Water is essential to the development of honey bee colonies. It is mainly used for larval jelly production and brood thermoregulation. While the mechanisms by which colonies collect water are fairly well documented, the fate of this resource within the colony is not. Understanding this could help us grasp how honey bees cope with climate change. To address this knowledge gap, we used a stable isotope approach to track the fate of water within a colony. Using 5% (v/v) deuterated water (D2O) we estimated the water turnover rate in adult honey bees, as well as the dynamics of the water used to produce larval jelly and eggs. Next, we investigated how ambient temperatures affect the water used by the colony, including bee water consumption, and the water used for the production of larval jelly and thermoregulation. Unexpectedly, our study showed that the water loss rate in adult bees is lower than in other insects dealing with a high-water-content diet, such as mosquitoes. Additionally, our results revealed the shift in the colony's water usage pattern due to the thermoregulation's need for water. At 32 °C, 80% of the water collected daily being consumed by the bees. Above 37 °C, however, this shifted so that about 50% of the water collected daily being used for thermoregulation and the remaining 50% being consumed by the bees. In conclusion, our results suggest that there may be a limit to the amount of water that colonies can collect, raising questions about their ability to cope with intense, long-lasting heatwaves.

Trimethylbenzene (TMB) isomers (1,2,3-TMB, 1,2,4-TMB, 1,3,5-TMB) are used as conservative tracers of alkylbenzenes in contaminated aquifers, but their resistance to anaerobic biodegradation remains uncertain. In this study, TMB degradation was investigated using enrichment cultures in microcosms under denitrifying, iron-, manganese- and sulfate-reducing conditions. Evidence for TMB biodegradation was gathered using concentration measurements, metabolites identification and multi-elemental compound specific isotope analysis (ME-CSIA). Degradation was >80 % under all anaerobic conditions and followed first-order reactions, after fluctuating lag phases depending on the condition and compound. In a mixture, a selective degradation pattern was observed with 1,2,4-TMB degradation starting almost immediately, whereas 1,3,5-TMB and 1,2,3-TMB degradation began only after 1,2,4-TMB was fully consumed. First-order biodegradation rates ranged from 0.03 ± 0.00 to 0.16 ± 0.02 day-1 for 1,2,3-TMB, from 0.16 ± 0.01 to 0.32 ± 0.05 day-1 for 1,2,4-TMB and from 0.02 ± 0.00 to 0.11 ± 0.02 day-1 for 1,3,5-TMB. Dimethylbenzoic acid isomers were detected, which are signature metabolic intermediates formed during the anaerobic degradation of TMBs via the fumarate addition pathway. Low carbon and hydrogen fractionation, associated with their strong variability, tends to suggest that non-fractionating steps provoke isotope fractionation masking. ME-CSIA permitted to reveal that TMB biodegradation is a complex multi-step process, with Λ ranging from 14 ± 9 to 107 ± 91 for 1,2,3-TMB, from 29 ± 6 to 120 ± 70 for 1,2,4-TMB and from 14 ± 6 to 58 ± 23 for 1,3,5-TMB. The results will allow to identify non-conservative behaviors of TMBs during reactive transport in groundwater.

By assessing the changes in stable isotope compositions within individual pesticide molecules, Compound Specific Isotope Analysis (CSIA) holds the potential to identify and differentiate sources and quantify pesticide degradation in the environment. However, the environmental application of pesticide CSIA is limited by the general lack of knowledge regarding the initial isotopic composition of active substances in commercially available formulations used by farmers. To address this limitation, we established a database aimed at cataloguing and disseminating isotopic signatures in commercial formulations to expand the use of pesticide CSIA. Our study involved the collection of 25 analytical standards and 120 commercial pesticide formulations from 23 manufacturers. Subsequently, 59 commercial formulations and 25 standards were extracted, and each of their active substance was analyzed for both δ13C (n = 84) and δ15N CSIA (n = 43). The extraction of pesticides did not cause significant isotope fractionation (Δ13C and Δ15N < 1‰). Incorporating existing literature data, stable carbon and nitrogen isotope signatures varied in a relatively narrow range among pesticide formulations for different pesticides (Δ13C and Δ15N < 10‰) and within different formulations for a single substance (Δ13C and Δ15N < 2‰). Overall, this suggests that pesticide CSIA is more suited for identifying pesticide transformation processes rather than differentiating pesticide sources. Moreover, an inter-laboratory comparison showed similar δ13C (Δ13C ≤ 1.2 ‰) for the targeted substances albeit varying GC-IRMS instruments. Insignificant carbon isotopic fractionation (Δ13C < 0.5‰) was observed after 4 years of storing the same pesticide formulations, confirming their viability for long-term storage at 4 °C and future inter-laboratory comparison exercises. Altogether, the ISOTOPEST database, in open access for public use and additional contributions, marks a significant advancement in establishing an environmentally relevant pesticide CSIA approach.

