Freezing-assisted sugaring-out liquid-liquid extraction coupled with LC-MS/MS for quantitative determination of perchlorate in honey

For the first time, a simple, quick, sensitive, and low cost method for quantification of perchlorate in honey using liquid chromatography-tandem mass spectrometry was developed. Through freezing-assisted sugaring-out liquid-liquid extraction, one-step simultaneous extraction and clean-up of perchlorate from honey were perfectly achieved. Glucose and fructose, the most abundant sugars in honey, were almost completely removed from the extract without use of any clean-up materials. Under optimum conditions, the proposed approach exhibited satisfactory linearity, negligible matrix effects, and low detection limit of 0.05 µg/kg, providing recoveries of 96.7 %-102.3 % with relative standard deviation of < 9 % for honey samples. The validated method was applied to the analysis of perchlorate in 36 honey samples, and detection rate was 94.4 %. This work provided a simple and reliable method for extensive monitoring of perchlorate in honey and opened- up new insights for analysis of contaminants in honey matrixes.

Chlorate and perchlorate in tea leaves from major producing regions in China and related human exposure risk

Chlorate and perchlorate are emerging pollutants that may interfere with thyroid function. Since they are highly water soluble, chlorate and perchlorate in tea leaves cause health concerns but have scarcely been studied. In this study, chlorate and perchlorate concentrations in 216 tea samples from different regions of China were determined. Perchlorate was detected in all the samples with a median concentration of 44.1 μg kg-1, while the chlorate detection frequency was 15.7%. We observed regional differences in perchlorate contents in tea leaves, with the highest quantity found in the central region of China. Except for dark tea, the concentration of perchlorate in tea infusions decreased with the increased number of times the tea leaves were brewed. The hazard quotients (HQs) of chlorate and perchlorate in all the samples were less than 1, suggesting negligible health risks caused by these pollutants from tea consumption. To the best of our knowledge, this is the first study to investigate chlorate and perchlorate contamination in tea infusions by simulating brewing behavior.

Quantification of Chlorate and Perchlorate in a Broad Range of Food Commodities, Including Baby Food, Nutritional Formulas, and Ingredients by LC-MS/MS: First Action AOAC 2022.06

BACKGROUND

Chlorate is an effective herbicide, but also a byproduct of chlorinating agents used to disinfect water, which is one of the reasons why it is regularly found in food. Perchlorate is a ubiquitous contaminant, which is naturally occurring in the environment but also released from anthropogenic sources such as the industrial use of certain natural fertilizers. Chlorate affects the hematological system, and perchlorate the thyroid.

OBJECTIVE

Implement and validate a simple and robust analytical method for the accurate determination of chlorate and perchlorate in baby food, infant and adult formulas, and ingredients thereof, which is suited for its application in routine environments where a broad variety of food commodities must be analyzed simultaneously.

METHOD

Typically, analytes are extracted with a mixture of water, acidified methanol, and dichloromethane. Optionally, for dairy products and byproducts, extraction can be performed with water, acidified methanol, and EDTA, followed by two steps of cleanup (freezing out and dispersive solid-phase extraction with C18 in acetonitrile). Quantitative determination is carried out by isotopic dilution liquid chromatography tandem mass spectrometry (LC-MS/MS).

RESULTS

The method was single-laboratory validated in five Nestlé Quality Assurance Centers (NQACs) in a comprehensive range of representative matrixes of different categories such as baby foods, infant/adult formulas, and ingredients, with results generally in agreement with the acceptance criteria of the Standard Method Performance Requirement (SMPR®) 2021.001 defined by AOAC INTERNATIONAL, in terms of representative matrixes validated, LOQs, trueness, and precision.The data generated during validation show that the method proposed is simple, accurate and robust enough to be implemented and applied in routine environments.

CONCLUSION

The data generated during validation show that the method proposed is simple, accurate and robust enough to be implemented and applied in routine environments.

HIGHLIGHTS

The AOAC Expert Review Panel approved the present method as AOAC Official First Action 2022.06.

A review of perchlorate contamination: Analysis and remediation strategies

Perchlorate has been categorised as a potential contaminant and researched for years, but there are still many unknowns regarding this anion's contamination impacts. In this review, the basic information about perchlorate is summarised and evaluated, including the physical-chemical properties, fate and transportation, toxicity, analysis, and remediation. Especially, recent advances on analysis and remediation are emphasised and evaluated, such as in-situ imaging analysis and on-site bio-remediation respectively. The high solubility and persistence of the perchlorate anion mean its contamination is different from others, particularly in terms of analysis and remediation that might lead to secondary contamination. The knowledge gaps are listed for future research.

Coremoval of Energetics and Oxyanions via the In Situ Coupling of Catalytic and Enzymatic Destructions: A Solution to Ammunition Wastewater Treatment

Ammunition wastewater contains toxic nitrated explosives like RDX and oxyanions like nitrate and perchlorate. Its treatment is challenged by low efficiency due to contaminant recalcitrance and high cost due to multiple processes needed for separately removing different contaminant types. This paper reports a H₂-based low-energy strategy featuring the treatment of explosives via catalytic denitration followed by microbial mineralization coupled with oxyanion reduction. After a nitrate- and perchlorate-reducing biofilm incapable of RDX biodegradation was coated with palladium nanoparticles (Pd⁰NPs), RDX was rapidly denitrated with a specific catalytic activity of 8.7 g_cat^-1 min^-1, while biological reductions of nitrate and perchlorate remained efficient. In the subsequent 30-day continuous test, >99% of RDX, nitrate, and perchlorate were coremoved, and their effluent concentrations were below their respective regulation levels. Detected intermediates and shallow metagenome analysis suggest that the intermediates after Pd-catalytic denitration of RDX ultimately were enzymatically utilized by the nitrate- and perchlorate-reducing bacteria as additional electron donor sources.

Perchlorate in shellfish from South China Sea and implications for human exposure

Shellfish can absorb and accumulate contaminants. The consumption of shellfish could expose humans to pollutants and increase related health risk. Perchlorate (ClO₄^-) is a ubiquitous pollutant and could affect thyroid functions, especially for children and pregnant women. However, knowledge on the contamination of perchlorate in aquatic food such as shellfish remains limited. This study aimed to investigate the abundances of perchlorate in shellfish from South China Sea and to assess human exposure risks. A total of 178 shellfish samples from eight species were collected from offshore aquaculture waters in South China Sea. Perchlorate was detected in 99.4% of them, suggesting widespread pollution in coastal waters. Concentrations of perchlorate ranged from not detected (N.D.) to 71.5 μg kg^-1, with a median value of 4.33 μg kg^-1. Estimated daily intake (EDI) and hazard quotient (HQ) were used to assess human exposure dose and health risks, respectively. The HQ values were determined to be less than 1, indicating no significant health risks to local residents via shellfish consumption. To our knowledge, this is the first study to investigate perchlorate contamination in South China shellfish and assess potential human risks.

Rapid Cleanup of a Perchlorate Plume from Fireworks

Perchlorate was detected in a municipal wellfield in Evart, Michigan in April 2015. Perchlorate concentrations were detected initially in six of the City's wells at concentrations ranging up to 20 μg/L. An investigation to identify the source determined that the perchlorate was from fireworks launched during the annual 4th of July show held at the fairgrounds located upgradient from the wellfield. The use of approximately 600 kg of fireworks during the annual display resulted in an annual loading of approximately 4 kg of perchlorate to groundwater. An aggressive groundwater extraction system began operation in June 2016 to restore water quality in the affected aquifer, and the 2016 fireworks display was relocated to a location outside the capture zone of the water supply wells. Within 18 months average perchlorate concentrations in the water supply wells had been reduced to about 0.6 μg/L. The extraction system continued to operate through the end of 2019, by which time the average perchlorate concentrations in the water supply wells were reduced to 0.2 μg/L. In 2019, approximately 0.4 kg of perchlorate were removed from the aquifer, about one-half of the amount removed in 2018, reflecting the slow leaching of perchlorate of fireworks residuals from vadose zone soils.

