Perchlorate in the Great Lakes: isotopic composition and origin

Occurrence and removal technologies of perchlorate in water: A systematic review and bibliometric analysis

The pollution resulting from the emergence of the contaminant perchlorate is anticipated to have a substantial effect on the water environment in the foreseeable future. Considerable research efforts have been devoted to investigating treatment technologies for addressing perchlorate contamination, garnering widespread international interest in recent decades. A systematic review was conducted utilizing the Web of Science, Scopus, and Science Direct databases to identify pertinent articles published from 2000 to 2024. A total of 551 articles were chosen for in-depth examination utilizing VOS viewer. Bibliometric analysis indicated that countries such as China, the United States, Chile, India, Japan, and Korea have been prominent contributors to the research on this topic. The order of ClO4- occurrence was as follows: surface water > groundwater > drinking water. Various remediation methods for perchlorate contamination, such as adsorption, ion-exchange, membrane filtration, chemical reduction, and biological reduction, have been suggested. Furthermore, the research critically evaluated the strengths and weaknesses of each approach and offered recommendations for addressing their limitations. Advanced technologies have shown the potential to achieve notably enhanced removal of perchlorate and co-contaminants from water sources. However, the low concentration of perchlorate in natural water sources and the high energy consumption related to these technologies need to be solved in order to effectively remove perchlorate from water.

The biogeochemical cycling of chlorine

Chlorine has important roles in the Earth's systems. In different forms, it helps balance the charge and osmotic potential of cells, provides energy for microorganisms, mobilizes metals in geologic fluids, alters the salinity of waters, and degrades atmospheric ozone. Despite this importance, there has not been a comprehensive summary of chlorine's geobiology. Here, we unite different areas of recent research to describe a biogeochemical cycle for chlorine. Chlorine enters the biosphere through volcanism and weathering of rocks and is sequestered by subduction and the formation of evaporite sediments from inland seas. In the biosphere, chlorine is converted between solid, dissolved, and gaseous states and in oxidation states ranging from -1 to +7, with the soluble, reduced chloride ion as its most common form. Living organisms and chemical reactions change chlorine's form through oxidation and reduction and the addition and removal of chlorine from organic molecules. Chlorine can be transported through the atmosphere, and the highest oxidation states of chlorine are produced by reactions between sunlight and trace chlorine gases. Partial oxidation of chlorine occurs across the biosphere and creates reactive chlorine species that contribute to the oxidative stress experienced by living cells. A unified view of this chlorine cycle demonstrates connections between chlorine biology, chemistry, and geology that affect life on the Earth.

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.

Isotopic composition of natural and synthetic chlorate (δ18O, Δ17O, δ37Cl, 36Cl/Cl): Methods and initial results

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.

Perchlorate - properties, toxicity and human health effects: an updated review

Interest in perchlorate as environmental pollutant has increased since 1997, when high concentrations have been found in the waters of the Colorado River, USA. Perchlorate is very persistent in nature and it is slowly degraded. Although harmful effects of large doses of perchlorate on thyroid function have been proven, the environmental effects are still unclear. The primary objective of the present review is to collect prevailing data of perchlorate exposure and to discuss its impact on human health. The results show that more than 50% of reviewed works found significant associations of perchlorate exposure and human health. This review consists of the following sections: general information of perchlorate sources, its properties and determination methods, role and sources in human body including food and water intake, overview of the scientific literature on the research on the effect of perchlorate on human health from 2010 to 2020. Finally, conclusions and recommendations on future perchlorate studies concerning human exposure are presented.

Sources and behavior of perchlorate in a shallow Chalk aquifer under military (World War I) and agricultural influences

Perchlorate (ClO₄^ö) has been detected at concentrations of concern for human health on a large scale in groundwater used for drinking water supplies in NE France. Two sources are suspected: a military source related to World War I (WWI) and an agricultural source related to past use of Chilean nitrate fertilizers. The sources and behavior of ClO₄^ö have been studied in groundwater and rivers near the Reims city, by monitoring monthly the major ions and ClO₄- concentrations for two years (2017-2019), and by measuring the isotopic composition of ClO₄^ö and NO₃^ö in water samples. ClO₄^ö was detected throughout the study area with high concentrations (> 4 μg⋅L^-1) detected mainly downgradient of the Champagne Mounts, where large quantities of ammunition were used, stored and destroyed during and after WWI. A WWI military origin of ClO₄- is inferred from isotopic analysis and groundwater ages. Different tendencies of ClO₄- variation are observed and interpreted by a combination of ClO₄- concentrations, aquifer functioning and historical investigations, revealing major sources of ClO₄- (e.g., unexploded ordnance, ammunition destruction sites) and its transfer mechanisms in the aquifer. Finally, we show that concentrations of ClO₄^ö in groundwater seems unlikely to decrease in the short- to medium-term.

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).

