Simultaneous heavy metal removal mechanism by dead macrophytes

The use of dead, dried aquatic plants, for water removal of metals derived from industrial activities as a simple biosorbent material has been increasing in the last years. The mechanism of simultaneous metal removal (Cd2+, Ni2+, Cu2+, Zn2+ and Pb2+) by 3 macrophytes biomass (Spirodela intermedia, Lemna minor and Pistia stratiotes) was investigated. L. minor biomass presented the highest mean removal percentage and P. stratiotes the lowest for all metals tested. Pb2+ and Cd2+ were more efficiently removed by the three of them. The simultaneous metal sorption data were analysed according to Langmuir and Freundlich isotherms. Data fitted the Langmuir model only for Ni and Cd, but Freundlich isotherm for all metals tested, as it was expected. The K(F) values showed that Pb was the metal more efficiently removed from water solution. The adsorption process for the three species studied followed first order kinetics. The mechanism involved in biosorption resulted ion exchange between monovalent metals as counter ions present in the macrophytes biomass and heavy metal ions and protons taken up from water. No significant differences were observed in the metal exchange amounts while using multi-metal or individual metal solutions.     

Persistence of Violation and Crash Behavior Over Time

This analysis examines the ability of previous offenses to predict future high-risk offenses, and similarly, the ability of crashes to predict future high-risk crashes, using the complete driver history data (up to 9 years) for a set of young Michigan subjects. As expected, those with previous ticketed offenses or reported crashes are at greater risk for future offenses or crashes; with a previous-year serious offense doubling the odds of serious offenses during the subsequent year, and a previous-year at-fault crash increasing the odds of subsequent-year at-fault crashes by nearly 50%. There is modest evidence that serious offenses and at-fault crashes may better predict subsequent behavior in females and in more experienced drivers. This latter finding is also evidenced by the fact that records of these young drivers are less predictive of subsequent driving history than is true for records of all drivers in general found in other studies. This suggests that, in the early stages of driving, offenses and crashes are, at least in part, attributable to inexperience, and hence, characteristic of all beginning drivers.     

A comparison of the comprehensive municipal solid waste management systems of the region of Prague and the principality of Asturias. the influence of collection systems and municipality size on the waste collection and the recycling rates

Journal of Material Cycles and Waste Management - The correct management of municipal solid waste (MSW) is a critical factor in the protection of the environment, as well as a source for the...     

Chronic exposure to lead acetate promotes changes in the alveolar bone of rats: microstructural and physical–chemical characterization

Environmental Science and Pollution Research - There are a few data relating to the effects of lead (Pb) exposure on the alveolar bone, which has very distinct morphophysiological characteristics...