Feeding characteristics of a golden alga (Poterioochromonas sp.) grazing on toxic cyanobacterium Microcystis aeruginosa

Microcystis aeruginosa has quickly risen in infamy as one of the most universal and toxic bloom-forming cyanobacteria. Here we presented a species of golden alga (Poterioochromonas sp. strain ZX1), which can feed on toxic M. aeruginosa without any adverse effects from the cyanotoxins. Using flow cytometry, the ingestion and maximal digestion rates were estimated to be 0.2∼1.2 and 0.2 M. aeruginosa cells (ZX1 cell)⁻¹ h⁻¹, respectively. M. aeruginosa in densities below 10⁷ cells mL⁻¹ could be grazed down by ZX1, but no significant decrease was observed when the initial density was 3.2 × 10⁷ cells mL⁻¹. ZX1 grazing was a little influenced by the light intensity (0.5∼2500 lx) and initial pH of the medium (pH = 5.0∼9.5). ZX1 could not survive in continuous darkness for longer than 10 days. The pH value was adjusted to 8 by ZX1 while to 10 by M. aeruginosa. This study may shed light on understanding the ecological interactions between M. aeruginosa and mixotrophic Poterioochromonas sp. in aquatic ecosystems.     

Precipitation of arsenic sulphide from acidic water in a fixed-film bioreactor

Arsenic (As) is a toxic element frequently present in acid mine waters and effluents. Precipitation of trivalent arsenic sulphide in sulphate-reducing conditions at low pH has been studied with the aim of removing this hazardous element in a waste product with high As content. To achieve this, a 400 mL fixed-film column bioreactor was fed continuously with a synthetic solution containing 100 mg L⁻¹ As(V), glycerol and/or hydrogen, at pH values between 2.7 and 5. The highest global As removal rate obtained during these experiments was close to 2.5 mg L⁻¹ h⁻¹. A switch from glycerol to hydrogen when the biofilm was mature induced an abrupt increase in the sulphate-reducing activity, resulting in a dramatic mobilisation of arsenic due to the formation of soluble thioarsenic complexes. A new analytical method, based on ionic chromatography, was used to evaluate the proportion of As present as thioarsenic complexes in the bioreactor. Profiles of pH, total As and sulphate concentrations suggest that As removal efficiency was linked to solubility of orpiment (As₂S₃) depending on pH conditions. Molecular fingerprints revealed fairly homogeneous bacterial colonisation throughout the reactor. The bacterial community was diverse and included fermenting bacteria and Desulfosporosinus-like sulphate-reducing bacteria. arrA genes, involved in dissimilatory reduction of As(V), were found and the retrieved sequences suggested that As(V) was reduced by a Desulfosporosinus-like organism. This study was the first to show that As can be removed by bioprecipitation of orpiment from acidic solution containing up to 100 mg L⁻¹ As(V) in a bioreactor.     

Application of the Nernst-Planck approach to lead ion exchange in Ca-loaded Pelvetia canaliculata

Ca-loaded Pelvetia canaliculata biomass was used to remove Pb²⁺ in aqueous solution from batch and continuous systems. The physicochemical characterization of algae Pelvetia particles by potentiometric titration and FTIR analysis has shown a gel structure with two major binding groups - carboxylic (2.8 mmol g⁻¹) and hydroxyl (0.8 mmol g⁻¹), with an affinity constant distribution for hydrogen ions well described by a Quasi-Gaussian distribution. Equilibrium adsorption (pH 3 and 5) and desorption (eluents: HNO₃ and CaCl₂) experiments were performed, showing that the biosorption mechanism was attributed to ion exchange among calcium, lead and hydrogen ions with stoichiometry 1:1 (Ca:Pb) and 1:2 (Ca:H and Pb:H). The uptake capacity of lead ions decreased with pH, suggesting that there is a competition between H⁺ and Pb²⁺ for the same binding sites. A mass action law for the ternary mixture was able to predict the equilibrium data, with the selectivity constants α_Ca^H = 9 ± 1 and α_Ca^Pb = 44 ± 5, revealing a higher affinity of the biomass towards lead ions. Adsorption (initial solution pH 4.5 and 2.5) and desorption (0.3 M HNO₃) kinetics were performed in batch and continuous systems. A mass transfer model using the Nernst-Planck approximation for the ionic flux of each counter-ion was used for the prediction of the ions profiles in batch systems and packed bed columns. The intraparticle effective diffusion constants were determined as 3.73 × 10⁻⁷ cm² s⁻¹ for H⁺, 7.56 × 10⁻⁸ cm² s⁻¹ for Pb²⁺ and 6.37 × 10⁻⁸ cm² s⁻¹ for Ca²⁺.     

