(210)Pb and composition data of near-surface sediments and interstitial waters evidencing anthropogenic inputs in Amazon River mouth, Macapá, Brazil

Activity profiles of excess ²¹⁰Pb determined in three sediment cores from Amazon River mouth, Macapá city, Brazil, provided the evaluation of sedimentation rates, contributing to a better knowledge of the hydrological conditions in the site that is the capital of Amapá State and is drained by the waters of the huge Amazon River. Chemical data were also determined in the sediments, allowing identify signatures coupled to anthropogenic inputs held in the past in Amapá State. Significant direct relationships between LOI (loss on ignition) and organic matter were found for all sediments profiles. Silica was found to be inversely related to organic matter in the three profiles; its decrease accompanied an increase on the specific surface of the sediments. This relationship was confirmed by a great number of inverse significant correlations among silica and oxides Na₂O, K₂O, CaO, MgO, Al₂O₃, P₂O₅, Fe₂O₃ and MnO. It was possible to identify the role of organic matter on adsorption of several oxides in the core sediments profiles. Apparent sediment mass accumulation rates corresponding to values between 450 and 2510 mg cm⁻² yr⁻¹ were obtained, and are compatible with the results of others studies. The ²¹⁰Pb activities in one sampling point suggested the occurrence of anthropogenic inputs related to the initial period of the mining activities conducted in Serra do Navio, Amapá State, for the commercialization of Mn ores. This was reinforced by the abrupt fluctuations in chemical data obtained for the sediments and composition of the interstitial waters occurring there. The Atlantic hurricane activity also appeared to affect the sedimentation rates in the area, as two different values were recorded in each profile.     

Effects of soil mechanical resistance on nematode community structure under conventional sugarcane and remaining of Atlantic Forest

Nematodes present high potential as a biological indicator of soil quality. In this work, it was evaluated relations between soil physical properties and nematode community under sugarcane cropping and remaining of Atlantic Forest areas in Northeastern Pernambuco, Brazil. Soil samples were collected from September to November 2009 along two 200-m transects in both remaining of Atlantic Forest and sugarcane field at deeps of 0–10, 10–20, 20–30, 30–40, and 40–50 cm. For soil characterization, it was carried out analysis of soil size, water content, total porosity, bulk density, and particle density. The level of soil mechanical resistance was evaluated through a digital penetrometer. Nematodes were extracted per 300 cm³ of soil through centrifugal flotation in sucrose being quantified, classified according trophic habit, and identified in level of genus or family. Data were analyzed using Pearson correlation at 5% of probability. Geostatistical analysis showed that the penetration resistance, water content, total porosity, and bulk density on both forest and cultivated area exhibited spatial dependence at the sampled scale, and their experimental semivariograms were fitted to spherical and exponential models. In forest area, the ectoparasites and free-living nematodes exhibited spherical model. In sugarcane field, the soil nematodes exhibited pure nugget effect. Pratylenchus sp. and Helicotylenchus sp. were prevalent in sugarcane field, but in forest, there was prevalence of Dorylaimidae and Rhabditidae. Total amount of nematode did not differ between environments; however, community trophic structure in forest presented prevalence of free-living nematodes: omnivores followed by bacterial-feeding soil nematodes, while plant-feeding nematodes were prevalent in sugarcane field. The nematode diversity was higher in the remaining of Atlantic Forest. However, the soil mechanical resistance was higher under sugarcane cropping, affecting more directly the free-living nematodes; especially Dorylaimidae which was the most sensible to changes in soil physical properties.     

Water quality of the Ribeirão Preto Stream, a watercourse under anthropogenic influence in the southeast of Brazil

It is known that Brazil still has a privileged position of water quantity and quality, but water use has not proceeded in a responsible manner and often results in impairment of quality. This study aims to evaluate limnological parameters, parasites and bacteria, and concentrations of heavy metals (Cd, Pb, Cu, Cr, Mn, Hg, and Zn) in surface water of Ribeirão Preto Stream. The Ribeirão Preto Stream is located in urban areas under anthropogenic influence. The results showed that the levels of dissolved oxygen values were lower than those established by the National Environmental Council (CONAMA Resolution No 357/2005). The reading of electrical conductivity showed values typical of impacted environments. The parasitological analysis revealed the presence of nematode larvae. The bacteriological analysis showed higher values for total coliform and Escherichia coli than those set by the Brazilian National Environment Council (CONAMA). The heavy metals Cd, Pb, Cu, Cr, Mn, Hg, and Zn showed concentrations in accordance with the guidelines established by CONAMA. The results provide data on the quality of these waters and showed the necessity to protect the watercourse from point sources of contamination, recommending their continued monitoring.     

Colorimetric determination of formaldehyde in air using a hanging drop of chromotropic acid

A simple and sensitive method to determine parts per billion (ppb) of atmospheric formaldehyde in situ, using chromotropic acid, is described. A colorimetric sensor, coupled to a droplet of 15.5 microL chromotropic acid, was constructed and used to sample and quantify formaldehyde. The sensor was set up with two optical fibers, a light emitting diode (LED) and two photodiodes. The reference and transmitted light were measured by a photodetection arrangement that converts the signals into units of absorbance. Air was sampled around the chromotropic acid droplet. A purple product was formed and measured after the sampling terminated (typically 7 min). The response is proportional to the sampling period, analyte concentration and sample flow rate. The detection limit is approximately 2 ppb and can be improved by using longer sampling times and/or a sampling flow rate higher than that used in this work, 200 mL min-1. The present technique affords a simple, inexpensive near real-time measurement with very little reagent consumption. The method is selective and highly sensitive. This sensor could be used either for outdoor or indoor atmospheres.     

