Emission Characteristics Of Volatile Compounds Research Articles

Determination of emission characteristics of volatile compounds from mosquito repellents (MRs) by headspace and chamber methods, and indoor levels related to use of MRs

Although the use of mosquito repellents (MRs) may lead to several adverse health effects, very limited information is available on exposure to their emissions. As such, the present study evaluated the emission characteristics of volatile pollutants from three different types of MRs (coil, mat, and liquid-vaporiser types) by headspace and/or chamber methods and measured apartment bedroom levels associated with the use of the MRs. By means of a headspace test, 18 to 22 compounds were tentatively identified from mat and liquid MRs. Six toxic/hazardous compounds identified in this headspace test were chosen as target compounds for a further chamber-emission test. An empirical equation was well fitted with time-series concentration levels in a small-scale chamber for all test MRs. Based on the chamber study, the coil MR exhibited the highest emission rate for the target compounds, with the exception of naphthalene, followed by liquid and mat MRs. It is noteworthy that naphthalene was emitted from the liquid MR only at a high emission rate (2.4 mg h−1). A comparison of apartment bedroom levels with predicted values, which were estimated by using the calculated emission data and the one-compartment mass balance equation, suggested that predictions obtained from the chamber study were similar to, or larger than, the measured bedroom levels. Furthermore, the apartment bedroom measurements suggested that the use of coil MR could significantly elevate the indoor levels of four compounds (benzene, ethyl benzene, and m, p-xylene) by up to 1.8 to 1.9 times, while the use of liquid MR could significantly increase the indoor levels of naphthalene by up to 4.2 times. The current findings can provide valuable information for the estimation of the population inhalation exposure to these emissions in indoor environments, and enhance the selection of safer MRs.

Emission characteristics of volatile compounds during sludges drying process

The emission characteristics of volatile compounds (VCs) during municipal sewage sludge (MSS) and paper mill sludge (PMS) drying process were investigated through experiments conducted on a lab-scale tubular drying furnace and a pilot-scale paddle dryer, respectively. The result indicated that five kinds of VCs, i.e. CO 2, NH 3, C 7H 16 ( n-heptane), volatile fatty acids (VFAs) and CH 4 were emitted during the drying process. It was found that the NH 3 and CO 2 were the primary compound released from the MSS drying process. In the case of the PMS, the VFAs and CO 2 were the main compounds released. The temperature and water content of sludge had great effects on the emission rates of NH 3, C 7H 16, CO 2 and VFAs. The pH and chemical oxygen demand (COD) of condensate from the paddle dryer were also studied. It showed that pH and COD of condensate from MSS were much higher than that from the PMS, and that the higher COD value of the MSS condensate interrelated to the higher ammonium and sulfur content of it.