Caffeine as an indicator of estrogenic activity in source water.

Caffeine has already been used as an indicator of anthropogenic impacts, especially the ones related to the disposal of sewage in water bodies. In this work, the presence of caffeine has been correlated with the estrogenic activity of water samples measured using the BLYES assay. After testing 96 surface water samples, it was concluded that caffeine can be used to prioritize samples to be tested for estrogenic activity in water quality programs evaluating emerging contaminants with endocrine disruptor activity.

Indoor air disinfection using a polyester supported TiO2 photo-reactor.

UNLABELLED: Among the decontamination methods applicable to indoor air, heterogeneous photocatalysis has received increasing attention in recent years. This decontamination method is based on the UV irradiation of a solid catalyst, normally TiO2, aiming at the generation of highly reactive hydroxyl radicals. In this work, a novel way to prepare the photocatalyst was used, incorporating pure P-25 TiO2 (Degussa) into polyester orthophthalic polymer. The film was coated onto the walls of a PVC reactor with a concentric 30 W germicidal lamp (254 nm). The efficiency of this prototype was evaluated against fungi and bacteria elimination in a 67 m3 confined room. The system was very efficient for bacteria reduction, decreasing the bacterial count to below the detection limit (1 CFU/plate during 30-min sampling) after 2 h of operation at 195 l/min. For fungi, the gas-phase reactor showed to be less efficient and silver doping of the catalyst showed no increase in biocide activity. PRACTICAL IMPLICATIONS: The use of a photocatalytic reactor based on TiO2 incorporated onto polyester orthophtalic polymer has been tested at 195 l/min, showing good performance in the air disinfection of a 67 m3 room.

Identification and photocatalytic destruction of malodorous compounds in sewage.

Malodorous compounds were identified in sewage samples using two different types of pre-concentration procedures: (a) pre-concentration onto adsorbent column (Tenax), (b) liquid-liquid extraction, in conjunction with sensory analysis. Sulphur and nitrogen containing compounds, hydrocarbons, substituted benzenes and components of essential oils and aldehydes were identified. These compounds were considered to be responsible for the septic and grassy/earthy odour described by sensory panellists. Studies on photodestruction of malodorous compounds present in the sewage samples showed that the main compounds were destroyed. This destruction was confirmed by both sensory analysis and gas chromatography through abatement in the intensity of odour as well as chromatogram peak areas. Comparing odour destruction using two processes, photocatalysis and loss due to mass transfer, the conversion rate was 71% at the beginning, later reaching a plateau of about 65%. Thus photocatalysis seems to be a promising technology in the degradation of malodorous compounds stripped to the atmosphere from sewage, especially when they are present at low concentrations.

Photocatalytic storing of O2 as H2O2 mediated by high surface area CuO. Evidence for a reductive-oxidative interfacial mechanism.

CuO powders with a high specific surface area are shown to be able to produce H(2)O(2) in aqueous solution under simulated light irradiation. The highest rate of peroxide production was observed under mild experimental conditions using O(2) and a large surface area photocatalyst CuO irradiated with a solar simulator having light intensities between 60 and 90 mW/cm(2). The CuO employed had a specific surface area (SSA) of 64.8-70.1 m(2)/g and was prepared in a tubular furnace by controlled thermal decomposition of precipitated copper oxalate. The CuO particles produced were 1 mum cubes with primary particles around 15 nm. No peroxide was produced under the same conditions with commercial CuO, with SSA 200 times lower. The CuO synthesized during this work was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), specific surface area [Brunauer-Emmett-Teller (BET)], porosity, and X-ray photoelectron spectroscopy (XPS). From XPS, it was observed that only Cu(II) was present in the unused and used CuO. This indicates that the redox transient species involving other Cu oxidation states disappear very fast during the reaction, regenerating Cu(II) during H(2)O(2) production. Diverse experiments provided some evidence for the possible interfacial reaction mechanism leading to H(2)O(2), following the initial step of O(2)(-)(.) formation on the CuO surface under irradiation with photons, with energies exceeding the band gap of CuO. A photocatalyzed degradation of a concentrated 4-chlorophenol (4-CP) solution was observed under solar-simulated light in the presence of CuO.

