A phycocyanin probe as a tool for monitoring cyanobacteria in freshwater bodies

In many countries, the presence of cyanobacteria in freshwater bodies used for both drinking water and recreational purposes is under increasing public health attention. Water managers are considering how to implement monitoring that leads to a minimization of the risks incurred by the users of potentially contaminated sites. To address this question, this study involved assessing the performance of a submersible probe for measuring phycocyanin-specific fluorescence as a function of cyanobacterial biomass, with the aim of applying it as a tool for surveillance management. Its advantages and limits compared to more traditional analyses are discussed. The monitoring of cyanobacteria in the water bodies of western France was carried out using a minifluorimeter specific to the fluorescence of phycocyanin, a pigment specific to cyanobacteria. The results are compared with the analyses recommended by the World Health Organisation (chlorophyll a and cell counting). This study based on nearly 800 samples shows a significant correlation between the phycocyanin content and the cyanobacterial biomass, expressed as the number of cells per mL (R2 = 0.73). This submersible probe is simple and rapid to use, making it possible to take into account horizontal and vertical heterogeneities in the proliferation growth. In this way, we are able to detect at an early stage the conditions that could potentially lead to a risk, in order to start sampling. Due to its sensitivity, this tool proves suitable for monitoring aimed at reducing the risks incurred by the users of contaminated sites and launching preventative actions. The use of the phycocyanin probe provides an effective tool to complement traditional analyses of cyanobacterial presence. It is suggested that a surveillance protocol based on phycocyanin concentration can significantly improved the accuracy of the extent of cyanobacterial bloom development in the light of spatial and temporal variabilities associated with these occurrences.     

Recovery of Francisella tularensis from soil samples by filtration and detection by real-time PCR and cELISA

The aim of this study was to develop a specific and highly sensitive method able to detect very low concentrations of Francisella tularensis in soil samples by real-time PCR (qPCR) with SYBR Green I. tul4 gene, which encodes the 17-kDa protein (TUL4) in F. tularensis strains, was amplified using a LightCycler (LC) device. We achieved a detection limit of 0.69 fg of genomic DNA from F. tularensis subp. holarctica live vaccine strain (LVS), corresponding to a value less than 3.4 genome equivalents per reaction. The qPCR was shown to be specific, highly sensitive and reproducible. In addition, we evaluated 2 new methods for recovering bacteria from soil based on 1-step filtration using glass fiber filters and PVDF filters. These filtration methods enabled us to recover F. tularensis efficiently from soil samples. As few as 50 CFU per 0.5 g of soil were detected by qPCR. Capture enzyme-linked immunosorbent assay (cELISA) allowed us to detect and quantify the amount of bacteria recovered from soil by an immunological method. Although qPCR was more sensitive than cELISA, we did not observe substantial differences in the amount of bacteria quantified by both methods.     

The effect of the number of counted traverses on the estimation of the total spore count sampled on a non-cultivable slit impactor

Various counting rules are used for spore trap analysis. Partial count can lead to concentration errors. This paper demonstrates that the number of traverses counted affects the final results.     

Soil solution and sugar maple response to NH4NO3 additions in a base-poor northern hardwood forest of Québec, Canada

Nitrogen additions (NH4NO3) at rates of three- and ten-fold ambient atmospheric deposition (8.5 kg ha(-1) year(-1)) were realised in an acid- and base-poor northern hardwood forest of Québec, Canada. Soil solution chemistry, foliar chemistry, crown dieback and basal area growth of sugar maple (Acer saccharum Marsh.) were measured. Except for a transitory increase of NO3 and NH4 concentrations, there was no persistent increase in their level in soil solution 3 years after N treatments, with the exception of one plot out of three, that received the highest N addition, beginning to show persistent and high NO3 concentrations after 2 years of N additions. Three years of N additions have significantly increased the N DRIS index of sugar maple but not N foliar concentration. Potassium, Ca and Mn foliar concentrations, as well as P and Ca DRIS indices, decreased in treated plots after 3 years. No treatment effect was observed for basal area growth and dieback rate. One unexpected result was the significant decrease in foliar Ca even in the treated plots that received low N rates, despite the absence of significant NO3-induced leaching of Ca. The mechanism responsible for the decrease in foliar Ca is not known. Our results, however, clearly demonstrate that increased N deposition at sites with low base saturation may affect Ca nutrition even when clear signs of N saturation are not observed.     

Dynamic extreme values modeling and monitoring by means of sea shores water quality biomarkers and valvometry

Water quality can be evaluated using biomarkers such as tissular enzymatic activities of endemic species. Measurement of molluscs bivalves activity at high frequency (e.g., valvometry) during a long time period is another way to record the animal behavior and to evaluate perturbations of the water quality in real time. As the pollution affects the activity of oysters, we consider the valves opening and closing velocities to monitor the water quality assessment. We propose to model the huge volume of velocity data collected in the framework of valvometry using a new nonparametric extreme values statistical model. The objective is to estimate the tail probabilities and the extreme quantiles of the distribution of valve closing velocity. The tail of the distribution function of valve closing velocity is modeled by a Pareto distribution with parameter ??_t,τ, beyond a threshold τ according to the time t of the experiment. Our modeling approach reveals the dependence between the specific activity of two enzymatic biomarkers (Glutathione-S-transferase and acetylcholinesterase) and the continuous recording of oyster valve velocity, proving the suitability of this tool for water quality assessment. Thus, valvometry allows in real-time in situ analysis of the bivalves behavior and appears as an effective early warning tool in ecological risk assessment and marine environment monitoring.     

