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Although many studies have assessed the bioaccumulation of perfluoroalkyl substances (PFAS) in plant tissues, to date there has been minimal research on the bioaccumulation of PFAS in soil invertebrates that results from consuming PFAS-contaminated media. The present study focused on two different consumption pathways in a population of crickets: individuals consuming PFAS-contaminated alfalfa and individuals consuming PFAS-spiked drinking water. Alfalfa was grown in a greenhouse and irrigated with PFAS-spiked water (∼1 ppm) containing seven unique PFAS. The alfalfa was then harvested and fed to crickets. Another population of crickets was supplied with PFAS-spiked drinking water at similar concentrations to irrigation water for direct consumption. Alfalfa accumulation of PFAS and subsequent consumption by the crickets resulted in overall similar tissue concentrations in the crickets who consumed PFAS-spiked water directly. This indicates that source concentration (water) may be an important factor in assessing the bioaccumulation of PFAS in organisms. To our knowledge, ours is the first study not only to assess the direct trophic transfer of PFAS from contaminated vegetation to invertebrates, but also to highlight the similarities in bioaccumulation regardless of ingestion pathway. Environ Toxicol Chem 2022;41:2981-2992. © 2022 SETAC.

Natural perchlorate (ClO4−) exists in many places on Earth, in lunar regolith, meteorites, and on the surface of Mars. Terrestrial natural ClO4− has widely variable Cl and O stable isotopic compositions (δ37Cl, δ18O, Δ17O). The δ18O and Δ17O values of ClO4− from the most hyper-arid locations co-vary. ClO4− from less arid areas has relatively little 17O excess and poor Δ17O-δ18O correlation. ClO4− from the Atacama Desert has unusually low δ37Cl (

Terrestrial toxicology data are limited for comprehensive ecotoxicological risk assessment (ERA) of ecosystems contaminated by per- and polyfluoroalkyl substances (PFAS) partly due to their existence as mixtures in the environment. This complicates logistical dose-response modeling and establishment of a threshold value characterizing the chronic toxicity of PFAS to ecological receptors. We examined reproduction, growth, and survival endpoints using a combination of hypothesis testing and logistical dose-response modeling of Northern Bobwhite quail (Colinus virginianus) exposed to perfluorohexanoic acid (PFHxA) alone and to PFHxA in a binary mixture with perfluorooctane sulfonic acid (PFOS) via the drinking water. The exposure concentration chronic toxicity value (CTV) representative of the lowest-observable-adverse-effect-level (LOAEL) threshold for chronic oral PFAS toxicity (based on reduced offspring weight and growth rate) was 0.10 ng/mL for PFHxA and 0.06 ng/mL for a PFOS:PFHxA (2.7:1) mixture. These estimates corresponded to an adult LOAEL average daily intake (ADI) CTV of 0.0149 and 0.0082 µg x kg bw-1 x d-1 , respectively. Neither no-observable-adverse-effect-level (NOAEL) threshold and representative CTVs nor a dose-response and predicted effective concentration (ECx ) values could be established for these two response variables. The findings indicate that reaction(s) occur among the individual PFAS components present in the mixture to alter the potential toxicity, demonstrating that mixture effects avian PFAS toxicity. Thus, chronic oral PFAS toxicity to avian receptors represented as the sum of the individual compound toxicities may not necessarily be the best method for assessing chronic mixture exposure risk at PFAS-contaminated sites. This article is protected by copyright. All rights reserved.

Per- and polyfluoroalkyl substances (PFAS) are globally distributed and present in nearly every environmental compartment. Characterizing the chronic toxicity of individual PFAS compounds and mixtures is necessary because many have been reported to cause adverse health effects. To derive toxicity reference values (TRVs) and conduct ecotoxicological risk assessments (ERAs) of PFAS-contaminated ecosystems for wildlife, species-specific PFAS chronic toxicity values (CTVs) are needed. The present study quantified PFAS residues from liver and eggs of birds chronically exposed to perfluorohexanoic acid (PFHxA) or a mixture of perfluorooctane sulfonate (PFOS) and PFHxA that produced a no-observable-adverse-effect level (NOAEL) and/or a lowest-observable-adverse-effectlevel (LOAEL). The CTVs we present are lower than those previously reported for birds and should be considered in future regulatory evaluations. From the estimated species- and tissue-specific PFAS CTVs, we found that PFOS and perfluorohexane sulfonate (PFHxS) were more bioaccumulative than PFHxA in avian tissues, but PFHxA was more toxic to reproducing birds than either PFOS or a PFOS:PFHxS mixture. We further determined that avian toxicity was not necessarily additive with respect to PFAS mixtures, which could have implications for PFAS ERAs. The PFAS LOAEL CTVs can be used to predict reproductive and possible population-level adverse health effects in wild avian receptors. Environ Toxicol Chem 2022;41:219-229. © 2021 SETAC.

This study contrasts the use of high-resolution passive sampling and traditional groundwater monitoring wells (GWMW) to characterize a chlorinated solvent site and assess the effectiveness of a biowall (mulch, compost and sand) that was installed to remediate trichloroethene (TCE), the primary contaminant of concern. High-resolution passive profilers (HRPPs) were direct driven hydraulically upgradient, within, and hydraulically downgradient of the biowall and in close proximity to existing GWMWs. Compared with hydraulically upgradient locations, the biowall was highly reducing, there were higher densities of bacteria/genes capable of reductive dechlorination, and TCE was being reductively transformed, but not completely, as cis-1,2-dichloroethene (cis-DCE) was detected within and hydraulically downgradient of the biowall. However, based on the high-resolution data, there were a number of important findings which were not discoverable using data from GWMWs alone. Data from the HRPPs indicate that the biowall was completely transforming TCE to ethene (C

