Development of a combined isotopic and mass-balance approach to determine dissolved organic carbon sources in eutrophic reservoirs

A combined mass-balance and stable isotope approach was set up to identify and quantify dissolved organic carbon (DOC) sources in a DOC-rich (9 mg L⁻¹) eutrophic reservoir located in Western France and used for drinking water supply (so-called Rophemel reservoir). The mass-balance approach consisted in measuring the flux of allochthonous DOC on a daily basis, and in comparing it with the effective (measured) DOC concentration of the reservoir. The isotopic approach consisted, for its part, in measuring the carbon isotope ratios (δ¹³C values) of both allochthonous and autochthonous DOC sources, and comparing these values with the δ¹³C values of the reservoir DOC. Results from both approaches were consistent pointing out for a DOC of 100% allochthonous origin. In particular, the δ¹³C values of the DOC recovered in the reservoir (−28.5 ± 0.2‰; n = 22) during the algal bloom season (May-September) showed no trace of an autochthonous contribution (δ¹³C in algae = −30.1 ± 0.3‰; n = 2) being indistinguishable from the δ¹³C values of allochthonous DOC from inflowing rivers (−28.6 ± 0.1‰; n = 8). These results demonstrate that eutrophication is not responsible for the high DOC concentrations observed in the Rophemel reservoir and that limiting eutrophication of this reservoir will not reduce the potential formation of disinfection by-products during water treatment. The methodology developed in this study based on a complementary isotopic and mass-balance approach provides a powerful tool, suitable to identify and quantify DOC sources in eutrophic, DOC-contaminated reservoirs.     

Photodegradation of azithromycin in various aqueous systems under simulated and natural solar radiation: kinetics and identification of photoproducts

This article describes the photolysis of azithromycin, a macrolide antibiotic with reported occurrence in environmental waters, under simulated solar radiation. The photodegradation followed first-order reaction kinetics in five matrices examined. In HPLC water, the degradation rate was the slowest (half-life: 20 h), whereas in artificial freshwater supplemented with nitrate (5 mg L⁻¹) or humic acids (0.5 mg L⁻¹) the degradation of azithromycin was enhanced by factors of 5 and 16, respectively, which indicated the role of indirect photolysis involving the formation of highly reactive species. Following chromatographic separation on a UPLC system, the characterization of the transformation products was accomplished using high-resolution QqToF-MS analysis. The presence of seven photoproducts was observed and their formation was postulated to originate from (bis)-N-demethylation in the desosamine sugar, O-demethylation in the cladinose sugar, combinations thereof, as well as from hydrolytic cleavages of the desosamine and/or cladinose residue. Two of these photoproducts could also be detected in natural photodegradation process in river water which was spiked with azithromycin.     

Fate of bisphenol A during treatment with the litter-decomposing fungi Stropharia rugosoannulata and Stropharia coronilla

Bisphenol A is an endocrine disrupting compound, which is ubiquitous in the environment due to its wide use in plastic and resin production. Seven day old cultures of the litter-decomposing fungus Stropharia coronilla removed the estrogenic activity of bisphenol A (BPA) rapidly and enduringly. Treatment of BPA with purified neutral manganese peroxidase (MnP) from this fungus also resulted in 100% reduction of estrogenic activity, as analyzed using a bioluminescent yeast assay, and in the formation of polymeric compounds. In cultures of Stropharia rugosoannulata, estrogenic activity also quickly disappeared but temporarily re-emerged in the further course of cultivation. LC-MS analysis of the extracted estrogenic culture liquid revealed [M−H]⁻ ions with m/z values of 219 and 235. We hypothesize that these compounds are ring fission products of BPA, which still exhibit one intact hydroxyphenyl group to interact with estrogen receptors displayed by the yeast.     

Nitrogen deposition effects on Mediterranean-type ecosystems: an ecological assessment

We review the ecological consequences of N deposition on the five Mediterranean regions of the world. Seasonality of precipitation and fires regulate the N cycle in these water-limited ecosystems, where dry N deposition dominates. Nitrogen accumulation in soils and on plant surfaces results in peaks of availability with the first winter rains. Decoupling between N flushes and plant demand promotes losses via leaching and gas emissions. Differences in P availability may control the response to N inputs and susceptibility to exotic plant invasion. Invasive grasses accumulate as fuel during the dry season, altering fire regimes. California and the Mediterranean Basin are the most threatened by N deposition; however, there is limited evidence for N deposition impacts outside of California. Consequently, more research is needed to determine critical loads for each region and vegetation type based on the most sensitive elements, such as changes in lichen species composition and N cycling.     

Cocaine and other illicit drugs in airborne particulates in urban environments: a reflection of social conduct and population size

Levels of cocaine and other psychoactive substances in atmospheric particulate matter (PM) were determined in urban environments representing distinct social behaviours with regard to drug abuse: night-life, university and residential areas. Three cities (with population >1 million and <0.3 million inhabitants) were selected. Mean daily levels of drugs in PM were 11-336 pg/m³ for cocaine, 23-34 pg/m³ for cannabinoids, and 5-90 pg/m³ for heroin. The highest levels were recorded on weekends, with factors with respect to weekdays of 1-3 for cocaine, 1-2 for cannabinoids and 1.1-1.7 for heroin. Higher levels were detected in the night-life areas, pointing towards consumption and trafficking as major emission sources, and possibly ruling out drug manufacture. The similarities in temporal trends at all sites suggested a city-scale transport of psychoactive substances. Correlations were detected between cocaine and amphetamine consumption (r² = 0.98), and between heroin and cannabinoids (r²>0.82).     