Pollution of French West Indies (FWI) soils by the organochlorine pesticide chlordecone poses environmental and societal concerns due to its long-term persistence. Assessing chlordecone degradation remains challenging due to analytical constraints to identify transformation products. Here, multielement compound-specific isotope analysis (ME-CSIA) was used to identify changes in stable isotope signatures of chlordecone produced during abiotic transformation reactions under reducing and oxidative conditions. Effective chlordecone transformation was shown in reactions with zerovalent iron (ZVI), vitamin B-12 and sodium sulfide (VSS), alkaline ascorbic acid (AA), and sodium persulfate activated by microwave irradiation (MWPS). Significant enrichment of C-13 and Cl-37 was observed in all abiotic reactions, with epsilon(C,bulk) and epsilon(Cl,bulk) values ranging from -4.3 +/- 0.4 parts per thousand to -2.3 +/- 0.2 parts per thousand and from -2.6 +/- 0.4 parts per thousand to -1.3 +/- 0.3 parts per thousand, respectively. Distinct mechanisms were evidenced in dual isotope plots, resulting in Lambda values of 1.17 +/- 0.28 for ZVI, 1.26 +/- 0.50 for VSS, 2.06 +/- 0.30 for AA, and 2.90 +/- 0.50 for MWPS. Two major products were formed, 10-monohydrochlordecone and 8-monohydrochlordecone. Cl-CSIA data suggested that the first Cl substitution at the C-10-position likely produced secondary Cl isotope effects (via nucleophilic substitution). Overall, results suggest that ME-CSIA can help quantify in situ chlordecone degradation, distinguishing between different ongoing degradation mechanisms and fingerprinting pollutant sources from chlordecone formulations (Curlone).

Many processes can contribute to the attenuation of the frequently detected and toxic herbicides atrazine and metolachlor in surface water, including photodegradation. Multi-element compound-specific isotope analysis has the potential to decipher between these different degradation pathways as Cl is a promising tool for both pathway identification and a sensitive indicator of degradation for both atrazine and metolachlor. In this study, photodegradation experiments of atrazine and metolachlor were conducted under simulated sunlight in buffered solutions (direct photodegradation) and with nitrate (indirect photodegradation by OH radicals) to determine kinetics, transformation products and isotope fractionation for C, N and for the first time Cl. For metolachlor, the C–Cl dual isotope slope (ΛC/Cl = 0.46 ± 0.19) is identical to previously reported values for hydrolysis and biodegradation in soils, suggesting the same reaction mechanism (C–Cl bond breakage by SN2 nucleophilic substitution). For atrazine, both direct and indirect photodegradation resulted in a pronounced inverse isotope effect for chlorine (εCl = 6.9 ± 3.3 ‰, and εCl = 2.3 ± 1.2 ‰, respectively), leading to characteristic dual isotope slopes (ΛC/Cl = −0.49 ± 0.17 and ΛC/Cl = −0.31 ± 0.10, respectively). These values are distinct from those previously reported for abiotic hydrolysis, biotic hydrolysis and oxidative dealkylation which are all relevant processes in surface water, opening the path for pathway identification in future field studies.