Microbes are widely assumed to be capable of colonizing even the most challenging terrestrial surface environments on Earth given enough time. We would not expect to find surface soils uninhabited by microbes as soils typically harbor diverse microbial communities and viable microbes have been detected in soils exposed to even the most inhospitable conditions. However, if uninhabited soils do exist, we might expect to find them in Antarctica. We analyzed 204 ice-free soils collected from across a remote valley in the Transantarctic Mountains (84 – 85°S, 174 – 177°W) and were able to identify a potential limit of microbial habitability. While most of the soils we tested contained diverse microbial communities, with fungi being particularly ubiquitous, microbes could not be detected in many of the driest, higher elevation soils - results that were confirmed using cultivation-dependent, cultivation-independent, and metabolic assays. While we cannot confirm that this subset of soils is completely sterile and devoid of microbial life, our results do show that microbial habitability and activity can be restricted by near-continuous exposure to cold, dry, and salty conditions, establishing the environmental conditions that constrain habitability in terrestrial surface environments. Constant exposure to these conditions for thousands of years has generated uninhabited surface soil environments, with either no detectable microbes or conditions which are not suitable to sustain microbial activity. Such uninhabited soils are unlikely to be unique to the studied region with this work challenging expectations about where microbes might, or might not, be able to thrive on Earth and other planets. Significance Statement Certain surface soils in Antarctica have remained effectively uninhabited due to a near-continuous exposure to cold-dry-salty conditions. This is an unexpected result because soils, even those in hyper-arid deserts, typically contain detectable microorganisms. Additionally, the prevalence of fungi at the colder, drier, higher elevation sites suggests that certain fungi may in fact be better adapted than bacteria or archaea to some of the most challenging soil environments on Earth.

Recent investigations have reported a widespread occurrence of chlorate (ClO3–) and perchlorate (ClO4–) throughout the solar system, including terrestrial arid environments. ClO3– and ClO4– are deposited/accumulated at an approximate equal molar ratio, with some exceptions, such as the Antarctica Dry Valley soils (MDV) and perhaps Martian surface material, where ClO4– is the dominate ClOx– species. All known ClO4– production mechanisms produce molar ratios of ClO3–/ClO4– equal to or much greater than 1, suggesting that reduced ratios may be due to post-depositional mechanism(s). The objective of this study was to investigate potential iron-mediated abiotic reduction of ClO3–, similar to transformation mechanisms reported for nitrate (NO3–) by Fe(II) minerals. Three types of Fe(II)-containing minerals, wustite (FeO), siderite (FeCO3), and sulfate green rust (GRSO42–), were investigated in completely mixed batch reactors as potential ClO3– reductants at a range of pH (4–9) and iron mineral concentrations (1...

This paper presents findings from a side-by-side operational comparison of granular road salt (RS) and MeltDown 20 (MD) deicing chemicals for snow and ice control from the perspective of “...

A new method has been developed to determine trace amounts of phosphite (HPO

Natural chlorate (ClO

Microbes are widely assumed to be capable of colonizing even the most challenging terrestrial surface environments on Earth given enough time. We would not expect to find surface soils uninhabited by microbes as soils typically harbor diverse microbial communities and viable microbes have been detected in soils exposed to even the most inhospitable conditions. However, if uninhabited soils do exist, we might expect to find them in Antarctica. We analyzed 204 ice-free soils collected from across a remote valley in the Transantarctic Mountains (84 – 85°S, 174 – 177°W) and were able to identify a potential limit of microbial habitability. While most of the soils we tested contained diverse microbial communities, with fungi being particularly ubiquitous, microbes could not be detected in many of the driest, higher elevation soils - results that were confirmed using cultivation-dependent, cultivation-independent, and metabolic assays. While we cannot confirm that this subset of soils is completely sterile and devoid of microbial life, our results do show that microbial habitability and activity can be restricted by near-continuous exposure to cold, dry, and salty conditions, establishing the environmental conditions that constrain habitability in terrestrial surface environments. Constant exposure to these conditions for thousands of years has generated uninhabited surface soil environments, with either no detectable microbes or conditions which are not suitable to sustain microbial activity. Such uninhabited soils are unlikely to be unique to the studied region with this work challenging expectations about where microbes might, or might not, be able to thrive on Earth and other planets.Significance StatementCertain surface soils in Antarctica have remained effectively uninhabited due to a near-continuous exposure to cold-dry-salty conditions. This is an unexpected result because soils, even those in hyper-arid deserts, typically contain detectable microorganisms. Additionally, the prevalence of fungi at the colder, drier, higher elevation sites suggests that certain fungi may in fact be better adapted than bacteria or archaea to some of the most challenging soil environments on Earth.

Widely distributed perchlorate on the Martian surface and over three orders of magnitude variation in bromine abundances in surface samples are difficult to explain solely by chloride and bromide aqueous geochemistry. New experiments show that photochemical oxidation (ultraviolet wavelength 254 nm) of chloride- and bromide-bearing evaporative brines in the presence of silica beads produces substantial perchlorate (ClO − 4 ), chlorate (ClO − 3 ), and bromate (BrO − 3 ) under conditions relevant to Mars. Neutral to alkaline aqueous environments result in the dominance of chlorate over perchlorate. Preferential atmospheric recycling of Br over Cl causes variable Br/Cl ratios, consistent with numerous in-situ measurements of Cl and Br abundances on Mars. Bromate reacts with organics more readily than chlorate or perchlorate, and its presence in subsurface brines could challenge habitability in the Martian subsurface.

The occurrence of chlorate (ClO3–) and perchlorate (ClO4–) in the terrestrial and extraterrestrial environments has been partly attributed to ozone (O3)-mediated oxidation of chlorine-bearing compounds. This is based on varying elevated Δ17O values in all measured terrestrial natural ClO4– as well as the nearly universal co-equal occurrence of ClO3– and ClO4–, which has only been reported to occur for dry oxidation of Cl–, a process for which little information is available. In this study, we examine possible factors influencing ClO4– and ClO3– formation by O3 oxidation of sodium chloride (NaCl) salt and hydrochloric acid (HCl) gas in glass reactor vessels. We show that longer reaction times increase production of ClO4– and ClO3–, with ClO3– production generally being lower than ClO4– by 1–2 orders of magnitude. For 1 day oxidation periods, ClO4–/ClO3– ratios were relatively constant (∼50) for low Cl– masses and decreased over 3 orders of magnitude for higher (∼100×) Cl– masses. Perchlorate mass increased...

