Polychlorinated naphthalenes (PCNs) are dioxin-like contaminants unintentionally generated during municipal solid waste incineration (MSWI). This study evaluated the concentrations, congener profiles, and dioxin-like toxicities of PCNs and PCDD/Fs in MSWI fly ash before and after low-temperature thermal dechlorination (LTD) at five full-scale facilities. LTD consistently induced stepwise dechlorination, reducing the average chlorination degree of PCNs by 1.1-1.5 points. Total PCN concentrations, however, exhibited facility-dependent behavior: decreases of 98-99 % were observed at some facilities, whereas others showed increases of 230-370 % relative to pre-LTD levels. This mass increase is plausibly attributed to the reformation of low-chlorinated PCNs on the fly ash carbon surfaces during the cooling phase. Despite these contrasting changes in mass concentrations, PCN-derived dioxin-like toxicity (PCN-TEQ) decreased substantially at all facilities (35-99 % reduction). This robust detoxification occurred because LTD preferentially degrades the highly chlorinated congeners (e.g., 1,2,3,6,7,8-hexaCN and 1,2,3,4,6,7-hexaCN) that dominate PCN-TEQ. The contribution of PCNs to total toxicity consequently declined from 0.18 to 0.45 % before LTD to 0.03-0.30 % afterward. For PCDD/Fs, LTD generally lowered mass concentrations, although PCDD/F-TEQ reductions varied among facilities due to differences in residual high-TEF congeners. These findings unequivocally demonstrate that LTD is a highly effective strategy for mitigating the dioxin-like toxicity associated with PCNs in MSWI fly ash. The results enhance understanding of chlorinated pollutant transformation during full-scale LTD operation and support its optimization for safer MSWI fly ash management.
Microplastics (MPs) have become a major concern for the general public. Although their sources and sinks have been studied, the fate of MPs in the environment remains unclear. Understanding their fate is essential for governments to develop effective countermeasures against MP pollution. In this study, MP pollution was investigated at 22 rivers and 11 beaches in Shizuoka Prefecture, Japan. Polyethylene (PE)-, polypropylene (PP)-, and polystyrene (PS)-MP concentrations in sediments ranged from 0.411 to 423, 0 to 206, and 0 to 45.1 particles kg-1, respectively. In river water and seawater, concentrations ranged from 0 to 14.7, 0 to 21.1, and 0 to 6.00 particles m-3, respectively. MP concentrations were rescaled to align with the 1 to 5,000-μm size range used to define the hazardous concentration for 5% of species (HC5). All aligned concentrations in this study were below the HC5 threshold. Population density was found to be significantly correlated with the PE-, PP-, and PS-MP concentrations in river water and with PE- and PP-MP concentrations in sediments, suggesting that local pollution sources drive MP pollution. The estimated ages of PE-MPs in river water, seawater, and sediments ranged from 0.061 to 5.5, 0.25 to 0.63, and 0.0 to 4.3 years, respectively. No significant differences in age were observed among sample types or sampling sites. These findings suggest that effective measures to reduce MP emissions could significantly decrease MP pollution within 1 year in Shizuoka Prefecture.
Despite the widespread prevalence of the genus Karenia, a notorious contributor to harmful algal blooms (HABs) worldwide, there are no reported instances of Amoebophrya spp. infecting Karenia. In 2020, we isolated infected Karenia mikimotoi cells, performed repeated inoculations of these infected cells to uninfected host cultures, and isolated a parasite strain of Amoebophrya from Osaka Bay, Japan. This strain exhibited infectivity toward K. mikimotoi and Karenia papilionacea but not Karenia selliformis or 14 other dinoflagellate species, highlighting its remarkable host specificity. Laboratory coculture experiments revealed pronounced host growth suppression upon introducing the parasite. The prevalence of infection surged rapidly, reaching a peak of 97
