Human Health Risk Assessment of the Photocatalytic Oxidation of BTEX over TiO2/Volcanic Glass.

This study demonstrates rapid photocatalytic oxidation of a benzene, toluene, ethylbenzene, and xylene (BTEX) mixture over TiO2/volcanic glass. The assessment of the photocatalytic oxidation of BTEX was conducted under conditions simulating those found in indoor environments affected by aromatic hydrocarbon release. We show, under UV-A intensities of 15 mW/cm2 and an air flow rate of 55 m3/h, that low ppmv levels of BTEX concentrations can be reduced to below detectable levels. Solid-phase microextraction technique was employed to monitor the levels of BTEX in the test chamber throughout the photocatalytic oxidation, lasting approximately 21 h. Destruction of BTEX from the gas phase was observed in the following sequence: o-xylene, ethylbenzene, toluene, and benzene. This study identified sequential degradation of BTEX, in combination with the stringent regulatory level set for benzene, resulted in the air quality hazard indexes (Total Hazard Index and Hazard Quotient) remaining relatively high during the process of photocatalytic oxidation. In the practical application of photocatalytic purification, it is crucial to account for the slower oxidation kinetics of benzene. This is of particular importance due to not only its extremely low exposure limits, but also due to the classification of benzene as a Group 1 carcinogenic compound by the International Agency for Research on Cancer (IARC). Our study underscores the importance of taking regulatory considerations into account when using photocatalytic purification technology.

Characterization of Environmental Levels of Pesticide Residues in Household Air and Dust Samples near a Bioenergy Plant Using Treated Seed as Feedstock.

Exposure to neonicotinoid insecticides is associated with adverse human health outcomes. There is environmental contamination in Saunders County, Nebraska, due to the accumulation of fungicides and insecticides from a now-closed ethanol plant using seed corn as stock. A pilot study quantified environmental contamination in nearby houses from residual pesticides by measuring dust and air (indoor/outdoor) concentrations of neonicotinoids and fungicides at the study site (households within two miles of the plant) and control towns (20-30 miles away). Air (SASS® 2300 Wetted-Wall Air Sampler) and surface dust (GHOST wipes with 4 × 4-inch template) samples were collected from eleven study households and six controls. Targeted analysis quantified 13 neonicotinoids, their transformation products and seven fungicides. Sample extracts were concentrated using solid phase extraction (SPE) cartridges, eluted with methanol and evaporated. Residues were re-dissolved in methanol-water (1:4) prior to analysis, with an Acquity H-Class ultraperformance liquid chromatograph (UPLC) and a Xevo triple quadrupole mass spectrometer. We compared differences across chemicals in air and surface dust samples at the study and control sites by dichotomizing concentrations above or below the detection limit, using Fisher's exact test. A relatively higher detection frequency was observed for clothianidin and thiamethoxam at the study site for the surface dust samples, similarly for thiamethoxam in the air samples. Our results suggest airborne contamination (neonicotinoids and fungicides) from the ethanol facility at houses near the pesticide contamination.

Analysis of Wastewater Samples to Explore Community Substance Use in the United States: Pilot Correlative and Machine Learning Study.

BACKGROUND: Substance use disorder and associated deaths have increased in the United States, but methods for detecting and monitoring substance use using rapid and unbiased techniques are lacking. Wastewater-based surveillance is a cost-effective method for monitoring community drug use. However, the examination of the results often focuses on descriptive analysis. OBJECTIVE: The objective of this study was to explore community substance use in the United States by analyzing wastewater samples. Geographic differences and commonalities of substance use were explored. METHODS: Wastewater was sampled across the United States (n=12). Selected drugs with misuse potential, prescriptions, and over-the-counter drugs and their metabolites were tested across geographic locations for 7 days. Methods used included wastewater assessment of substances and metabolites paired with machine learning, specifically discriminant analysis and cluster analysis, to explore similarities and differences in wastewater measures. RESULTS: Geographic variations in the wastewater drug or metabolite levels were found. Results revealed a higher use of methamphetamine (z=-2.27, P=.02) and opioids-to-methadone ratios (oxycodone-to-methadone: z=-1.95, P=.05; hydrocodone-to-methadone: z=-1.95, P=.05) in states west of the Mississippi River compared to the east. Discriminant analysis suggested temazepam and methadone were significant predictors of geographical locations. Precision, sensitivity, specificity, and F1-scores were 0.88, 1, 0.80, and 0.93, respectively. Finally, cluster analysis revealed similarities in substance use among communities. CONCLUSIONS: These findings suggest that wastewater-based surveillance has the potential to become an effective form of surveillance for substance use. Further, advanced analytical techniques may help uncover geographical patterns and detect communities with similar needs for resources to address substance use disorders. Using automated analytics, these advanced surveillance techniques may help communities develop timely, tailored treatment and prevention efforts.

