Oxidative degradation and mineralization of bentazone from water.

Bentazone degradation efficiency and mineralization in water solutions using chlorine dioxide treatment were evaluated. Double distilled water and a river water sample spiked with bentazone were studied and compared after chlorine dioxide treatment. Degradation efficiency was determined using high-performance liquid chromatography (HPLC). Daphnia magna toxicity testing and total organic carbon (TOC) analysis were used to ascertain the toxicity of the degraded solutions and mineralization degree. Bentazone degradation products were identified using gas chromatography with a triple quadrupole mass detector (GC-MS-MS). A simple mechanistic scheme for oxidative degradation of bentazone was proposed based on the degradation products that were identified. Decrease in D. magna mortality, high degradation efficiency and partial bentazone mineralization were achieved by waters containing bentazone degradation products, which indicate the formation of less toxic compounds than the parent bentazone and effective removal of bentazone from the waters. Bentazone degraded into four main degradation products. Humic acid from Sava River water influenced bentazone degradation, resulting in a lower degradation efficiency in this matrix (about 10% lower than in distilled water). Chlorine dioxide treatment of water to degrade bentazone is efficient and offers a novel approach in the development of new technology for removal of this herbicide from contaminated water.

Leaching of polycyclic aromatic hydrocarbons from power plant lignite ash--influence of parameters important for environmental pollution.

Nikola Tesla B power plant (TENT B), located at the Sava River, in Obrenovac, 50 km west from the Serbian's capital, Belgrade, is the second largest coal-fired power plant in the country, consisting of two blocks, each of 620 MW capacity. In order to investigate the threat polycyclic aromatic hydrocarbons (PAHs) from deposited coal ash, obtained by coal combustion in this power plant, can represent for the surrounding environment, samples of coal ash were submitted to extraction with river water used for transport of coal ash to the dump, as well as with water of different ionic strength and acidity. It was found that, out of 16 EPA priority PAHs, only naphthalene, acenaphthylene, fluorene, phenantrene, fluoranthene, and pyrene were found in measurable concentrations in the different extracts. Their combined concentration was around 0.1 µg/L, so they do not, in terms of leached concentrations, represent serious danger for the surrounding environment. In all cases of established (and leached) PAH compounds, changes of ionic strength, acidity, or the presence of organic compounds in river water may to some extent influence the leached concentrations. However, under the examined conditions, similar to those present in the environment, leached concentrations were not more than 50 % greater than the concentrations leached by distilled water. Therefore, water desorption is likely the most important mechanism responsible for leaching of PAH compounds from filter coal ash.