Bioreactors for space habitation systems have unique constraints. One type of reactor that could meet these constraints are membrane aerated biological reactors (MABRs). The objective of this work was to establish the performance and optimal loading capacities of multiple MABRs with a variety of habitation waste streams. The MABRs operated over a large range of organic nitrogen (ON) and organic carbon (OC) loading rates (36–220 g/m3-d and 20–200 g/m3-d, respectively) across all wastewaters excluding humidity condensate (HC) where ON and OC loading rates ranged from 1.6 to 11 g/m3-d and 7–55 g/m3-d, respectively. OC and ON transformation rates (29–210 g/m3-d and 23–170 g/m3-d, respectively) were proportional to loading rates and similar to MABRs treating terrestrial high strength wastewaters at similar loadings. MABR maximum loading rates are limited by ON oxidation which controls pH. Above a pH of ~7.8 ON removal is inhibited by free ammonium due to the elevated concentrations of ON in all wastewaters excluding HC. While loading rates are lower than typical terrestrial systems, the MABRs stably operated for up to 5 years with limited maintenance and no solids processing. This work supports the use of MABRs to reliably stabilize habitation wastewaters with minimal consumables. These results also support the use of these MABRs for terrestrial high strength, low volume wastewaters where complex technology may be unsupportable, such as in rural or developing communities with no centralized treatment or for applications where typical two-phase aeration can lead to undesirable off gassing.

Natural chlorate (ClO3−) is widely distributed in terrestrial and extraterrestrial environments. To improve understanding of the origins and distribution of ClO3−, we developed and tested methods to determine the multi-dimensional isotopic compositions (δ18O, Δ17O, δ37Cl, 36Cl/Cl) of ClO3− and then applied the methods to samples of natural nitrate-rich caliche-type salt deposits in the Atacama Desert, Chile, and Death Valley, USA. Tests with reagents and artificial mixed samples indicate stable-isotope ratios were minimally affected by the purification processes. Chlorate extracted from Atacama samples had δ18O = +7.0 to +11.1‰, Δ17O = +5.7 to +6.4‰, δ37Cl = −1.4 to +1.3‰, and 36Cl/Cl = 48 × 10−15 to 104 × 10−15. Chlorate from Death Valley samples had δ18O = −6.9 to +1.6‰, Δ17O = +0.4 to +2.6‰, δ37Cl = +0.8 to +1.0‰, and 36Cl/Cl = 14 × 10−15 to 44 × 10−15. Positive Δ17O values of natural ClO3− indicate that its production involved reaction with O3, while its Cl isotopic composition is consistent with a tropospheric or near-surface source of Cl. The Δ17O and δ18O values of natural ClO3− are positively correlated, as are those of ClO4− and NO3− from the same localities, possibly indicating variation in the relative contributions of O3 as a source of O in the formation of the oxyanions. Additional isotopic analyses of ClO3− could provide stronger constraints on its production mechanisms and/or post-formational alterations, with applications for environmental forensics, global biogeochemical cycling of Cl, and the origins of oxyanions detected on Mars.

This paper presents findings from a side-by-side field comparison of the effectiveness of sodium chloride-based road salt brine (RSB) and magnesium chloride-based Meltdown Apex™ liquid (MDA) as anti-icing chemicals for snow and ice control associated with winter roadway maintenance. The study was sponsored by the Texas Department of Transportation (TxDOT) to support operational decision-making for chemical treatment selections based on the perspective of pavement conditions observed by “the maintenance worker in the truck.” The field test site was a portion of rural service road near Canyon, Texas, located at latitude 35° N. The site was divided into eight 305 m sections that were treated with RSB at 141 l/lane km, MDA at 47 l/lane km, or left untreated for control. Two storm events at the test site during Winter 2014–2015 met pre-established research criteria for snow accumulation and other variables. Test sections were subjected to cycles of plowing, slushing, and additional anti-icing liquid treatment. Digital video data and still image (photo) data were collected throughout the storm events to allow estimation of visible pavement, and vehicle-based decelerometer tests were used to measure pavement friction. Overall results from multiple performance measures indicated comparable effectiveness of RSB and MDA at the applied rates. It was also noted that application of MDA on dry pavement prior to the storm events significantly reduced the pavement friction.

Nitrate was recently detected in Gale Crater sediments on Mars at abundances up to approximately 600 mg/kg, confirming predictions of its presence at abundances consistent with models based on impact-generated nitrate and other sources of fixed nitrogen. Terrestrial Mars analogs, Mars meteorites, and other solar system materials help establish a context for interpreting in situ nitrate measurements on Mars, particularly in relation to other cooccuring salts. We compare the relative abundance of nitrates to oxychlorine (chlorate and/or perchlorate, hereafter (per)chlorate) salts on Mars and Earth. The nitrate/(per)chlorate ratio on Mars is greater than 1, significantly lower than on Earth (nitrate/(per)chlorate greater than 10(exp.3)), suggesting not only the absence of biological activity but also different (per)chlorate formation mechanisms on Mars than on Earth.

A membrane-aerated biofilm reactor (MABR) was designed for the treatment of a source-separated urine wastewater formulated to mimic conditions on an early planetary space habitation. Literature suggested that a MABR would not work effectively for nitrogen removal for this wastewater since it is nitrogen dominant (total organic carbon to nitrogen ratio 2 mg/L). Dissolved organic carbon (DOC) removal and nitrification rates were reported as high as 0.33 ± 0.12 g-C/m2-d and 0.32 ± 0.02 g-N/m2-d, respectively. Additionally, the MABR achieved total nitrogen (TN) removal efficiency of 36.5 %. Additionally, the operational parameters of hydraulic retention time, intramembrane partial oxygen pressure, recycle ratio and liquid velocity linked with bulk DO concentration were evaluated. It was observed that TN removal was significantly impacted by the variation of those parameters, but DOC removal efficiency and nitrification rate did not change significantly. This study helps to establish the efficacy of MABR systems for the treatment of nitrogen dominant, space-based wastewater.