Cytotoxic and genotoxic effects of silver nanoparticle/carboxymethyl cellulose on <Emphasis Type="Italic">Allium cepa</Emphasis>

Several mutagenic agents may be present in substances released in the environment, which may cause serious environmental impacts. Among these substances, there is a special concern regarding the widespread use of silver nanoparticles (AgNP) in several products due to their widely known bactericidal properties, including in the medical field and the food industry (e.g., active packaging). The assessment of the effects of AgNP released in the environment, having different concentrations, sizes, and being associated or not to other types of materials, including polymers, is therefore essential. In this research, the objective was to evaluate the genotoxic and cytotoxic effects of AgNP (size range between 2 and 8 nm) on root meristematic cells of Allium cepa (A. cepa). Tests were carried out in the presence of colloidal solution of AgNP and AgNP mixed with carboxymethylcellulose (CMC), using distinct concentrations of AgNP. As a result, when compared to control samples, AgNP induced a mitotic index decrease and an increase of chromosomal aberration number for two studied concentrations. When AgNP was in the presence of CMC, no cytotoxic potential was verified, but only the genotoxic potential for AgNP dispersion having concentration of 12.4 ppm.     

2,5,6,9,10-Pentabromocyclododecanols (PBCDOHs): a new class of HBCD transformation products

Pentabromocyclododecanols (PBCDOHs) are potential environmental transformation products of hexabromocyclododecanes (HBCDs). They are also potential stage one metabolites of biological HBCD transformations. Herein, we present analytical evidence that PBCDOHs are also constituents of technical HBCDs and flame-proofed polystyrenes (FP-PSs). PBCDOHs are possibly formed during the synthesis of technical HBCD, presumably during the bromination of cyclododecatrienes in aqueous isobutanol together with isobutoxypentabromocyclododecanes (iBPBCDs), which have been identified in these materials recently. Of the 64 stereoisomers possible, eight pairs of enantiomers, named α-, β-, γ-, δ-, ε-, ζ-, η-, and θ-PBCDOHs were separated with a combination of normal-, reversed- and chiral-phase LC. Crystal structure analysis revealed the stereochemistry of the α-PBCDOH pair of enantiomers, which was assigned to (1S,2S,5R,6S,9S,10R)-2,5,6,9,10-pentabromocyclododecanol and its enantiomer. Mass spectrometric data are in accordance with the expected isotope patterns. On a C₁₈-RP-column, the polar PBCDOHs eluted before the HBCD and iBPBCD classes of compounds. PBCDOHs were also found in FP-PS materials. The stereoisomer patterns varied considerably in these materials like those of HBCDs and iBPBCDs. Expanded polystyrenes were rich in late-eluting stereoisomers, similar to technical HBCD mixtures. Extruded polystyrenes contained more of the polar, faster-eluting isomers. The presented chromatographic and analytical methods allow a stereoisomer-specific search for PBCDOHs in biota samples, which might have experienced metabolic HBCD transformation reactions. Besides this potential source, it has to be recognized that PBCDOHs are by-products in technical HBCDs and in flame-proofed polystyrenes. Therefore, it is likely that PBCDOHs and iBPBCDs are released to the environment together with HBCD-containing plastic materials.     

The toxicity of phthalocyanines to the aquatic plant Lemna minor (duckweed) - testing of 31 compounds

Phthalocyanines are prospective chemicals that have applications in industry, medicine and biology due especially to their architectural flexibility and production of reactive oxygen species. Although they are used in so many areas of human activities nowadays, there is still little knowledge of their ecotoxicity. Here we present the first observation of their toxic effects on representatives of the aquatic plants Lemna minor. The tested phthalocyanines possess a wide spectrum of phytotoxicity ranging from seldom (>50 mg L⁻¹) to highly toxic 0.11 mg L⁻¹. Moreover, the potential of phthalocyanines to be used as selective cyanocides or herbicides is discussed as well.     

Air Pollution Effects of Incinerator Firing Practices and Combustion Air Distribution

A survey of academic programs in air pollution control was made. Results from the 127 schools reporting are tabulated by state. Faculty involved in air pollution instruction are identified. Some conclusions and recommendations are presented.     

Gas-Particle Distribution Factors for Organic and Other Pollutants in the Los Angeles Atmosphere

The distribution of organic pollutants between the gas and particu-late phases was measured for 6 days Including one with the highest ozone level observed in Pasadena In 1973 (7/25). Gas phase pollutants were monitored continuously while particulates were sampled over a one hour interval by filtration. The filters were extracted using a polar and a non-polar solvent; particulate organic carbon was determined using a carbon analyzer, and chemical analysis carried out by fractionation, gas chromatography, infrared, and CHON analysis.

The organic carbon fraction (OCF) was always large, up to 43% of the total particulates (TP). Most of the organics were oxygenated compounds of photochemical origin. There was a linear relation between O₃, OCF, and the infrared carbonyl band intensities of the extracts. Hourly variations of OCF and TP are discussed with respect to the gas phase pollutants and conversion processes.

Although secondary pollutant concentrations were found in the order: organics > nitrates > sulfates, nitrates were more efficient than organics in visibility degradation, based on a statistical evaluation of the data. The secondary aerosol contribution varied with O₃, accounting for up to 95% of TP when the O₃ peaked. The unusual nitrate peak observed for 7/25 is discussed with the atmospheric chemistry of other nitrogen compounds.

We define an organic carbon distribution factor: f_c = particulate organic carbon (POC, μg/m³C)/[POC + gas phase reactive hydrocarbons (μg/m³C)]. The gas-particle distribution factors for organics (f_c), nitrates (f_N) and sulfates (f_s) are in inverse order of their aerosol concentrations: f_c < f_N < f_s . The measured f_c are low: average 2–3%, highest value 6% for 7/25, and correspond to a conversion rate ≤2% hour^?1. Ambient f_c are much lower than f_c measured for certain specific hydrocarbon precursors.