Dual Activation of Peroxymonosulfate Using MnFe2O4/g-C3N4 and Visible Light for the Efficient Degradation of Steroid Hormones: Performance, Mechanisms, and Environmental Impacts.

Single activation of peroxymonosulfate (PMS) in a homogeneous system is sometimes insufficient for producing reactive oxygen species (ROS) for water treatment applications. In this work, manganese spinel ferrite and graphitic carbon nitride (MnFe2O4/g-C3N4; MnF) were successfully used as an activator for PMS under visible light irradiation to remove the four-most-detected-hormone-contaminated water under different environmental conditions. The incorporation of g-C3N4 in the nanocomposites led to material enhancements, including increased crystallinity, reduced particle agglomeration, amplified magnetism, improved recyclability, and increased active surface area, thereby facilitating the PMS activation and electron transfer processes. The dominant active radical species included singlet oxygen (1O2) and superoxide anions (O2•-), which were more susceptible to the estrogen molecular structure than testosterone due to the higher electron-rich moieties. The self-scavenging effect occurred at high PMS concentrations, whereas elevated constituent ion concentrations can be both inhibitors and promoters due to the generation of secondary radicals. The MnF/PMS/vis system degradation byproducts and possible pathways of 17ß-estradiol and 17α-methyltestosterone were identified. The impact of hormone-treated water on Oryza sativa L. seed germination, shoot length, and root length was found to be lower than that of untreated water. However, the viability of both ELT3 and Sertoli TM4 cells was affected only at higher water compositions. Our results confirmed that MnF and visible light could be potential PMS activators due to their superior degradation performance and ability to produce safer treated water.

Occurrence and persistence of antibiotics administered to cattle in a newly established feedlot.

The practice of using therapeutic and prophylactic veterinary antibiotics in livestock farming is a worldwide phenomenon. Over the last decade, there has been a growing concern of antibiotic residues entering the environment via animal manure. Similar studies have focused on the occurrence and biological effects of antibiotics in land-applied animal feedlots; however, limited research has been conducted on the occurrence and persistence of antibiotics in animal feedlots. Therefore, the objective of this study was to evaluate antibiotic persistence, fate, and transport in surface water runoff and feedlot sediment in feedlot pens with livestock either receiving or not receiving antibiotic treatments through injection and feed. The two antibiotics (tylosin and monensin) added to animal feed were observed to persist in the soil environment for more than 30 days along with injected florfenicol. Monensin (5.6× higher) and tylosin (20× higher) were significantly higher in livestock pens receiving antibiotics compared to livestock pens not receiving the antibiotics. Further, rainfall was observed to significantly impact soil surface concentrations of florfenicol. Other antibiotics administrated by injection were not observed to statistically increase in concentrations in runoff or feedlot sediment. Our findings emphasize antibiotics administered in feedlots have the potential to persist and remain in feedlot sediment and runoff, particularly in instances of regular administration in feed.

Reaction Steps in Heterogeneous Photocatalytic Oxidation of Toluene in Gas Phase-A Review.

A review of the current literature shows there is no clear consensus regarding the reaction mechanisms of air-borne aromatic compounds such as toluene by photocatalytic oxidation. Potential oxidation reactions over TiO2 or TiO2-based catalysts under ultraviolet and visible (UV/VIS) illumination are most commonly considered for removal of these pollutants. Along the pathways from a model pollutant, toluene, to final mineralization products (CO2 and H2O), the formation of several intermediates via specific reactions include parallel oxidation reactions and formation of less-reactive intermediates on the TiO2 surface. The latter may occupy active adsorption sites and causes drastic catalyst deactivation in some cases. Major hazardous gas-phase intermediates are benzene and formaldehyde, classified by the International Agency for Research on Cancer (IARC) as Group 1 carcinogenic compounds. Adsorbed intermediates leading to catalyst deactivation are benzaldehyde, benzoic acid, and cresols. The three most typical pathways of toluene photocatalytic oxidation are reviewed: methyl group oxidation, aromatic ring oxidation, and aromatic ring opening.

