Chlorinated pesticides (2,4-D and DDT) biodegradation at high concentrations using immobilized Pseudomonas fluorescens

Degradation of two chlorinated pesticides (2,4-D and DDT) using a 54-mL glass column packed with tezontle (a low-cost basaltic scoria) was tested. Bacteria were cultured in YPG (yeast, peptone, and glucose) liquid medium at 32 degrees C. The rich medium was pumped during 24 h through the column to inoculate it. Later, the wasted medium was discharged and the pesticide added. Optical densities, TOC, and pesticide concentration were determined. Pesticide removals for 2,4-D (with initial concentration between 100 and 500 mg/L) were about 99%. DDT removal (at initial concentration of up to 150 mg/L) was as high as 55-99%. TOC removals for 2,4-D was in the 36-87% interval, whereas for DDT they were as high as 36-78%.     

Metabolism,enzymic activities and cold adaptation in Antarctic mesopelagic fishes

Several species of Antarctic mesopelagic fishes that have different minimal depths of occurrence but the same environmental temperature were collected in November–December 1983 and in March 1986 between 0 and 1 000 m in the open water near the marginal ice zone in the vicinity of 60°S 40°W (1983) and 65°S 46°W (1986), and oxygen consumption rate (V _{O 2}) and the activity of two metabolic enzymes, lactate dehydrogenase (LDH, an indicator of the anaerobic potential of locomotory muscle) and citrate synthase (CS, an indicator of citric acid cycle activity or aerobic potential), were determined. In four dominant species, whole-individual oxygen-consumption rate (y, ml O₂ individual^–1 h^–1) varied with weight (X, g) according to the equation y=aX ^b, with b values falling between 0.889 and 1.029. The relation of weight-specific LDH activity (y, U g^–1 wet wt) with weight (x, g) was also described by the equation y=aX ^b, with b values varying between 0.229 and 1.025. Weight-specific CS activity declined with weight, with b values from-0.031 to-0.369. V _{2 O}, LDH activity and CS activity all declined markedly with increased species' minimum depth of occurrence (the depth below which 90% of a species' population lives). Comparisons with previous studies on ecologically equivalent species of the California Borderland indicate that depth-related decreases in metabolism are the result of adapted traits of deeper-living species, not declining temperature within the water column. The metabolic rate of Antarctic mesopelagic fishes is approximately twice that of California species at equivalent temperatures; similar rates were found at the normal habitat temperatures of the two groups. Thus, a well-developed compensation for temperature is present in the Antarctic fishes: cold adaptation. Differences in enzymic activity among species, and among different sized individuals of a species are related to differences in metabolic rate and locomotory capacity. Enzymic indices can be used to estimate metabolic rates and evaluate ecological parameters such as predatory strategies and niche separation.     

Total peroxides in rainwater at two mountainous sites and in Mexico City,Mexico

Rainwater samples were collected in the western sector of Mexico City (MC) and at Rancho Viejo (RV), 80 km west-south-west of MC, from 2001 to 2005, and Orizaba City (OC), about 90 km from the Gulf of Mexico, where rainwater collections were only possible on some weekends in 2001. Rainwater samples were treated in the field, and analysed by fluorescence at the laboratory. The volume-weighted mean concentration (VWMC) of H₂O₂ was 13.2 μM at RV, and 11.2 μM in MC, for the period 2001–2005. The highest VWMC was observed in OC (21.6 μM). The VWMCs for each year were 9.5, 14.4, 11.5, 16.7, and 14.3 μM at RV, and 12.2, 12.2, 14.3, 11.8, and 9.9 μM in MC, for 2001–2005, respectively. Hydrogen peroxide in rainwater correlated significantly and negatively with sulfate in both MC and RV, but not, however, in OC. This study confirmed that H₂O₂ concentration in rainwater is controlled by a complex combination of rain intensity, washout processes and in-cloud formation of H₂O₂, acting simultaneously. This was suggested by the fact that rain intensity seemed to predominate in certain rain fractions of a rain event, while washout processes seemed to predominate in other fractions of the same rain event.     

Evaluation of human exposure to ambient PM10 in the metropolitan area of Mexico City using a GIS-based methodology.