(210)Po and (210)Pb in the tissues of the deep-sea hydrothermal vent mussel Bathymodiolus azoricus from the Menez Gwen field (Mid-Atlantic Ridge)

The hydrothermal deep-sea vent fauna is naturally exposed to a highly specific environment enriched in potentially toxic species such as sulfides, metals and natural radionuclides due to the convective seawater circulation inside the oceanic crust and its interaction with basaltic or ultramafic host rocks. However, data on radionuclides in biota from such environment are very limited. An investigation was carried out on tissue partitioning of ²¹⁰Po and ²¹⁰Pb, two natural radionuclides within the ²³⁸U decay chain, in Bathymodiolus azoricus specimens from the Mid-Atlantic Ridge (Menez Gwen field). These two elements showed different distributions with high ²¹⁰Pb levels in gills and high ²¹⁰Po levels in both gills and especially in the remaining parts of the body tissue (including the digestive gland). Various factors that may explain such partitioning are discussed. However, ²¹⁰Po levels encountered in B. azoricus were not exceptionally high, leading to weighted internal dose rate in the range 3 to 4 μGy h^− 1. These levels are slightly higher than levels characterizing coastal mussels (~ 1 μGy h^− 1).     

Water, vegetation and sediment gradients in submerged aquatic vegetation mesocosms used for low-level phosphorus removal

Gradients in phosphorus (P) removal and storage were investigated over 6 years using mesocosms (each consisting of three tanks in series) containing submerged aquatic vegetation (SAV) grown on muck and limerock (LR) substrates. Mean inflow total P concentrations (TP) of 32 μg L⁻¹ were reduced to 15 and 17 μg L⁻¹ in the muck and LR mesocosms, respectively. Mesocosm P loading rates (mean = 1.75 g m⁻² year⁻¹) varied widely during the study and were not correlated with outflow TP, which instead varied seasonally with lowest monthly mean values in December and January.The mesocosms initially were stocked with Najas guadalupensis, Ceratophyllum demersum, and Chara zeylanica, but became dominated by C. zeylanica. At the end of the study, highest vegetative biomass (1.1 and 1.4 kg m⁻² for muck and LR substrates) and tissue P content (1775 and 1160 mg kg⁻¹) occurred in the first tank in series, and lowest biomass (1.0 and 0.2 kg m⁻²) and tissue P (147 and 120 mg kg⁻¹) in the third tank. Sediment accretion rates (2.5, 1.9 and 0.9 cm yr⁻¹ on muck substrates), accrued sediment TP (378, 309 and 272 mg kg⁻¹), and porewater soluble reactive P (SRP) concentrations (40, 6 and 4 μg L⁻¹) in the first, second and third tanks, respectively, exhibited a similar decreasing spatial trend. Plant tissue calcium (Ca) near mesocosm inflow (19-30% dry weight) and outflow (23-26%) were not significantly different, and sediment Ca was also similar (range of 24 to 28%) among sequential tanks.Well-defined vegetation and sediment enrichment gradients developed in SAV wetlands operated under low TP conditions. While the mesocosm data did not reflect deterioration in treatment performance over 6 years, accumulation of P-enriched sediments near the inflow could eventually compromise hydraulic storage and P removal effectiveness of these shallow systems.     

Mercury bioacumulation in four tissues of Podocnemis erythrocephala (Podocnemididae: Testudines) as a function of water parameters