Adsorptive-Photocatalytic Performance for Antibiotic and Personal Care Product Using Cu0.5Mn0.5Fe2O4.

The amount of antibiotics and personal care products entering local sewage systems and ultimately natural waters is increasing and raising concerns about long-term human health effects. We developed an adsorptive photocatalyst, Cu0.5Mn0.5Fe2O4 nanoparticles, utilizing co-precipitation and calcination with melamine, and quantified its efficacy in removing paraben and oxytetracycline (OTC). During melamine calcination, Cu0.5Mn0.5Fe2O4 recrystallized, improving material crystallinity and purity for the adsorptive-photocatalytic reaction. Kinetic experiments showed that all four parabens and OTC were removed within 120 and 45 min. We found that contaminant adsorption and reaction with active radicals occurred almost simultaneously with the photocatalyst. OTC adsorption could be adequately described by the Brouers-Sotolongo kinetic and Freundlich isotherm models. OTC photocatalytic degradation started with a series of reactions at different carbon locations (i.e., decarboxamidation, deamination, dehydroxylation, demethylation, and tautomerization). Further toxicity testing showed that Zea mays L. and Vigna radiata L. shoot indexes were less affected by treated water than root indexes. The Zea mays L. endodermis thickness and area decreased considerably after exposure to the 25% (v/v)-treated water. Overall, Cu0.5Mn0.5Fe2O4 nanoparticles exhibit a remarkable adsorptive-photocatalytic performance for the degradation of tested antibiotics and personal care products.

Interplay of legacy irrigation and nitrogen fertilizer inputs to spatial variability of arsenic and uranium within the deep vadose zone.

The vadose zone is a reservoir for geogenic and anthropogenic contaminants. Nitrogen and water infiltration can affect biogeochemical processes in this zone, ultimately affecting groundwater quality. In this large-scale field study, we evaluated the input and occurrence of water and nitrogen species in the vadose zone of a public water supply wellhead protection (WHP) area (defined by a 50-year travel time to groundwater for public supply wells) and potential transport of nitrate, ammonium, arsenic, and uranium. Thirty-two deep cores were collected and grouped by irrigation practices: pivot (n = 20), gravity (n = 4) irrigated using groundwater, and non-irrigated (n = 8) sites. Beneath pivot-irrigated sites, sediment nitrate concentrations were significantly (p < 0.05) lower, while ammonium concentrations were significantly (p < 0.05) higher than under gravity sites. The spatial distribution of sediment arsenic and uranium was evaluated against estimated nitrogen and water loading beneath cropland. Irrigation practices were randomly distributed throughout the WHP area and presented a contrasting pattern of sediment arsenic and uranium occurrence. Sediment arsenic correlated with iron (r = 0.32, p < 0.05), uranium negatively correlated to sediment nitrate (r = -0.23, p < 0.05), and ammonium (r = -0.19 p < 0.05). This study reveals that irrigation water and nitrogen influx influence vadose zone geochemistry and mobilization of geogenic contaminants affecting groundwater quality beneath intensive agricultural systems.

Enhanced degradation of herbicides in groundwater using sulfur-containing reductants and spinel zinc ferrite activated persulfate.

