration of TTC and OTC by Al-WTR, the effect was minimal and insignificant (p > 0.1). The presence of sulfate had a minimal/negligible effect on the sorption of TCs by Al-WTR. A significant negative effect (p < 0.001) on the adsorption of TCs by Al-WTR was observed in the pH range below 5 and at higher TCs:Ca(2+) ratios, probably due to TCs-Ca(2+) complex formation. Fourier transform infrared (FTIR) analysis indicated the possibility of inner-sphere-type bonding by the functional groups of OTC/TTC on Al-WTR surface. Results from the batch sorption study indicate high affinity of Al-WTR for TCs in the pH range 4-8 (majorly encountered pH in the environment) in the presence of competing ligands and complexing metal.

Ambovex(®) as a novel immunological modulator drug for the treatment of hepatocellular carcinoma (HCC) in the liver: a Phase II clinical trial

Hepatocellular carcinoma (HCC) is a global public health problem, based on it being the fifth most common cancer and third leading cause of cancer-related mortality worldwide. The approved conventional treatment methods for HCC have shown life-threatening side effects with limited or negligible success, especially in multifocal HCC. As a consequence, new therapeutic approaches are being explored, including immunoregulatory molecules that may have the potential to treat or delay the progression of HCC. A novel pharmaceutical botanical drug - Ambovex(®), an immune-modulator molecule - was tested to treat or delay the progress of HCC. We conducted a 6-month randomized clinical trial with an additional 3-month washing period (no treatment) to evaluate the safety and efficacy of low-dose Ambovex oral spray in treating patients with HCC. The clinical study involved a total of 40 patients, with 33 in the treatment group and seven in the control group. The α-fetoprotein (AFP) levels were measured every month and ultrasound scans were performed at time zero and every 2 months thereafter. Computed tomography (CT) scans were performed for patients in the treatment group. Ambovex proved to be safe, as there were no significant side effects although some patients found that the drug has unpleasant taste. AFP analysis showed a significant decrease in its level (α=0.05; 95% confidence interval) in the treatment group when compared to the control group at 3 months (P=0.0031) and at 6 months (P=0.007). The ultrasound results showed improvement in the treated group, as evidenced by a significant decrease in the lesion numbers and sizes. The lesions in 38% of treated patients decreased from multiple to single with major improvements; 35% of patients exhibited a decrease from multiple lesions to multiple lesions with minor improvements, whereas 27% had stabilized lesions. CT scans in the treated group showed significant improvement, as there was complete disappearance of the lesions after 6 months of treatment with Ambovex in two patients. This clinical study showed the effective and promising results of Ambovex as an immunological modulator in treating HCC. Further exploration of Ambovex is recommended.

Effectiveness of urea in enhancing the extractability of 2,4,6-trinitrotoluene from chemically variant soils

One of the major challenges in developing an effective phytoremediation technology for 2,4,6-trinitrotoluene (TNT) contaminated soils is limited plant uptake resulting from low solubility of TNT. The effectiveness of urea as a solubilizing agent in increasing plant uptake of TNT in hydroponic systems has been documented. Our preliminary greenhouse experiments using urea were also very promising, but further characterization of the performance of urea in highly-complex soil-solution was necessary. The present study investigated the natural retention capacity of four chemically variant soils and optimized the factors influencing the effectiveness of urea in enhancing TNT solubility in the soil solutions. Results show that the extent of TNT sorption and desorption varies with the soil properties, and is mainly dependent on soil organic matter (SOM) content. Hysteretic desorption of TNT in all tested soils suggests irreversible sorption of TNT and indicates the need of using an extractant to increase the release of TNT in soil solutions. Urea significantly (p<0.0001) enhanced TNT extraction from all soils, by increasing its solubility at the solid/liquid interface. Soil organic matter content and urea application rates showed significant effects, whereas pH did not exert any significant effect on urea catalysis of TNT extraction from soil. The optimum urea application rates (125 or 350 mg kg(-1)) for maximizing TNT extraction were within the limits set by the agronomic fertilizer-N rates used for major agricultural crops. The data obtained from this batch study will facilitate the optimization of a chemically-catalyzed phytoremediation model for cleaning up TNT-contaminated soils.