Chlordecone (CLD; C10Cl10O) is an organochlorine pesticide extensively used between 1960s and 1990s in the French West Indies (FWI). Its massive use led to soil and river pollution which prompted its ban in 1993. CLD has a bis-homocubane structure and various chlorine atoms making it highly recalcitrant in the environment. To date, several environmental compartments of the FWI continue facing the legacy of CLD pollution. This study aims at improving the monitoring of the degradation (or recalcitrance) extent of CLD in the soils of the FWI following in situ chemical reduction (ISCR). Multi-element compound-specific isotope analysis (ME-CSIA) was used to identify changes of stable isotopes of CLD (i.e., 13C/12C and 37Cl/35Cl) produced during distinct abiotic reductive transformation reactions. Reductive transformation of CLD was tested in abiotic microcosms in the presence of either zero-valent iron, ascorbic acid, vitamin B12, or persulfate activated by microwave irradiation. CLD transformation was evidenced by the detection of several hydrochlordecones (after losses of one or two chlorine atoms) under all conditions. Enrichment of the 13C isotopes of CLD relative to 12C revealed distinct signatures during transformation reactions of CLD to maximum Δδ13C of +7.2 ‰. A novel stable Cl isotope analysis was performed by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS). Ongoing Cl isotope analysis may establish a multi-element assessment in which abiotic CLD degradation pathways may be distinguished based on stable C-Cl signatures. Altogether, our results may provide an improved strategy to elucidate CLD degradation in contaminated soils of the FWI.

AbstractCompound-specific isotope analysis (CSIA) is an advanced characterization tool increasingly used by field practitioners to demonstrate degradation of compounds such as benzene, toluene, ethylbenzene, and xylene (BTEX) in petroleum hydrocarbon-contaminated aquifer systems. Formerly used to demonstrate occurrence of in situ biodegradation of BTEX during natural attenuation in groundwater, CSIA underwent substantial research and development to confidently be applied in the frame of engineered remediation efforts. Due to the feasibility to demonstrate destruction of contaminants by tracking the change in isotopic composition caused by either biotic or abiotic processes, mass destruction process initiated by the remediation treatment can be distinguished from other co-occurring non-destructive mass removal process(es) such as sorption and dilution. For this reason, CSIA has become a valuable characterization tool to directly assess the performance of the remediation treatment on specifically selected contaminants. This chapter presents the principles of CSIA application to assess performance of in situ remediation treatments applied to BTEX-contaminated sites. The information introduced herein on CSIA is presented from the perspective of supporting field practitioners in their intention to implement the tool at field sites.

Climate change is altering both dissolved organic matter (DOM) properties and phytoplankton dynamics in lakes. High‐altitude lakes are good sentinels of global change. However, their value as sentinels depends on how well we understand their functioning. This study analysed physical, chemical and biological data during three pre‐defined periods running from complete ice‐cover right to the end of the ice‐free season, in a high‐altitude oligotrophic lake. A functional approach was used to assess how relationships between DOM and the planktonic community vary over time. Phytoplankton functional change was found to occur with shifts in DOM. During the ice‐influenced period, from February to the end of the thaw, the phytoplankton community was dominated by small autotrophs and mixotrophic flagellates and DOM from sediment and terrestrial origin dominated the DOM pool of the lake. Phytoplankton diversity and richness increased during the post‐snowmelt overturn period, when terrestrial DOM dominated the DOM pool. Finally, large siliceous autotrophs, competitive under low nitrogen concentrations and high temperature, dominated almost exclusively during the late summer period (LSP). Increased phytoplankton biomass meant that phytoplankton‐derived DOM was dominant during the LSP. These phenological changes in the phytoplankton community resulted in functional shifts at the base of the food web. Based on the relationships between the variables in the study, it can be deduced that the nature of the relationship between phytoplankton and bacteria progressively shifted from strong top‐down control exerted by phytoplankton over bacteria towards predominantly bottom‐up control at the end of the ice‐free season. Synthesis . Using a field survey starting from complete ice‐cover and lasting right to the end of the ice‐free season in a sentinel lake, we show seasonal shifts in the link between DOM properties and plankton community traits. Differences in environmental conditions and DOM origin explained variation in phytoplankton community structure and function, pointing to seasonal shifts in microbial food web interactions. Our research suggests that, under climate change, the balance between mixotrophy and autotrophy and the control exerted by phytoplankton over bacterioplankton will change in oligotrophic high‐altitude lakes with large, vegetated catchments.