Perchlorate occurrence in foodstuffs and water: Analytical methods and techniques for removal from water - A review

Perchlorate (ClO₄^-), a type of contaminant with high diffusivity and durability, has been widely detected in water and foodstuffs, arousing a global concern. It can interfere with normal function of the human thyroid gland, affecting human health. Therefore, determination of perchlorate in water and foodstuffs, and removal from water are important. This review focuses on the occurrence of perchlorate, mainly in water and foodstuffs, and provides an overview of analytical methods for determination of perchlorate over the last two decades. In addition, merits and drawbacks of the various methods have been considered. This review also highlights the most commonly used approaches for removal of perchlorate from water. Finally, current trends and future perspectives in determination of perchlorate and removal from water are proposed. This review provided a comprehensive understanding of perchlorate occurrence and its removal from water, and had practical significance in reducing the harm of perchlorate to human.

Dietary exposure and risk assessment of perchlorate in diverse food from Wuhan, China

The perchlorate levels in 330 foods belonging to 5 varieties obtained from Wuhan were monitored. An ultra-high performance liquid chromatography coupled with triple quadrupoles mass spectrometry in combination with Cl¹⁸O₄^- internal standard method was performed to determine the level of perchlorate in various foods. Hereafter, dietary exposure and risk assessment of perchlorate was evaluated. The results revealed that the average level of perchlorate was 15.04 µg/kg with a detection of 95% among the whole food groups. The level of perchlorate in vegetables was the highest among the 5 varieties of food with an average content of 27.39 µg/kg, which in meat was the lowest with an average of 3.65 µg/kg. Estimated dietary intake results illustrated that males showed exposure in the range 0.004-0.18 µg/kg bw/day, which for females was 0.01-0.21 µg/kg bw/day. The results indicated that exposure to perchlorate via the food consumption for Wuhan people was evaluated as safe.

Dietary exposure assessment to perchlorate in the Taiwanese population: A risk assessment based on the probabilistic approach

Perchlorate is an endocrine-disrupting chemical (EDC) that contaminate various foodstuffs. Exposure to perchlorate may cause severe health problems, mainly thyroid dysfunction. However, information on perchlorate contamination of consumer foods in Taiwan is limited. This study investigated perchlorate levels in 310 food samples belonging to 12 food groups collected from Taiwanese markets. A probabilistic risk assessment was conducted to assess the related exposure to Taiwanese people. Perchlorate was detected in 65% of the samples and high levels were identified in certain plant-origin, fruit, and processed food samples. A probabilistic approach was used to estimate daily dietary dose (Monte Carlo-estimated 95th percentile dietary exposure [MCS 95]) by using the Taiwan National Food Consumption database for 14 sex/age groups. The highest and lowest average daily doses (ADDs) were in the age groups of >65 years (MCS 95 = 3.60/3.90 [male/female] μg/kg bw/day) and 16-18 years (MCS 95 = 1.70/1.47 [M/F] μg/kg bw/day), respectively. The 95th percentile of the hazard index of exposure to perchlorate of all sex/age groups far exceeded the tolerable daily intake (0.3 μg/kg bw/day) and reference dose (0.7 μg/kg bw/day) set by the European Food Safety Authority and US EPA, respectively, but it was lower than the provisional maximum tolerable daily intake (10 μg/kg bw/day) suggested by the Joint FAO/WHO Expert Committee on Food Additives. The intake quantity and concentrations of perchlorate from vegetables, fruits, and whole grains are the critical contributors for the ADDs and integrated risk of dietary exposure to perchlorate. Long-term exposure through diets should be considered, instead of focusing on individual EDC during dietary risk assessment in specific populations. Furthermore, cumulative risks for exposure to multiple contaminants, particularly those causing thyroid adverse effects, may be higher than that from perchlorate exposure alone.

Runoff from firework manufacturing as major perchlorate source in the surface waters around Diwali in Ahmedabad, India

Fireworks events during the annual Indian festival of Diwali has been heavily criticised in recent times. Perchlorate is an essential component of fireworks. The effects of the fireworks on perchlorate (ClO₄^-) concentrations and quality parameters of the ambient waters of Ahmedabad, Gujarat, India were studied. As expected, ClO₄^- concentrations in the (Kankaria) lake adjoining the fireworks site were below detection prior to the Diwali event and increased to 0.97 and 1.03 μg/L at 48 and 288 h after the event, respectively. However, samples from the Sabarmati River surprisingly contained an extremely high concentration of ClO₄^- (65 μg/L) one day before the event, which decreased to 1.14 μg/L after 48 h and was below detection limit after 7 days of the event. This finding raises questions such as: (a) which has greater impact, fireworks manufacturing or burning; (b) can unregulated release of untreated effluents be a major critical source of pollution needing immediate attention from removal, environmental regulation and policy perspectives; c) is policy pertaining to unskilled labour in the manufacturing of fireworks and other ClO₄^--containing products needed in developing countries; and d) is ClO₄^- being a strong oxidiser, detrimental to the soil, groundwater, and aquatic environment?

Extension of shelf life of semi-dry longan pulp with gaseous chlorine dioxide generating film

A packaging system using gaseous chlorine dioxide generating film (CDGF) in a sealed container was developed to extend the shelf life of semi-dry longan pulp (moisture content 38.8 wt%; a_w0.8). The antimicrobial properties, formation of chloroxyanion residues and effects of CDGF on the quality of semi-dry longan pulp were investigated. CDGF was triggered by the moisture vapor from semi-dry longan pulp in the sealed container and released gaseous ClO₂ into the headspace of the container. The antifungal test showed that CDGF significantly inactivated artificially inoculated molds in semi-dry longan pulp and achieved reductions of over 3 log CFU/g after 28 days storage at room temperature (25 °C). CDGF reduced total aerobic bacterial populations by over 6.4 log CFU/g and maintained these population levels at around 2.0 log CFU/g throughout the 180-day storage period at room temperature. The residual concentrations of chloride, chlorate and perchlorate in longan pulp increased and then decreased during the 180-day storage. Residual chloride levels were maintained at 1.5 mg/g after Day 120 and residual chlorate and perchlorate levels were not detected after Day 120 and Day 180, respectively, in CDGF-treated samples. CDGF treatments reduced total polyphenol content but didn't have any significant impact on the levels of polysaccharides in samples. There were no significant differences between CDGF-treated and control samples in color changes during storage. The content of 5-hydroymethylfurfural (5-HMF) in both samples increased during storage, suggesting that the Maillard reaction occurred. This study demonstrated an effective approach to develop a new antimicrobial packaging system for semi-dry longan pulp.

Environmental fluxes of perchlorate in rural catchments, Ontario, Canada

Quantitative information about fluxes of perchlorate in the environment is lacking. This study reports analyses of perchlorate in various environmental waters sampled from rural headwater catchments in the Thames River basin in southern Ontario (Canada) that provide evidence about the fluxes and fate of perchlorate in the environment. Concentrations in streams (16 to 1047 ng/L) were used to estimate exports from these rural catchments (228-1843 mg/(ha·year)), atmospheric deposition (1480 ± 230 mg/(ha·year)), as well as variable rates of microbial degradation of perchlorate, which appeared to be enhanced in catchments with higher percentages of wetlands. Groundwater data supported earlier evidence that degradation of perchlorate occurs in the subsurface under oxygen-depleted conditions. The stream data suggest that the rate of degradation varies strongly between catchments and ranges up to >1000 mg/(ha·year).