The cold (−13.4°C), cryoencapsulated, anoxic, interstitial brine of the >27 m thick ice of Lake Vida (Victoria Valley, Antarctica) contains 49 µg · L−1 of perchlorate and 11 µg · L−1 of chlorate. Lake Vida brine (LVBr) may provide an analog for potential oxychlorine-rich subsurface brine on Mars. LVBr volatiles were analyzed by solid-phase microextraction (SPME) gas chromatography–mass spectrometry (GC-MS) with two different SPME fibers. With the exception of volatile organic sulfur compounds, most other volatiles observed were artifacts produced in the GC injector when the thermal decomposition products of oxychlorines reacted with reduced carbon derived from LVBr and the SPME fiber phases. Analysis of MilliQ water with perchlorate (40 µg · L−1) showed low level of organic artifacts, reflecting carbon limitation. In order to observe sample-derived organic compounds, both in analog samples and on Mars, the molar abundance of reduced carbon in a sample must exceed those of O2 and Cl2 produced during decomposition of oxychlorines. This suggests that the abundance of compounds observed by the Sample Analysis at Mars (SAM) instruments in Sheepbed samples (CB-3, CB5, and CB6) may be controlled by an increase in the reduced-carbon/oxychlorine ratio of these samples. To increase chances of in situ detection of Martian organics during pyrolysis-GC-MS, we propose that the derivatization agents stored on SAM may be used as an external source of reduced carbon, increasing artificially the reduced-carbon to perchlorate ratio during pyrolysis, allowing the expression of more abundant and perhaps more diverse Martian organic matter.

The objective of this study was to investigate Joule heating/electric swing adsorption (ESA) as a mode of regeneration and to compare the carbon dioxide (CO2) adsorption capacity of pristine graphene films and reduced graphene oxide (rGO) aerogels. Joule heating/ESA has not been previously demonstrated in graphene based structures. Various forms of graphene have been previously evaluated for their use as a CO2 adsorbent, but most of these studies have focused on graphene oxide powders and films. We utilize both pristine graphene and rGO; we also highlight regeneration through Joule heating in contrast to heating under vacuum or by pressure swing. The amount of CO2 captured by graphene films and rGO aerogels was 0.52 ± 0.02 and 0.94 ± 0.02 g of CO2 per g of adsorbate, respectively. This adsorption capacity of pristine graphene films and rGO aerogels was found to be stable over multiple samples and multiple cycles of adsorption and electrical current stimulated desorption.

Perchlorate ( ClO 4 − ) and chlorate ( ClO 3 − ) are ubiquitous on Earth and ClO 4 − has also been found on Mars. These species can play important roles in geochemical processes such as oxidation of organic matter and as biological electron acceptors, and are also indicators of important photochemical reactions involving oxyanions; on Mars they could be relevant for human habitability both in terms of in situ resource utilization and potential human health effects. For the first time, we extracted, detected and quantified ClO 4 − and ClO 3 − in extraterrestrial, non-planetary samples: regolith and rock samples from the Moon, and two chondrite meteorites (Murchison and Fayetteville). Lunar samples were collected by astronauts during the Apollo program, and meteorite samples were recovered immediately after their fall. This fact, together with the heterogeneous distribution of ClO 4 − and ClO 3 − within some of the samples, and their relative abundance with respect to other soluble species (e.g., NO 3 − ) are consistent with an extraterrestrial origin of the oxychlorine species. Our results, combined with the previously reported widespread occurrence on Earth and Mars, indicate that ClO 4 − and ClO 3 − could be present throughout the Solar System.

The fate and transport of groundwater contaminants depends partially on groundwater velocity, which can vary appreciably in highly stratified aquifers. A high-resolution passive profiler (HRPP) was developed to evaluate groundwater velocity, contaminant concentrations, and microbial community structure at ∼20 cm vertical depth resolution in shallow heterogeneous aquifers. The objective of this study was to use mass transfer of bromide (Br- ), a conservative tracer released from cells in the HRPP, to estimate interstitial velocity. Laboratory experiments were conducted to empirically relate velocity and the mass transfer coefficient of Br- based on the relative loss of Br- from HRPP cells. Laboratory-scale HRPPs were deployed in flow boxes containing saturated soils with differing porosities, and the mass transfer coefficient of Br- was measured at multiple interstitial velocities (0 to 100 cm/day). A two-dimensional (2D) quasi-steady-state model was used to relate velocity to mass transfer of Br- for a range of soil porosities (0.2-0.5). The laboratory data indicate that the mass transfer coefficient of Br- , which was directly-but non-linearly-related to velocity, can be determined with a single 3-week deployment of the HRPP. The mass transfer coefficient was relatively unaffected by sampler orientation, length of deployment time, or porosity. The model closely simulated the experimental results. The data suggest that the HRPP will be applicable for estimating groundwater velocity ranging from 1 to 100 cm/day in the field at a minimum depth resolution of 10 cm, depending on sampler design.

Aluminum/iodine pentoxide (Al/I2O5) composites are currently receiving much attention for their capabilities as potential anthrax combatants. Their high halogen gas release, coupled with high temperature evolution from combustion, renders them effective in bacterial deactivation. Despite extensive research on the energetic capacities of these compounds, limited information is currently available in relation to their potential environmental (non-target) effects. We evaluated the effects of Al/I2O5 on aquatic (Daphnia magna) and terrestrial (Eisenia fetida, Acheta domesticus) invertebrates, as well as alfalfa (Medicago sativa) seed germination. Polytetrafluoroethylene (PTFE, or DuPont Teflon® MP1150) was examined concurrently to assess whether observations were general to halogen, or element specific. Our observations were based on mortality and reproduction (hatchability) for the terrestrial and aquatic assays. In all Al/I2O5 assays, mortality was concentration dependent, ranging from 0% mortality in the control samples to partial and complete mortality in the contaminated cases. The PTFE assays showed no mortality at all contaminant concentrations. At a maximum Al/I2O5 contaminant concentration of 1000 μg/g (ppm), 100% mortality was observed in cricket assay conducted in sand within 72 h exposure and earthworm assay conducted in soil within 4 days exposure. In the aquatic assay, a water concentration of 200 μg/mL (ppm) caused 100% mortality to D. magna in less than 12 h. The effect of aluminum/iodine pentoxide on earthworm cocoon hatching success was also determined. At soil concentrations ≤ 400 μg/g, hatching success for earthworm cocoons was equivalent to control (un-contaminated) soil; above this concentration, hatching success was reduced by a factor of 2. Alfalfa germination tests were performed at a single contaminant concentration of 1000 μg/g. This soil concentration was completely inhibitory to seed germination.

