Organochlorine pesticides (OCPs), classified as persistent organic pollutants (POPs), have been banned as pesticides since around 1970 in Japan. Declining trends in atmospheric OCP concentrations began decreasing gradually in recent years, ranging from a few pg/m³ to 1,000 pg/m³, but data related to their nationwide distribution in the atmosphere remain sparse. A large-scale passive air sampling survey was therefore conducted across Japan. Polyurethane foam disks were deployed simultaneously at 54 sites to evaluate OCPs distribution in the atmosphere, during March 21 to May 16, 2008.
Analyses of OCPs revealed a descending order of the concentrations (geological average: concentration range pg/m³): chlordanes (146:12-1290) > endosulfans (70:14-269) > HCHs (46:12-405) > hexachlorobenzen (42:21-107) > DDTs (23:2.6-579) > drins (11:2.7-11) > heptachlors (7.6-0.44-37) > mirex (0.24: 0.082-0.88) and, furthermore, confirmed the characteristics of the region on the OCP concentrations. The results on the OCPs concentration ranges and orders are consistent with those of the atmospheric monitoring data by an active air sampler (AAS), taken by the Ministry of the Environment in Japan.
Source diagnostic analysis by metabolites and isomers of OCPs, and trajectories suggested that DDTs, for instance, mainly come from DDT pesticide applied in Japan in past years. This was deduced form the ratio of p,p'-DDT/p,p'-DDE. Therefore, the simultaneous PAS monitoring has a potential to evaluate the OCP concentration distribution in the atmosphere in an extensive area and the source/region of OCPs emissions.

View full abstract

To learn the effects of coexisting surfactants on the rates and pathways of the reductive dechlorination of chloroethylenes by zerovalent iron powder, we investigated the effects of two anionic, one cationic and two nonionic surfactants on the decomposition of tetrachloroethylene (PCE), trichloroethylene (TCE), and cis-1, 2-dichloroethylene (c-DCE). The decomposition rates of c-DCE were the slowest among these three compounds for all the solution systems. The decomposition rates of PCE were faster than those of TCE in pure water and in two anionic surfactants contained solution systems, whereas the rates were almost similar when the solution contained cationic or two nonionic surfactants. Analysis of the reaction products showed that the decomposition reactions were controlled by both β-elimination and hydrogenolysis. The concentration profiles of the starting compound and the reaction products as function of time were simulated using the decomposition rate constants of these compounds. The reactions proceeded mainly via β-elimination when the solution contained cationic or nonionic surfactants, whereas the contributions of β-elimination and hydrogenolysis were almost similar when the solution contained no surfactant or anionic surfactants.

View full abstract

Utilization of biomass as alternative fuel sources has gained an increasing interest. The biomass with high nitrogen content, however, would cause atmospheric pollution during their conversion and energy application. The objective of this study is to convert a high nitrogen content waste, methane fermentation sludge (MFS) into char using superheated steam pyrolysis (SSP). The carbon and nitrogen mass balances in the SSP process were investigated and the potential application of the derived char as a solid fuel was discussed. The results show that the input and output of C and N agree well at 300 and 350°C but deviate from each other at 400°C. The dehydration and deamination essentially occur at 300°C, whereas tars and lower class hydrocarbons are dominantly formed at 400°C. Nitrogen prefers to convert into NH₄-N rather than to reform as NO₂-N, NO₃-N or organic nitrogen, showing that SSP is an environmentally friendly way for the conversion of high nitrogen-contained biomass. The HHV of char derived at 300°C is 15.8 MJ/kg. It decreases to 13.3 and 11.4 MJ/kg at 350 and 400°C respectively. For a solid fuel, high H/C with low O/C and N/C ratios is always desired. Accordingly, the MFS-derived chars obtained at above 350°C by SSP can be potential solid fuels used by mixing with other coal.

View full abstract