Response of PM_(2.5)-bound elemental species to emission variations and associated health risk assessment during the COVID-19 pandemic in a coastal megacity

The coronavirus(COVID-19)pandemic is disrupting the world from many aspects.In this study,the impact of emission variations on PM_(2.5)-bound elemental species and health risks associated to inhalation exposure has been analyzed based on real-time measurements at a remote coastal site in Shanghai during the pandemic.Most trace elemental species decreased significantly and displayed almost no diel peaks during the lockdown.After the lockdown,they rebounded rapidly,of which V and Ni even exceeded the levels before the lockdown,suggesting the recovery of both inland and shipping activities.Five sources were identified based on receptor modeling.Coal combustion accounted for more than 70%of the measured elemental concentrations before and during the lockdown.Shipping emissions,fugitive/mineral dust,and waste incineration all showed elevated contributions after the lockdown.The total non-carcinogenic risk(HQ)for the target elements exceeded the risk threshold for both children and adults with chloride as the predominant species contributing to HQ.Whereas,the total carcinogenic risk(TR)for adults was above the acceptable level and much higher than that for children.Waste incineration was the largest contributor to HQ,while manufacture processing and coal combustion were the main sources of TR.Lockdown control measures were beneficial for lowering the carcinogenic risk while unexpectedly increased the non-carcinogenic risk.From the perspective of health effects,priorities of control measures should be given to waste incineration,manufacture processing,and coal combustion.A balanced way should be reached between both lowering the levels of air pollutants and their health risks.

Isolation and Identification of a Functional Centromere Element in the Wild Rice Species Oryza granulata with the GG Genome

The centromere of eukaryotic chromosomes is the crucial locus responsible for sister chromatid cohesion and for correct segregation of chromosomes to daughter cells during cell division. In the structural genomics era, centromeres represent the last frontiers of higher eukaryotic genomes because of their densely methylated, highly repetitive and, heterochromatic DNA （Hall et al., 2004）. Although these functions are conserved among all eukaryotes, centromeric DNA sequences are evolving rapidly （Jiang et al., 2003）.

Hylocomium splendens (Hedw.) B.S.G.and Pleurozium schreberi (Brid.) Mitt.as trace element bioindicators:Statistical comparison of bioaccumulative properties

The principal objective of this study was to compare bioaccumulative properties of two terrestrial moss species Hylocomium splendens and Pleurozium schreberi from the Kielce area （south-central Poland）, using various statistical techniques. Forty-six moss samples from 23 sampling sites located within the city limits were analyzed for 33 trace elements. The results indicated that 17 elements （Ba, Ce, Co, Cu, Eu, Fe, Gd, Hg, La, Mo, Nd, Ni, Pb, Pr, Sm, V, Y） dominated in H. splendens, whereas only three elements （Mn, Sr, Zn） occurred in excessive amounts in P. schreberi. No differences in the distribution pattern of Dy, Er, Ho, Sn, Tb, Th and Yb were observed. The element concentration ratio （PI/Hy） varied from 0.50 to 1.19. For 14 elements （Ce, Co, Cu, Fe, Gd, Hg, La, Mo, Nd, Ni, Pb, Sm, Th, V）, PI/Hy 〈 1; for 4 elements （Cd, Mn, Sr, Zn）, PI/Hy 〉 1; for 7 elements （Ba, Dy, Er, Eu, Pr, Y, Yb）, PI/Hy = equalled 1. Czekanowski＇s method showed similarities in rare earth element concentrations for both moss species. The cluster analysis exhibited three significant clusters at D link /D max × 100 〈 50 for both moss species. Strong positive Spearman correlations between both moss species were recorded for the following pairs：Ba-Ba, Co-Co, Er-Er, Eu-Eu, Gd Gd, Mn-Mn, Ni-Ni, Pb-Pb, Pr-Pr, Sm-Sm, Th-Th, Y-Y, and Yb-Yb. Nonparametric tests （Sign test, Wilcoxon tests） showed statistically significant differences only for Cd, Ce, Co, Cu, Hg, Mo, Ni, Pb and Sr. The scanning electron microscope study of H. splendens and P. schreberi revealed a different morphology of these species with no injuries.