Natural perchlorate (ClO 4 − ) is of increasing interest due to its wide-spread occurrence on Earth and Mars, yet little information exists on the relative abundance of ClO 4 − compared to other major anions, its stability, or long-term variations in production that may impact the observed distributions. Our objectives were to evaluate the occurrence and fate of ClO 4 − in groundwater and soils/caliche in arid and semi-arid environments (southwestern United States, southern Africa, United Arab Emirates, China, Antarctica, and Chile) and the relationship of ClO 4 − to the more well-studied atmospherically deposited anions NO 3 − and Cl − as a means to understand the prevalent processes that affect the accumulation of these species over various time scales. ClO 4 − is globally distributed in soil and groundwater in arid and semi-arid regions on Earth at concentrations ranging from 10 −1 to 10 6 μg/kg. Generally, the ClO 4 − concentration in these regions increases with aridity index, but also depends on the duration of arid conditions. In many arid and semi-arid areas, NO 3 − and ClO 4 − co-occur at molar ratios (NO 3 − /ClO 4 − ) that vary between ∼10 4 and 10 5 . We hypothesize that atmospheric deposition ratios are largely preserved in hyper-arid areas that support little or no biological activity (e.g. plants or bacteria), but can be altered in areas with more active biological processes including N 2 fixation, N mineralization, nitrification, denitrification, and microbial ClO 4 − reduction, as indicated in part by NO 3 − isotope data. In contrast, much larger ranges of Cl − /ClO 4 − and Cl − /NO 3 − ratios indicate Cl − varies independently from both ClO 4 − and NO 3 − . The general lack of correlation between Cl − and ClO 4 − or NO 3 − implies that Cl − is not a good indicator of co-deposition and should be used with care when interpreting oxyanion cycling in arid systems. The Atacama Desert appears to be unique compared to all other terrestrial locations having a NO 3 − /ClO 4 − molar ratio ∼10 3 . The relative enrichment in ClO 4 − compared to Cl − or NO 3 − and unique isotopic composition of Atacama ClO 4 − may reflect either additional in-situ production mechanism(s) or higher relative atmospheric production rates in that specific region or in the geological past. Elevated concentrations of ClO 4 − reported on the surface of Mars, and its enrichment with respect to Cl − and NO 3 − , could reveal important clues regarding the climatic, hydrologic, and potentially biologic evolution of that planet. Given the highly conserved ratio of NO 3 − /ClO 4 − in non-biologically active areas on Earth, it may be possible to use alterations of this ratio as a biomarker on Mars and for interpreting major anion cycles and processes on both Mars and Earth, particularly with respect to the less-conserved NO 3 − pool terrestrially.

Due to the high volume of crude oil released by the Deepwater Horizon oil spill, the salt marshes along the gulf coast were contaminated with crude oil. Biodegradation of crude oil in salt marshes is primarily limited by oxygen availability due to the high organic carbon content of the soil, high flux rate of S(2-), and saturated conditions. Chlorate, nitrate, and perchlorate were evaluated for use as electron acceptors in comparison to oxygen by comparing oil transformation and mineralization in mesocosms consisting of oiled salt marsh sediment from an area impacted by the BP Horizon oil spill. Mineralization rates were determined by measuring CO2 production and δ (13)C of the produced CO2 and compared to transformation evaluated by measuring the alkane/hopane ratios over a 4-month period. Total alkane/hopane ratios decreased (~55-70 %) for all treatments in the following relative order: aerated ≈ chlorate > nitrate > perchlorate. Total CO2 produced was similar between treatments ranging from 550-700 mg CO2-C. The δ (13)C-CO2 values generally ranged between the indigenous carbon and oil values (-17 and -27‰, respectively). Oil mineralization was greatest for the aerated treatments and least for the perchlorate amended. Our results indicate that chlorate has a similar potential as oxygen to support oil mineralization in contaminated salt marshes, but nitrate and perchlorate were less effective. The use of chlorate as a means to promote oil mineralization in situ may be a promising means to remediate contaminated salt marshes while preventing unwanted secondary impacts related to nutrient management as in the case of nitrate amendments.

The identification and characterization of aqueous minerals within ancient lacustrine environments on Mars are a high priority for determining the past habitability of the red planet. Terrestrial analog studies are useful both for understanding the mineralogy of lacustrine sediments, how the mineralogy varies with location in a lacustrine environment, and for validating the use of certain techniques such as visible–near-infrared (VNIR) spectroscopy. In this study, sediments from the Pilot Valley paleolake basin of the Great Salt Lake desert were characterized using VNIR as an analog for Martian paleolake basins. The spectra and subsequent interpretations were then compared to mineralogical characterization by ground truth methods, including X-ray diffraction, automated scanning electron microscopy, and several geochemical analysis techniques. In general, there is good agreement between VNIR and ground truth methods on the major classes of minerals present in the lake sediments and VNIR spectra can also easily discriminate between clay-dominated and salt-dominated lacustrine terrains within the paleolake basin. However, detection of more detailed mineralogy is difficult with VNIR spectra alone as some minerals can dominate the spectra even at very low abundances. At this site, the VNIR spectra are dominated by absorption bands that are most consistent with gypsum and smectites, though the ground truth methods reveal more diverse mineral assemblages that include a variety of sulfates, primary and secondary phyllosilicates, carbonates, and chlorides. This study provides insight into the limitations regarding the use of VNIR in characterizing complex mineral assemblages inherent in lacustrine settings.

Natural perchlorate (ClO4−) in soil and groundwater exhibits a wide range in stable isotopic compositions (δ37Cl, δ18O, and Δ17O), indicating that ClO4− may be formed through more than one pathway and/or undergoes post-depositional isotopic alteration. Plants are known to accumulate ClO4−, but little is known about their ability to alter its isotopic composition. We examined the potential for plants to alter the isotopic composition of ClO4− in hydroponic and field experiments conducted with snap beans (Phaseolus vulgaris L.). In hydroponic studies, anion ratios indicated that ClO4− was transported from solutions into plants similarly to NO3− but preferentially to Cl− (4-fold). The ClO4− isotopic compositions of initial ClO4− reagents, final growth solutions, and aqueous extracts from plant tissues were essentially indistinguishable, indicating no significant isotope effects during ClO4− uptake or accumulation. The ClO4− isotopic composition of field-grown snap beans was also consistent with that of ClO4− in varying proportions from irrigation water and precipitation. NO3− uptake had little or no effect on NO3− isotopic compositions in hydroponic solutions. However, a large fractionation effect with an apparent e (15N/18O) ratio of 1.05 was observed between NO3− in hydroponic solutions and leaf extracts, consistent with partial NO3− reduction during assimilation within plant tissue. We also explored the feasibility of evaluating sources of ClO4− in commercial produce, as illustrated by spinach, for which the ClO4− isotopic composition was similar to that of indigenous natural ClO4−. Our results indicate that some types of plants can accumulate and (presumably) release ClO4− to soil and groundwater without altering its isotopic characteristics. Concentrations and isotopic compositions of ClO4− and NO3− in plants may be useful for determining sources of fertilizers and sources of ClO4− in their growth environments and consequently in food supplies.