A number of environmental factors influence the dynamics of Hg in aquatic ecosystems, yet few studies have examined these factors for turtles, especially from South America. Red-headed river turtle (Podocnemis erythrocephala) is easy to capture in the black waters of Rio Negro, making it the turtle species that is consumed most often by people of the region. In this study, environmental factors and turtle size were investigated to determine their influence on the Hg concentration in blood, muscle, liver and carapace of the red-headed river turtle. Factors investigated included turtle length, pH, dissolved organic carbon and availability of potential methylation sites (floodplain forests and hydromorphic soils). The study was conducted in the Rio Negro basin, where we collected water and turtle blood, muscle, liver and carapace samples from 12 tributaries for chemical analysis. Through radar imagery and existing soil maps with GIS, the percentage of alluvial floodplains and hydromorphic soils (potential methylation sites) was estimated for each drainage basin at sampling points. The mean Hg concentration in blood of P. erythrocephala was 1.64 ng g^− 1 (SD = 1.36), muscle 33 ng g^− 1 (SD = 11), liver 470 ng g^− 1 (SD = 313) and carapace 68 ng g^− 1 (SD = 32). Sex or length did not influence the Hg concentration in P. erythrocephala blood, muscle and liver, but Hg increased in carapace tissue when length size increased (ANCOVA p = 0.007). In the multiple regression analysis, none of the environmental factors studied had a significant relation with blood, muscle, liver and carapace. P. erythrocephala moves among habitats and in the open and interconnected aquatic systems of the Amazon basin, characterized by high levels of limnological variability, a good bioindicator of Hg concentration needs to be relatively sedentary to represent a specific habitat. However, the levels of Hg in liver were sufficient to pose a potential risk to humans that consume them, suggesting the usefulness of P. erythrocephala as a bioindicator.     

Simultaneous determination of microcystin contaminations in various vertebrates (fish, turtle, duck and water bird) from a large eutrophic Chinese lake, Lake Taihu, with toxic Microcystis blooms

This is the first to conduct simultaneous determination of microcystin (MC) contaminations in multi-groups of vertebrates (fish, turtle, duck and water bird) from Lake Taihu with Microcystis blooms. MCs (-RR, -YR, -LR) in Microcystis scum was 328 μg g^− 1 DW. MCs reached 235 μg g^− 1 DW in intestinal contents of phytoplanktivorous silver carp, but never exceeded 0.1 μg g^− 1 DW in intestinal contents of other animals. The highest MC content in liver of fish was in Carassius auratus (150 ng g^− 1 DW), followed by silver carp and Culter ilishaeformis, whereas the lowest was in common carp (3 ng g^− 1 DW). In livers of turtle, duck and water bird, MC content ranged from 18 to 30 ng g^− 1 DW. High MC level was found in the gonad, egg yolk and egg white of Nycticorax nycticorax and Anas platyrhynchos, suggesting the potential effect of MCs on water bird and duck embryos. High MC contents were identified for the first time in the spleens of N. nycticorax and A. platyrhynchos (6.850 and 9.462 ng g^− 1 DW, respectively), indicating a different organotropism of MCs in birds. Lakes with deaths of turtles or water birds in the literatures had a considerably higher MC content in both cyanobacteria and wildlife than Lake Taihu, indicating that toxicity of cyanobacteria may determine accumulation level of MCs and consequently fates of aquatic wildlife.     

Degradation of diclofenac by TiO2 photocatalysis: UV absorbance kinetics and process evaluation through a set of toxicity bioassays

In the present study the degradation kinetics and mineralization of diclofenac (DCF) by the TiO₂ photocatalysis were investigated in terms of UV absorbance and COD measurements for a wide range of initial DCF concentrations (5-80 mg L⁻¹) and photocatalyst loadings (0.2-1.6 g TiO₂ L⁻¹) in a batch reactor system. A set of bioassays (Daphnia magna, Pseudokirchneriella subcapitata and Artemia salina) was performed to evaluate the potential detoxification of DCF. A pseudo-first-order kinetic model was found to fit well most of the experimental data, while at high initial DCF concentrations (40 and 80 mg L⁻¹) and at 1.6 g TiO₂ L⁻¹ photocatalyst loading a second-order kinetic model was found to fit the data better. The toxicity of the treated DCF samples on D. magna and P. subcapitata varied during the oxidation, probably due to the formation of some intermediate products more toxic than DCF. Unicellular freshwater algae was found to be very sensitive to the treated samples as well as the results from D. magna test were consistent to those of algae tests. A. salina was not found to be sensitive under the investigated conditions. Finally, UV absorbance analysis were found to be an useful tool for a fast and easy to perform measurement to get preliminary information on the organic intermediates that are formed during oxidation and also on their disappearance rate.     

