Effects of Different Types of Zeolites on the Degradation Kinetics of Malathion Pesticide in Water

The study examined the effects of selected types of zeolites as an environmentally benign and friendly way to degrade, S-1, 2-bis (ethoxycarbonyl) ethyl O, O-dimethylphosphorodithioate (malathion), used as a model pesticide, from river water. The effect of the size of zeolite channels and dimensionality (such as 1D, 2D, and 3D), Si/Al ratio, and operating pH were studied to find a suitable type of zeolite and conditions to optimize the pesticide degradation. Mordenite (MOR (1D): Si/Al=6.83, and Si/Al=10.72), ferrierite (FER (2D): Si/Al=10.71), ZSM-5 (MFI (3D): Si/Al=6.83 and Si/Al=10.72) and USY (FAU (3D): Si/Al=2.77) zeolites were individually mixed with a water sample collected from Monjolinho River in São Carlos (SP), Brazil and the degradation trend studied. The results showed that all the zeolites accelerated the degradation of malathion. Nevertheless, lower zeolite Si/Al ratio and larger 3D channels or cavities had a positive influence on the degradation rate. The FAU zeolite presented the stronger degradation of the malathion with a half-life of 16.5 followed by ZSM-5 with 24.8, ferrierite with 29.7, and finally mordenite with 30.3 hours.

Influence of environmental quality of the tributaries of the Monjolinho River on the relative condition factor (Kn) of the local ichthyofauna

The relative condition factors (Kn) of the fishes Astyanax paranae, Phalloceros harpagos and Poecilia reticulata were used as a means of assessing the influence of environmental conditions on the well-being of sub - populations of these species, with the eventual aim of using them as bioindicators of disturbance in tributary streams of the Monjolinho River, in São Carlos - SP. The power-law curve generated by the length-weight relationship indicated a positive allometric growth for the three species studied. Overall, the canonical correspondence analysis (CCA) positively correlated average Kn of A. paranae with well oxygenated and oligotrophic environments, typical of conserved areas or near the natural state. For the average value of Kn obtained for Phalloceros harpagosspecies, there was no significant difference between natural and disturbed areas. However, the CCA positively correlated the mean Kn of the speciesP. reticulata from similar environments with higher trophic level, suggesting that this species is indicative of disturbance.

Analyses of the sediment toxicity of Monjolinho River, São Carlos, São Paulo State, Brazil, using survey, growth and gill morphology of two fish species (Danio rerio and Poecilia reticulata)

The objective of this work was to evaluate the toxicity of the sediments of the Monjolinho River (São Carlos - São Paulo/Brazil), through partial chronic toxicity bioassays with juveniles of D. rerio and P. reticulata. Histological analyses of the gills and biometric measurements were conducted to detect the possible deleterious effects that caused the death. In all points the sampled the alterations were found in the gills (hyperplasia, fusion of secondary lamellas and dilation of blood vessels), with the most intense lesions (second stage) occurring at the point two. The biometric analysis pointed to inadequate conditions for the growth of the test-organisms when exposed to the sediment samples. These results showed that the conditions of these environments were not suitable for the survival and growth of these fishes.

Oligochaeta (Annelida, Clitellata) in lotic environments in the state of São Paulo, Brazil

Despite the importance of Oligochaeta to the dynamics of aquatic ecosystems and to studies of the biology of pollution, there is currently a dearth of information on this group's ecology in Brazil. The aim of this study was to describe the Oligochaeta fauna in four watercourses - three urban and one rural - in the state of São Paulo: the Pinheirinho stream, the Água Branca stream, the Monjolinho River and the Gouveia stream, respectively. Sediment samples were taken with a Van Veen grab in two areas from each watercourse, during the summer and winter of 2001. In all collection areas, measurements of the pH, electrical conductivity, dissolved oxygen and turbidity of the water were made with a Horiba U-10 device. Principal component analysis showed that axes 1 and 2 explained 68.18% of the results' variability, with the first axis predominantly associated with the granulometric data and the second one with the limnological data. Cluster analysis indicated that area II of the Monjolinho River differed from the other collection sites. In the present study, the Oligochaeta group was represented by Tubificidae, Naididae, Alluroididae, Narapidae and Enchytraeidae. Among the three species of Tubificidae, Limnodrilus hoffmeisteri Claparede, 1862, was the most abundant and most frequent species. The results provided important information on the ecology and distribution of limnic Oligochaeta.