A novel ex-situ bio-remediation process for perchlorate contaminated soil

A novel, ex-situ remediation process for perchlorate contaminated soil is reported in this study. This approach comprises washing the contaminated soil with water, followed by treatment of the wash water in a bioreactor. The treated water reused for the next batch of soil, and the cycle continued. The pilot-scale treatment unit comprising of a soil washing unit (0.75 m3) and a fixed-film bioreactor (140 L), both connected in series for continuous operation for a period of three months. The bioreactor was inoculated with a novel perchlorate reducing microbial consortium comprising Serratia marcescens (Gen bank no. HM751096), Bacillus pumilus (Gen bank no. JQ820452) and Micrococcus sp. (Gen bank no. KJ410671). The microbial activity was supported by glucose (glucose/perchlorate ratio = 5), and trace mineral solution. In a typical washing cycle, 2.5 g perchlorate (KClO4) spiked in 670 kg soil was completely removed in three washing cycles, that completed in 6.3 h consuming ∼360 L water. The pooled wash water containing perchlorate at 8.5 mg/L was treated completely in the bioreactor operated at 4.5 h HRT and -200 mV ORP. Compared with both in-situ and ex-situ remediation methods reported, the present approach has many advantages for treating perchlorate contaminated soil.

A Colorimetric Artificial Olfactory System for Airborne Improvised Explosive Identification

The detection of ultralow or nonvolatile target analytes remains a significant challenge for artificial olfactory systems even after decades of development, which severely limits their widespread application. To overcome this challenge, an artificial olfactory system based on a colorimetric hydrogel array is constructed for the first time as a universal representative. As an effective extension of conventional artificial olfactory systems that integrates the merits of its predecessors, the proposed system accurately mimics olfactory mucosa and specific odorant binding proteins using hydrogels endowed with specific colorimetric reagents for the detection of hypochlorite, chlorate, perchlorate, urea, and nitrate. Therefore, the proposed system is capable of detecting and discriminating between these five airborne improvised explosive microparticulates with a detection limit as low as 39.4 pg. Additionally, the system demonstrates good reusability over ten cycles, rapid response time of ≈0.2 s, and excellent discrimination properties, despite significant variation. This proof-of-concept study on colorimetric artificial olfactory systems yields a novel strategy for the direct and discriminative detection of nonvolatile airborne microparticulates.

Uncommon chemical species in PM2.5 and PM10 and its potential use as industrial and vehicular markers for source apportionment studies

Chemical characterization of PM_2.5 and PM₁₀ is important to identify potential compounds that induce biological responses that translate into cardio-respiratory health problems. This study shows the reliability of the use of crystalline phases, identified in samples from receptor sites, as source markers, helping researchers to infer the main sources of air pollution, even without the use of receptor models. PM_2.5 and PM₁₀ samples were collected at two sites in an urban industrialized region located at southeast of Brazil and analyzed by Synchrotron X-ray Diffraction to identify crystalline compounds. Results show 5 PM₁₀ and PM_2.5 species not previously reported in the literature. We propose reaction mechanisms for these species and identify specific sources for each crystalline phase found: BaTiO₃ was found in PM₁₀ receptor samples and proved to be a vehicular marker formed during brake action; maghemite (γ-Fe₂O₃), pyracmonite [(NH₄)₃Fe(SO₄)₃], ammonium perchlorate (NH₃OHClO₄) and potassium ferrate (K₂Fe₂O₄) were found in PM_2.5 proved to be markers of industrial activities. The crystalline phases found in PM samples from receptor sites and the mechanisms of reactions showed the reliability of the use of crystalline phases as source markers in the identification of potential sources of air pollution without misinterpretation of the likely source.

Nitrate effects on perchlorate reduction in a H2/CO2-based biofilm

The H₂/CO₂-based membrane biofilm reactor (H₂/CO₂-MBfR) that effectively combines microporous diffusions of H₂ and CO₂ is efficient in removing perchlorate (ClO₄^-). Nitrate (NO₃^-) is a common oxidized contaminant frequently coexists with ClO₄^- in water, with the NO₃^- concentration in most ClO₄^--contaminated waters being several orders of magnitude higher than ClO₄^-. Determining the effect of NO₃^- on ClO₄^- reduction is a critical issue in practice. The ClO₄^- reduction performance, biofilm microbial community and influencing mechanism were investigated under a series of feed NO₃^- loadings in this work. ClO₄^- reduction was slightly promoted when NO₃^--N levels were <10 mg/L and inhibited at higher NO₃^--N levels. Denitrification competed more strongly for H₂ than ClO₄^- reduction, regardless of H₂ availability. A higher NO₃^--N loading was a strong driving force to change the biofilm microbial community. Betaproteobacteria were the dominant bacteria at all stages, and the biofilm reactor was enriched in Methyloversatilis and Zoogloea (31.9-56.5% and 10.6-25.8%, respectively). Changes in the relative amounts of Methyloversatilis and Zoogloea coincided with changes in the ClO₄^- fluxes and removal efficiencies and the relative abundances of nitrogen cycle functional genes. These results suggest that Methyloversatilis and Zoogloea likely follow independent reduction mechanisms for ClO₄^- removal.

LC-ESI-MS/MS determination of oxyhalides (chlorate, perchlorate and bromate) in food and water samples, and chlorate on household water treatment devices along with perchlorate in plants

The results of the validation study of the LC-ESI-MS/MS method for the determination of chlorate (ClO₃^-), perchlorate (ClO₄^-) and bromate (BrO₃^-) in water and food samples are summarized. Towards this, 284 samples of drinking water were analysed, out of which the 69% contained chlorate above the limit of quantitation (LOQ) of 0.01 mg/L, with maximum amount of 1.1 mg/L. Only 6 samples were found to be positive with perchlorate at levels <0.01 mg/L. Bromate was detected in 5 drinking water samples at levels above the LOQ, at concentrations up to 0.026 mg/L. For the validation of the method in food, 108 blank samples were spiked with chlorate and perchlorate for the LC-MS/MS analysis at two levels. In total 247 food samples from the market of 19 different commodities including fruits, vegetables, cereals and wine, were analysed. The maximum concentration of chlorate was found at 0.83 mg/kg in a sample of cultivated mushrooms. The number of samples contaminated with perchlorate was also small, with all the determined concentrations below the LOQ of 0.05 mg/kg. Experiments for the chlorate reduction in drinking water, showed that reverse osmosis treatment is effective in particular with newly installed cartridges. Finally, according to the results of the pilot study when chlorinated water is used for the plant irrigation, accumulation of chlorate is observed, especially in the green parts of the plant. Perchlorate was also detected in leafy samples, although it was not present in the irrigation water.

Perchlorate behavior in the context of black carbon and metal cogeneration following fireworks emission at Oak Lake, Lincoln, Nebraska, USA

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

Contamination of water resources of a small island state by fireworks-derived perchlorate: A case study from Malta

We have previously reported on the ubiquitous presence of perchlorate in the deposited and airborne fine dusts of Malta and shown that the source of the chemical in the dusts of this small central Mediterranean island is fireworks. There are no local geologic or anthropogenic sources of perchlorate other than firework manufacture and display. The hypothesis was tested that ground-deposited perchlorate will be mobilized in runoff and would partly migrate to the water table and eventually also affect tap water, one third of which being derived from groundwater. Forty four percent of 36 groundwater samples contained perchlorate above detection limit with mean and median values of 1.09 and 1.1 μg L^-1. Sixty-two percent of 16 runoff samples collected during storms contained perchlorate above detection limit with mean and maximum concentrations, respectively, of 50.8 and 129 μg L^-1, values which are far too high to be explained by atmospheric inputs given that rainwater perchlorate levels are typically <3 μg L^-1. Between 42 and 89% of the tap waters analyzed in three sampling campaigns contained perchlorate above detection limit and had mean concentrations ranging from 0.4 to 1.6 μg L^-1 suggesting contamination levels similar to those reported from China but lower than levels reported from the USA. The phenomenon of contamination of the water resources of Malta by perchlorate is probably unique in that it results not from geologic or industrial inputs but from an intense and prolonged pyrotechnic activity that is deeply rooted in the popular culture of the islanders.