A challenge to successfully implementing an injection-based remedial treatment in aquifers is to ensure that the oxidative reaction is efficient and lasts long enough to contact the contaminated plume. Our objective was to determine the efficacy of zinc ferrite nanocomposites (ZnFe2O4) and sulfur-containing reductants (SCR) (i.e., dithionite; DTN and bisulfite; BS) to co-activate persulfate (S2O82-; PS) and treat herbicide-contaminated water. We also evaluated the ecotoxicity of the treated water. While both SCRs delivered excellent PS activation in a 1:0.4 ratio (PS:SCR), the reaction was relatively short-lived. By including ZnFe2O4 in the PS/BS or PS/DTN activations, herbicide degradation rates dramatically increased by factors of 2.5 to 11.3. This was due to the SO4- and OH reactive radical species that formed. Radical scavenging experiments and ZnFe2O4 XPS spectra results revealed that SO4- was the dominant reactive species that originated from S(IV)/PS activation in solution and from the Fe(II)/PS activation that occurred on the ZnFe2O4 surface. Based on liquid chromatography mass spectrometry (LC-MS), atrazine and alachlor degradation pathways are proposed that involve both dehydration and hydroxylation. In 1-D column experiments, five different treatment scenarios were run using 14C-labeled and unlabeled atrazine, and 3H2O to quantify changes in breakthrough curves. Our results confirmed that ZnFe2O4 successfully prolonged the PS oxidative treatment despite the SCR being completely dissociated. Toxicity testing showed treated 14C-atrazine was more biodegradable than the parent compound in soil microcosms. Post-treatment water (25 %, v/v) also had less impact on both Zea Mays L. and Vigna radiata L. seedling growth, but more impact on root anatomies, while ≤4 % of the treated water started to exert cytotoxicity (<80 % viability) on ELT3 cell lines. Overall, the findings confirm that ZnFe2O4/SCR/PS reaction is efficient and relatively longer lasting in treating herbicide-contaminated groundwater.

Labile carbon and soil texture control nitrogen transformation in deep vadose zone.

Understanding transient nitrogen (N) storage and transformation in the deep vadose zone is critical for controlling groundwater contamination by nitrate. The occurrence of organic and inorganic forms of carbon (C) and nitrogen and their importance in the deep vadose zone is not well characterized due to difficulty in sampling and the limited number of studies. We sampled and characterized these pools beneath 27 croplands with different vadose zone thicknesses (6-45 m). We measured nitrate and ammonium in different depths for the 27 sites to evaluate inorganic N storage. We measured total Kjeldahl nitrogen (TKN), hot-water extractable organic carbon (EOC), soil organic carbon (SOC), and δ13C for two sites to understand the potential role of organic N and C pools in N transformations. Inorganic N stocks in the vadose zone were 21.7-1043.6 g m-2 across 27 sites; the thicker vadose zone significantly stored more inorganic N (p < 0.05). We observed significant reservoirs of TKN and SOC at depths, likely representing paleosols that may provide organic C and N to subsurface microbes. The occurrence of deep C and N needs to be addressed in future research on terrestrial C and N storage potential. The increase of ammonium and EOC and δ13C value in the proximity of these horizons is consistent with N mineralization. An increase of nitrate, concurrent with the sandy soil texture and the water-filled pore space (WFPS) of 78 %, suggests that deep vadose zone nitrification may be supported in vadose zones with organic-rich layers such as paleosol. A profile showing the decrease of nitrate concentrations, concurrent with the clay soil texture and the WFPS of 91 %, also suggests denitrification may be an important process. Our study shows that microbial N transformation may be possible even in deep vadose zone with co-occurrence of C and N sources and controlled by labile C availability and soil texture.

Nitrate-Stimulated Release of Naturally Occurring Sedimentary Uranium.

Groundwater uranium (U) concentrations have been measured above the U.S. EPA maximum contaminant level (30 µg/L) in many U.S. aquifers, including in areas not associated with anthropogenic contamination by milling or mining. In addition to carbonate, nitrate has been correlated to uranium groundwater concentrations in two major U.S. aquifers. However, to date, direct evidence that nitrate mobilizes naturally occurring U from aquifer sediments has not been presented. Here, we demonstrate that the influx of high-nitrate porewater through High Plains alluvial aquifer silt sediments bearing naturally occurring U(IV) can stimulate a nitrate-reducing microbial community capable of catalyzing the oxidation and mobilization of U into the porewater. Microbial reduction of nitrate yielded nitrite, a reactive intermediate, which was further demonstrated to abiotically mobilize U from the reduced alluvial aquifer sediments. These results indicate that microbial activity, specifically nitrate reduction to nitrite, is one mechanism driving U mobilization from aquifer sediments in addition to previously described bicarbonate-driven desorption from mineral surfaces, such as Fe(III) oxides.

Importance of snowmelt on soil nitrate leaching to groundwater - A model study.

