Seasonal trend of fog water chemical composition in the Po Valley

Fog frequency in the Po Valley, Northern Italy, can be as high as 30% of the time in the fall-winter season. High pollutant concentrations have been measured in fog water samples collected in this area over the past few years. The combined effects of high fog occurrence and high pollutant loading of the fog droplets can determine, in this area, appreciable chemical deposition rates. An automated station for fog water collection was developed, and deployed at the field station of S. Pietro Capofiume, in the eastern part of the Po Valley for an extended period: from the beginning of November 1989 to the end of April 1990. Time-resolved sampling of fog droplets was carried out during all fog events occurring in this period, and chemical analyses were performed on the collected samples. Statistical information on fog occurrence and fog water chemical composition is reported in this paper, and a tentative seasonal deposition budget is calculated for H+, NH4+, NO3- and SO4(2-) ions. The problems connected with fog droplet sampling in sub-freezing conditions are also addressed in the paper.     

Seveso Women's Health Study: does zone of residence predict individual TCDD exposure?

The compound, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is produced as an unwanted by-product of various chemical reactions and combustion processes, including the manufacture of chlorinated phenols and derivatives. In animals, TCDD exposure is associated with toxic, carcinogenic, developmental, and reproductive effects. In 1976, a chemical plant explosion in Seveso, Italy, exposed the residents in the surrounding community to the highest exposure to TCDD known in humans. Materials from an aerosol cloud of sodium hydroxide, sodium trichlorophenate and TCDD were deposited over an 18.1 km2 area. As evidence of the significant level of TCDD exposure, numerous animals died and 193 cases of chloracne were reported among residents of the area. Initially, the contaminated area was divided into three major exposure Zones (A, B, R) based on the concentration of TCDD in surface soils. To date, the majority of epidemiologic studies conducted in Seveso have used Zone of residence as a proxy measure of exposure. The purpose of the present study is to validate the use of Zone of residence in Seveso as a proxy measure of exposure against individual serum TCDD measurement, and to determine whether questionnaire information can improve the accuracy of the exposure classification. Using data collected from the Seveso Women's Health Study (SWHS), the first comprehensive epidemiologic study of the reproductive health of women in Seveso, we determined that Zone of residence is a good predictor of individual serum TCDD level, explaining 24% of the variance. Using questionnaire information could have improved prediction of individual exposure levels in Seveso, increasing the percent of the variation in serum TCDD levels explained to 42%.     

Time to death response in carabid beetles exposed to multiple stressors along a gradient of heavy metal pollution

We investigated the responses of invertebrates inhabiting polluted environments to multiple stressors. Carabid beetles (Pterostichus oblongopunctatus F.) were subjected to food deprivation and insecticide treatment (dimethoate) to resolve trends associated with a gradient of heavy metal pollution. Metal concentrations along the gradient of five sites ranged from approximately 150 to 10,500 mg/kg Zn, 136 to 2600 mg/kg Pb, and 0.84 to 81.9 mg/kg Cd. There was no difference in body mass along the pollution gradient. However, the beetles originating from the most contaminated sites were significantly less tolerant to food deprivation than beetles from the reference site. Median survival time was 120 h for the two most polluted sites, compared with 168 h at the reference site. Beetles from the two most polluted sites were also significantly more susceptible to dimethoate at 0.1 microgram active ingredient/beetle. Median survival times were 12 and 123 h for beetles from the two most polluted sites and 359 h for the reference site. Carabid beetles exposed to chronic pollution, therefore, exhibit elevated susceptibility to additional stressors.     