The main goal of this study was to evaluate the magnitude of outdoor exposure to fine particulate matter (PM10) potentially experienced by the population of metropolitan Mexico City. With the use of a geographic information system (GIS), spatially resolved PM10 distributions were generated and linked to the local population. The PM10 concentration exceeded the 24-hr air quality standard of 150 microg/m3 on 16% of the days, and the annual air quality standard of 50 microg/m3 was exceeded by almost twice its value in some places. The basic methodology described in this paper integrates spatial demographic and air quality databases, allowing the evaluation of various air pollution reduction scenarios. Achieving the annual air quality standard would represent a reduction in the annual arithmetic average concentration of 14 microg/m3 for the typical inhabitant. Human exposure to particulate matter (PM) has been associated with mortality and morbidity in Mexico City; reducing the concentration levels of this pollutant would represent a reduction in mortality and morbidity and the associated cost of such impacts. This methodology is critical to assessing the potential benefits of the current initiative to improve air quality implemented by the Environmental Metropolitan Commission of Mexico City.     

Use of two-surfactants mixtures to attain specific HLB values for assisted TPH-diesel biodegradation

In a surfactant assisted biodegradation process, the choice of surfactant(s) is of crucial importance. The question is: does the type of surfactant(i, e. chemical family) affect the biodegradation process at fixed hidrophillic-lypofillic balance(H/B) values? Microcosm assessments were developed using contaminated soil, with around of 5000 mg/kg of hydrocarbons as TPH-diesel. Mixtures of three nonionic surfactants were employed to get a wide range of specific HLB values. Tween20 and Span20 were mixed in the appropriate proportions to get HLB values between 8.6 and 16.7. Tween/Span60 mixtures reached HLB values between 4.7 and 14.9. Finally,Tween/Span80 combinations yielded HLB values between 4.3 and 1.5. TPH-diesel biodegradation was measured at the beginning, and after 8 weeks, as well as the FCU/grsod, as a measure of microorganisms‘ development during the biodegradation period. A second aim of this work was to assess the use of guar gum as a biodegradation enhancer instead of synthetic products. The conclusions of this work are that surfactant chemical family, and not only the HLB value clearly affects the assisted biodegradation rate. Surfactant‘s synergism was clearly observed. Regarding the use of guar gum, no biodegradation enhancement was observed for the three assessed concentrations,i.e., 2, 20, and 200 mg/kg, respectively. On the contrary, TPH-diesel removal was lower as the gum concentration increased. It is quite possible that guar gum was used as a microbial substrate.     

Evaluation of the possible adverse effects of legacy persistent organic pollutants (POPs) on the brown booby (Sula leucogaster) along the Brazilian coast

This study aimed to investigate the impact of contamination by persistent organic pollutants (POPs) on Brazilian wildlife. The concentrations of certain POPs, including dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCBs), in the eggs of the brown booby (Sula leucogaster) were measured. The eggs were collected from breeding colonies located on three archipelagos (Saint Peter and Saint Paul, Abrolhos and Cagarras Islands) in the Atlantic Ocean, which are located at different distances from the Brazilian coast (range 4-1010 km). In addition, possible alterations in eggshell characteristics were evaluated. The average values of POPs found in eggs from the archipelago of Saint Peter and Saint Paul (0.05 μg g⁻¹ of ΣPCBs and 0.01 μg g⁻¹ of ΣDDT) and the archipelago of Abrolhos (0.19 μg g⁻¹ of ΣPCBs and 0.03 μg g⁻¹ of ΣDDT) were low compared to the reference values reported in the literature. In contrast, the concentrations measured in eggs from Cagarras (8.4 μg g⁻¹ of ΣPCBs and 1.8 μg g⁻¹ of ΣDDT) were the highest, and this total PCB level is close to the threshold values considered to be harmful to birds. Our findings indicate that the brown booby colony closest to the Rio de Janeiro coast has recently been exposed to DDT. Despite the high pollution levels found on the Cagarras Islands, no alterations in the eggshell weight or the thickness of the analyzed eggs were detected. Hence, more detailed studies are recommended to determine the actual effects of the selected POPs on the Cagarras breeding colony.     

Evaluation of cetacean exposure to organotin compounds in Brazilian waters through hepatic total tin concentrations

In Brazil, there is no restriction to the use of organotins (OTs). Previous investigations have shown that hepatic ∑Sn in cetaceans is predominantly organic. Hepatic ∑Sn concentrations were determined by GFAAS in 67 cetaceans (13 species) that stranded on Rio de Janeiro (RJ) and Espirito Santo (ES) states. Concentrations (in ng/g wet wt.) of marine tucuxis (n = 20) from the highly contaminated Guanabara Bay (in RJ) varied from 1703 to 9638. Concentrations of three marine tucuxi foetuses and one newborn calf (all from Guanabara Bay) varied between 431 and 2107. Contrastingly, the maximum level among 19 oceanic dolphins was 346, and 15 out of these 19 specimens presented concentrations below detection limit. The levels of Sn in six marine tucuxis from a less contaminated area (ES) varied from below detection limit to 744. Comparing to the literature, coastal cetaceans from Brazil appear to be highly exposed to OTs.     

