Tácio Mauro Pereira de Campos

HCH distribution and microbial parameters after liming of a heavily contaminated soil in Rio de Janeiro

The closing down of a lindane factory near Rio de Janeiro, over 45 years ago, left an area heavily contaminated with hexachlorocyclohexane (HCH). Remediation by soil liming was applied by government authorities in 1995. This study aims to evaluate the HCH distribution and impact on soil microbiota due to contamination and liming. Microcosm experiments with uncontaminated soil mixed with HCH and lime indicated that lime-promoted dechlorination of HCH molecules led to leaching and volatilization of metabolites. The treatment applied transformed but did not solve the problem as most of the HCH remains in the soil. Reduced microbial respiratory activity was measured in contaminated field samples. Higher respiration rates in uncontaminated soil were reduced by HCH and lime addition; the sole addition of HCH caused a temporary increase in soil respiration, and stimulation occurred with oxygen and/or nutrient addition. A heterotrophic bacterial population around 10(9)CFU/g was found in polluted field soil, some well-known degraders having been isolated. Native soil microbiota showed resistance to high amounts of HCH and alkaline pH. The results allow considering bioremediation rather than chemical treatments to clean up the area.

Infiltração de atrazina em latossolo submetido aos sistemas de plantio direto e convencional

O objetivo deste trabalho foi comparar a lixiviacao e o potencial de contaminacao de lencois de agua com atrazina, em solos sob manejo de plantio direto (PD) e convencional (PC). Foram realizados experimentos em campo e em colunas com Latossolo Vermelho-Escuro distroferrico, submetido ao manejo PD e PC, em Dourados, MS, Brasil. Os valores de condutividade hidraulica e potencial matrico, determinados com o permeâmetro de Guelph no PD, demonstram fluxo continuo de agua no solo. A maior condutividade na superficie, associada ao potencial matrico negativo, demonstrou descontinuidade hidrologica, na comparacao das camadas subjacentes, verificada no PC em relacao ao PD. No entanto, o PD apresentou deslocamento vertical de atrazina menor que o PC. Os resultados mostraram que as perdas de atrazina por lixiviacao ocorreram mais intensamente com as primeiras chuvas, logo apos a aplicacao do produto. O PD apresentou maior concentracao de atrazina em comparacao ao PC, tendo reduzido as perdas por lixiviacao. Os dados indicam que a tecnologia de plantio direto pode reduzir o impacto ambiental provocado pelos pesticidas.

Pesticide dispersion by spraying under tropical conditions

ABSTRACT Pesticide air pollution by spraying was evaluated under different temperature, humidity and wind climatic conditions in Brazil. Field experiments were performed with application towards the soil and in guava orchards, where spray dispersion was monitored by adding p-aminobenzoic acid (PABA), a fluorescent substance, as a tracer to the water contained in the spray tanks. Samples were collected with filter membranes (Whatman 180025), and the PABA was extracted from the filters by shaking with water in a Petri dish and measured in a spectrofluorometer. A spray aimed towards the soil with filters positioned on the ground and hung at different heights did not show different upward dispersion as observed when lateral pulverization was conducted. In this case, a tractor with a sprayer moved through a 3 m high and 6 m wide frame with filter membranes mounted at 60 cm intervals. Spray dispersion patterns were modified by guava leaf resistance. No influence of temperature and humidity was observed in this short-lived spraying process. Nevertheless, wind drift can occur during airborne dispersion and is an important pesticide pollution source which requires control. Droplets with PABA powered by assisted spraying upwards returned to the ground by gravity and, therefore, did not constitute a vertical source of atmospheric pollution.

Spatial variability and seasonal toxicity of dredged sediments from Guanabara Bay (Rio de Janeiro, Brazil): acute effects on earthworms

The toxicity of dredged sediments from Guanabara Bay (Rio de Janeiro, Brazil) was evaluated using acute bioassays with Eisenia andrei and metal determination. The sediments were collected in August 2014 (winter) and February 2015 (summer) and in five areas distributed along the Bay: Port of Rio de Janeiro, Port of Niterói, Meriti River mouth, Iguaçu River mouth, and the Environmental Protection Area (APA) of Guapimirim. The sediments were mixed with a ferralsol (a representative Brazilian tropical soil) in proportions varying between 0 (pure soil) and 30%. The acute bioassays with E. andrei followed a standard protocol (ISO 11268-2:2012). Total metal determination in the sediments was performed by ICP-OES. The medium lethal earthworm concentration (LC50) was estimated through PriProbit analysis. The sediments from the APA of Guapimirim, which is a control area at the Guanabara Bay, were the only ones whose total metal concentrations were in agreement with the limits established by Brazilian law for land disposal of dredged sediments. However, the sediments collected in the APA of Guapimirim were the most toxic ones among the study areas due to very high contents of salts in these materials. Winter sediments were generally more toxic compared to the summer ones due to the increase of metal concentrations and salt precipitation to bottom sediments during the winter. The exceptions were (i) the sediments from APA of Guapimirim, where the toxicity in the summer (LC50 = 3.99%) and winter (LC50 = 4.60%) were relatively similar to each other, since the toxicity is linked to salt in excess; and (ii) the Iguaçu River mouth, where the presence of mangrove areas might be associated with the filtering of pollution sources (winter LC50 = 12.67%; summer LC50 = 11.58%). In the Port of Rio de Janeiro, LC50 obtained in the winter (7.30%) was almost three times lower than that found in the summer (19.64%). The sediments from Meriti River mouth showed the highest total metal concentrations, were the most toxic sediments among the study areas (excluding the APA of Guapimirim), and its winter LC50 (6.64%) was almost twice lower than that obtained in the summer (12.55%). By following the same tendency, summer LC50 (17.52%) found for the sediment collected in the Port of Niterói was also higher than the value found in the winter (12.34%). Finally, the dredged sediments from Guanabara Bay were toxic to earthworms in mixtures with pure ferralsol and winter samples were generally more toxic than the summer ones, in agreement with the increase of metal and salt concentrations during the winter.

Solos: Subsídio Para Estudos de Geologia de Engenharia

The objective of this paper was to discuss in simplified and multidisciplinary terms and through an engineering geology point of view the different variables related to the development of residual, transported, organic, expansive and lateritic soils, contributing to standardize concepts of geotechnical interest mineralogical and chemical data from five profiles whose respective saprolitic soils were formed by the action of weathering processes on gneissic metamorphic rocks in tropical and subtropical climatic environment were presented and discussed. The residual soils developed from these rock, besides the great abundance in the state of Rio de Janeiro, have thicknesses greater than 10 meters, being associated with large landslides and mass movements occurred in the last 50 years both in that state and in others. The article emphasizes finally that the presence of relict heterogeneities in saprolitic soils and saprock inherited from their source rocks should not be discarded in the analysis of slope stability and foundations projects.

Water Retention Curve and Shrinkage of Sludge from a Leachate Treatment Plant

This paper presents the results of physical–mineralogical and morphological characterization analysis performed on sludge from a leachate treatment plant (SLTP). Water retention drying and wetting paths were followed using specimens with similar initial water content (arrived at the laboratory). Based on the compaction curve, different moisture contents were chosen for the preparation of specimens for shrinkage tests. Results are analysed and discussed, bearing in mind the possibility of the sludge being used as part of the final cover system of a municipal solid waste landfill.