Hydrophobic modified vermiculite mixed with soil was investigated in biodegradation experiments of naphthalene and anthracene. The experiments had been carried out on mixtures of soil and vermiculite at a proportion of 2%, 10%, and 15% and also in the absence of clay used for control. Biodegradation of the pollutants was followed by the decline of naphthalene and anthracene concentration, measured by CG. Compound mineralization was also proved by the evolution of CO 2 . The results showed that in the mixture with a higher proportion of vermiculite biodegradation is enhanced compared to that performed in the absence of vermiculite. In general, when vermiculite proportions are increased, the rate of degradation increases, which may account for the bioavailability of compounds. Bioavailability is an important factor for the degradation of compounds with low solubility. Comparison of biodegradation rates shows that naphthalene is degraded faster than anthracene. The chemical structure could be responsible for this observation. However, although we did not identify the microorganism that was in the soil, we can conclude that vermiculite could be an alternative for the bioavailability of such compounds. Vermiculite in the modified form could also be very useful as a barrier to retain organic pollutants in accidental spills.

The presence of polycyclic aromatic hydrocarbons (PAHs) in samples of marine sediments from Paranagua Bay on the southern coast of Brazil was investigated. Paranagua Bay is the location of a major port, one of the busiest in Brazil. The region has a great potential for tourism and port-related industries and activities. Due to its characteristics as a venue for tourism, two major campaigns were planned: one 3 months before the summer (between December and February) and a second after the vacation season. Total concentration of PAHs in sediments ranged from 26.33 to 406.76 ng/g (in both campaigns). The highest values were found in sediments with higher organic carbon content. We found no substantial differences between the two campaigns, and the values are quite similar. Ternary diagrams show that points P5 and P6 were considered polluted, while others were classified as non-polluted. Molecular ratios indicate that the main sources of PAHs are petrogenic and the burning of fossil fuels. Sediment toxicity was assessed by the presence of PAHs in terms of benzo(a)pyrene (BaP) concentration. The toxicity of PAHs mixtures can be characterized more accurately by developing and establishing toxic equivalency factors (TEFs) for PAHs. Considering TEFs, the BaP(eq) concentrations vary between 0.264 and 5.922 ng/g (considering both campaigns). Thus, two points are above the maximum level recommended (3 ng/g) by the Netherlands sediment quality guidelines. In fact, sites P5 and P6 apparently are exposed to a greater number of pollution sources, thus reflecting the higher concentration of PAHs compounds in sediments.

The presence of polylcyclic aromatic hydrocarbons (PAHs) in surface sediments of Barigui River was investigated. PAHs are considered highly toxic and persistent compounds because of their structure. They originate from incomplete combustion of fossil fuels or biomass. The Barigui River crosses the metropolitan region of Curitiba, and some regions are highly polluted and located near the possible sources of pollution. The results showed that concentrations of total PAHs ranged from 44.6 to 880.2 ng g −1 , and the highest values were found at the sites previously investigated and identified as critically polluted. At sites located away from the traffic and possible pollution sources, the total PAHs was lower, 44.6 ng g −1 . Due to their hydrophobic character, sediments with high silt and clay content retain greater amounts of PAHs. The granulometric composition of the sediments revealed that most of them are composed basically by silt and clay, and those samples showed high concentration of PAHs. The organic carbon content also confirms this observation. The other sites investigated showed a high capacity to adsorb hydrophobic compounds mainly due to the granulometric composition and organic matter that adsorb poorly water soluble compounds. Finally, we found that the main sources of PAHs are petrogenic; however, at some sites, it is hard to confirm this pattern, and possibly, a mixture of the source would be more appropriate.

The removal of naphthalene from aqueous solutions by filtration using columns filled with sand and natural vermiculite and sand and hydrophobic vermiculite in different proportions of 2%, 5%, and 10% was evaluated. Batch experiments had shown that the removal was higher than 90% when the filled adsorbent was constituted by 10% of hydrophobic vermiculite. When vermiculite was in lower concentration, that is, 2% and 5%, the removal percentage was lower than 74%. The removal of the naphthalene by the column filled with sand and natural vermiculite did not exceed 25%. The capacity of the columns was tested passing four volumes of aqueous solution of 0.01 mol L −1 naphthalene. After the third volume, the capacity dropped but still retained the major part of pollutant. However, the removal can be reached in higher levels (higher than 90%) when it is filled with 10% of modified vermiculite and increasing the length of the column. With 5% of vermiculite, it is possible to remove 94%, increasing the length of column by a factor of 1.1 times, that is, increasing the original length of 25 to 27.5 cm. The results had demonstrated that the columns are efficient in the removal of the naphthalene and bring speculations to remove other possible organic compounds.

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