One-step sample processing method for the determination of perchlorate in human urine, whole blood and breast milk using liquid chromatography tandem mass spectrometry

A one-step sample processing was developed to determine the levels of perchlorate in human urine, whole blood and breast milk by using liquid chromatography tandem mass spectrometry (LC-MS/MS). Athena C18-WP column was used to separate and analyze perchlorate. Perchlorate and isotope-labeled perchlorate (Cl¹⁸O₄^-) internal standards were spiked in the sample matrix through vortex mixing, centrifugation, and filtration. The filtrate was collected and subjected to LC analysis. The developed method was validated for its reproducibility, linearity, trueness, and recovery. Satisfactory recovery of perchlorate ranged from 81% to 117% with intraday relative standard deviations (RSDs) (n = 3) and inter-day RSDs (n = 9) of 5-18% and of 5-16%, respectively. Good linearity (R² ≥ 0.99) was observed. Limits of detection and quantification for perchlorate ranged from 0.06 µg/L to 0.3 µg/L and from 0.2 µg/L to 1 µg/L, respectively. Perchlorate concentrations were found in human urine (n = 38) and whole blood (n = 8) samples with the range of 6.5-288.6 µg/L and 0.3-2.8 µg/L, respectively. These results indicate the applicability of our developed method in determining perchlorate level in real samples. Moreover, this method is also highly reliable, sensitive and selective in detecting perchlorate in human urine, whole blood and breast milk samples and may be applicable to other matrixes i.e. saliva, serum, plasma, milk powder and dairy milk.

Biological perchlorate reduction: which electron donor we can choose?

Biological reduction is an effective method for removal of perchlorate (ClO₄^-), where perchlorate is transformed into chloride by perchlorate-reducing bacteria (PRB). An external electron donor is required for autotrophic and heterotrophic reduction of perchlorate. Therefore, plenty of suitable electron donors including organic (e.g., acetate, ethanol, carbohydrate, glycerol, methane) and inorganic (e.g., hydrogen, zero-valent iron, element sulfur, anthrahydroquinone) as well as the cathode have been used in biological reduction of perchlorate. This paper reviews the application of various electron donors in biological perchlorate reduction and their influences on treatment efficiency of perchlorate and biological activity of PRB. We discussed the criteria for selection of appropriate electron donor to provide a flexible strategy of electron donor choice for the bioremediation of perchlorate-contaminated water.

Evidence for Biotic Perchlorate Reduction in Naturally Perchlorate-Rich Sediments of Pilot Valley Basin, Utah

The presence of perchlorate on Mars suggests a possible energy source for sustaining microbial life. Perchlorate-reducing microbes have been isolated from perchlorate-contaminated soils and sediments on the Earth, but to date, never from an environment that is naturally enriched in perchlorate. The arid Pilot Valley paleolake basin in Utah is a Mars analog environment whose sediments are naturally enriched with up to ∼6.5 μg kg^-1 perchlorate oxyanions. Here, we present results of field and laboratory studies indicating that perchlorate-reducing microorganisms co-occur with this potential electron acceptor. Biogeochemical data suggest ongoing perchlorate reduction; phylogenetic data indicate the presence of diverse microbial communities; and laboratory enrichments using Pilot Valley sediments show that resident microbes can reduce perchlorate. This is the first article of the co-existence of perchlorate-reducing microbes in an environment where perchlorate occurs naturally, arguing for Pilot Valley's utility as an analog for studying biogeochemical processes that may have occurred, and may yet still be occurring, in ancient martian lacustrine sediments.

Seasonal Variation and Exposure Risks of Perchlorate in Soil, Indoor Dust, and Outdoor Dust in China

A total of 97 paired soil, outdoor dust, and indoor dust samples were collected in the national scale of China in summer, and the perchlorate levels were compared with those in soil and outdoor dust samples collected in winter in our previous study. The median perchlorate concentrations in the outdoor dust, indoor dust, and soil samples were 8.10, 11.4, and 0.05 mg/kg, respectively, which were significantly lower than those in the winter samples due to the natural factors and human activities. No significant differences in perchlorate concentrations were found between Northern and Southern China in the dust samples, whereas the difference was obtained in the soil samples. In the terms of possible source, the perchlorate levels in the outdoor dust exhibited strong correlation with SO₄^2- (r² = 0.458**) and NO₃^- (r² = 0.389**), indicating part of perchlorate in outdoor environment was likely from atmospheric oxidative process in summer. The perchlorate, SO₄^2-, and Cl^- levels in the indoor dust were significantly related to those in the outdoor dust, suggesting that outdoor contaminants might be an important source for indoor environment. Furthermore, the human exposure to perchlorate was under relatively safe state in China except for special sites or periods with high perchlorate levels. Dust made an unexpected contribution of 41.3% to the total daily perchlorate intake for children, whereas 2.46% for adults in China based on biomonitoring, which deserves more attention.

Evaluation of the Tindouf Basin Region in Southern Morocco as an Analogue Site for Soil Geochemistry on Noachian Mars

Locations on Earth that provide insights into processes that may be occurring or may have occurred throughout martian history are often broadly deemed "Mars analog environments." As no single locale can precisely represent a past or present martian environment, it is important to focus on characterization of terrestrial processes that produce analogous features to those observed in specific regions of Mars or, if possible, specific time periods during martian history. Here, we report on the preservation of ionic species in soil samples collected from the Tindouf region of Morocco and compare them with the McMurdo Dry Valleys of Antarctica, the Atacama Desert in Chile, the martian meteorite EETA79001, and the in situ Mars analyses from the Phoenix Wet Chemistry Laboratory (WCL). The Moroccan samples show the greatest similarity with those from Victoria Valley, Beacon Valley, and the Atacama, while being consistently depleted compared to University Valley and enriched compared to Taylor Valley. The NO₃/Cl ratios are most similar to Victoria Valley and Atacama, while the SO₄/Cl ratios are similar to those from Beacon Valley, Victoria Valley, and the Atacama. While perchlorate concentrations in the Moroccan samples are typically lower than those found in samples of other analog sites, conditions in the region are sufficiently arid to retain oxychlorines at detectable levels. Our results suggest that the Tindouf Basin in Morocco can serve as a suitable analogue for the soil geochemistry and subsequent aridification of the Noachian epoch on Mars.

Collective Ion-Pair Single-Drop Microextraction Attenuated Total Reflectance Fourier Transform Infrared Spectroscopic Determination of Perchlorate in Bioenvironmental Samples

Perchlorate (ClO4-) is an environmental pollutant that affects human health. Perchlorate acts as a competitive inhibitor of iodine uptake in the thyroid gland (sodium-iodide symporter inhibitor); thus, its determination is important for public health concerns. Water and milk constitute a significant portion of the human diet. Because regular intake leads to an increase in perchlorate concentration in the human body, the estimation of perchlorate is of great concern. In this work, ion-pair single-drop microextraction (SDME) combined with attenuated total reflectance (ATR)-FTIR spectroscopy has been developed for the determination of perchlorate in bioenvironmental (soil, water, dairy milk, breast milk, and urine) samples. Perchlorate was extracted in a single drop of methyl isobutyl ketone as an - with the cationic surfactant cetyltrimethylammonuim bromide under optimized conditions. The strongest IR peak (at 1076 cm-1) was selected for the quantification of perchlorate among three observed vibrational peaks. Eight calibration curves for different concentration ranges of perchlorate were prepared, and excellent linearity was observed for absorbance and peak area in the range of 0.03-100 ng/mL perchlorate, with r values of 0.977 and 0.976, respectively. The RSDs (n = 8) for the perchlorate concentration ranges of 0.03-100, 0.03-0.5, 0.5-10, and 10-100 ng/mL were in the range of 1.9-2.7% for the above calibration curves. The LOD and LOQ in the present work were 0.003 and 0.02 ng/mL, respectively. The extracted microdrop was analyzed directly by ATR-FTIR spectroscopy. The parameters affecting SDME, i.e, effect of pH, stirring rate, reagent concentration, microdrop volume, and extraction time, were optimized, and the role of foreign species was also investigated. F- and t-tests were performed to check the analytical QA of the method. A noteworthy feature of the reported method is the noninterference of any of the associated ions. The results were compared with those of the ion chromatography MS method, and a high degree of acceptability was found. The method was successfully applied for the determination of perchlorate in bioenvironmental samples.