Influence of pH on bioactivity of cinnamon oil against Legionella pneumophila and its disinfection efficacy in hot springs

Cinnamon oil extracted from leaves of Cinnamomum osmophloeum has recently been proved as a promising antibacterial agent against Legionella pneumophila, an etiological agent of human pneumonia known as Legionnaires' disease. However, the pH effects on the efficacy of cinnamon oil against L. pneumophila and its applicability to recreational spring water remain unknown. We therefore determined the bactericidal activity of cinnamon oil at pH 3-10 in phosphate-buffered saline (PBS) and in four kinds of springs with various conductivity (259-5595 μs cm⁻¹) and pH (2.1-7.7) levels. Results show L. pneumophila cells were more susceptible to cinnamon oil at pH 8-10 than at pH 4-6 in PBS, which became more evident as increasing contact time from 10 to 60 min. An increase in concentration of cinnamon oil and contact time significantly increased the anti-L. pneumophila activity (P ≤ 0.001), indicating a consistent biocidal effect regardless of pH. Interestingly, this dose-response biocidal effect was also observed in spring waters. Moreover, L. pneumophila of 4 log CFU ml⁻¹ in spring waters was completely inactivated within 60 min by cinnamon oil at 300-750 μg ml⁻¹, with the highest inactivation in alkaline hydrogen carbonate spring. The great bioactivity of cinnamon oil demonstrates its potential to be used to control Legionella growth in recreational spring water and possibly other niches generally at basic pH, e.g., cooling towers.     

Comparison of toxicity and release rates of Cu and Zn from anti-fouling paints leached in natural and artificial brackish seawater

Biocide-containing anti-fouling paints are regulated and approved according to the added active ingredients, such as Cu. Biocide-free paints are considered to be less environmentally damaging and do not need an approval. Zn, a common ingredient in paints with the potential of causing adverse effects has received only minor attention. Laboratory experiments were conducted in artificial brackish seawater (ASW) and natural brackish seawater (NSW) to quantify release rates of Cu and Zn from biocide-containing and biocide-free labeled eroding anti-fouling paints used on commercial vessels as well as leisure boats. In addition, organisms from three trophic levels, the crustacean Nitocra spinipes, the macroalga Ceramium tenuicorne and the bacteria Vibrio fischeri, were exposed to Cu and Zn to determine the toxicity of these metals. The release rate of Cu in NSW was higher from the paints for professional use (3.2-3.6 µg cm⁻² d^− 1) than from the biocide leaching leisure boat paint (1.1 µg cm⁻² d^− 1). Biocide-free paints did leach considerably more Zn (4.4-8.2 µg cm⁻² d^− 1) than biocide-containing leisure boat paint (3.0 µg cm⁻² d^− 1) and ship paints (0.7-2.0 µg cm⁻² d^− 1). In ASW the release rates of both metals were notably higher than in NSW for most tested paints. The macroalga was the most sensitive species to both Cu (EC₅₀ = 6.4 µg l^− 1) and Zn (EC₅₀ = 25 µg l^− 1) compared to the crustacean (Cu, LC₅₀ = 2000 µg l^− 1 Zn, LC₅₀ = 890 µg l^− 1), and the bacteria (Cu, EC₅₀ = 800 µg l^− 1 and Zn, EC₅₀ = 2000 µg l^− 1). The results suggest that the amounts of Zn and Cu leached from anti-fouling paints may attain toxic concentrations in areas with high boat density. To fully account for potential ecological risk associated with anti-fouling paints, Zn as well as active ingredients should be considered in the regulatory process.     

Assessing the risk posed to free-living soil nematodes by a genetically modified maize expressing the insecticidal Cry3Bb1 protein

Before pest-resistant genetically modified maize can be grown commercially, the risks for soil-beneficial, non-target organisms must be determined. Here, a tiered approach was used to assess the risk to free-living soil nematodes posed by maize genetically modified to express the insecticidal Cry3Bb1 protein (event Mon88017), which confers resistance towards western corn rootworm (Diabrotica virgifera; Coleoptera). The toxicity of purified Cry3Bb1 for the nematode Caenorhabditis elegans was determined using a bioassay and gene expression analysis. In addition, a soil toxicity test was used to assess the effects on C. elegans of rhizosphere soil obtained from plots of an experimental field grown with Mon88017, the near-isogenic cultivar, or either of two conventional cultivars. Finally, the indigenous nematode communities from the experimental field site with Mon88017 and from the control cultivars were analyzed. The results showed a dose-dependent inhibitory effect of Cry3Bb1 on the growth and reproduction of C. elegans, with EC50 values of 22.3 mg l⁻¹ and 7.9 mg l⁻¹, respectively. Moreover, Cry-protein-specific defense genes were found to be up-regulated in the presence of either Cry1Ab or Cry3Bb1. However, C. elegans was not affected by rhizosphere soils from Mon88017 compared to the control plots, due to the very low Cry3Bb1 concentrations, as indicated by quantitative analyses (< 1 ng g⁻¹ soil). Nematode abundance and diversity were essentially the same between the various maize cultivars. At the last sampling date, nematode genus composition in Bt-maize plots differed significantly from that in two of the three non-Bt cultivars, including the near-isogenic maize, but the shift in genus composition did not influence the composition of functional guilds within the nematode communities. In conclusion, the risk to free-living soil nematodes posed by Mon88017 cultivation can be regarded as low, as long as Cry3Bb1 concentrations in soil remain four orders of magnitude below the toxicity threshold.     