Organochlorinated pesticides are highly persistent organic pollutants having important adverse effects in the environment. To study their fate, compound-specific isotope analysis (CSIA) may be used to investigate their degradation pathways and mechanisms but is currently limited to 13C isotope ratios. The assessment of 37Cl isotope ratios from mass spectra is complicated by the large number of isotopologues of polychlorinated compounds. For method development, chlordecone (C10Cl10O2H2; hydrate form), an organochlorine insecticide that led to severe contamination of soils and aquatic ecosystems of the French West Indies, was taken as a model analyte. Chlorine isotope analysis of chlordecone hydrate was evaluated using high-resolution liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS), enabling smooth ionization to detect the molecular ion. First, a new evaluation scheme is presented to correct for multiple isotope presence in polychlorinated compounds. The scheme is based on probability calculations of the most frequent isotopologues, distributions by binomial probability functions, and corrections for the presence of nonchlorine heavy isotopes. Second, mobile-phase modifiers, ionization energy (sampling cone tension) and scan time were optimized for accurate chlorine isotope ratios. Chlordecone standard samples were measured up to 10-fold and bracketed with a second chlordecone external standard. δ37Cl values were obtained after conversion to the SMOC scale by a two-point calibration. The robustness of the analysis method and evaluation scheme were tested and gave satisfactory results with standard errors (σm) of ±0.34‰ for precision and ±0.89‰ for long-term accuracy of chlorine isotope ratios of chlordecone hydrate. This work opens perspectives for applications of the C-Cl CSIA approach to investigate the fate of highly toxic and low reactive polychlorinated compounds in the environment.

In this work, chloride ions were used as conservative tracers and supplemented with conservative amounts of chloroethenes (PCE, TCE, Cis-DCE, 1,1-DCE), chloroethanes (1,1,1-TCA, 1,1-DCA), and the carbon isotope ratios of certain compounds, the most representative on the sites studied, which is a novelty compared to the optimization methods developed in the scientific literature so far. A location of the potential missing sources is then proposed in view of the balances of the calculated mixing fractions. A test of the influence of measurement errors on the results shows that the uncertainties in the calculation of the mixture fractions are less than 11%, indicating that the source identification method developed is a robust tool for identifying sources of chlorinated solvents in groundwater.

Analytical and numerical models describing the evolution of contaminant concentrations in the plume associated with the dissolution of NAPL source and degradation processes were presented in the literature. At real sites and particularly in complex aquifers like chalk, it is difficult to understand how the sources of contaminants evolve with time. 1,1,1-Trichloroethane (1,1,1-TCA) is one of the few compounds with a well-known hydrolysis constant, that can help to improve knowledge of the contaminant sources and transport rates of dissolved contaminants in groundwater by dating the spill. In this work, different scenarios that could explain the evolution of the concentrations of 1,1,1-TCA and its degradation product 1,1-Dichloroethene (1,1-DCE) at a real contaminated site were investigated by analytical and numerical modelling. The results show that (1) the peaks of concentration time series do not correspond to a single contamination event even in the case of a complex medium, (2) the multiphasic behavior of the concentration time series is dictated by the dissolution in a heterogeneous medium, and (3) the persistence of the concentrations can arise from a small residual organic phase or transport in dual domain medium.

This work proposes a suitable treatment for the leachates from a sewage sludge composting process using a specific windrow (biopile). The biopile’s evolution and organic content degradation were followed for 2 months with regular leachate spraying to assess the physico-chemical and biological impacts, and determine the risk of enrichment with certain monitored pollutants. The final objective was the valorization of the biopile substrates in the composting process, while respecting the quality standards of use in a circular economy way. Classical physico-chemical parameters (pH, conductivity, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), etc.) were measured in the leachates and in the water-extractable and dry-solid fractions of the biopile, and the catabolic evolution of the micro-organisms (diversity and activities), as well as the enrichment with persistent organic pollutants (POPs) (prioritized PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated biphenyls)), were determined. The results showed that the microbial populations that were already present in the biopile, and that are responsible for biodegradation, were not affected by leachate spraying. Even when the studied compost leachate was highly concentrated with ammonium nitrogen (10.4 gN L−1 on average), it significantly decreased in the biopile after 2 weeks. A study on the evolution of the isotopic signature (δ15 N) confirmed the loss of leachate nitrogen in its ammoniacal form. The bio-physico-chemical characteristics of the biopile at the end of the experiment were similar to those before the first spraying with leachate. Moreover, no significant enrichment with contaminants (metal trace elements, volatile fatty acids, or persistent organic pollutants) was observed. The results show that it would be possible for composting platforms to implement this inexpensive and sustainable process for the treatment of leachates.