Habitat related growth and reproductive investment in estuarine waters,illustrated for the tellinid bivalve <Emphasis Type="Italic">Macoma balthica</Emphasis> (L.) in the western Dutch Wadden Sea

In estuarine areas, bivalve species can be found in a variety of environments, where they experience large differences in environmental conditions. In the present paper, the importance of different habitats (intertidal, subtidal and adjacent coastal waters) for the persistence of the population was evaluated for the bivalve Macoma balthica (L.) in the western Dutch Wadden Sea estuary. Intra-specific variation in growth and reproductive output were followed during the year and related to local abiotic conditions. Significant differences in growth and reproductive investment were found between locations. Young individuals were mostly found in the intertidal area, where growth in terms of somatic mass was good. These areas were not favourable for adult individuals, since growth in shell length was low and many individuals did not reproduce. In the subtidal, where the highest densities were found, somatic and gonadal mass indices were low. Coastal areas had the lowest densities and showed high growth in terms of shell length and body mass. The habitat with the highest reproductive effort per individual was not the most important habitat in terms of reproductive output due to differences in density and in size of the habitat type. For M. balthica, the subtidal habitat contributed the most to the reproductive output of the western Dutch Wadden Sea population although the highest reproductive output per individual was in the coastal area.     

Application of geostatistical methods to arsenic data from soil samples of the Cova dos Mouros mine (Vila Verde-Portugal)

A total of 286 soil samples were collected in the Cova dos Mouros area. All samples were dry sieved into the <200 mesh size fraction and analysed for Fe, Cu, Zn, Pb, Co, Ni, Bi and Mn by atomic absorption spectrometry (AAS) and for As, Se, Sb and Te by atomic absorption spectrometry-hydrid generation (AAS-HG). Only the results of arsenic are discussed in this paper although the survey was extended to all analysed chemical elements. The purpose of this study was to make a risk probability mapping for arsenic that would allow better knowledge about the vulnerability of the soil to arsenic contamination. To achieve this purpose, the initial variable was transformed into an indicator variable using as thresholds the risk-based standards (intervention values) for soils, as proposed by [Swartjes 1999. Risk based assessment of soil and groundwater quality in the Netherlands: Standards and remediation. J. Geochem. Explor.73 1–10]. To account for spatial structure, sample variograms were computed for the main directions of the sampling grid and a spherical model was fitted to each sample variogram (arsenic variable and indicator variables). The parameters of the spherical model fitted to the arsenic variable were used to predict arsenic concentrations at unsampled locations. A risk probability mapping was also done to assess the vulnerability of the soil towards the mining works. The parameters of the spherical model fitted to each indicator variable were used to estimate probabilities of exceeding the corresponding threshold. The use of indicator kriging as an alternative to ordinary kriging for the soil data of Cova dos Mouros produced unbiased probability maps that allowed assessment of the quality of the soil.     

Mercury pollution in the Tapajos River basin, Amazon: mercury level of head hair and health effects.

There is increasing concern about the potential neurotoxic effects of exposure to methylmercury for the 6 million people living in the Amazon, even in regions situated far away from the gold mines (garimpos), considered to be the major source of mercury pollution. In November 1998, a spot investigation on mercury contamination was conducted in three fishing villages (Barreiras, Rainha, and Sao Luiz do Tapajos) on the Tapajos River, an effluent of the Amazon, situated several hundred kilometers downstream from the gold-mining areas. A total of 132 fishermen and their families volunteered for the current study. As was anticipated, the total mercury levels in the head hair collected from the fishing villages were relatively high (14.1-20.8 ppm on the average) and the number of subjects with a high total mercury level over 10 ppm (the least upper bound of a normal value) was 103 (78.0%) in total, along with various symptoms, thereby suggesting wide mercury contamination in the Tapajos River basin. Moreover, in view of the absence of other diseases (e.g., alcoholism or malaria), a high intake of fish containing a methylmercury level, and high hair mercury levels in addition to the various symptoms such as sensory disturbance (especially glove-and-stocking type, which is characteristic of Minamata disease), tremor, failure in two-point discrimination, and slight balancing failure, several subjects examined were diagnosed with mild Minamata disease. The findings obtained suggest, thus, that the mercury pollution in the Amazon should be crucially observed for head hair mercury level and health in a much broader region.     

Experimental and statistical validation of SPME-GC-MS analysis of phenol and chlorophenols in raw and treated water

A procedure based on solid-phase microextraction (SPME) and gas chromatography coupled with mass spectrometry (GC-MS) was developed and validated in order to analyse 10 phenols in water samples. The optimised conditions were obtained using polyacrylate fibre (PA), 20ml of sample volume, 10% NaCl, pH 4.0 and direct extraction at 35 degrees C and 1000rpm, for 40min. The linear range and quantification limits for these compounds by SPME-GC-MS were defined. An evaluation of the main uncertainty sources of this method is included, which allows expanded uncertainties in the 9.4-35% range for the majority of the compounds. The main source of uncertainty is associated with matrix effects. The validated method is suitable for monitoring the production and distribution of potable water and was used, in field trials, for the analysis of samples from main intakes of water (surface or underground) and from water supply system of a large area (Lisbon and neighbour municipalities).