Evidences of non-reactive mercury-selenium compounds generated from cultures of Pseudomonas fluorescens

This work was designed to determine chemically inert mercury-selenium (Hg-Se) compounds formed in a culture of Pseudomonas fluorescens exposed to Hg²⁺ and Se^IV (selenite). To isolate these compounds, different digestion methods were studied and sodium dodecyl sulfate (SDS) lysis was selected. The Hg⁰ and non-reactive Hg were determined in two series of cultures containing 0.0-6.00 μg L⁻¹ Se^IV (0.0-76.0 μmol L⁻¹) in combination with low 5.00 μg L⁻¹ (0.025 μmol L⁻¹) or high 100 μg L⁻¹ (0.500 μmol L⁻¹) Hg²⁺. It was found that Hg⁰ formed in the culture decreased with the increase of initial Se^IV, while the non-reactive Hg increased with the Se^IV. In cultures with low initial [Hg²⁺], a median Se^IV (2.0 μg L⁻¹ or 25.3 μmol L⁻¹) resulted in about 70% of the added Hg²⁺ sequestered as non-reactive Hg, and in culture with high initial Hg²⁺, about 40% was sequestered. P. fluorescens was proved to be indispensible for the formation of the non-reactive Hg-Se compounds. The Hg:Se molar ratio in the non-reactive Hg-Se compounds was close to 1, suggesting the existence of mercuric selenide in cells. Mechanisms for the formation of the non-reactive Hg-Se compounds are proposed.     

Nitrate removal, communities of denitrifiers and adverse effects in different carbon substrates for use in denitrification beds

Denitrification beds are containers filled with wood by-products that serve as a carbon and energy source to denitrifiers, which reduce nitrate (NO₃⁻) from point source discharges into non-reactive dinitrogen (N₂) gas. This study investigates a range of alternative carbon sources and determines rates, mechanisms and factors controlling NO₃⁻ removal, denitrifying bacterial community, and the adverse effects of these substrates. Experimental barrels (0.2 m³) filled with either maize cobs, wheat straw, green waste, sawdust, pine woodchips or eucalyptus woodchips were incubated at 16.8 °C or 27.1 °C (outlet temperature), and received NO₃⁻ enriched water (14.38 mg N L⁻¹ and 17.15 mg N L⁻¹). After 2.5 years of incubation measurements were made of NO₃⁻-N removal rates, in vitro denitrification rates (DR), factors limiting denitrification (carbon and nitrate availability, dissolved oxygen, temperature, pH, and concentrations of NO₃⁻, nitrite and ammonia), copy number of nitrite reductase (nirS and nirK) and nitrous oxide reductase (nosZ) genes, and greenhouse gas production (dissolved nitrous oxide (N₂O) and methane), and carbon (TOC) loss. Microbial denitrification was the main mechanism for NO₃⁻-N removal. Nitrate-N removal rates ranged from 1.3 (pine woodchips) to 6.2 g N m⁻³ d⁻¹ (maize cobs), and were predominantly limited by C availability and temperature (Q₁₀ = 1.2) when NO₃⁻-N outlet concentrations remained above 1 mg L⁻¹. The NO₃⁻-N removal rate did not depend directly on substrate type, but on the quantity of microbially available carbon, which differed between carbon sources. The abundance of denitrifying genes (nirS, nirK and nosZ) was similar in replicate barrels under cold incubation, but varied substantially under warm incubation, and between substrates. Warm incubation enhanced growth of nirS containing bacteria and bacteria that lacked the nosZ gene, potentially explaining the greater N₂O emission in warmer environments. Maize cob substrate had the highest NO₃⁻-N removal rate, but adverse effects include TOC release, dissolved N₂O release and substantial carbon consumption by non-denitrifiers. Woodchips removed less than half of NO₃⁻ removed by maize cobs, but provided ideal conditions for denitrifying bacteria, and adverse effects were not observed. Therefore we recommend the combination of maize cobs and woodchips to enhance NO₃⁻ removal while minimizing adverse effects in denitrification beds.     