Attempt to adsorb N-nitrosamines in solution by use of zeolites

The strong adsorption of zeolite for N-nitrosamines in solution was first revealed by use of adsorption, and temperature programmed surface reaction (TPSR) techniques. N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR) as well as N-nitrosohexamethyleneimine (NHMI) can be adsorbed on zeolite Y, ZSM-5 and A in the solution of methylene chloride or water, which will be helpful for removal of the N-nitrosamines pollution in environmental protection. The equilibrium data were fitted to Freundlich-type isotherms, but the adsorption capacity of zeolites mainly depended on their pore size, surface area and acid-basic properties. Molecular size of adsorbate and solute-solvent interaction also strongly affected the adsorption of N-nitrosamines on zeolite in solution. The extraordinary adsorption properties of NaA zeolite for N-nitrosamines in aqueous solution is first reported and discussed.     

On the hydro-dispersive equivalence between multi-layered mineral barriers

In the context of municipal solid waste and hazardous waste disposal, the notion of "equivalence" between different barrier designs appears in regulatory documents from several industrialized countries. While in the past, equivalence has been thought of mainly in terms of contaminant travel times, in recent years it has been defined more in terms of the magnitude of a disposal site's potential impact on groundwater resources. This paper presents some original analytical solutions to the problem of contaminant migration through a multi-layered mineral barrier. The solutions account for the two major mechanisms of subsurface contaminant migration, namely, advection and diffusion-dispersion. An example application using the proposed solutions and a numerical model illustrates how one multi-layered mineral barrier can be considered superior to another from a strictly hydro-dispersive viewpoint. The influence of partial saturation of the mineral barrier is investigated using a numerical solution to the Richards equation for unsaturated flow. It is emphasized that conclusions relative to the superiority of one multi-layered barrier, with respect to another, should not only consider hydro-dispersive aspects, but also other processes such as the mechanical and chemical evolutions of the different barrier components. Although such phenomena are poorly addressed by existing models, failure to take them into account, at least in a qualitative fashion, may lead to unconservative conclusions with respect to barrier equivalence.     

Effects of butachlor on microbial populations and enzyme activities in paddy soil

This paper reports the influences of the herbicide butachlor (n-butoxymethlchloro -2', 6'-diethylacetnilide) on microbial populations, respiration, nitrogen fixation and nitrification, and on the activities of dehydrogenase and hydrogen peroxidase in paddy soil. The results showed that the number of actinomycetes declined significantly after the application of butachlor at different concentrations ranging from 5.5 microg g(-1) to 22.0 microg g(-1) dried soil, while that of bacteria and fungi increased. Fungi were easily affected by butachlor compared to the bacteria. The growth of fungi was retarded by butachlor at higher concentrations. Butachlor however, stimulated the growth of anaerobic hydrolytic fermentative bacteria, sulfate-reducing bacteria (SRB) and denitrifying bacteria. The increased concentration of butachlor applied resulted in the higher number of SRB. Butachlor inhibited the growth of hydrogen-producing acetogenic bacteria. The effect of butachlor varied on methane-producing bacteria (MPB) at different concentrations. Butachlor at the concentration of 1.0 microg g(-1) dried soil or less than this concentration accelerated the growth of MPB, while at 22.0 microg g(-1) dried soil showed an inhibition. Butachlor enhanced the activity of dehydrogenase at increasing concentrations. The soil dehydrogenase showed the highest activity on the 16th day after application of 22.0 microg g(-1) dried soil of butachlor. The hydrogen peroxidase could be stimulated by butachlor. The soil respiration was depressed during the period from several days to more than 20 days, depending on concentrations of butachlor applied. Both the nitrogen fixation and nitrification were stimulated in the beginning but reduced greatly afterwards in paddy soil.     

Synergetic effects of anodic-cathodic electrocatalysis for phenol degradation in the presence of iron(II)

A novel electrocatalysis method for phenol degradation was described using a β-PbO₂ anode modified with fluorine resin and a Ni–Cr–Ti alloy cathode. In case of air sparging at the cathodic zone, the techniques of anodic–cathodic electrocatalysis (ACEC) and ferrous ion catalyzed anodic–cathodic electrocatalysis (FACEC) in the presence of iron(II) were developed. Both of ACEC and FACEC were more effective than anodic electrocatalysis (AEC). The percentage of phenol eliminated by FACEC could increase by nearly 30% compared with that of AEC, and the current efficiency could reach to 70%. Important operating factors such as ferrous ion concentration, air-sparging rate and applied current were investigated and it was found that such beneficial effects could be achieved at a suitable current and ratio of the concentration of ferrous ion to the air sparged. The mechanism of phenol degradation is proposed to be the generation of hydroxyl radicals concerned with the two electrodes. Results also indicated that the process provided an efficient way to regenerate ferrous ion compared with the conventional Fenton's system.     