The movement of nitrate to surface water bodies during snow accumulation and melting has been extensively studied, but there are only limited studies on the influence of snow processes on nitrate leaching to groundwater. The present study investigated the impact of snow processes on nitrate leaching to groundwater based on a simulation modeling approach using HYDRUS-1D. HYDRUS-1D model has a temperature threshold-based snow model in addition to water, solute, and heat simulation components. The snow component in HYDRUS-1D was previously not applied to snow simulation studies since the method does not consider a detailed physical and process-based representation of snow accumulation and melting. In the present study, HYDRUS-1D was used to simulate snow accumulation and melting over 30 years for a location in Waverly, Lancaster County, Nebraska, USA. From the simulations, it was observed that the calibrated temperature threshold based snow module in HYDRUS-1D is effective in simulating snow accumulation and melting, as shown by the index of agreement and root mean squared error of 0.74 and 2.70 cm for calibration (15 years) and 0.88 and 2.70 cm for validation (15 years), respectively. The impact of snow melt on nitrate leaching was studied based on a study area with corn cultivation (Waverly, Nebraska, USA). A long-term (60 years) analysis was carried out for irrigated and non-irrigated agriculture with and without precipitation as snow. A higher nitrate leaching to groundwater was observed in the order of irrigated-with snow (54,038 kg/ha), irrigated-without snow (53,516 kg/ha), non-irrigated-with snow (7,431 kg/ha), and non-irrigated-without snow (7,090 kg/ha). This displays a 0.98% and 4.81% increase in nitrate leaching due to snow in irrigated and non-irrigated conditions, respectively. When extrapolated over the corn cultivated regions in Nebraska, this resulted in a difference of 1.2E+09 kg and 6.1E+08 kg of nitrate when considering snow in irrigated and non-irrigated areas over 60 years. This is the first study that has analyzed the long-term impact of snow on nitrate transport to groundwater based on a simulation modeling approach. The results show that snow accumulation and melting plays a vital role in the nitrate leaching into the groundwater and indicates the importance of considering snow components in similar studies.

Preparation of entrapment-based microcolumns for analysis of drug-humic acid interactions by high-performance affinity chromatography.

Reversible interactions between drugs and humic acid in water can be an important factor in determining the bioavailability and effects of these pharmaceuticals as micropollutants in the environment. In this study, microcolumns containing entrapped humic acid were used in high-performance affinity chromatography (HPAC) to examine the binding of this agent with the drugs tetracycline, carbamazepine, ciprofloxacin, and norfloxacin. Parameters that were varied to optimize the entrapment of humic acid within HPLC-grade porous silica included the starting concentration of humic acid, the mass ratio of humic acid vs silica, and the method of mixing the reagents with the support for the entrapment process. The highest retention for the tested drugs was obtained when using supports that were prepared using an initial humic acid concentration of 80 mg mL-1 and a humic acid vs silica mass ratio of 600 mg per g silica, along with preincubation of the humic acid with hydrazide-activated silica before the addition of a capping agent (i.e., oxidized glycogen). Characterization of the humic acid support was also carried out by means of TGA, FTIR, SEM, and energy-dispersive X-ray spectroscopy. The binding constants measured by HPAC for the given drugs with entrapped Aldrich humic acid gave good agreement with values reported in the literature under similar pH and temperature conditions for this and other forms of humic acid. Besides providing valuable data on the binding strength of various drugs with humic acid, this work illustrates how HPAC may be used as an analytical tool for screening and characterizing the interactions of drugs and man-made contaminants with humic acid or related binding agents in water and the environment.

Evaluation of dissolved and acid-leachable trace element concentrations in relation to practical water quality standards in the Syr Darya, Aral Sea Basin, South Kazakhstan.

The Syr Darya is one of the major rivers supplying the Aral Sea with freshwater. Soviet programs aimed at maximizing agricultural productivity in the Syr Darya basin increased diversion of water drastically affecting its water quality with significant consequences to its suitability for irrigation, fisheries and other uses. While water quality standards for trace elements are typically measured in the dissolved phase, there is evidence that adsorbed phases may also be relevant. Here we report potentially available heavy metals and metalloid concentrations in the Syr Darya water through the treatment of unfiltered waters samples with dilute nitric acid. Significant differences were found for most studied elements (Mann-Whitney U Test, p < 0.05) between their dissolved and acid-leachable concentrations. For Sr and Se in both sampling campaigns, no significant differences were found between their dissolved and acid-leachable concentrations, indicating their low geochemical reactivity. Dissolved V concentrations and acid-leachable Ni and Zn were found to exceed Kazakhstan Maximum Permissible Concentrations (MPC) values for the protection of fishery water quality. Our study evaluates the importance of considering regulatory issues of measuring trace metal concentrations to assess the water suitability for fisheries and irrigation.