Removal of EDTA by UV-C/hydrogen peroxide.

Mineralization of a 5 mM EDTA solution at pH 3 was evaluated via TOC removal under UV-C irradiation in the presence of H2O2 at various conditions. The highest TOC removal (78%) was obtained using a 40:1 H2O2/EDTA molar ratio, after 540 min irradiation. However, a 20:1 ratio gave slightly lower results, being economically more attractive. Best results of TOC removal were obtained under pH controlled conditions. Addition of TiO2 (1 g l(-1)) was detrimental, even in the presence of H2O2, indicating that at this concentration, TiO2 inhibits the mineralization, probably by scattering or by screening of the light.

Mercury biomagnification in a tropical black water, Rio Negro, Brazil.

The population living along the riverbanks of the Amazon basin depends heavily on fish for nutritional support. Mono-methyl-mercury (MMHg) concentrates in fish, which can contaminate humans, the risk depending not only on fish MMHg concentration but also on the amount of fish consumed. We sampled nine locations of the Rio Negro basin, differing in water pH, Hg concentrations, and dissolved organic carbon (DOC), and determined total Hg from 951 fish samples of species representative of the food web: herbivorous, detritivorous, omnivorous, and piscivorous. Mercury concentrations varied widely in all species but showed a trend that depended on fish feeding strategies. The highest mean concentration was found in the piscivorous species (688.90 ng/g(-1)), followed by omnivorous (190.30 ng/g(-1)), detritivorous (136.04 ng/g(-1)), and herbivorous (70.39 ng/g(-1)). Fish Hg concentrations exceeding current safe limits (500 ng/g(-1)) for human consumption were found mainly in the piscivorous species (60%). Significant positive correlation between fish weight and Hg concentration was seen for the piscivorous Serrasalmus spp. (n = 326; r = 0.3977; p < 0.0001), Cichla spp. (n = 125; r = 0.4600; p < 0.0001), and Pimelodus spp. (n = 12; r = 0.8299; p = 0.0008), known locally as Piranha, Tucunaré, and Mandi, respectively. However, a negative correlation was seen for non-piscivorous Potamorhina latior (n = 30; r -0.3763; p = 0.0404) and Leporinus spp. (n = 44; r = -3987; p = 0.0073), known as Branquinha (detritivorous) and Aracu (omnivorous). Fish-Hg concentrations in the acidic waters (pH range, 4.09-6.31) of the Rio Negro habitat, with its wide gradient of Hg concentrations (3.4-11.9 microg/L(-1)) and DOC (1.85-15.3 mg/L(-1))--but no history of gold mining activity-are comparable to other Amazonian rivers. Opportunity fish catches in the Rio Negro habitat show high muscle-Hg derived from natural sources, but no systematic association with site-dependent geochemistry.

Is the Negro River Basin (Amazon) impacted by naturally occurring mercury?

In order to investigate the major sources and cycling of mercury in the Negro River Basin (Amazon), total metal measurements were carried out in soils, in river and lake waters, in the atmosphere, and in bulk precipitation during the period 1995 throughout 1998. Median values of 1.3 ng m(-3) in the atmosphere, 172 microg kg(-1) in soils, 4.6-7.5 ng l(-1) in three different lakes, 4.5 ng l(-1) in 17 different Negro River tributaries and 20.3 microg m(-2) year(-1) in bulk precipitation were found. Mercury concentrations in rivers and lakes waters, as well as in soils and bulk precipitation were high, considering the scarcity of anthropogenic point sources in the region. Mercury leaching from soil, the largest regional reservoir of this metal, was considered to be the major pathway to mercury enrichment in the region.

Measuring the CO2 flux at the air/water interface in lakes using flow injection analysis.