We report on 475 measurements of depth to ice-cemented ground in four high-elevation valleys of the Quartermain Mountains, McMurdo Dry Valleys, Antarctica. These valleys have pervasive ice-cemented ground, and the depth to ice-cemented ground and the ice composition may be indicators of climate change. In University Valley, the measured depth to ice-cemented ground ranges from 0–98 cm. There is an overall trend of increasing depth to ice-cemented ground with distance from a small glacier at the head of the valley, with a slope of 32 cm depth per kilometre along the valley floor. For Farnell Valley, the depth to ice-cemented ground is roughly constant (c. 30 cm) in the upper and central parts of the valley, but increases sharply as the valley descends into Beacon Valley. The two valleys north of University Valley also have extensive ice-cemented ground, with depths of 20–40 cm, but exhibit no clear patterns of ice depth with location. For all valleys there is a tendency for the variability in depth to ice-cemented ground at a site to increase with increasing depth to ice. Snow recurrence, solar insolation, and surface albedo may all be factors that cause site to site variations in these valleys.

Aqueous chlorine solutions (defined as chlorine solutions (Cl(2,T)) containing solely or a combination of molecular chlorine (Cl(2)), hypochlorous acid (HOCl), and hypochlorite (OCl(-))) are known to produce toxic inorganic disinfection byproduct (e.g., chlorate and chlorite) through photoactivated transformations. Recent reports of perchlorate (ClO(4)(-)) production-a well-known thyroid hormone disruptor- from stored bleach solutions indicates the presence of unexplored transformation pathway(s). The evaluation of this potential ClO(4)(-) source is important given the widespread use of aqueous chlorine as a disinfectant. In this study, we perform detailed rate analysis of ClO(4)(-) generation from aqueous chlorine under varying environmental conditions including ultraviolet (UV) light sources, intensity, solution pH, and Cl(2,T) concentrations. Our results show that ClO(4)(-) is produced upon UV exposure of aqueous chlorine solutions with yields ranging from 0.09 × 10(-3) to 9.2 × 10(-3)% for all experimental conditions. The amount of ClO(4)(-) produced depends on the starting concentrations of Cl(2,T) and ClO(3)(-), UV source wavelength, and solution pH, but it is independent of light intensity. We hypothesize a mechanistic pathway derived from known reactions of Cl(2,T) photodecomposition that involves the reaction of Cl radicals with ClO(3)(-) to produce ClO(4)(-) with calculated rate coefficient (k(ClO4-)) of (4-40) × 10(5) M(-1) s(-1) and (3-250) × 10(5) M(-1) s(-1) for UV-B/C and UV-A, respectively. The measured ClO(4)(-) concentrations for both UV-B and UV-C experiments agreed well with our model (R(2) = 0.88-0.99), except under UV-A light exposure (R(2) = 0.52-0.93), suggesting the possible involvement of additional pathways at higher wavelengths. Based on our results, phototransformation of aqueous chlorine solutions at concentrations relevant to drinking water treatment would result in ClO(4)(-) concentrations (~0.1 μg L(-1)) much below the proposed drinking water limits. The importance of the hypothesized mechanism is discussed in relation to natural ClO(4)(-) formation by atmospheric transformations.

Reverse osmosis (RO) is a treatment technology that may be used for the recovery of graywater terrestrially as well as the recovery of wastewater on board long duration, manned space flights. As with terrestrial RO applications, concentration polarization and membrane fouling lead to decreased productivity and increased energy demands with time. Physiochemical and biological pretreatment options can enhance the performance of the RO system; also, biological pretreatment has the advantages of low energy and consumable requirements as compared to other physiochemical pretreatment options. To determine the degree to which the incorporation of biological treatment enhances RO performance, a series of bench-scale experiments were performed. Observed resistances indicate that biological pretreatment alleviated the degree of non-reversible fouling while also improving the rate of permeate flux in a downstream RO process to further treat water. Results also indicated that enhanced urea hydrolysis, pH reduction, and carbon oxidation serve as the primary benefits of biological pretreatment of space-based graywater. The observations of this study may also benefit engineers considering the treatment of graywaters for terrestrial water-reuse applications.

GeneDB (http://www.genedb.org) is a genome database for prokaryotic and eukaryotic pathogens and closely related organisms. The resource provides a portal to genome sequence and annotation data, which is primarily generated by the Pathogen Genomics group at the Wellcome Trust Sanger Institute. It combines data from completed and ongoing genome projects with curated annotation, which is readily accessible from a web based resource. The development of the database in recent years has focused on providing database-driven annotation tools and pipelines, as well as catering for increasingly frequent assembly updates. The website has been significantly redesigned to take advantage of current web technologies, and improve usability. The current release stores 41 data sets, of which 17 are manually curated and maintained by biologists, who review and incorporate data from the scientific literature, as well as other sources. GeneDB is primarily a production and annotation database for the genomes of predominantly pathogenic organisms.

The massive oil release from the Deep Water Horizon disaster has reemphasized the need to remediate oil impacted marshes. Due to the physically fragile nature of salt water marshes, bioremediation is often proposed as an appropriate technology and nutrient amendment is often proposed as a means of accelerating biodegradation of crude oil. However, no information is currently available concerning the efficacy of in situ nutrient amendments in Gulf Coast salt marshes. An experimental crude oil spill (142 l over 100 m2) was conducted to evaluate the efficacy of nitrogen amendment to stimulate bioremediation in a Spartina alterniflora dominated Louisiana salt marsh. A randomized complete block design with replication (n = 10) was utilized to test the hypothesis that additions of fast-release ammonium nitrate (60 g N/m2) and slow-release urea (30 g N/m2) fertilizers could enhance biodegradation of selected crude oil components in the marsh. Crude oil degradation was monitored by analyzing sediment samples for branched and unbranched alkanes over the 180-day study period. The compound/hopane ratio was used to correct for nonbiological losses. No consistent statistically significant effect of fertilizer addition on degradation rates was observed, despite success in increasing the porewater ammonium and NaCl-extractable ammonium over the time frame of the trial. Intrinsic pseudo-first order degradation rates of alkanes in all plots were substantial (0.003–0.008 day−1). Existing, background levels of N did not appear to limit biodegradation rates in Spartina-dominated salt marshes. These results suggest that nutrient amendments will not be successful in stimulation biodegradation of crude oil in these systems.