Bromoform (CHBr3) belongs to very-short-lived substances (VSLSs), which are important precursors of reactive bromine species (BrOx) contributing to tropospheric and stratospheric chemistry. To date, most models calculating bromine product emissions to the atmosphere only consider the natural production of CHBr3 from marine organisms such as macroalgae and phytoplankton. However, CHBr3 has many other anthropogenic sources (coastal industrial sites, desalination and wastewater plants, ballast waters, and seawater toilets) that may drastically increase the amounts emitted in the atmosphere. Here, we report the levels of CHBr3 released in water and air (according to real-time and offline measurements by protontransfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) and gas chromatography with electron capture detection (GC-ECD)) in a highly industrialized area where 3 million cubic meters of chlorinated seawater is released each day, which were measured during six field campaigns (at sea and on land) distributed over 3 years. The highest levels found during this survey (which were correlated to the physical-chemical characteristics of the water, meteorological and hydrological conditions, salinity, and temperature gradients along the water column) reached 34.6 mu g L-1 in water (100-10 000 times higher than reported natural levels) and 3.9 ppbv in the air (100 times higher than the maximum reported value to date). These findings suggest the need to undertake sampling and analysis campaigns as dose as possible to chlorinated discharges, as anthropogenic CHBr3 sources from industrial discharges may be a missing factor in global flux estimates or organic bromine to the atmosphere.

The transfer of pesticides from agricultural soils to food and drinking water is a major health issue. There are actually few robust methods to identify, characterize and quantify the dissipation of pesticides in complex media such as soils, waters and sediments. Here, we review multi-elemental compound-specific isotope analysis to study sources and transformations of pesticides in agricultural soils. First, we discuss advanced extraction and purification techniques for pesticides in soils. Then, analytical techniques for reliable measurements of the stable isotope composition of the pesticides are presented. We report a unique dataset of 547 isotopic compositions of 71 active molecules produced by various pesticide manufacturers, for the following isotopes: 13C, 15N, 37Cl, and 2H. We also report 270 isotope fractionation values for 33 compounds, which might help to elucidate the mechanisms of pesticide transformation by biodegradation, photodegradation and other abiotic processes. Compounds include legacy pesticides such as atrazine, lindane, dichlorodiphenyltrichloroethane, chlordecone and organophosphorus compounds. Transformation processes may be identified and quantified using the Rayleigh concept for isotope fractionation during reaction.

Short-chain chlorinated paraffins (SCCPs) are under regulation through the European Water Framework Directive and were recently classified as POPs. Consecutively, the increasing use of middle-chain chlorinated paraffins (MCCPs) becomes of growing concern. Knowledge on the occurrence of chlorinated paraffins (CPs) is still scarce particularly in water phase. To achieve sufficient method sensitivity, the passive sampling approach, acting as a relevant alternative to usual grab sampling, has been considered only very recently for the monitoring of CPs in water. The present work aimed at determining the diffusion coefficients in silicone (Ds) and the silicone-water partition coefficients (Ksw) of various CP groups, having different chlorine contents and carbon chain lengths, in four commercial CP mixtures. Log Ds (-10.78 to -10.21) was found to vary little and to be high for the groups of CPs studied. Thus, their uptake in silicone is controlled by the water boundary layer, which allows to consider the release of performance and reference compounds for in-field estimation of the sampling rate. Moreover, CPs partitioned strongly towards silicone rubbers. Both the chlorination degree and the carbon chain length of CPs cause large uncertainties in the partitioning between silicone and water (log Ksw between 4.85 and 6.30), indicating that instead of an average value, differentiated Ksw should be used to estimate aqueous CPs more accurately. Even so, the probable influence of chlorine atoms position on polarity and partitioning may be an argument for favoring sampling in the kinetic stage.