Responses of microbial community to different concentration of perchlorate in the Qingyi River

Perchlorate is a refractory and mobile contaminant that is wildly distributed in surface water, and due to its tremendous inhibitory effect on mammalian thyroid function, it has gained much attention in recent years. Numerous studies have focused on environmental detection of perchlorate, especially in water. However, less attention has been paid to the effects of perchlorate on the composition of the microbial community in rivers. Upstream of the Qingyi River, an important source of drinking water for local residents, there are two perchlorate manufacturers. In this study, we selected eight study sites from upstream to downstream of the Qingyi River, including sites located upstream and downstream of the perchlorate manufacturers. Our results indicated that perchlorate was detected in all sites except for QYR2, QYR3, and QYR10. The concentration of perchlorate in the five study sites was much higher than the reference dose proposed by the National Academy of Science, and ranged from 187 to 9647.00 μg/L. We utilized 16S rDNA high throughput sequencing to analyze changes in the composition of the microbial community, based on the Illumina 2 × 250 MiSeq platform. The results showed that, when microbial communities were exposed to high concentration of perchlorate, there was an increase in the ratio of Betaproteobacteria, Bacteroidetes, Actinobacteria, and Saccharibacteria in the microbial community along with a decrease in the ratio of Chloroflexi, Verrucomicrobia, and Gammaproteobacteria. Our study has provided a theoretical basis for the alteration of the microbial community caused by the perchlorate pollution, which maybe have a truly important impact on the quality of groundwater.

Worldwide occurrence and origin of perchlorate ion in waters: A review

Perchlorate (ClO₄^-) is a persistent water soluble oxyanion of growing environmental interest. Perchlorate contamination can be a health concern due to its ability to disrupt the use of iodine by the thyroid gland and the production of metabolic hormones. Its widespread presence in surface water and groundwater makes the aquatic environment a potential source of perchlorate exposure. However, the amount of published data on perchlorate origins and water contamination worldwide remains spatially limited. Here, we present an overview of research on perchlorate origins and occurrences in water, and the methodology to distinguish the different perchlorate sources based on isotope analysis. All published ranges of isotopic content in perchlorate from different sources are presented, including naturally occurring and man-made perchlorate source types, as well as the effects of isotope fractionation that accompanies biodegradation processes. An example of a case study in France is presented to emphasize the need for further research on this topic.

Bio-reduction of free and laden perchlorate by the pure and mixed perchlorate reducing bacteria: Considering the pH and coexisting nitrate

Pure bacteria cell (Azospira sp. KJ) and mixed perchlorate reducing bacteria (MPRB) were employed for decomposing the free perchlorate in water as well as the laden perchlorate on surface of quaternary ammonium wheat residuals (QAWR). Results indicated that perchlorate was decomposed by the Azospira sp. KJ prior to nitrate while MPRB was just the reverse. Bio-reduction of laden perchlorate by Azospira sp. KJ was optimal at pH 8.0. In contrast, bio-reduction of laden perchlorate by MPRB was optimal at pH 7.0. Generally, the rate of perchlorate reduction was controlled by the enzyme activity of PRB. In addition, perchlorate recovery (26.0 mg/g) onto bio-regenerated QAWR by MPRB was observed with a small decrease as compared with that (31.1 mg/g) by Azospira sp. KJ at first 48 h. Basically, this study is expected to offer some different ideas on bio-regeneration of perchlorate-saturated adsorbents using biological process, which may provide the economically alternative to conventional methods.

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.

Chlorine isotopic composition of perchlorate in human urine as a means of distinguishing among exposure sources

Perchlorate (ClO4(-)) is a ubiquitous environmental contaminant with high human exposure potential. Natural perchlorate forms in the atmosphere from where it deposits onto the surface of Earth, whereas synthetic perchlorate is manufactured as an oxidant for industrial, aerospace, and military applications. Perchlorate exposure can potentially cause adverse health effects in humans by interfering with the production of thyroid hormones through competitively blocking iodide uptake. To control and reduce perchlorate exposure, the contributions of different sources of perchlorate exposure need to be quantified. Thus, we demonstrate a novel approach for determining the contribution of different perchlorate exposure sources by quantifying stable and radioactive chlorine isotopes of perchlorate extracted from composite urine samples from two distinct populations: one in Atlanta, USA and one in Taltal, Chile (Atacama region). Urinary perchlorate from the Atlanta region resembles indigenous natural perchlorate from the western USA (δ(37)Cl=+4.1±1.0‰; (36)Cl/Cl=1 811 (±136) × 10(-15)), and urinary perchlorate from the Taltal, Chile region is similar to natural perchlorate in nitrate salt deposits from the Atacama Desert of northern Chile (δ(37)Cl=-11.0±1.0‰; (36)Cl/Cl=254 (±40) × 10(-15)). Neither urinary perchlorate resembled the isotopic pattern found in synthetic perchlorate. These results indicate that natural perchlorate of regional provenance is the dominant exposure source for the two sample populations, and that chlorine isotope ratios provide a robust tool for elucidating perchlorate exposure pathways.

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.

Temporal evolution of (36)Cl abundances in the Great Lakes

The observed (36)Cl isotopic abundance in Great Lakes water decreases from west to east, with the highest (36)Cl/Cl ratio of 1332 × 10(-15) in Lake Superior and the lowest (36)Cl/Cl ratio of 151 × 10(-15) in Lake Erie, whereas the (36)Cl concentration ((36)Cl atoms/L) is lowest in Lake Superior and higher in the other Great Lakes. The (36)Cl concentration in Lake Superior is much higher than expected from normal atmospheric deposition over the basin, consistent with deposition of nuclear bomb-produced (36)Cl during 1952-1964. A conservative mass-balance model constrained by hydrological parameters and available (36)Cl fluence measurements predicts the (36)Cl abundances in the Great Lakes from 1945 to 2015, in excellent agreement with available data for Lakes Superior, Michigan, and Huron, but the model underestimates (36)Cl abundances for Lakes Erie and Ontario. However, assuming that (36)Cl demonstrates non-conservative behavior and is significantly retained in the drainage basins, a model incorporating a delayed input parameter successfully predicts observed (36)Cl concentrations in all of the Great Lakes.