Enhancement of perchlorate removal from groundwater by cationic granular activated carbon: Effect of preparation protocol and surface properties

In order to obtain a high adsorption capacity for perchlorate, the epoxide-forming quaternary ammonium (EQA) compounds were chemically bonded onto granular activated carbon (GAC) surface by cationic reaction. The optimum preparation condition of the cationic GAC was achieved while applying softwood-based Gran C as the parent GAC, dosing EQA first at a pH of 12, preparation time of 48 h, preparation temperature of 50 °C, and mole ratio of EQA/oxygen groups of 2.5. The most favorable cationic GAC that had the QUAB360 pre-anchored exhibited the highest perchlorate adsorption capacity of 24.7 mg/g, and presented the longest bed volumes (3000 BV) to 2 ppb breakthrough during rapid small scale column tests (RSSCTs), which was 150 times higher than that for the pristine Gran C. This was attributed to its higher nitrogen amount (1.53 At%) and higher positive surface charge (0.036 mmol/g) at pH 7.5. Also, there was no leaching of the quaternary ammonium detected in the effluent of the RSSCTs, indicating there was no secondary pollution occurring during the perchlorate removal process. Overall, this study provides an effective and environmental-friendly technology for improving GAC perchlorate adsorption capacity for groundwater treatment.

Update on dietary intake of perchlorate and iodine from U.S. food and drug administration's total diet study: 2008-2012

The U.S. Food and Drug Administration's (FDA) Total Diet Study (TDS) monitors the US food supply for pesticide residues, industrial chemicals, radionuclides, nutrients, and toxic elements. Perchlorate and iodine intakes based on concentrations in TDS samples collected between 2008 and 2012 were estimated in order to update an earlier TDS dietary assessment. Perchlorate is used as an oxidizing agent in rocket and missile fuel, is formed naturally in the atmosphere, and occurs naturally in some soils. Because of perchlorate's presence in soil, and in irrigation, processing, and source water, it is widely found in food. Iodine was included in the study because perchlorate at high doses interferes with iodide uptake in the thyroid. Iodine (the elemental form of iodide) is essential for growth and development, and metabolism. This study uses a novel statistical method based on a clustered zero-inflated lognormal distribution model to estimate mean and 95^th percentile confidence interval concentrations for perchlorate and iodine in US foods. These estimates were used to estimate mean perchlorate and iodine exposures for the total US population and for 14 age/sex groups in the US population. Estimated mean perchlorate intake for the total US population was 0.13 μg/kg bw/day, with mean intakes for the 14 age/sex groups between 0.09 and 0.43 μg/kg bw/day. The estimated mean intakes of perchlorate for all age/sex groups were below EPA's reference dose (RfD) of 0.7 μg/kg bw/day. The estimated mean iodine intake for the total US population was 216.4 μg/person/day, with mean intakes ranging from 140.9 to 296.3 μg/person/day for the 14 age/sex groups, with all age/sex groups exceeding their respective estimated average requirements (EARs).

37Cl/35Cl isotope ratio analysis in perchlorate by ion chromatography/multi collector -ICPMS: Analytical performance and implication for biodegradation studies

In the present study we propose a new analytical method for ³⁷Cl/³⁵Cl analysis in perchlorate by Ion Chromatography(IC) coupled to Multicollector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS). The accuracy of the analytical method was validated by analysis of international perchlorate standard materials USGS-37 and USGS -38; analytical precision better than ±0.4‰ was achieved. ³⁷Cl/³⁵Cl isotope ratio analysis in perchlorate during laboratory biodegradation experiment with microbial cultures enriched from the contaminated soil in Israel resulted in isotope enrichment factor ε³⁷Cl = -13.3 ± 1‰, which falls in the range reported previously for perchlorate biodegradation by pure microbial cultures. The proposed analytical method may significantly simplify the procedure for isotope analysis of perchlorate which is currently applied in environmental studies.

Spatio-temporal distribution of perchlorate and its toxicity in Hydrilla verticillata

The spatio-temporal distribution of perchlorate in water sources around an ammonium perchlorate production unit and its toxicity response on a dominant aquatic plant, Hydrilla verticillata are reported in this study. Samples (n=453) from ground water (open well) and surface water sources within 5km from the production unit over a period of 12 months (2014, June - 2015, May) were screened for ClO₄^-. During the period, ClO₄^-concentration in ground water samples close to the production unit increased to >40,000μg/L, and ClO₄^- was detected at 1740μg/L in well water 1.6km away from the production unit. A community pond in the area also showed an increase in ClO₄^- level up to 29,000μg/L. In all water sources, ClO₄^- level was maximum during the rainy season (July, monsoon). A natural degradation of ClO₄^- was not observed in the area as evident from its persistent level and spreading to more areas. H. verticillata, the dominant vegetation in the pond exhibited severe toxic response like massive decay and loss of photosynthetic pigments such as chlorophyll and carotene due to ClO₄^- exposure. The plant accumulated ClO₄^- up to 60^±0.8mg/kg wet weight with a Bio-Concentration Factor 2.06±0.005. This is the first report on spatio-temporal distribution of ClO₄^- at higher levels in a natural environment and its toxicity response to plants under natural condition.

Stable isotopic composition of perchlorate and nitrate accumulated in plants: Hydroponic experiments and field data

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 ε (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.

Occurrence of perchlorate in groundwater, paired farmland soil, lettuce, and rhizosphere soil from Chengdu, China

A total of 28 groundwater, paired farmland soil, lettuce, and its rhizosphere soil samples were collected from Chengdu, China to detect perchlorate levels and to evaluate the relationships of perchlorate concentrations among these matrices. The perchlorate concentrations in the groundwater, farmland soil, lettuce, and rhizosphere soil samples ranged from below detection limit to 60.2 μg L-1, from below detection limit to 249 μg kg-1 dry weight (dw), from 2.07 to 1010 μg kg-1 wet weight, and from below detection limit to 314 μg kg-1 dw, respectively. Significant correlation was found in the perchlorate levels among the farmland soil, lettuce, and rhizosphere soil, suggesting that they have common pollution sources, or perchlorate might transfer from farmland soil-rhizosphere soil-plant. However, there is no significant correlation between groundwater and the other three matrices, indicating that infiltration from perchlorate contaminated farmland soil was not the predominant source for groundwater pollution in Chengdu. The perchlorate concentrations in the farmland soil and lettuce samples were significantly higher than those in the rhizosphere soil, primarily due to uptake of perchlorate through the rhizosphere micro-environment by lettuce, or accelerated degradation by rhizospheric microorganisms, which contributed more needs further investigation.