Road deicing salt irreversibly disrupts osmoregulation of salamander egg clutches

It has been postulated that road deicing salts are sufficiently diluted by spring rains to ameliorate any physiological impacts to amphibians breeding in wetlands near roads. We tested this conjecture by exposing clutches of the spotted salamander (Ambystoma maculatum) to three chloride concentrations (1 mg/L, 145 mg/L, 945 mg/L) for nine days, then transferred clutches to control water for nine days, and measured change in mass at three-day intervals. We measured mass change because water uptake by clutches reduces risks to embryos associated with freezing, predation, and disease. Clutches in controls sequestered water asymptotically. Those in the moderate concentrations lost 18% mass initially and regained 14% after transfer to control water. Clutches in high concentration lost 33% mass and then lost an additional 8% after transfer. Our results suggest that spring rains do not ameliorate the effects of deicing salts in wetlands with extremely high chloride concentrations.     

TiO₂-based nanoparticles released in water from commercialized sunscreens in a life-cycle perspective: structures and quantities

This work investigates the physical-chemical evolution during artificial aging in water of four commercialized sunscreens containing TiO₂-based nanocomposites. Sunscreens were analyzed in terms of mineralogy and TiO₂ concentration. The residues formed after aging were characterized in size, shape, chemistry and surface properties. The results showed that a significant fraction of nano-TiO₂ residues was released from all sunscreens, despite their heterogeneous behaviors. A stable dispersion of submicronic aggregates of nanoparticles was generated, representing up to 38 w/w% of the amount of sunscreen, and containing up to 30% of the total nano-TiO₂ initially present in the creams. The stability of the dispersion was tested as a function of salt concentration, revealing that in seawater conditions, a major part of these nano-TiO₂ residues will aggregate and sediment. These results were put in perspective with consumption and life cycle of sunscreens to estimate the amount of nano-TiO₂ potentially released into AQUATIC environment.     

Validation of an analytical method for the quantification of pyrethrins on lemons and apricots using high-performance liquid chromatography/mass spectrometry

An analytical procedure has been developed for the determination of natural pyrethrins (pyrethrin I, pyrethrin II, jasmolin I, jasmolin II, cinerin I and cinerin II) in lemon and apricot. The QuEChERS method, which stands for quick, easy, cheap, effective, rugged and safe was used for extraction. Analysis of the extract was performed by liquid-chromatography-electrospray ionisation-tandem mass spectrometry. The ions prominent in the ESI spectra were [M+H]+ for the six compounds. A Zorbax SB-C18 column was used with a programmed gradient mobile phase consisting of (A) water containing 0.1% formic acid and 5 mM ammonium formate and (B) ACN. The method was linear within the investigated concentration range, displaying a calibration curve correlation factor of 0.99. The coefficients of variation obtained (RSD) were below 20% and the recoveries were in the 70-110% range.     

Determination of sixteen pesticides in peppers using high-performance liquid chromatography/mass spectrometry

A method for the detection and quantification of 16 pesticides: flufenoxuron, fenoxycarb, dimethomorph, acetamiprid, imidacloprid, lufenuron, thiacloprid, thiabendazole, thiophanate-methyl, spinosad, fenbutatin oxide, methoxyfenozide, oxamyl, clothianidin, thiamethoxam and carbendazim has been developed based on high-performance liquid chromatography-mass spectrometry. Pesticide residues were extracted from the samples according to the QuEChERS method which stands for quick, essay, cheap, effective, rugged and safe. Homogenised analytical portions (10 g ± 0.1) of samples of peppers were spiked at two levels (10 and 100 μg kg?1) with a small volume of an appropriate standard mixture solution containing each pesticide. Analyses were performed using electrospray ionization (ESI) and a MSD trap system. Chromatography separation was achieved using a ZORBAX SB-C18 3.5 μm particle size analytical column, 2.1 × 50 mm from Agilent, with gradient elution at a flow-rate of 0.4 mL/min with mobile phases: waters-0.1 % HCOOH-5 mM HCOONH? and MeOH-5 mM HCOONH?. The method has been validated based on the SANCO European Guidelines. Under the optimized conditions the recoveries (n = 7) were in the range 70-110 % with satisfactory precision (CV ≤ 20 %). A linear dynamic range was obtained over a range of concentrations from 10 to 100 μg kg?1 for each of the analytes, with correlation coefficients >0.997.     

Field sampling of soil pore water to evaluate trace element mobility and associated environmental risk

Monitoring soil pollution is a key aspect in sustainable management of contaminated land but there is often debate over what should be monitored to assess ecological risk. Soil pore water, containing the most labile pollutant fraction in soils, can be easily collected in situ offering a routine way to monitor this risk. We present a compilation of data on concentration of trace elements (As, Cd, Cu, Pb, and Zn) in soil pore water collected in field conditions from a range of polluted and non-polluted soils in Spain and the UK during single and repeated monitoring, and propose a simple eco-toxicity test using this media. Sufficient pore water could be extracted for analysis both under semi-arid and temperate conditions, and eco-toxicity comparisons could be effectively made between polluted and non-polluted soils. We propose that in-situ pore water extraction could enhance the realism of risk assessment at some contaminated sites.