Population Health Metrics During the Early Stages of the COVID-19 Pandemic: Correlative Pilot Study.

BACKGROUND: COVID-19 has caused nearly 1 million deaths in the United States, not to mention job losses, business and school closures, stay-at-home orders, and mask mandates. Many people have suffered increased anxiety and depression since the pandemic began. Not only have mental health symptoms become more prevalent, but alcohol consumption has also increased during this time. Helplines offer important insight into both physical and mental wellness of a population by offering immediate, anonymous, cheap, and accessible resources for health and substance use disorders (SUD) that was unobstructed by many of the mandates of the pandemic. Further, the pandemic also launched the use of wastewater surveillance, which has the potential for tracking not only population infections but also consumption of substances such as alcohol. OBJECTIVE: This study assessed the feasibility of using multiple public surveillance metrics, such as helpline calls, COVID-19 cases, and alcohol metabolites in wastewater, to better understand the need for interventions or public health programs in the time of a public health emergency. METHODS: Ethanol metabolites were analyzed from wastewater collected twice weekly from September 29 to December 4, 2020, in a Midwestern state. Calls made to the helpline regarding housing, health care, and mental health/SUD were correlated with ethanol metabolites analyzed from wastewater samples, as well as the number of COVID-19 cases during the sampling period. RESULTS: Correlations were observed between COVID-19 cases and helpline calls regarding housing and health care needs. No correlation was observed between the number of COVID-19 cases and mental health/SUD calls. COVID-19 cases on Tuesdays were correlated with the alcohol metabolite ethyl glucuronide (EtG). Finally, EtG levels were negatively associated with mental health/SUD helpline calls. CONCLUSIONS: Although helpline calls provided critical services for health care and housing-related concerns early in the pandemic, evidence suggests helpline calls for mental health/SUD-related concerns were unrelated to COVID-19 metrics. Instead, COVID metrics were associated with alcohol metabolites in wastewater. Although this research was formative, with continued and expanded monitoring of population metrics, such as helpline usage, COVID-19 metrics, and wastewater, strategies can be implemented to create precision programs to address the needs of the population.

Neonicotinoid pesticide and nitrate mixture removal and persistence in floating treatment wetlands.

Mesocosm and microcosm experiments were conducted to explore the applicability of floating treatment wetlands (FTWs), an ecologically based management technology, to remove neonicotinoid insecticides and nitrate from surface water. The mesocosm experiment evaluated three treatments in triplicate over a 21-d period. Floating treatment wetland mesocosms completely removed nitrate-N over the course of the experiment even when neonicotinoid insecticides were present. At the completion of the experiment, 79.6% of imidacloprid and degradation byproducts and 68.3% of thiamethoxam and degradation byproducts were accounted for in the water column. Approximately 3% of imidacloprid and degradation byproducts and 5.0% of thiamethoxam and degradation byproducts were observed in above-surface biomass, while ∼24% of imidacloprid and degradation byproducts, particularly desnitro imidacloprid, and <0.1% of thiamethoxam and degradation byproducts were found in the below surface biomass. Further, 1 yr after the experiments, imidacloprid, thiamethoxam, and degradation byproducts persisted in biomass but at lower concentrations in both the above- and below-surface biomass. Comparing the microbial communities of mature FTWs grown in the presence and absence of neonicotinoids, water column samples had similar low abundances of nitrifying Archaeal and bacterial amoA genes (below detection to 104  ml-1 ) and denitrifying bacterial nirK, nirS, and nosZ genes (below detection to 105  ml-1 ). Follow-up laboratory incubations found the highest denitrification potential activities in FTW plant roots compared with water column samples, and there was no effect of neonicotinoid addition (100 ng L-1 ) on potential denitrification activity. Based on these findings, (a) FTWs remove neonicotinoids from surface water through biomass incorporation, (b) neonicotinoids persist in biomass long-term (>1 yr after exposure), and (c) neonicotinoids do not adversely affect nitrate-N removal via microbial denitrification.

Enrofloxacin and Sulfamethoxazole Sorption on Carbonized Leonardite: Kinetics, Isotherms, Influential Effects, and Antibacterial Activity toward S. aureus ATCC 25923.