A review of perchlorate (ClO4-) occurrence in fruits and vegetables

Since the 1990s, a large number of studies around the world have reported the presence of perchlorate in different types of environmental matrices. In view of their inherent characteristics, such as high solubility, mobility, persistence, and low affinity for the surface of soil, perchlorates are mobilized through the water-soil system and accumulate in edible plant species of high human consumption. However, the ingestion of food products containing perchlorate represents a potential health risk to people due to their adverse effects on thyroid, hormone, and neuronal development, mainly in infants and fetuses. At present, research has been centered on determining sources, fates, and remediation methods and not on its real extension in vegetables under farming conditions. This review presents a comprehensive overview and update of the frequent detection of perchlorate in fruits and vegetables produced and marketed around the world. Additionally, the impact of fertilizer on the potential addition of perchlorate to soil and its mobility in the water-soil-plant system is discussed. This review is organized into the following sections: sources of perchlorate, mobility in the water-soil system, presence in fruits and vegetables in different countries, international regulations, and toxicological studies. Finally, recommendations for future studies concerning perchlorate in fruits and vegetables are presented.

Impacts of nitrate and electron donor on perchlorate reduction and microbial community composition in a biologically activated carbon reactor

The sensitivity of perchlorate reduction and microbial composition to varied nitrate and acetate loadings was studied in a biologically activated carbon reactor with perchlorate loading and empty bed contact time fixed at 5 mg/L and 226 min, respectively. In stage 1, the sole electron acceptor ClO₄^- realized complete removal with ≥21.95 mg C/L of acetate supply. As nitrate loading gradually increased to 5 mg/L (stage 2), perchlorate reduction was slightly promoted and both ClO₄^- and NO₃^- were completely removed at an acetate loading of 29.7 mg C/L. When nitrate loading continued increasing to 10-60 mg/L (stage 3), perchlorate reduction converted to be inhibited, along with nondetectable NO₃^- and approximately exhausted DOC in effluent. When acetate loading increased to 43.9 mg C/L in stage 4, both ClO₄^- and NO₃^- were again removed, though lags still existed in perchlorate reduction. β-Proteobacteria accounted for about 60%, 55%, 58%, 61% and 12% in samples from the base and top of the filter in stage 1 and those from the base, middle and top in stage 4, respectively. These findings implied that ratio of NO₃^- to ClO₄^- loadings and acetate loading were two key factors impacting ClO₄^- reduction and microbial structure along the filter.

Formation and Persistence of Brine on Mars: Experimental Simulations throughout the Diurnal Cycle at the Phoenix Landing Site

In the last few years, water ice and salts capable of melting this ice and producing liquid saline water (brine) have been detected on Mars. Moreover, indirect evidence for brine has been found in multiple areas of the planet. Here, we simulate full diurnal cycles of temperature and atmospheric water vapor content at the Phoenix landing site for the first time and show experimentally that, in spite of the low Mars-like chamber temperature, brine forms minutes after the ground temperature exceeds the eutectic temperature of salts in contact with water ice. Moreover, we show that the brine stays liquid for most of the diurnal cycle when enough water ice is available to compensate for evaporation. This is predicted to occur seasonally in areas of the polar region where the temperature exceeds the eutectic value and frost or snow is deposited on saline soils, or where water ice and salts coexist in the shallow subsurface. This is important because the existence of liquid water is a key requirement for habitability. Key Words: Mars-Ice-Perchlorates-Brine-Water-Raman spectroscopy. Astrobiology 16, 937-948.

Effects of salinity on simultaneous reduction of perchlorate and nitrate in a methane-based membrane biofilm reactor

This study builds upon prior work showing that methane (CH₄) could be utilized as the sole electron donor and carbon source in a membrane biofilm reactor (MBfR) for complete perchlorate (ClO₄^-) and nitrate (NO₃^-) removal. Here, we further investigated the effects of salinity on the simultaneous removal of the two contaminants in the reactor. By testing ClO₄^- and NO₃^- at different salinities, we found that the reactor performance was very sensitive to salinity. While 0.2 % salinity did not significantly affect the hydrogen-based MBfR for ClO₄^- and NO₃^- removals, 1 % salinity completely inhibited ClO₄^- reduction and significantly lowered NO₃^- reduction in the CH₄-based MBfR. In salinity-free conditions, NO₃^- and ClO₄^- removal fluxes were 0.171 g N/m²-day and 0.091 g/m²-day, respectively, but NO₃^- removal fluxes dropped to 0.0085 g N/m²-day and ClO₄^- reduction was completely inhibited when the medium changed to 1 % salinity. Scanning electron microscopy (SEM) showed that the salinity dramatically changed the microbial morphology, which led to the development of wire-like cell structures. Quantitative real-time PCR (qPCR) indicated that the total number of microorganisms and abundances of functional genes significantly declined in the presence of NaCl. The relative abundances of Methylomonas (methanogens) decreased from 31.3 to 5.9 % and Denitratisoma (denitrifiers) decreased from 10.6 to 4.4 % when 1 % salinity was introduced.

Distribution, Identification, and Quantification of Residues after Treatment of Ready-To-Eat Salami with 36Cl-Labeled or Nonlabeled Chlorine Dioxide Gas

When ready-to-eat salami was treated in a closed system with ³⁶Cl-labeled ClO₂ (5.5 mg/100 g of salami), essentially all radioactivity was deposited onto the salami. Administered ³⁶ClO₂ was converted to ³⁶Cl-chloride ion (>97%), trace levels of chlorate (<2%), and detectable levels of chlorite. In residue studies conducted with nonlabeled ClO₂, sodium perchlorate residues (LOQ, 4 ng/g) were not formed when reactions were protected from light. Sodium chlorate residues were present in control (39.2 ± 4.8 ng/g) and chlorine dioxide treated (128 ± 31.2 ng/g) salami. If sanitation occurred under conditions of illumination, detectable levels (3.7 ± 1.5 ng/g) of perchlorate were formed along with greater quantities of sodium chlorate (183.6 ± 75.4 ng/g). Collectively, these data suggest that ClO₂ is chemically reduced by salami and that slow-release formulations might be appropriate for applications involving the sanitation of ready-to-eat meat products.

Perchlorate Exposure Through Water and Milk in Istanbul

Perchlorate is a chemical pollutant that inhibits iodide uptake and may possibly impair thyroid function. Our previous study found widespread perchlorate exposure in non-pregnant, non-lactating, healthy women residing in Istanbul. The aim of this study is to assess the relative amounts of perchlorate exposure attributable to consumption of municipal water, bottled water and boxed milk available in Istanbul. Only trace levels of perchlorate were found in treated municipal water (58 % detectable, mean = 0.13 µg/L, maximum = 0.75 µg/L) and bottled water (7.4 % detectable, mean = <LOD, maximum = 0.19 µg/L). Conversely, all 30 boxed milk samples contained measurable levels of perchlorate (mean = 4.53 µg/L; maximum = 6.21 µg/L). Median perchlorate exposure attributable to water and milk (0.007 µg/kg/day) is small compared both to the reference dose (0.7 µg/kg/day) and to total perchlorate exposure (0.13 µg/kg/day) in Istanbul. Therefore, additional studies are needed to identify the major sources of perchlorate exposure in Istanbul.

Perchlorate in Water Supplies: Sources, Exposures, and Health Effects

Perchlorate exposure occurs from ingestion of natural or man-made perchlorate in food or water. Perchlorate is used in a variety of industrial products including missile fuel, fireworks, and fertilizers, and industrial contamination of drinking water supplies has occurred in a number of areas. Perchlorate blocks iodide uptake into the thyroid and decreases the production of thyroid hormone, a critical hormone for metabolism, neurodevelopment, and other physiologic functions. Occupational and clinical dosing studies have not identified clear adverse effects, but may be limited by small sample sizes, short study durations, and the inclusion of mostly healthy adults. Expanding evidence suggests that young children, pregnant women, fetuses, and people co-exposed to similarly acting agents may be especially susceptible to perchlorate. Given the ubiquitous nature of perchlorate exposure, and the importance of thyroid hormone for brain development, studying the impact of perchlorate on human health could have far-reaching public health implications.