Effect of particle size of drinking-water treatment residuals on the sorption of arsenic in the presence of competing ions

Arsenite [As(III)] and arsenate [As(V)] sorption by Fe- and Al-based drinking-water treatment residuals (WTR) was studied as a function of particle size at different pHs, and in the presence of competing ligands, namely, phosphate, citrate, and oxalate. Both WTRs showed high affinity for As oxyanions. However, Al-WTR showed higher As(III) and As(V) sorption capacity than Fe-WTR because of their greater surface area. The effect of particle size on As sorption was pronounced on Fe-WTR, where the smaller fraction sorbed more As(III) and As(V) than the larger fractions, whereas relatively minor effects of particle size on As sorption was observed for Al-WTR. Arsenite sorption on both WTRs increased with increasing pH up to circum-neutral pHs and then decreased at higher pHs, whereas As(V) sorption decreased steadily with increasing pH. The capacity of competing ligands to inhibit sorption was greater for As(III) than As(V) on both WTRs (particularly on Al-WTR) following the sequence: oxalate<citrate<phosphate. It was also a function of As ion residence time on the WTR surfaces: the longer the residence time, the less effective were the competing ligands in As desorption.

Effectiveness of Aluminum-based Drinking Water Treatment Residuals as a Novel Sorbent to Remove Tetracyclines from Aqueous Medium

Low levels of various veterinary antibiotics (VAs) have been found in water resources across the United States as a result of nonpoint-source pollution. As the first phase of developing a potential green sorbent for tetracycline (TTC) and oxytetracycline (OTC), we examined the effects of solution chemistry, pH, ionic strength (IS), sorbate:sorbent ratio (SSR), and reaction time on TTC and OTC sorption by a waste byproduct of the drinking-water treatment process, namely, Al-based drinking-water treatment residuals (Al-WTR). The sorption of TTC and OTC on Al-WTR increased with increasing pH up to pH 7 and decreased in the pH range of 8 to 11. A concentration of 20 g L was deemed as optimum SSR, where more than 95% of the initially added TTC and OTC were sorbed and equilibrium was reached in 2 h. A pseudo-second-order model ( = 0.99) was used for Al-WTR sorption for TTC and OTC. The data best fit the linearized form of the Freundlich isotherm ( = 0.98). No significant effect ( > 0.05) of IS on sorption of TTC and OTC was observed between 0.05 and 0.5 mmol L. However, at higher initial concentrations (>1 mmol L), IS dependence on TTC and OTC sorption was observed. Surface complexation modeling and Fourier transform infrared spectroscopy analysis indicated the possibility of TTC and OTC forming a mononuclear monodentate surface complex through strong innersphere-type bonds on Al-WTR. The results show promising potential of Al-WTR for use as a "green" and cost-effective sorbent to immobilize and stabilize TTC in soils and waters.

Mechanisms of ciprofloxacin removal by nano-sized magnetite

An understanding of the interaction mechanisms of antibiotics with environmentally relevant sorbents is important to determine the environmental fate of antibiotics and to develop wastewater treatment strategies. Magnetite (Fe(3)O(4)(s)) is ubiquitous in the environment and occurs as a secondary corrosion product of iron nanoparticles that are commonly used as a remediation material. In this study, we aimed to assess the sorption mechanisms of ciprofloxacin (CIP), an important class of fluoroquinolone antibiotics, with magnetite nanoparticles using a combination of wet chemical and in situ ATR-FTIR spectroscopic measurements. Ciprofloxacin sorption was characterized as a function of pH (3.4-8.0), CIP concentration (1-500 μM), ionic strength (0.5, 0.1, and 0.01 M NaCl), and competing anion such as phosphate (0.1mM) to cover a broad range of environmentally relevant geochemical conditions. Results indicated a bell-shaped sorption envelop where sorption of CIP on nano-Fe(3)O(4)(s) increased from 45% to 80% at pH 3.44-5.97; beyond that sorption gradually decreased to a value of 25% at pH 8.39. Phosphate had negligible effect on CIP sorption. In situ ATR-FTIR results indicated inner-sphere coordination of CIP at the magnetite surface mediated by carboxylic acid groups. Results suggest that nano-Fe(3)O(4)(s) has the potential to remove CIP from wastewater effectively.