Dry deposition of gaseous radioiodine and particulate radiocaesium onto leafy vegetables

Radionuclides released to the atmosphere during dry weather (e.g. after a nuclear accident) may contaminate vegetable foods and cause exposure to humans via the food chain. To obtain experimental data for an appropriate assessment of this exposure path, dry deposition of radionuclides to leafy vegetables was studied under homogeneous and controlled greenhouse conditions. Gaseous ¹³¹I-tracer in predominant elemental form and particulate ¹³⁴Cs-tracer at about 1 μm diameter were used to identify susceptible vegetable species with regard to contamination by these radionuclides. The persistence was examined by washing the harvested product with water. The vegetables tested were spinach (Spinacia oleracea), butterhead lettuce (Lactuca sativa var. capitata), endive (Cichorium endivia), leaf lettuce (Lactuca sativa var. crispa), curly kale (Brassica oleracea convar. acephala) and white cabbage (Brassica oleracea convar. capitata). The variation of radionuclides deposited onto each vegetable was evaluated statistically using the non-parametric Kruskal-Wallis Test and the U-test of Mann-Whitney. Significant differences in deposited ¹³¹I and ¹³⁴Cs activity concentration were found among the vegetable species.For ¹³¹I, the deposition velocity to spinach normalized to the biomass of the vegetation was 0.5-0.9 cm³ g^− 1 s^− 1 which was the highest among all species. The particulate ¹³⁴Cs deposition velocity of 0.09 cm³ g^− 1 s^− 1 was the highest for curly kale, which has rough and structured leaves. The lowest deposition velocity was onto white cabbage: 0.02 cm³ g^− 1 s^− 1 (iodine) and 0.003 cm³ g^− 1 s^− 1 (caesium). For all species, the gaseous iodine deposition was significantly higher compared to the particulate caesium deposition. The deposition depends on the sensitive parameters leaf area, stomatal aperture, and plant morphology. Decontamination by washing with water was very limited for iodine but up to a factor of two for caesium.     

Adsorption, sedimentation, and inactivation of E. coli within wastewater treatment wetlands

Bacteria fate and transport within constructed wetlands must be understood if engineered wetlands are to become a reliable form of wastewater treatment. This study investigated the relative importance of microbial treatment mechanisms in constructed wetlands treating both domestic and agricultural wastewater. Escherichia coli (E. coli) inactivation, adsorption, and settling rates were measured in the lab within two types of wastewater (dairy wastewater lagoon effluent and domestic septic tank effluent). In situ E. coli inactivation was also measured within a domestic wastewater treatment wetland and the adsorption of E. coli was also measured within the wetland effluent.Inactivation of E. coli appears to be the most significant contributor to E. coli removal within the wastewaters and wetland environments examined in this study. E. coli survived longer within the dairy wastewater (DW) compared to the domestic wastewater treatment wetland water (WW). First order rate constants for E. coli inactivation within the WW in the lab ranged from 0.09 day⁻¹ (d⁻¹) at 7.6 °C to 0.18 d⁻¹ at 22.8 °C. The average in situ rate constant observed within the domestic wetland ranged from 0.02 d⁻¹ to 0.03 d⁻¹ at an average water temperature of 17 °C. First order rate constants for E. coli inactivation within the DW ranged from 0.01 d⁻¹ at 7.7 °C to 0.04 d⁻¹ at 24.6 °C. Calculated distribution coefficients (K_d) were 19,000 mL g⁻¹, 324,000 mL g⁻¹, and 293 mL g⁻¹ for E. coli with domestic septic tank effluent (STE), treated wetland effluent (WLE), and DW, respectively. Approximately 50%, 20%, and 90% of E. coli were “free floating” or associated with particles <5 μm in size within the STE, WLE, and DW respectively. Although 10-50% of E. coli were found to associate with particles >5 μm within both the STE and DW, settling did not appear to contribute to E. coli removal within sedimentation experiments, indicating that the particles the bacteria were associated with had very small settling velocities.The results of this study highlight the importance of wastewater characterization when designing a treatment wetland system for bacterial removal. This study illustrated the level of variability in E. coli removal processes that can be observed within different wastewater, and wetland environments.     