Perchlorate as an emerging contaminant in soil, water and food

Perchlorate ( [Formula: see text] ) is a strong oxidizer and has gained significant attention due to its reactivity, occurrence, and persistence in surface water, groundwater, soil and food. Stable isotope techniques (i.e., ((18)O/(16)O and (17)O/(16)O) and (37)Cl/(35)Cl) facilitate the differentiation of naturally occurring perchlorate from anthropogenic perchlorate. At high enough concentrations, perchlorate can inhibit proper function of the thyroid gland. Dietary reference dose (RfD) for perchlorate exposure from both food and water is set at 0.7 μg kg(-1) body weight/day which translates to a drinking water level of 24.5 μg L(-1). Chromatographic techniques (i.e., ion chromatography and liquid chromatography mass spectrometry) can be successfully used to detect trace level of perchlorate in environmental samples. Perchlorate can be effectively removed by wide variety of remediation techniques such as bio-reduction, chemical reduction, adsorption, membrane filtration, ion exchange and electro-reduction. Bio-reduction is appropriate for large scale treatment plants whereas ion exchange is suitable for removing trace level of perchlorate in aqueous medium. The environmental occurrence of perchlorate, toxicity, analytical techniques, removal technologies are presented.

Bacterial reduction of highly concentrated perchlorate: Kinetics and influence of co-existing electron acceptors, temperature, pH and electron donors

Perchlorate reduction kinetics and effects of various environmental conditions on removal of perchlorate from synthetic water were investigated to seek high-strength perchlorate removal using mixed perchlorate reducing bacteria. Results demonstrated that perchlorate (50-1500 mg L(-1)) could be degraded rapidly within 28 h under the optimal conditions. The maximum specific perchlorate reduction rate (qmax) and half saturation constant (Ks) were 0.92 mg-perchlorate (mg-dry weight)(-1) h(-1) and 157.7 mg L(-1), respectively. In the ClO4(-)-NO3(-) systems obvious but recoverable lags were caused in perchlorate reduction and the lag time increased with the ratio of nitrate to perchlorate concentration increasing from 0.5 to 3. While in the ClO4(-)-SO4(2-) systems inhibitions didn't occur until the ratio of sulfate to perchlorate concentration exceeded 10. The optimum temperature and pH value were 35 °C and 6.85, respectively. The optimal acetate-to-perchlorate ratio that could consume all perchlorate and acetate simultaneously was about 2. Dechloromonas, one of the most prominent perchlorate reducing bacteria, was identified as the dominant bacterium in the acclimated culture (69.33% of the whole clones). The study demonstrated that the perchlorate-acclimated mixed microorganisms can readily and efficiently realize reduction of highly concentrated perchlorate in wastewater.

Perchlorate levels found in tap water collected from several cities in Turkey

Perchlorate is an inorganic anion that inhibits iodide transport to the thyroid by sodium-iodide transporters. Because perchlorate is highly soluble, stable, and mobile in water, drinking water is a potential source of perchlorate exposure. When exposed to perchlorate, thyroid dysfunction can be observed in sensitive populations (pregnant woman, infants, and children), especially those with iodide deficiency. The aim of this study was to determine the perchlorate levels in tap water from five cities in Turkey. Perchlorate concentrations of 145 tap water samples collected from Ankara, Isparta, Istanbul, Kayseri, and Sakarya were determined by liquid chromatography-tandem mass spectrometry. Mean and median values were found to be 0.15 and 0.07 μg/L, respectively. The median values (25-75 % percentile) of Istanbul, Ankara, Sakarya, Isparta, and Kayseri were 0.08 μg/L (0.04-0.09 μg/L), 0.07 μg/L (0.07-0.21 μg/L), 0.04 μg/L (0.04-0.04 μg/L), 0.03 μg/L (0.02-0.07 μg/L), and 0.25 μg/L (0.23-0.31 μg/L), respectively. The median perchlorate level observed in Kayseri was significantly higher than those found at other cities (p < 0.05). Perchlorate concentrations in water samples were lower than the interim drinking water health advisory level (15 μg/L) determined by the US Environmental Protection Agency. This study showed that perchlorate in drinking water is not the main source of exposure in these cities. Future studies should be performed to determine perchlorate levels in other potential sources, such as food products.

Particle size distribution and perchlorate levels in settled dust from urban roads, parks, and roofs in Chengdu, China

A total of 27 settled dust samples were collected from urban roads, parks, and roofs in Chengdu, China to investigate particle size distribution and perchlorate levels in different size fractions. Briefly, fine particle size fractions (<250 μm) were the dominant composition in the settled dust samples, with mean percentages of 80.2%, 69.5%, and 77.2% for the urban roads, roofs, and the parks, respectively. Perchlorate was detected in all of the size-fractionated dust samples, with concentrations ranging from 73.0 to 6160 ng g(-1), and the median perchlorate levels increased with decreasing particle size. The perchlorate level in the finest fraction (<63 μm) was significantly higher than those in the coarser fractions. To our knowledge, this is the first report on perchlorate concentrations in different particle size fractions. The calculated perchlorate loadings revealed that perchlorate was mainly associated with finer particles (<125 μm). An exposure assessment indicated that exposure to perchlorate via settled road dust intake is safe to both children and adults in Chengdu, China. However, due to perchlorate mainly existing in fine particles, there is a potential for perchlorate to transfer into surface water and the atmosphere by runoff and wind erosion or traffic emission, and this could act as an important perchlorate pollution source for the indoor environment, and merits further study.

Perchlorate formation during the electro-peroxone treatment of chloride-containing water: Effects of operational parameters and control strategies

This study investigated the degradation of clofibric acid and formation of perchlorate during the electro-peroxone (E-peroxone) treatment of chloride-containing (26.1-100 mg L(-1)) water (Na2SO4 electrolytes and secondary effluents). The E-peroxone process involves sparging O2 and O3 gas mixture into an electrolysis reactor where a carbon-based cathode is used to electrochemically convert the sparged O2 to H2O2. The electro-generated H2O2 then reacts with sparged O3 to produce OH, which can rapidly oxidize pollutants in the bulk solution. When boron-doped diamond (BDD) electrodes were used as the anode, perchlorate concentrations increased significantly from undetectable levels to ∼15-174 mg L(-1) in the different water samples as the applied current density was increased from 4 to 32 mA cm(-2). In contrast, no ClO4(-) was detected when Pt/Ti anodes were used in the E-peroxone process operated under similar reaction conditions. In addition, when sufficient O3 was sparged to maximize OH production from its peroxone reaction with electro-generated H2O2, the E-peroxone process with Pt/Ti anodes achieved comparable clofibric acid degradation and total organic carbon (TOC) removal yields as that with BDD anodes, but did not generate detectable ClO4(-). These results indicate that by optimizing operational parameters and using Pt/Ti anodes, the E-peroxone process can achieve the goal of both fast pollutant degradation and ClO4(-) prevention during the treatment of chloride-containing wastewater.

Levels, indoor-outdoor relationships and exposure risks of airborne particle-associated perchlorate and chlorate in two urban areas in Eastern Asia

Indoor and outdoor concentrations of PM2.5-associated perchlorate (ClO4(-)) and chlorate (ClO3(-)) were investigated in Jinan, China, and size-resolved perchlorate and chlorate were studied in Kumamoto, Japan. The average outdoor PM2.5-associated concentrations of perchlorate and chlorate were 4.18 ng m(-3) and 2.82 ng m(-3), respectively, in Jinan. Perchlorate and chlorate were mainly distributed in fine particles, and their approximate PM2.5-associated concentrations were 0.04 ng m(-3) and 4.14 ng m(-3), respectively, in Kumamoto. The ratios of ClO3(-)/ClO4(-) ranged from 18.72 to 360.22 in Kumamoto and from 0.03 to 7.45 in Jinan. The highest concentration of perchlorate (173.76 ng m(-3)) was observed on Spring Festival Eve. This finding and the significant correlation between perchlorate and fireworks-related components (Cl(-) and K(+)) indicated that the fireworks display was a significant source of perchlorate in Jinan. The indoor concentrations of perchlorate and chlorate in Jinan were 3.54 ng m(-3) (range, 0.14-125.14 ng m(-3)) and 0.94 ng m(-3) (range, 0.10-1.80 ng m(-3)), respectively. In the absence of an indoor source of perchlorate, the occurrence of indoor concentrations higher than those found outdoors was a common effect of individual fireworks displays near the sampling sites, coupled with meteorological influences and poor indoor diffusion conditions. The exposure risks of perchlorate and chlorate indoors indicated that the potential risk of perchlorate exposure to children during fireworks displays is deserving of concern.