Phytoremediation potential of vetiver grass [Chrysopogon zizanioides (L.)] for tetracycline

The presence of veterinary and human antibiotics in soil and surface water is an emerging environmental concern. The current study was aimed at evaluating the potential of using vetiver grass as a phytoremediation agent in removing Tetracycline (TC) from aqueous media. The study determined uptake, translocation, and transformation of TC in vetiver grass as function of initial antibiotic concentrations and exposure time. Vetiver plants were grown for 60 days in a greenhouse in TC contaminated hydroponic system. Preliminary results show that complete removal of tetracycline occurred within 40 days in all TC treatments. Initial concentrations of TC had significant effect (p < 0.0001) on the kinetics of removaL Tetracycline was detected in the root as well as shoot tissues, confirming uptake and root-to-shoot translocation. Liquid-chromatography-tandem-mass-spectrometry analysis of plant tissue samples suggest presence of metabolites of TC in both root and shoot tissues of vetiver grass. The current data is encouraging and is expected to aid in developing a cost-effective, in-situ phytoremediation technique to remove TC group of antibiotics from wastewater.

Antimony sorption at gibbsite-water interface

Antimony (Sb) is extensively used in flame retardants, lead-acid batteries, solder, cable coverings, ammunition, fireworks, ceramic and porcelain glazes and semiconductors. However, the geochemical fate of antimony (Sb) remained largely unexplored. Among the different Sb species, Sb (V) is the dominant form in the soil environment in a very wide redox range. Although earlier studies have examined the fate of Sb in the presence of iron oxides such as goethite and hematite, few studies till date reported the interaction of Sb (V) with gibbsite, a common soil Al-oxide mineral. The objective of this study was to understand the sorption behavior of Sb (V) on gibbsite as a function of various solution properties such as pH, ionic strength (I), and initial Sb concentrations, and to interpret the sorption-edge data using a surface complexation model. A batch sorption study with 20 g L(-1) gibbsite was conducted using initial Sb concentrations range of 2.03-16.43 μM, pH values between 2 and 10, and ionic strengths (I) between 0.001 and 0.1M. The results suggest that Sb (V) sorbs strongly to the gibbsite surface, possibly via inner-sphere type mechanism with the formation of a binuclear monodentate surface complex. Weak I effect was noticed in sorption-edge data or in the isotherm data at a low surface coverage. Sorption of Sb (V) on gibbsite was highest in the pH range of 2-4, and negligible at pH 10. Our results suggest that gibbsite will likely play an important role in immobilizing Sb (V) in the soil environment.

Symbiotic role of Glomus mosseae in phytoextraction of lead in vetiver grass [Chrysopogon zizanioides (L.)]

Lead (Pb) has limited solubility in the soil environment owing to complexation with various soil components. Although total soil Pb concentrations may be high at a given site, the fraction of soluble Pb that plants can extract is very small, which is the major limiting factor for Pb phytoremediation. The symbiotic effect of arbuscular mycorrhizal (AM) fungus, Glomus mosseae was examined on growth and phytoextraction of lead (Pb) by vetiver grass [Chrysopogon zizanioides (L.)]. A hydroponic study, Phase I (0, 1, 2, and 4mM Pb) was conducted followed by an incubation pot study, Phase II (0, 400, 800, and 1200 mg kg(-1) Pb) where vetiver plants were colonized with G. mosseae. The results obtained indicate that plants colonized by the AM fungi not only exhibit better growth (increase in plant biomass), but also significantly increase Pb uptake in root and higher translocation to the shoot at all given treatments. Moreover, plants colonized with AM fungi had higher chlorophyll content and reduced levels of low molecular weight thiols, indicating the ability to better tolerate metal-induced stress. Results from this study indicate that vetiver plants in association with AM fungi can be used for improved phytoextraction of Pb from contaminated soil.