Assessment of organic and inorganic contaminants in sediments of an urban tropical eutrophic reservoir

Although the Ibirité reservoir (an urban tropical eutrophic reservoir) has been the recipient of the discharge of a large volume of raw urban sewage, the key cause of ecosystem degradation has been historically solely attributed to the discharge of effluents from an oil refinery. This fact motivated an investigation to unravel the compositions of contaminants in the sediments to evaluate their distributions, possible sources, and potential impacts on sediment–water quality. The concentrations of polycyclic aromatic and aliphatic hydrocarbons and of metals and metalloids were, in general, significantly lower than some selected polluted sites used for comparison. Calculated distribution indexes showed that the hydrocarbon sources were petrogenic, pyrogenic, and biogenic. Only a few PAHs exceeded the threshold effects level (TEL) guideline. Industrial activities are the presumed sources of metals and metalloids except for copper, which is from copper sulfate used as algaecide in the reservoir. The bioavailable concentrations of some metal and metalloid exceeded the TEL–PEL guidelines. The acid volatile sulfide concentration was greater than that of the simultaneously extracted metals in the clayey–silty reservoir sediments, whereas the opposite result was observed for the sandy sediments of the tributaries. The sediment interstitial water toxic units were >1 for metals, thus indicating that metals are potentially toxic to the benthos. Considering the data set generated in this study, it can be concluded that the degradation of Ibirité reservoir and its tributaries cannot be solely attributed to the input of hydrocarbons, but predominantly to the discharge of raw urban sewage and effluents from other industrial sources.     

Local mate competition and precise sex ratios in Telenomus fariai (Hymenoptera: Scelionidae), a parasitoid of triatomine eggs

Telenomus fariai is a gregarious endoparasitoid of the eggs of several species of Triatominae (Hemiptera) with a high degree of sibmating: males fertilize their sisters inside the host egg before emergence or emerge first and copulate with their sisters as these emerge. Our results show that, when laying alone, T. fariai behaves adaptively, minimizing offspring mortality and conforming to the prediction of local mate competition (LMC) theory by laying a single male, which is sufficient to fertilize all the sisters. When more than one wasp was placed with one host, sex ratios still conformed to LMC predictions but, despite the decreasing number of eggs laid per wasp, clutch size could not be completely adjusted to avoid mortality. This is not surprising, as superparasitism is rare in the field. Offspring production was independent of the contacts between conspecifics but was affected by the number of mothers laying on a single host egg. The sex of the progeny was precisely determined: a female produced one male per clutch when laying on both unparasitized or previously parasitized hosts. On the other hand, a mother produced less daughters when superparasitizing. Under crowded conditions, the number of eggs laid per female wasp and per host decreased as the number of mothers increased. Developmental mortality also increased with the number of T. fariai eggs per host, determining a maximum of approximately 14 emerged adults. Host resources per individual affected male and female adult size with similar intensity, and male adult mortality was slightly higher than that for females. These results, and previous findings, suggest that T. fariai attains Hamiltonian sex ratios by laying one male and a variable number of females, and that the detection of chemical marks left by conspecifics provides information on the number of foundresses sharing a patch. Received: 4 February 2000 / Received in revised form: 19 April 2000 / Accepted: 20 May 2000     

Relationship between geographical origin and contents of Pb,Cd, and Cr in honey samples from the state of Paraná (Brazil) with chemometric approach

The aim of this study was to determine the trace elements, Pb, Cd, and Cr in honey samples from eight different regions from the state of Paraná (Brazil), using slurry sampling graphite furnace atomic absorption spectrometry. Chemometric analysis (principal component analysis (PCA)) was applied to classify honey samples according to their levels of the trace elements Pb, Cd, and Cr, which is also related to the geographical origin of honey samples. The mean concentration for the elements followed the order Pb?>?Cr >?>?Cd. The mean values were 200?±?76, 88?±?14, and 4.1?±?4 ng g^?1 for Pb, Cr, and Cd, respectively. It could be verified that honey samples are geographically separated, especially with regard to Pb and Cd contents. Thus, honey can be considered a bioindicator of environmental contamination, suggesting possible contamination in soil, water, and air. This contamination can be related to natural or anthropogenic sources present in the study regions.