Perchlorate in dust fall and indoor dust in Malta: An effect of fireworks

We report on the presence of perchlorate in the settleable dust of Malta, a small central Mediterranean island. Both dust fall collected directly as it precipitated from atmosphere over a period of one month and deposited indoor dust from domestic residences were studied. Perchlorate was determined by ion chromatography of water extracts of the collected dusts. Dust fall was collected from 43 towns during 2011 to 2013 and indoor dust was sampled from homes in the same localities. Perchlorate was detected in 108 of 153 samples of dust fall (71%) and in 28 of 37 indoor dust samples (76%). Detectable perchlorate in dust fall ranged from 0.52μgg(-1) to 561μgg(-1) with a median value of 6.2μgg(-1); in indoor dust, levels were from 0.79μgg(-1) to 53μgg(-1) with a median value of 7.8μgg(-1), the highest recorded anywhere to date. Statistical analysis suggested that there was no significant difference in perchlorate content of indoor dust and dust fall. Perchlorate levels in dust fall escalate during the summer in response to numerous religious feasts celebrated with fireworks and perchlorate persists at low μgg(-1) concentrations for several months beyond the summer festive period. In Malta, perchlorate derives exclusively from KClO4, imported for fireworks manufacture. Its residue in dust presents an exposure risk to the population, especially via ingestion by hand to mouth transfer. Our results suggest that wherever intensive burning of fireworks takes place, the environmental impact may be much longer lived than realised, mainly due to re-suspension and deposition of contaminated settled dust in the urban environment.

Perchlorate in Lake Water from an Operating Diamond Mine

Mining-related perchlorate [ClO4(-)] in the receiving environment was investigated at the operating open-pit and underground Diavik diamond mine, Northwest Territories, Canada. Samples were collected over four years and ClO4(-) was measured in various mine waters, the 560 km(2) ultraoligotrophic receiving lake, background lake water and snow distal from the mine. Groundwaters from the underground mine had variable ClO4(-) concentrations, up to 157 μg L(-1), and were typically an order of magnitude higher than concentrations in combined mine waters prior to treatment and discharge to the lake. Snow core samples had a mean ClO4(-) concentration of 0.021 μg L(-1) (n=16). Snow and lake water Cl(-)/ClO4(-) ratios suggest evapoconcentration was not an important process affecting lake ClO4(-) concentrations. The multiyear mean ClO4(-) concentrations in the lake were 0.30 μg L(-1) (n = 114) in open water and 0.24 μg L(-1) (n = 107) under ice, much below the Canadian drinking water guideline of 6 μg L(-1). Receiving lake concentrations of ClO4(-) generally decreased year over year and ClO4(-) was not likely [biogeo]chemically attenuated within the receiving lake. The discharge of treated mine water was shown to contribute mining-related ClO4(-) to the lake and the low concentrations after 12 years of mining were attributed to the large volume of the receiving lake.

Simultaneous detection of perchlorate and bromate using rapid high-performance ion exchange chromatography-tandem mass spectrometry and perchlorate removal in drinking water

Perchlorate and bromate occurrence in drinking water causes health concerns due to their effects on thyroid function and carcinogenicity, respectively. The purpose of this study was threefold: (1) to advance a sensitive method for simultaneous rapid detection of perchlorate and bromate in drinking water system, (2) to systematically study the occurrence of these two contaminants in Missouri drinking water treatment systems, and (3) to examine effective sorbents for minimizing perchlorate in drinking water. A rapid high-performance ion exchange chromatography-tandem mass spectrometry (HPIC-MS/MS) method was advanced for simultaneous detection of perchlorate and bromate in drinking water. The HPIC-MS/MS method was rapid, required no preconcentration of the water samples, and had detection limits for perchlorate and bromate of 0.04 and 0.01 μg/L, respectively. The method was applied to determine perchlorate and bromate concentrations in total of 23 selected Missouri drinking water treatment systems during differing seasons. The water systems selected include different source waters: groundwater, lake water, river water, and groundwater influenced by surface water. The concentrations of perchlorate and bromate were lower than or near to method detection limits in most of the drinking water samples monitored. The removal of perchlorate by various adsorbents was studied. A cationic organoclay (TC-99) exhibited effective removal of perchlorate from drinking water matrices.

Perchlorate in indoor dust and human urine in China: contribution of indoor dust to total daily intake

Perchlorate is used in fireworks and China is the largest fireworks producer and consumer in the world. Information regarding human exposure to perchlorate is scarce in China, and exposure via indoor dust ingestion (EDI indoor dust) has rarely been evaluated. In this study, perchlorate was found in indoor dust (detection rate: 100%, median: 47.4 μg/g), human urine (99%, 26.2 ng/mL), drinking water (100%, 3.99 ng/mL), and dairy milk (100%, 12.3 ng/mL) collected from cities that have fireworks manufacturing areas (Yueyang and Nanchang) and in cities that do not have fireworks manufacturing industries (Tianjin, Shijiazhuang, Yuxi and Guilin) in China. In comparison with perchlorate levels reported for other countries, perchlorate levels in urine samples from fireworks sites and nonfireworks sites in China were higher. Median indoor dust perchlorate concentrations were positively correlated (r = 0.964, p < 0.001) with outdoor dust perchlorate levels reported previously. The total daily intake (EDI total) of perchlorate, estimated based on urinary levels, ranged from 0.090 to 27.72 μg/kg body weight (bw)/day for all studied participants; the percentage of donors who had EDI total exceeding the reference dose (RfD) recommended by the United States Environmental Protection Agency (US EPA) was 79%, 48%, and 25% for toddlers (median: 1.829 μg/kg bw/day), adults (0.669 μg/kg bw/day), and children (median: 0.373 μg/kg bw/day), respectively. Toddlers (0.258 μg/kg bw/day) had the highest median EDI indoor dust, which was 2 to 5 times greater than the EDI indoor dust calculated for other age groups (the range of median values: 0.044 to 0.127 μg/kg bw/day). Contribution of indoor dust to EDItotal was 26%, 28%, and 7% for toddlers, children, and adults, respectively. Indoor dust contributed higher percentage to EDI total than that by dairy milk (0.5-5%).

Detection of trace organics in Mars analog samples containing perchlorate by laser desorption/ionization mass spectrometry

Evidence from recent Mars missions indicates the presence of perchlorate salts up to 1 wt % level in the near-surface materials. Mixed perchlorates and other oxychlorine species may complicate the detection of organic molecules in bulk martian samples when using pyrolysis techniques. To address this analytical challenge, we report here results of laboratory measurements with laser desorption mass spectrometry, including analyses performed on both commercial and Mars Organic Molecule Analyzer (MOMA) breadboard instruments. We demonstrate that the detection of nonvolatile organics in selected spiked mineral-matrix materials by laser desorption/ionization (LDI) mass spectrometry is not inhibited by the presence of up to 1 wt % perchlorate salt. The organics in the sample are not significantly degraded or combusted in the LDI process, and the parent molecular ion is retained in the mass spectrum. The LDI technique provides distinct potential benefits for the detection of organics in situ on the martian surface and has the potential to aid in the search for signs of life on Mars.