Alternative amendment for soluble phosphorus removal from poultry litter

BACKGROUND, AIM, AND SCOPE

Alum (aluminum sulfate) is the currently preferred chemical amendment for phosphorus (P) treatment in poultry litter (PL). Aluminum-based drinking-water treatment residuals (Al-WTRs) are the waste by-product of the drinking-water treatment process and have been effectively used to remove P from aqueous solutions, but their effectiveness in PL water extracts has not been studied in detail. Elevated cost associated with alum could be minimized by using the equally effective WTRs to remove soluble P from PL, and they can be obtained at a minimal cost from drinking-water treatment plants.

MATERIALS AND METHODS

We set up batch and incubation experiments to determine: (1) the effect of WTR amendment rates on PL water-extractable P (WEP) concentrations and (2) the effects of incubation time, pH, and temperature on WEP concentrations of WTR-amended PL.

RESULTS

Removal of PL-soluble P by the WTR was biphasic, showing an initial fast reaction (60% removal within 10 min) followed by a slower reaction that was completed within 12 days (90% removal). Phosphorus removal by the WTR was unaffected by pH changes in the range of 3-8. Incubation experiments showed that all WTR rates (2.5-15 wt.%) significantly (p < 0.001) lowered WEP concentrations in PL to approximately 40% of the unamended PL (no WTR) at 23 degrees C.

DISCUSSION

Minimal reduction (20% of the unamended PL) in WEP concentrations for all WTR rates were observed up to 18 days, possibly due to P diffusion limitations. Increasing the temperature to 35 degrees C resulted in overcoming such diffusion limitations by increasing P removal rate of reaction.

CONCLUSIONS

Assuming year-round availability of adequate quantities in nearby drinking-water treatment plants, WTR may be a cost-effective treatment to reduce P availability in poultry litter.

RECOMMENDATIONS AND PERSPECTIVES

Field experiments are greatly needed in order to demonstrate the excellent performance of WTR in this laboratory-based study to remove soluble P concentrations in animal waste.

Fate of arsenic in swine waste from concentrated animal feeding operations

Swine diets are often supplemented by organoarsenicals, such as 3-nitro-4-hydroxyphenylarsonic acid (roxarsone) to treat animal diseases and promote growth. Recent work reported roxarsone degradation under anaerobic conditions in poultry litter, but no such data exist for swine wastes typically stored in lagoons nearby concentrated animal feeding operations (CAFOs). The objectives of this study were to: (i) characterize a suite of swine wastes collected from 19 randomly selected CAFOs for soluble arsenate [As(V)], arsenite [As(III)], dimethylarsenic acid (DMA), monomethylarsonic acid (MMA), 3-amino-4-hydroxyphenylarsonic acid (3-HPPA), p-arsanilic acid, and roxarsone, and (ii) determine the geochemical fate of roxarsone in storage lagoons nearby CAFOs. Swine waste suspensions were spiked with roxarsone and incubated under dark/light and aerobic/anaerobic conditions to monitor roxarsone degradation kinetics. Arsenic speciation analysis using liquid chromatography and inductively coupled plasma mass spectrometry (LC-ICPMS) illustrated the prevalence of As(V) in swine waste suspensions. Roxarsone underwent degradation to either organoarsenicals (3-HPPA) or As(V) and a number of unidentified metabolites. Roxarsone degradation occurred under anaerobic conditions for suspensions low in solids content, but suspensions higher in solids content facilitated roxarsone degradation under both anaerobic and aerobic conditions. Increased solids content enhanced roxarsone degradation kinetics under aerobic conditions. According to current waste storage and sampling practices, arsenic in swine wastes stored in lagoons has been overlooked as a possible environmental health issue.