Baseline levels of PCDD/Fs in soil and herbage samples collected in the vicinity of a new hazardous waste incinerator in Catalonia,Spain

The construction in Constantí (Catalonia, Spain) of a new hazardous waste incinerator (HWI), which is the first one in Spain, finished in 1999. In order to determine the temporal variation (1996–1998) in the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in the vicinity of the new HWI, 40 soil and 40 herbage samples were collected (1998) at the same sampling points in which samples had been taken two years before (1996). Each sample was analyzed for PCDDs and PCDFs by high resolution gas chromatography/high resolution mass spectrometry. In the 1996 survey, PCDD/F concentrations in soils ranged from 0.13 to 24.20 ng I-TEQ/kg (d.m.), with median and mean values of 0.67 and 1.68 ng I-TEQ/kg (d.m.), respectively. In the present study, PCDD/F concentrations ranged from 0.12 to 17.20 ng I-TEQ/kg (d.m.), with a median value of 0.75 ng I-TEQ/kg (d.m.) and a mean value of 1.59 ng I-TEQ/kg (d.m.). In turn, in the present study PCDD/F concentrations in vegetation ranged from 0.14 to 2.01 ng I-TEQ/kg (d.m.) (median and mean values: 0.23 and 0.31 ng I-TEQ/kg, respectively), while in the 1996 survey PCDD/F concentrations ranged from 0.24 to 1.22 ng I-TEQ/kg (d.m.) (median and mean values: 0.53 and 0.61 ng I-TEQ/kg, respectively). According to the present (1998) and the previous (1996) levels of PCDD/Fs found in soils and vegetation, the area under potential influence of the new facility shows a rather low contamination by these compounds. The current results should be useful to establish the environmental impact of the HWI.     

Photocatalytic oxidation of volatile organic compounds using fluorescent visible light

Photocatalytic oxidation (PCO) of volatile organic compounds (VOCs) is a highly attractive alternative technology for purification and deodorization of indoor air. The main objectives of this study were to demonstrate that a common fluorescent visible light (FVL) lamp can be used to effectively remove by PCO low concentrations of VOCs from slightly contaminated air and to provide some fundamental and technical details on the process. The target VOC was n-butanol, which is a standard reference odorant. Its PCO was studied under a long residence time in a 3.7-L cylindrical reactor with commercial titanium dioxide (TiO2) as the reference photocatalyst and using mostly FVL for illumination. For comparison only, a UV (black) light lamp was used. The gas-phase products were detected and quantified online by gas chromatography (GC). The effects of reactor residence time, of inlet concentration, and of the relative light intensity on the efficiency of the process were also evaluated. At a high n-butanol concentration (0.1 vol %), butanal and propanal were identified as the intermediate products of the process; ethanal appeared when the initial concentration was < or = 850 ppm(v). This indicates that PCO leading to CO2 and H2O is relatively slow and proceeds in a stepwise manner. Although the efficiency of the process with an FVL lamp was significantly lower than when using a UV black light, complete PCO of low concentrations was achieved for 100 ppm(v). In a search for a material with photoactivation extended to higher wavelengths or increased photoactivity, several samples of transition metal- or silver ion-doped (2 atomic %) TiO2 as well as SrTi(1-x-)Fe(x)O3 (x = 0.1 and 0.15) perovskites were included in the study. None of these materials was more active than pure TiO2. The results of this study open new horizons in the area of in door air quality (IAQ) control.