A modified membrane-aerated biofilm reactor (mMABR) that combined oxygen permeable membranes and inert attachment media to support both nitrification and denitrification was used to treat a carbon-limited (COD:N = 1.8) and ammonium-rich (NH4+ = 650 g-N/m3) space habitation waste stream. An eight-fold increase in intramembrane air pressure did not affect process performance; however, for an air pressure of 11 kPa (gauge), lower and upper hydraulic loading limits for the mMABR were identified at 30 g-N/m3 x d and 123 g-N/m3 x d, respectively. Oxygen limitation occurred at the highest loading rate and alkalinity limitation occurred at the lowest loading rate. Partial nitrification was noted at both limitations. Additionally, increased recirculation ratios were shown to decrease denitrification efficiency. Mean carbon and nitrogen removal rates were as high as 75.3 g-C/m3 x d (0.26 g-C/m2d) and 63.8 g-N/m3 x d (0.22 g-N/m2 x d), respectively. The mMABR achieved maximal nitrification and denitrification performance given the stoichiometric nature of the waste.

Much focus has been placed on the impact of exposure to perchlorate (ClO4(-)) from drinking water. Recently, it has become more apparent that a significant percentage of the total ClO4(-) exposure may be due to ingestion of food. Most studies have only evaluated the uptake and distribution of ClO4(-) by plants without considering the potential for uptake of iodine (I) by the plant and the subsequent impacts on ClO4(-) uptake and distribution on human health. The objectives of this research effort were to evaluate the relative uptake of ClO4(-) and I supplied as either KI or KIO3, the two major environmental forms of I in a standard hydroponic nutrient solution using butter head lettuce. No interaction of ClO4(-) uptake and distribution was found in the presence of I(-) or IO3(-) relative to previous studies evaluating ClO4(-) alone. Bioconcentration factors for ClO4(-) and total I in butter head lettuce when coexposed to both anions were similar for outer (292 ± 17 and 294 ± 12 L kg(-1) of dry weight, respectively) and inner (76 ± 18 and 60 ± 8 L kg(-1) of dry weight, respectively) leaves but not for roots (23 ± 3.7 and 359 ± 1.7 L kg(-1) of dry weight, respectively) when the iodine was supplied as I(-). The uptake of iodine was lower (BCF = 47 ± 3.8, 19 ± 0.6, and 189 ± 16, L kg(-1) of dry weight for the outer and inner leaves and roots, respectively) for all tissues when iodine was supplied as IO3(-), with the greatest accumulation by the roots. These results suggest that if lettuce is grown using fertilizers containing both ClO4(-) and I(-), then the final ratio of IT/ClO4 in the leaves will be essentially equal to the ratio in the fertilizer but lower if the I is supplied as IO3(-). Therefore, the impact of the consumption of lettuce containing ClO4(-) may be mitigated if the lettuce is grown using fertilizer with an appropriate amount of I to maintain the existing ratio of serum I to total goitrogen load (TGL). Nevertheless, the TGL in lettuce appeared to be almost completely dominated by NO3(-) with only a minor contribution of ClO4(-), even for the highest exposure to ClO4(-).

A new ion chromatography electrospray tandem mass spectrometry (IC-ESI/MS/MS) method has been developed for quantification and confirmation of chlorate (ClO3−) in environmental samples. The method ...

Perchlorate (ClO4(-)) is ubiquitous in the environment. It is produced naturally by atmospheric photochemical reactions, and also is synthesized in large quantities for military, aerospace, and industrial applications. Nitrate-enriched salt deposits of the Atacama Desert (Chile) contain high concentrations of natural ClO4(-), and have been exported worldwide since the mid-1800s for use in agriculture. The widespread introduction of synthetic and agricultural ClO4(-) into the environment has contaminated numerous municipal water supplies. Stable isotope ratio measurements of Cl and O have been applied for discrimination of different ClO4(-) sources in the environment. This study explores the potential of 36Cl measurements for further improving the discrimination of ClO4(-) sources. Groundwater and desert soil samples from the southwestern United States (U.S.) contain ClO4(-) having high 36Cl abundances (36Cl/Cl = 3100 x 10(-15) to 28,800 x 10(-15)), compared with those from the Atacama Desert (36Cl/Cl = 0.9 x 10(-15) to 590 x 10(-15)) and synthetic ClO4(-) reagents and products (36Cl/Cl = 0.0 x 10(-15) to 40 x 10(-15)). In conjunction with stable Cl and O isotope ratios, 36Cl data provide a clear distinction among three principal ClO4(-) source types in the environment of the southwestern U.S.

Natural perchlorate is believed to be of atmospheric origin, yet no systematic study has been conducted to evaluate perchlorate deposition rate and possible seasonal or spatial variations. This study evaluated perchlorate concentrations in weekly composite wet deposition samples acquired through the National Atmospheric Deposition Program from 26 sites across the continental United States, Alaska, and Puerto Rico for a 1-3 year period. Perchlorate concentrations varied from5 ng/L to a high of 102 ng/L with a mean of 14.1 +/- 13.5 ng/L for the 1578 total samples. The annual perchlorate flux by site ranged from a low of 12.5 (TX) to 157 mg/ha-year (NE) and averaged 65 +/- 30 mg/ha-year for all sites. Perchlorate concentrations and flux in wet deposition were generally highest in May-August declining to lows in December-February. Average annual perchlorate flux was correlated (r0.5; p0.001) with Ca2+, K+, NH4+, NO3(-), Cl(-), and SO4(-2). Wet deposition rate of ClO4(-) in the conterminous United States (excluding Alaska, Hawaii, and Puerto Rico) while diffuse, represents a potential annual net mass flux of 51,000 kg, a value comparable to the estimated annual environmental releases from other known ClO4(-) sources.