The carbon dioxide flux at the air/water interface in lakes was calculated after the determination of H2CO3* (free CO2) and atmospheric CO2 using flow injection analysis (FIA) coupled to a conductometric detector. The method is based on the diffusion of CO2 through a hydrophobic membrane into a flow of deionized water, generating a gradient of conductivity proportional to the concentration of CO2 in the sample. Using one experimental set-up, the speciation of the inorganic carbon (H2CO3* and dissolved inorganic carbon) was accomplished by simply adjusting the sample pH. The determination of CO2 in the atmosphere was carried out by direct injection of the gaseous samples. The FIA apparatus was taken into the field and CO2 fluxes were evaluated in several Brazilian lakes. In these lakes, representing different eutrophic stages, the CO2 flux varied from -242 (invasive) up to 3227 (evasive) mumol CO2 m-2 h-1.

Hair mercury speciation as a function of gender, age, and body mass index in inhabitants of the Negro River basin, Amazon, Brazil.

Human mercury contamination can be monitored through hair analysis of mercury's inorganic and organic form as methylmercury (Me-Hg). Hair total mercury and Me-Hg were studied in a Negro River fish-eating population in relation to age, gender, and body mass index (BMI). This riverbank population eats fish at least twice a day and is exposed to high levels of Me-Hg. Total mercury ranged from 1.51 microg/g to 59.01 microg/g, with only 21% of the sampled population having Hg concentration of less than 10 microg/g hair. The mean percentage of Me-Hg was 71.3% (range 34% to 100%) of the total mercury in hair. No statistically significant differences were found in regard to age groups (children and adults) or BMI. However, women had significantly lower total mercury in hair than men, but the percentage of Me-Hg was not significantly different. Women in fertile age (15-40 years) had hair total mercury ranging from 1.65-32.63 microg/g, and 65% in this subgroup had hair mercury above 10 microg/g hair. The percentage of Me-Hg concentration in hair of this freshwater, fish-eating population is comparable to populations eating ocean fish from different parts of the world and does not seem to be affected by age, gender, and BMI.

Selective trace level analysis of phenolic compounds in water by flow injection analysis--membrane introduction mass spectrometry.

Flow injection analysis coupled with membrane introduction mass spectrometry (FIA-MIMS) with on-line derivatization is shown to allow fast, accurate, nearly interference-free, and sensitive (low microgram/L) quantitation of phenolic compounds in water. On-line FIA derivatization of the phenolic compounds is performed by acetic anhydride acetylation in a K2CO3-buffered alkaline medium. The phenol acetates so formed efficiently permeate a silicone membrane and are directly transferred to the mass spectrometer, in which they are analyzed with selectivity and high sensitivity via selected ion monitoring. FIA-MIMS analysis was performed for aqueous solutions of phenol, 2-methylphenol, 4-chlorophenol, 4-chloro-3-methylphenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol, and detection limits in the 0.5-20 micrograms/L (ppb) range were observed for an analytical frequency of six samples/h. FIA-MIMS for phenolic compound analysis is considerably less time-consuming and labor intensive than most chromatographic methods based on liquid-liquid extraction and preconcentration procedures and is therefore applicable for on-line and in-situ monitoring of phenols in wastewaters and in the environment. FIA-MIMS employing acetic anhydride derivatization is also virtually free of interferences since it combines chemical, membrane, and enhanced MS selectivity; hence quantitation of phenolic compounds can be performed in the presence of congeners.

Adaptation of a cold vapour mercury analyser to flow injection analysis.

Minor modifications to a Coleman MAS-50A Mercury Analyser System allowed the determination of mercury by flow injection analysis. Using sample volumes of 600 mul it was possible to analyse up to 120 samples per hour, with a detection limit of 0.2 mug. l(-1) (120 pg) of mercury. The authors also report on a simple digestion procedure which replaces the time- and reagent-consuming EPA procedure, when the sample content permits.

Copper toxicity to cyanobacteria and its dependence on extracellular ligand concentration and degradation.

Copper toxicity to the cyanobacteriumPlectonema boryanum (UTEX 594) has been investigated in the presence of citrate and nitrilotriacetic acid (NTA) using a copper-saturated culture medium. The coppercitrate complex was biodegradable, and toxicity was dependent on the free ligand concentration. The ratio of citrate to copper also affected the extent of metal toxicity. NTA was not degraded byP. boryanum. Ligand degradation in the cyanobacterial culture increased the ionic copper concentration and caused a concomitant reduction in growth. The ecological implications of these findings are discussed.