Greening of arid cities by residual water reuse: a multidisciplinary project in northern Chile

This paper describes a project in northern Chile aimed to promote the development of appropriate green areas and gardens for arid regions under prevalent conditions of shortage of water and high salt content in soil and water. Field studies were conducted to test the suitability of selected salt-tolerant native and introduced plants for ornamental use. Plant growth, water and soil quality, marine spray, climate, wastewater treatment and irrigation operating problems were the subject of specific studies and discussion.     

Impact of wildfires on the air quality of Mexico City, 1992-1999

Wildfires in Mexico increased in 1998, compared to information for the last 6 years. The average number of wildfires in the Mexico City Metropolitan Area (MCMA) for this year (1998) were 58% (1916 events) more events than the 1992-1997 (average cases 1217 events). Mexico City affected area corresponds to 1.3% of the national affected area. The purpose of this paper is to evaluate the impact on the particles air quality due to the wildfire emissions at the MCMA and surrounding areas. Using the corresponding US EPA emission factors for wildfires, the tons of particulate matter, nitrogen oxides, carbon monoxide, and total hydrocarbons emitted by this source for the MCMA case were obtained. The calculated emissions during wildfires were correlated with the levels of particles present in the atmosphere. A comparison of the concentration levels of particles, both as PM10 as well as TSP, were made for the years 1992-1998, during wet and dry season, being March, April, and May the critical months due to the presence of wildfires. A good correlation is observed between particulate wildfire emissions and particulate air quality, being stronger for TSP. A clear impact on the particles air quality due to the increase of wildfires in 1998, is observed when this year is compared with 1997, presenting an increment of 200-300% for some monitoring stations.     

Lesions induced by 2,4-D and chlorpyrifos in tench (Tinca tinca L.): implication in toxicity studies

This study was undertaken to demonstrate the toxicity of two pesticides, chlorpyrifos (O,O-diethyl 0-3,5,6-trichloro-2-pyridyl phosphorothioate) and 2,4-D (Dichlorophenoxyacetic acid) to tench (Tinca tinca Linnaeus). Pathological samples of damaged tench kidney showing lesions were taken for statistical analysis in order to quantify different parameters. Analysis revealed differences in the action and/or action time of the two pesticides. These differences were more acute in the case of 2,4-D thereby indicating a greater toxicity. These differences, expressed by mathematical formulae of numerical variables, would enable, a priori, the identification of the responsible pesticide and the time of acting in new natural cases of poisonings with these substances.     

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.     

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.     

Influence of the application of sewage sludge on the degradation of pesticides in the soil

A study was made of the influence of the application of sewage sludge on the degradation of pesticides in the soil. Two kinds of sludge were used, with different characteristics, one from an urban treatment plant and one from a food processing plant. Three organophosphorus insecticides, fenitrothion, diazinon and dimethoate, were studied. The relative importance was determined of the chemical and biological degradation processes, which involved experiments on soil and sterile soil samples. A comparative study was also made of the degradation of pesticide residues and the evolution of the microbial population. The application of sludge seems to have a complex effect on the degradation of pesticides, determined by the bioavailability and biodegradability of their active ingredient. The biodegradation of pesticide residues brings about alterations in the microorganism population of the soil.     

Rapid regional recovery from sulfate and nitrate pollution in streams of the western Czech Republic--comparison to other recovering areas

Hydrochemical changes between 1991 and 2001 were assessed based on two synoptic stream surveys from the 820-km2 region of the Slavkov Forest and surrounding area, western Czech Republic. Marked declines of sulfate, nitrate, chloride, calcium and magnesium in surface waters were compared with other areas of Europe and North America recovering from acidification. Declines of sulfate concentration in the Slavkov Forest (-30 microeq L(-1) yr(-1)) were more dramatic than declines reported from other sites. However, these dramatic declines of strong acid anions did not generate a widespread increase of stream water pH in the Slavkov Forest. Only the most acidic streams experienced a slight increase of pH by 0.5 unit. An unexpected decline of stream water pH occurred in slightly alkaline streams.     

Comparative study of methodologies for the analysis of PCDDs and PDCFs in powdered full-fat milk. PCB, PCDD and PCDF levels in commercial samples from Spain

Feasibility of two different extraction methods involving solid-liquid extraction and Soxhlet extraction, previously used for the determination of lipid contents and PCB levels on powdered full-fat milk, are now examined for simultaneous PCDD/F analysis. The results of this study are consistent with those found for PCBs. The solid-liquid procedure provides the most efficient extraction of both labelled spiked and endogenous PCDD/Fs with the lowest variability. The average recoveries were 101% (R.S.D. = 6.9%) for 13C12-2,3,7,8-TCDD and 95% (R.S.D. = 11%) for 13C12-1,2,3,4,7,8-HxCDD. The R.S.D.s for endogenous 2,3,7,8-PCDD/Fs were in the 9.3-25% range. In addition, this methodology simplified the subsequent clean-up step as it allowed a semi-selective extraction of the apolar lipids from the milk. The proposed method was applied to simultaneous PCB and PCDD/F analyses in different brands of powdered full-fat milks commercially available in Spain. In all cases, very similar PCB and PCDD/F levels were found. Differences among batches from the same manufacturer were even lower. The total i-TEQ average for PCDDs and PCDFs in the 22 powdered full-fat milk samples analysed was 1.87 pg/g fat basis. This value was similar to those found in cow's milk from other European countries.     

Genome-size variation in bivalve molluscs determined by flow cytometry

Six of the nine described species of the mole crab genus Emerita are distributed in the Americas, two [E. analoga (Stimpson, 1857) and E. rathbunae Schmitt, 1935] on the west coast, and four [E. benedicti Schmitt, 1935, E. brasiliensis Schmitt, 1935, E. portoricensis Schmitt, 1935 and E. talpoida (Say, 1817)] on the east. The presence of an extended planktonic larval stage in all Emerita species suggests high dispersal potential and the possibility of extensive gene flow among conspecific populations. Two taxa were sampled to study the extent of gene flow between widely separated conspecific populations: E. analoga (California and Chile) and E. talpoida (Massachusetts, South Carolina, and the west coast of Florida), while all other taxa were characterized from a single location. Portions of two mitochondrial genes, cytochrome oxidase I (COI) and 16S ribosomal RNA (16S rRNA) were sequenced. For data analysis, approximately 500 bp (COI) and 400 bp (16S rRNA) were examined. Estimated genetic divergence of 5.41% in COI between E. talpoida populations sampled from the Gulf of Mexico and the Atlantic coast, and 3.47% between E. analoga sampled in Chile and California, indicates that in both cases there has been no recent gene flow between disjunct populations. Additional molecular and morphological studies are necessary to decide whether disjunct populations should be accorded specific status. We predict that many marine invertebrates with antitropical distributions similar to E. analoga may consist of sibling species. In contrast to relationships inferred earlier from distribution patterns, parsimony analyses of both COI and 16S rRNA data yield similar phylogenetic trees in which E. analoga is separated from a clade composed of other species in the Americas; a bootstrap value (67%) in the COI inferred tree marginally supports the separation, but the same tree topology with a higher bootstrap value (84%) is obtained with 16S rRNA sequence data. Genetic divergence among the taxa indicates that the Emerita species constitute an old group and that distribution of species has been modified by past climatic and geological events.