Distribution of gasification products and emission of heavy metals and dioxins from municipal solid waste at the low temperature pyrolysis stage.

Gasification is widely regarded as one of the most practical, economical, and environmentally friendly waste disposal technologies for municipal solid waste (MSW). The pyrolysis stage (300-500 °C) is crucial for weight loss during MSW gasification, as a considerable amount of organic matter breaks down, producing high-value synthesis gas. This study investigated the product distribution and pollutant emission characteristics within this temperature range and its influencing factors during MSW gasification using a self-designed MSW gasification device. Results indicated that MSW underwent approximately 70% weight loss within this temperature range, yielding low amounts of inorganic and short-chain organic products, with mainly long-chain organic compounds of C16-C34. The atmosphere variation had minimal effect on the elemental composition and content of solid phase products. X-ray fluorescence spectrometry (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) analyses showed that Mn and Zn were the primary components of heavy metal leaching toxicity in solid phase products, with their contents increasing as temperature increased. Synthesis gas showed the highest content of heavy metal As element, reaching a peak at 400 °C. Higher gasification temperature and lower oxygen flow rate significantly reduced the dioxin content and I-TEQ values, with highly chlorinated isomers being the predominant dioxin isomers. Nonetheless, low-chlorinated dioxins accounted for more than 50% of the I-TEQ. This study improves our understanding of the gasification process of MSW.

Study on genetic polymorphism of Platycodon grandiflorum based on barcoding of ITS2 / 中国中药杂志

<p><b>OBJECTIVE</b>ITS2 of DNA barcoding was used to study genetic polymorphism of Platycodon grandiflorum.</p><p><b>METHOD</b>Total genomic DNA was isolated from P. grandiflorum. PCR was used to amplified the region of internal transcribed spacer 2 (ITS2), and PCR products were sequenced. The sequences of ITS2 were analyzed and compared by Clustal. The intraspecies genetic distance was calculated based on Kimura 2-parameter model by using MEGA 5.05. The ITS2 sequence of Codonopsis pilosula was used as the outreach value for plants of the genus, and the phylogenic tree used constructed by Neighbor-Joining (NJ) method.</p><p><b>RESULT</b>The K2-P's genetic distance of all samples were ranged from 0 to 0.930. The K2-P's genetic distance of samples at the same area were ranged from 0 to 0.178. The K2-P's genetic distance of samples at different areas were ranged from 0.735 to 0.930. The analytical result showed that the degree of genetic variation were heavy in intraspecies of P. grandiflorum and significantly correlated with geographical location.</p><p><b>CONCLUSION</b>The DNA barcoding of ITS2 can applied to study the intraspecific genetic diversity, it provides a reference for further development of DNA barcoding technology applications.</p>