Overwhelming evidence now exists that perchlorate is produced through natural processes and can be ubiquitously found at environmentally relevant concentrations in arid and semi-arid locations. A number of potential production mechanisms have been hypothesized and ClO(4)(-) production by ozone oxidation of surface bound Cl(-) was demonstrated. However, no information concerning the impact of concentration, final reaction products distribution, impact of reaction phase, or oxidation of important oxychlorine intermediates has been reported. Using IC-MS-MS analysis and replicate oxidation experiments, we show that exposing aqueous solutions or Cl(-) coated sand or glass surfaces to O(3) (0.96%) generated ClO(4)(-) with molar yields of 0.007 and 0.01% for aqueous Cl(-) solutions and 0.025 and 0.42% for Cl(-) coated sand and glass, respectively. Aqueous solutions of Cl(-) produced less ClO(4)(-) than Cl(-) coated sand or glass as well as a higher ratio of ClO(3)(-) to ClO(4)(-). Reduction of the initial Cl(-) mass resulted in substantially higher molar yields of ClO(4)(-) and ClO(3)(-). In addition, alkaline absorbers that captured gaseous products contained substantial quantities of Cl(-), ClO(3)(-), and ClO(4)(-). Solutions of possible oxychlorine intermediates (OCl(-) and ClO(3)(-)) exposed to O(3) produced only scant amounts of ClO(4)(-) while a ClO(2)(-) solution exposed to O(3) produced substantial molar yields of ClO(4)(-) (4% molar yield). Scanning electron microscopy coupled with energy energy-dispersive X-ray analysis demonstrated a significant loss of Cl(-) and an increase in oxygen on the Cl(-) coated silica sand exposed to O(3). While the experimental conditions are not reflective of natural conditions this work clearly demonstrates the relative potential of Cl(-) precursors in perchlorate production and the likely importance of dry aerosol oxidation over solution phase reactions. It also suggests that ClO(2)(-) may be a key intermediate while ClO(3)(-) and OCl(-) are unlikely to play a significant role.

Recent studies have shown that natural perchlorate may be an important component to the general population exposure. These studies indicate that natural perchlorate is likely deposited by atmospheric deposition. Perchlorate concentration of total (dry + wet) deposition is relatively unstudied yet these measurements will aid in understanding natural levels in the environment. We sampled total deposition monthly at six sites in Suffolk County, Long Island, NY from November 30, 2005 until July 5, 2007. The mean perchlorate concentration is 0.21 ± 0.04 (standard error) μg L−1 with a maximum value of 2.78 μg L−1 . Here we show up to an 18-fold increase above the mean concentration in July 2006 and July 2007 samples. It appears that this increase in perchlorate in total deposition is associated with Fourth of July fireworks.

A study on perchlorate distribution was conducted in male adult prairie voles (Microtus ochrogaster). Excretion via urine was the major pathway for perchlorate fate in the body, with the highest concentrations of perchlorate detected in urine after exposure to perchlorate through drinking water [250 μg/ml Mg(ClO4)2], and an average of 34% and 88% of perchlorate intake recovered in urine in the 4- and 8-h exposure groups, respectively. Perchlorate mass in kidney, thyroid, blood, and urine were related to perchlorate intake (254.5–2687.7 μg). Perchlorate excretion and depuration patterns via urine were tested further using male adult deer mice (Peromyscus maniculatus). Animals were exposed to perchlorate through dosed drinking water (0, 17, 165, and 1600 ng/ml). Perchlorate concentrations in urine showed a significant difference among the three dosed groups during a 28-day exposure period. However, no difference was found in urine among the three dosages in terms of mass percentage of perchlorate intake from water at each sampling time over the 28-day exposure period. Both concentrations of perchlorate and mass percentage in urine reached a steady state after 1 day in all treatments. On average 46%, 46%, and 61% of perchlorate intake from water was recovered in urine over the exposure period in high, medium, and low dose groups, respectively. Including perchlorate consumption from rodent chow (1.44 ng/g), less than 46% of perchlorate intake was recovered in urine in the high and medium dose groups, and 0.99 in both the low and high dose groups; half-lives of perchlorate in deer mice were estimated as 9.12 and 7.25 h in the low and high dose groups, respectively. Endogenous generation of perchlorate and/or some degree of retention or metabolism of perchlorate may occur in deer mice, based in part on the uncompleted mass balance in the excretion and depuration experiments. The data reported herein should provide additional insight for perchlorate fate determination in animals and humans and valuable information for perchlorate risk assessment in the environment, especially wildlife.

Runoff of organic and inorganic contaminants from live firing ranges is a challenging issue because of the extensive size, the variable nature of runoff, the random occurrence of surface contamination, and general inaccessibility. This is particularly true with energetic compounds such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). One potentially promising technology for addressing runoff in a passive, sustainable, and low-cost manner is the use of constructed wetlands to intercept flow. This research effort investigated the ability of down-flow constructed wetlands to remediate RDX-contaminated water at varying loading rates over a period of 2 years. The impact of competing electron acceptors (NO3− and SO42−), the role of plants in the remediation process, and the production of initial daughter products were determined. Significant RDX removal occurred (89–96%) for all loading rates (160–1600 mg/(m2 day)) at a hydraulic retention time of approximately 2 days. RDX degradation occurred in both NO3− and SO42− dominated electron acceptor zones. RDX and NO3− degradation rate constants (kRDX and k N O 3 − ) were also determined using a 1D transport model with dispersion. KRDX declined with the increase of influent RDX (6.2 − 0.8 d−1 for planted mesocosms). Changes in degradation rates may be the result of changing bioavailability of carbon released by the peat moss. k N O 3 − followed similar trends but was relatively greater than kRDX. Removal of plants is believed to have a small impact on overall RDX removal. RDX concentration in plant tissue was found to be semi-logarithmically related to RDX concentration in the rhizosphere. MNX, DNX, and TNX were observed as transient products generally proportional to RDX loading and low concentrations of MNX and DNX were detected in plant tissue at high RDX loading rates. Cessation of RDX exposure substantially reduced RDX concentrations plants over 6 weeks. These results support the use of constructed wetlands for the remediation of low-level RDX-contaminated water.