Estimation and field measurement of methane emission from waste landfills in Hanoi, Vietnam

A methodology for estimating the methane emissions from waste landfills in Hanoi, Vietnam, as part of a case study on Asian cities, was derived based on a survey of documents and statistics related to waste management, interviews with persons in charge, and field investigations at landfill sites. The waste management system in Hanoi was analyzed to evaluate the methane emissions from waste landfill sites. The quantity of waste deposited into the landfill was evaluated from an investigation of the waste stream. The composition of municipal waste was surveyed in several districts in the Hanoi city area, and the quantities of degradable organic waste that had been deposited into landfill for the past 15 years were estimated. Field surveys on methane emissions from landfills of different ages (0.5, 2, and 8 years) were conducted and their methane emissions were estimated to be 120, 22.5, and 4.38 ml/min/m², respectively. The first-order reaction rate of methane generation was obtained as 0.51/year. Methane emissions from waste landfills were calculated by a first-order decay model using this emission factor and the amount of landfilled degradable waste. The estimates of methane emissions using the model accorded well with the estimates of the field survey. These results revealed that methane emissions from waste landfills estimated by regional-specific and precise information on the waste stream are essential for accurately determining the behavior of methane emissions from waste landfills in the past, present, and future.     

Abiotic degradation of four phthalic acid esters in aqueous phase under natural sunlight irradiation

Abiotic degradability of four phthalic acid esters (PAEs) in the aquatic phase was evaluated over a wide pH range 5–9. The PAE solutions in glass test tubes were placed either in the dark and under the natural sunlight irradiation for evaluating the degradation rate via hydrolysis or photolysis plus hydrolysis, respectively, at ambient temperature for 140 d from autumn to winter in Osaka, Japan. The e ciency of abiotic degradation of the PAEs with relatively short alkyl chains, such as butylbenzyl phthalate (BBP) and di-nbutyl phthalate (DBP), at neutral pH was significantly lower than that in the acidic or alkaline condition. Photolysis was considered to contribute mainly to the total abiotic degradation at all pH. Neither hydrolysis nor photolysis of di-ethylhexyl phthalate (DEHP) proceeded significantly at any pH, especially hydrolysis at neutral pH was negligible. On the other hand, the degradation rate of diisononyl phthalate (DINP) catalyzed mainly by photolysis was much higher than those of the other PAEs, and was almost completely removed during the experimental period at pH 5 and 9. As a whole, according to the half-life (t1=2) obtained in the experiments, the abiotic degradability of the PAEs was in the sequence: DINP (32–140 d) > DBP (50–360 d), BBP (58–480 d) > DEHP (390–1600 d) under sunlight irradiation (via photolysis plus hydrolysis). Although the abiotic degradation rates for BBP, DBP, and DEHP are much lower than the biodegradation rates reported, the photolysis rate for DINP is comparable to its biodegradation rate in the acidic or alkaline condition.     

Methods for selenium removal from contaminated waters: a review

Environmental Chemistry Letters - Worldwide contamination of waters by metals, metalloids, and organometallic pollutants is a major health issue. In particular, the occurrence of the selenium...