Disturbance response indicators of Impatiens walleriana exposed to benzene and chromium.

The purpose of this study was to evaluate the remediation potential and disturbance response indicators of Impatiens walleriana exposed to benzene and chromium. Numerous studies over the years have found abundant evidence of the carcinogenicity of benzene and chromium (VI) in humans. Benzene and chromium are two toxic industrial chemicals commonly found together at contaminated sites, and one of the most common management strategies employed in the recovery of sites contaminated by petroleum products and trace metals is in situ remediation. Given that increasing interest has focused on the use of plants as depollution agents, direct injection tests and benzene misting were performed on I. walleriana to evaluate the remediation potential of this species. I. walleriana accumulated hexavalent chromium, mainly in the root system (164.23 mg kg-1), to the detriment of the aerial part (39.72 mg kg-1), and presented visible damage only at the highest concentration (30 mg L-1). Unlike chromium (VI), chromium (III) was retained almost entirely by the soil, leaving it available for removal by phytotechnology. However, after the contamination stopped, I. walleriana responded positively to the detoxification process, recovering its stem stiffness and leaf color. I. walleriana showed visible changes such as leaf chlorosis during the ten days of benzene contamination. When benzene is absorbed by the roots, it is translocated to and accumulated in the plant's aerial part. This mechanism the plant uses ensures its tolerance to the organic compound, enabling the species to survive and reproduce after treatment with benzene. Although I. walleriana accumulates minor amounts of hexavalent chromium in the aerial part, this amount suffices to induce greater oxidative stress and to increase the amount of hydrogen peroxide when compared to that of benzene. It was therefore concluded that I. walleriana is a species that possesses desirable characteristics for phytotechnology.

Solid waste from aluminum recycling process: characterization and reuse of its economically valuable constituents.

Due to economic advantages, many companies in Brazil recover Al from the process of crushing and water-leaching of secondary aluminum dross. Wastes from this process (non-metallic products and salts) are usually landfilled or disposed without treatment, causing many environmental damages. The purpose of this work is to investigate, in a recycling company sited in Sao Paulo metropolitan area (Brazil), the potential use of the non-metallic product (NMP) in the production of concrete blocks and to evaluate the presence of important chemical compounds that may be useful for other applications. Chemical and mineralogical analyses revealed that NMP is composed of refractory and abrasive oxides (alpha-Al2O3, MgAl2O4, SiO2) and an important source of transition alumina: alpha-Al(OH)3. Concrete blocks were made by adding two parts of NMP to one part of cement and four parts of sand. The blocks were tested according to the Brazilian standard (NBR7173/1982) and they passed dimension, humidity and absorption tests but not compressive strength tests. However, particular NMP constituents have accelerated the strength rate development of the blocks, thus decreasing working time. The commercial use of NMP can reduce the amount of discarded wastes contributing to environmental preservation.