Excessive antibiotic use in veterinary applications has resulted in water contamination and potentially poses a serious threat to aquatic environments and human health. The objective of the current study was to quantify carbonized leonardite (cLND) adsorption capabilities to remove sulfamethoxazole (SMX)- and enrofloxacin (ENR)-contaminated water and to determine the microbial activity of ENR residuals on cLND following adsorption. The cLND samples prepared at 450 °C and 850 °C (cLND450 and cLND550, respectively) were evaluated for structural and physical characteristics and adsorption capabilities based on adsorption kinetics and isotherm studies. The low pyrolysis temperature of cLND resulted in a heterogeneous surface that was abundant in both hydrophobic and hydrophilic functional groups. SMX and ENR adsorption were best described using a pseudo-second-order rate expression. The SMX and ENR adsorption equilibrium data on cLND450 and cLND550 revealed their better compliance with a Langmuir isotherm than with four other models based on 2.3-fold higher values of qmENR than qmSMX. Under the presence of the environmental interference, the electrostatic interaction was the main contributing factor to the adsorption capability. Microbial activity experiments based on the growth of Staphylococcus aureus ATCC 25923 revealed that cLND could successfully adsorb and subsequently retain the adsorbed antibiotic on the cLND surface. This study demonstrated the potential of cLND550 as a suitable low-cost adsorbent for the highly efficient removal of antibiotics from water.

Ferrihydrite enrichment in the rhizosphere of unsaturated soil improves nutrient retention while limiting arsenic and uranium plant uptake.

Improvement of nutrient use efficiency and limiting trace elements such as arsenic and uranium bioavailability is critical for sustainable agriculture and food safety. Arsenic and uranium possess different properties and mobility in soils, which complicates the effort to reduce their uptake by plants. Here, we postulate that unsaturated soil amended with ferrihydrite nanominerals leads to improved nutrient retention and helps reduce uptake of these geogenic contaminants. Unsaturated soil is primarily oxic and can provide a stable environment for ferrihydrite nanominerals. To demonstrate the utility of ferrihydrite soil amendment, maize was grown in an unsaturated agricultural soil that is known to contain geogenic arsenic and uranium. The soil was maintained at a gravimetric moisture content of 15.1 ± 2.5%, typical of periodically irrigated soils of the US Corn Belt. Synthetic 2-line ferrihydrite was used in low doses as a soil amendment at three levels (0.00% w/w (control), 0.05% w/w and 0.10% w/w). Further, the irrigation water was fortified (~50 µg L-1 each) with elevated arsenic and uranium levels. Plant dry biomass at maturity was ~13.5% higher than that grown in soil not receiving ferrihydrite, indicating positive impact of ferrihydrite on plant growth. Arsenic and uranium concentrations in maize crops (root, shoot and grain combined) were ~ 20% lower in amended soils than that in control soils. Our findings suggest that the addition of low doses of iron nanomineral soil amendment can positively influence rhizosphere geochemical processes, enhancing nutrient plant availability and reduce trace contaminants plant uptake in sprinkler irrigated agroecosystem, which is 55% of total irrigated area in the United States.

Occurrence of arsenite in surface and groundwater associated with a perennial stream located in Western Nebraska, USA.

Dissolved arsenic typically results from chemical weathering of arsenic rich sediments and is most often found in oxidized forms in surface water. The mobility of arsenic is controlled by its valence state and also by its association with iron oxides minerals, the forms of which are both influenced by abiotic and biotic processes in aqueous environment. In this study, speciation methods were used to measure and confirm the presence of reduced arsenic species in the surface water of Frenchman creek, a gaining stream that crosses the Colorado-Nebraska border. Selective extraction analysis of aquifer and stream bed sediments shows that the bulk of the arsenic occurs with labile iron-rich oxy(hydroxide) minerals. Total dissolved arsenic in surface and groundwater ranged from ~3-18 µg L-1, and reduced arsenic species comprise about 41% of the total dissolved arsenic (16.0 µg L-1) in Frenchman creek. Leachable arsenic in the aquifer sediment samples ranged up to 1553 µg kg-1, while samples from Frenchman creek bed sediments contained 4218 µg kg-1. Dynamic surface and groundwater interaction sustains arsenite in iron-rich surface headwaters, and the implied toxicity of reduced arsenic in this hydrogeological setting, which can be important in surface water environments around the globe.