Heat balance and tracer gas technique for airflow rates measurement and gaseous emissions quantification in naturally ventilated livestock buildings

Experiments were performed to study the airflow rates (AFRs) in a naturally ventilated building through four summer seasons and three winter seasons. The AFRs were determined using heat balance (HB), tracer gas technique (TGT) and CO₂-balance as averages of the values of all experiments carried out through the different seasons. The statistical analyses were correlation analysis, regression model and t-test. Continuous measurements of gaseous concentrations (NH₃, CH₄, CO₂ and N₂O) and temperatures inside and outside the building were performed. The HB showed slightly acceptable results through summer seasons and unsatisfactory results through winter seasons. The CO₂-balance showed unexpected high differences to the other methods in some cases. The TGT showed reliable results compared to HB and CO₂-balance. The AFRs, subject to TGT, were 0.12 m³ s⁻¹ m⁻², 1.15 m³ s⁻¹ cow⁻¹, 0.88 m³ s⁻¹ LU⁻¹, 56 h⁻¹, 395 m³ s⁻¹ and 470 kg s⁻¹ through summer seasons, and 0.08 m³ s⁻¹ m⁻², 0.83 m³ s⁻¹ cow⁻¹, 0.64 m³ s⁻¹ LU⁻¹ 39 h⁻¹, 275 m³ s⁻¹ and 328 kg s⁻¹ through winter seasons. The AFRs are not independent values, rather they were estimated for specific reference values, which are: area, cow and LU as well as rates. The emission rates through summer seasons, subject to TGT, were 9.4, 40, 3538 and 2.3 g h⁻¹ cow⁻¹; and through winter seasons were 4.8, 19, 2332 and 2.6 g h⁻¹ cow⁻¹, for NH₃, CH₄, CO₂ and N₂O, respectively.     

Impact of toxic cyanobacteria on gastropods and microcystin accumulation in a eutrophic lake (Grand-Lieu, France) with special reference to Physa (= Physella) acuta

Hepatotoxic microcystins (MCs) produced by cyanobacteria are known to accumulate in gastropods following grazing of toxic cyanobacteria and/or absorption of MCs dissolved in water, with adverse effects on life history traits demonstrated in the laboratory. In the field, such effects may vary depending on species, according to their relative sensitivity and ecology. The aims of this study were to i) establish how various intensities of MC-producing cyanobacteria proliferations alter the structure of gastropod community and ii) compare MC tissue concentration in gastropods in the field with those obtained in our previous laboratory experiments on the prosobranch Potamopyrgus antipodarum and the pulmonate Lymnaea stagnalis. We explored these questions through a one-year field study at three stations at Grand-Lieu Lake (France) affected by different intensities of cyanobacteria proliferations. A survey of the community structure and MC content of both cyanobacteria and gastropods was associated with a caging experiment involving P. antipodarum and L. stagnalis. In total, 2592 gastropods belonging to 7 prosobranch and 16 pulmonate species were collected. However, distribution among the stations was unequal with 62% vs 2% of gastropods sampled respectively at the stations with the lowest vs highest concentrations of MC. Irrespective of the station, pulmonates were always more diverse, more abundant and occurred at higher frequencies than prosobranchs. Only the pulmonate Physa acuta occurred at all stations, with abundance and MC tissue concentration (≤ 4.32 µg g DW^− 1) depending on the degrees of MC-producing cyanobacteria proliferations in the stations; therefore, P. acuta is proposed as a potential sentinel species. The caging experiment demonstrated a higher MC accumulation in L. stagnalis (≤ 0.36 µg g DW^− 1 for 71% of individuals) than in P. antipodarum (≤ 0.02 µg g DW^− 1 for 12%), corroborating previous laboratory observations. Results are discussed in terms of differential gastropod sensitivity and MC transfer through the food web.     

