Considerable researches have documented the negative effects of ozone on woody species in North America and Europe; however, little is known about how woody tree species respond to elevated O3 in subtropical China, and most of the previous studies were conducted using pot experiment. In the present study, Machilus ichangensis Rehd. et Wils (M. ichangensis) and Taxus chinensis (Pilger) Rehd. (T. chinensis), evergreen tree species in subtropical China, were exposed to non-filtered air (NF), 100 nmol mol?1 O3 (E1) and 150 nmol mol?1 O3 (E2), in open-top chambers under field conditions from 21st March to 2nd November 2015. In this study, O3 fumigation significantly reduced net photosynthesis rate (Pn) in M. ichangensis in the three measurements and in T. chinensis in the last measurement. Also, non-stomatal factors should be primarily responsible for the decreased Pn. O3 fumigation-induced increase in malondialdehyde, superoxide dismutase, and reduced ascorbic acid levels indicated that antioxidant defense mechanism had been stimulated to prevent O3 stress and repair the oxidative damage. Yet, the increase of antioxidant ability was not enough to counteract the harm of O3 fumigation. Because of the decrease in CO2 assimilation, the growth of the two tree species was restrained ultimately. The sensitivity of the two tree species to O3 can be determined: M. ichangensis > T. chinensis. It suggests a close link between the rising O3 concentrations and the health risk of some tree species in subtropics in the near future. 相似文献
Antibiotic resistance genes (ARGs) in urban rivers are a serious public health concern in regions with poorly planned, rapid development. To gain insights into the predominant factors affecting the fate of ARGs in a highly polluted urban river in eastern China, a total of 285 ARGs, microbial communities, and 20 physicochemical parameters were analyzed for 17 sites. A total of 258 unique ARGs were detected using high-throughput qPCR, and the absolute abundance of total ARGs was positively correlated with total organic carbon and total dissolved nitrogen concentrations (P < 0.01). ARG abundance and diversity were greatly altered by microbial community structure. Variation partitioning analysis showed that the combined effects of multiple factors contributed to the profile and dissemination of ARGs, and variation of microbial communities was the major factor affecting the distribution of ARGs. The disparate distribution of some bacteria, including Bacteroides from mammalian gastrointestinal flora, Burkholderia from zoonotic infectious diseases, and Zoogloea from wastewater treatment, indicates that the urban river was strongly influenced by point-source pollution. Results imply that microbial community shifts caused by changes in water quality may lead to the spread of ARGs, and point-source pollution in urban rivers requires greater attention to control the transfer of ARGs between environmental bacteria and pathogens.
Fullerenes are set to be produced on an industrial scale in anticipation of their wide applications. This calls for research on their environmental and health impacts. This study investigates and compares the cell toxicity of different aqueous fullerene aggregates. Popular C60 dispersal methods were used to prepare four types of nC60 aggregates. These aggregates were tested against the indicator species Escherichia coli (E. coli) AMC 198. With aggregates of around 150 nm in diameter, the THF/nC60 suspension was very toxic and gave rise to a half maximal effective concentration (EC50) of 0.54 mg L−1 in E. coli. By contrast, the Tol/nC60 suspension exhibited a cytoprotective role while the Aqu-N2/nC60 and Aqu-O2/nC60 suspensions enhanced the metabolism of E. coli. Although some toxicants, such as THF and THF-peroxide, were introduced into the THF/nC60 suspension during the dispersion, the toxicity of nC60 itself cannot be neglected. 相似文献