Aromatic photonitration in homogeneous and heterogeneous aqueous systems

This work describes the nitration of aromatics upon near-UV photolysis of nitrate and nitrite in aqueous solution and upon photocatalytic oxidation of nitrite in TiO2 suspensions. Phenol is used in this work as a model aromatic molecule and as a probe for *NO2/N2O4. The photoinduced nitration of phenol in aqueous systems occurs upon the reaction between phenol and *NO2 or N2O4, and is enhanced by the photocatalytic oxidation of nitrite to *NO2 by TiO2. Aromatic photonitration in the liquid phase can play a relevant role in the formation of nitroaromatics in natural waters and atmospheric hydrometeors, thus being a potential pathway for the condensed-phase nitration of aromatics. Furthermore, the photoinduced oxidation of nitrite to nitrogen dioxide suggests a completely new role for nitrite in natural waters and atmospheric aerosols.     

Coping with uncertainty: a call for a new science-policy forum

The scientific and policy worlds have different goals, which can lead to different standards for what constitutes "proof" of a change or phenomena, and different approaches for characterizing and conveying uncertainty and risk. These differences can compromise effective communication among scientists, policymakers, and the public, and constrain the types of socially compelling questions scientists are willing to address. In this paper, we review a set of approaches for dealing with uncertainty, and illustrate some of the errors that arise when science and policy fail to coordinate correctly. We offer a set of recommendations, including restructuring of science curricula and establishment of science-policy forums populated by leaders in both arenas, and specifically constituted to address problems of uncertainty.     

Distribution coefficients (Kd) and desorption rates of 137Cs and 241Am in Black Sea sediments

The distribution coefficients (K_d) and desorption rates of ¹³⁷Cs and ²⁴¹Am radionuclides in bottom sediments at different locations in the Black Sea were studied under laboratory conditions. The K_d values were found to be 500 for ¹³⁷Cs and 3800 for ²⁴¹Am at the steady state and described exponential curves. Rapid uptake of the radionuclides occurred during the initial period and little accumulation happened after four days. The desorption rates for ¹³⁷Cs in different bottom sediments were best described by a three-component exponential model. The desorption half-times of ¹³⁷Cs ranged from 26 to 50 d at the slow components. However, the desorption rate of ²⁴¹Am described one component for all sediment samples and desorption half-time was found to be 75 d. In general, the results showed that the ²⁴¹Am radionuclide is more effectively transferred to bottom sediment and has longer turnover time than ¹³⁷Cs under Black Sea conditions.     

Remediation of BTEX and trichloroethene

The widespread use of industrial chemicals in our highly industrialized society has often caused contamination of large terrestrial and marine areas due to the deliberate and accidental release of organic pollutants into the soil and groundwater. In this review, environmental problems arising from the use of chlorinated solvents and BTEX compounds are described, and an overview about active management strategies for remediation with special emphasis on phytoremediation are presented to achieve a reduction of the total mass of chlorinated solvents and BTEX compounds in contaminated areas. Phytoremediation has been proposed as an efficient, low-cost remediation technique to restore areas contaminated with chlorinated solvents and BTEX compounds. The feasibility of phytoremediation as a remediation tool for these compounds is discussed with particular reference to the uptake and metabolism of these compounds, and a future perspective on the use of phytoremediation for the removal of chlorinated solvents and BTEX compounds is given.     

New large solar photocatalytic plant: set-up and preliminary results

A European industrial consortium called SOLARDETOX has been created as the result of an EC-DGXII BRITE-EURAM-III-financed project on solar photocatalytic detoxification of water. The project objective was to develop a simple, efficient and commercially competitive water-treatment technology, based on compound parabolic collectors (CPCs) solar collectors and TiO2 photocatalysis, to make possible easy design and installation. The design, set-up and preliminary results of the main project deliverable, the first European industrial solar detoxification treatment plant, is presented. This plant has been designed for the batch treatment of 2 m3 of water with a 100 m2 collector-aperture area and aqueous aerated suspensions of polycrystalline TiO2 irradiated by sunlight. Fully automatic control reduces operation and maintenance manpower. Plant behaviour has been compared (using dichloroacetic acid and cyanide at 50 mg l(-1) initial concentration as model compounds) with the small CPC pilot plants installed at the Plataforma Solar de Almería several years ago. The first results with high-content cyanide (1 g l(-1)) waste water are presented and plant treatment capacity is calculated.     