Sediment reworking rates in deep sediments of the Mediterranean Sea

Different pelagic areas of the Mediterranean Sea have been investigated in order to quantify physical and biological mixing processes in deep sea sediments. Herein, results of eleven sediment cores sampled at different deep areas (> 2000 m) of the Western and Eastern Mediterranean Sea are presented.²¹⁰Pb_xs and ¹³⁷Cs vertical profiles, together with ¹⁴C dating, are used to identify the main processes characterising the different areas and, finally, controlling mixing depths (SML) and bioturbation coefficients (D_b). Radionuclide vertical profiles and inventories indicate that bioturbation processes are the dominant processes responsible for sediment reworking in deep sea environments.Results show significant differences in sediment mixing depths and bioturbation coefficients among areas of the Mediterranean Sea characterised by different trophic regimes. In particular, in the Oran Rise area, where the Almeria-Oran Front induces frequent phytoplankton blooms, we calculate the highest values of sediment mixing layers (13 cm) and bioturbation coefficients (0.187 cm² yr⁻¹), and the highest values of ²¹⁰Pb_xs and ¹³⁷Cs inventories. Intermediate values of SML and D_b (~ 6 cm and ~ 0.040 cm² yr⁻¹, respectively) characterise the mesothrophic Algero-Balearic basin, while in the Southern Tyrrhenian Sea mixing parameters (SML of 3 cm and D_b of 0.011 cm² yr⁻¹) are similar to those calculated for the oligotrophic Eastern Mediterranean (SML of 2 cm and D_b of ~ 0.005 cm² yr⁻¹).     

Degradation of the antibiotic oxolinic acid by photocatalysis with TiO2 in suspension

In the work presented here, a photocatalytic system using titanium Degussa P-25 in suspension was used to evaluate the degradation of 20 mg L⁻¹ of antibiotic oxolinic acid (OA). The effects of catalyst load (0.2-1.5 g L⁻¹) and pH (7.5-11) were evaluated and optimized using the surface response methodology and the Pareto diagram. In the range of variables studied, low pH values and 1.0 g L⁻¹ of TiO₂ favoured the efficiency of the process. Under optimal conditions the evolution of the substrate, chemical oxygen demand, dissolved organic carbon, toxicity and antimicrobial activity on Escherichia coli cultures were evaluated. The results indicate that, under optimal conditions, after 30 min, the TiO₂ photocatalytic system is able to eliminate both the substrate and the antimicrobial activity, and to reduce the toxicity of the solution by 60%. However, at the same time, ∼53% of both initial DOC and COD remain in solution. Thus, the photocatalytical system is able to transform the target compound into more oxidized by-products without antimicrobial activity and with a low toxicity. The study of OA by-products using liquid chromatography coupled with mass spectrometry, as well as the evaluation of OA degradation in acetonitrile media as solvent or in the presence of isopropanol and iodide suggest that the reaction is initiated by the photo-Kolbe reaction. Adsorption isotherm experiments in the dark indicated that under pH 7.5, adsorption corresponded to the Langmuir adsorption model, indicating the dependence of the reaction on an initial adsorption step.     

Effect of COD/SO4ratio and Fe(II) under the variable hydraulic retention time (HRT) on fermentative hydrogen production

The effect of chemical oxygen demand/sulfate (COD/SO₄²⁻) ratio on fermentative hydrogen production using enriched mixed microflora has been studied. The chemostat system maintained with a substrate (glucose) concentration of 15 g COD L⁻¹ exhibited stable H₂ production at inlet sulfate concentrations of 0-20 g L⁻¹ during 282 days. The tested COD/SO₄²⁻ ratios ranged from 150 to 0.75 (with control) at pH 5.5 with hydraulic retention time (HRT) of 24, 12 and 6 h. The hydrogen production at HRT 6 h and pH 5.5 was not influenced by decreasing the COD/SO₄²⁻ ratio from 150 to 15 (with control) followed by noticeable increase at COD/SO₄²⁻ ratios of 5 and 3, but it was slightly decreased when the COD/SO₄²⁻ ratio further decreased to 1.5 and 0.75. These results indicate that high sulfate concentrations (up to 20,000 mg L⁻¹) would not interfere with hydrogen production under the investigated experimental conditions. Maximum hydrogen production was 2.95, 4.60 and 9.40 L day⁻¹ with hydrogen yields of 2.0, 1.8 and 1.6 mol H₂ mol⁻¹ glucose at HRTs of 24, 12 and 6 h, respectively. The volatile fatty acid (VFA) fraction produced during the reaction was in the order of butyrate > acetate > ethanol > propionate in all experiments. Fluorescence In Situ Hybridization (FISH) analysis indicated the presence of Clostridium spp., Clostridium butyricum, Clostridium perfringens and Ruminococcus flavefaciens as hydrogen producing bacteria (HPB) and absence of sulfate reducing bacteria (SRB) in our study.