An evaluation of olive-tree bark for the biological monitoring of airborne trace-elements at ground level

There is a need to start looking into the possibility of tree bark for biomonitoring. Bark from olive trees (Olea europaea Linn.) has been collected over an area in northwestern Portugal, featuring a blend of rural lands, industrial towns and coastal environments. Samples were analysed through INAA and PIXE for their elemental contents. Results from both techniques were reconciled and then compared with an extensive database on 46 trace elements in Parmelia spp. thalli from the same sites and mostly from the very bark substrates. Distribution-free, nonparametric statistics show that, despite signal magnitude, variation patterns of bark and lichen concentrations follow one another in a most significant way. Selected elements in bark also correlate to a superior extent. As far as this investigation goes, there is no reason whatsoever for discarding bark as an alternative to lower epiphytes.     

Carbonyls in the metropolitan area of Mexico City: calculation of the total photolytic rate constants Kp(s(-1)) and photolytic lifetime (tau) of ambient formaldehyde and acetaldehyde

A great number of studies on the ambient levels of formaldehyde and other carbonyls in the urban rural and maritime atmospheres have been published because of their chemical and toxicological characteristics, and adverse health effects. Due to their toxicological effects, it was considered necessary to measure these compounds at different sites in the metropolitan area of Mexico City, and to calculate the total rate of photolytic constants and the photolytic lifetime of formaldehyde and acetaldehyde. Four sites were chosen. Sampling was carried out at different seasons and atmospheric conditions. The results indicated that formaldehyde was the most abundant carbonyl, followed by acetone and acetaldehyde. Data sets obtained from the 4 sites were chosen to calculate the total rate of photolysis and the photolytic lifetime for formaldehyde and acetaldehyde. Maximum photolytic rate values were obtained at the maximum actinic fluxes, as was to be expected.     

Holocene biomass burning and global dynamics of the carbon cycle

Fire regimes have changed during the Holocene due to changes in climate, vegetation, and in human practices. Here, we hypothesise that changes in fire regime may have affected the global CO2 concentration in the atmosphere through the Holocene. Our data are based on quantitative reconstructions of biomass burning deduced from stratified charcoal records from Europe, and South-, Central- and North America, and Oceania to test the fire-carbon release hypothesis. In Europe the significant increase of fire activity is dated approximately 6000 cal. yr ago. In north-eastern North America burning activity was greatest before 7500 years ago, very low between 7500-3000 years, and has been increasing since 3000 years ago. In tropical America, the pattern is more complex and apparently latitudinally zonal. Maximum burning occurred in the southern Amazon basin and in Central America during the middle Holocene, and during the last 2000 years in the northern Amazon basin. In Oceania, biomass burning has decreased since a maximum 5000 years ago. Biomass burning has broadly increased in the Northern and Southern hemispheres throughout the second half of the Holocene associated with changes in climate and human practices. Global fire indices parallel the increase of atmospheric CO2 concentration recorded in Antarctic ice cores. Future issues on carbon dynamics relatively to biomass burning are discussed to improve the quantitative reconstructions.     

Risk assessment of etofenprox (Vectron) on non-target aquatic fauna compared with other pesticides used as Simulium larvicide in a tropical environment

Within the rotational scheme developed by the Programme to fight the resistance of Simulium damnosum to chemical larvicides, there was an operational gap at discharges between 5 and 70 m³ s⁻¹ for the treatment of rivers where resistance to organophosphates was present. The use of permethrin and carbosulfan was precluded because of risk of environmental impact and, Bacillus thuringiensis ser. H-14 treatments were not envisageable due to cost and logistics constraints. Among the possible complementary groups of larvicides tested, the pseudo-pyrethroids, held promise, because of a mode of action similar to that of pyrethroids, but along with a usually lower toxicity for fish. Etofenprox, one of the pseudo-pyrethroids tested, shows a global detachment of non-target insects in 24 h close to that of pyraclofos, an organo-phosphorus compound (27 against 23%). In laboratory conditions, six times the operational dose which is 0.03 mg l⁻¹ 10 min, is needed to cause 50% mortality of Caridina sp. (a small shrimps species) and 30 times this same dose for 95% mortality. For fish species, a safety margin of 400–800 times the operational dose is observed for Oreochromis niloticus and 200–400 times for Tilapia zillii.     

Solubilization of substituted indole compounds by beta-cyclodextrin in water

The solubilization of four pairs of substituted indole compounds (SICs) by β-cyclodextrin (β-CD) in water was investigated. The results show that 1,2,3,4-tetrahydrocarbazole and N-methyl-1,2,3,4-tetrahydrocarbazole form 1:1 inclusion complexes with β-CD, while the other six SICs form 1:2 inclusion complexes, respectively. To each pair of SICs with similar structures, the differences between their solubilization in β-CD/water solutions has been explained by the difference of their contact area within the β-CD cavity, the difference of their molecule polarity, or the presence of hydrogen bond between SIC molecule and β-CD molecule.