Correlations between physical activity, sedentary behavior and physical posture disorders in primary school students / 中国学校卫生

Objective@#To explore correlations between physical activity (PA), sedentary behavior (SB) and physical posture disorders in primary school students, and to provide reference for the prevention and correction of adverse body posture in this group.@*Methods@#From September to December 2020, 206 children from 4 primary schools in Chaoyang District of Beijing were selected by multistage stratified cluster random sampling method. Body posture and PA were assessed using a body posture tester and a triaxial accelerometer. Children s Leisure Activity Questionnaire was used to investigate SB.@*Results@#The detection rate of abnormal body posture in primary school students was 76.70%. PA showed positive assocation with high and low shoulder, X/O leg, pelvis forward, spine curvature and comprehensive evaluation ( β =0.17, 0.21, 0.19, 0.24, 0.19, P <0.05). SB had significant negative linear correlation with high and low shoulder, X/O leg,pelvis forward, spine curvature and comprehensive evaluation ( β = -0.24 , -0.22, -0.36, -0.24, -0.27, P <0.05). In the combination analysis, children with high PA plus low SB ( OR=2.12, 95%CI= 1.46-3.37, P <0.05) and children with low PA plus high SB had the highest and lowest advantages of qualified rate of body posture assessment,respectively. Compare with low SB and low PA( OR=1.71, 95%CI=1.41-2.74, P <0.05), high PA and high SB ( OR=1.85, 95%CI=1.38-2.86, P <0.05) had higher qualified rate of body posture assessment.@*Conclusion@#Physical activity shows positive effects on physical posture while sedentary behavior shows negative effects on physical posture. The combination of PA and SB has a counteracting or synergistic interaction effect.

[Concentration and Source of Dissolved Organic Carbon in Snowpits of the Tibetan Plateau].

Snowpit samples of three glaciers (Laohugou NO. 12 Glacier (LHG), Small Dongkemadi Glacier on Mount Tanggula (TGL) and East Ronghuk Glacier on Mount Everest (ZF)) in the Tibetan Plateau were collected. Concentrations of DOC and major ions were analyzed. The results showed that average DOC concentrations of the snowpits of LHG, TGL and ZF were (250.30 +/- 157.10), (216.92 +/- 142.82) and (152.50 +/- 56.11) microg x L(-1), respectively. DOC of TGL and ZF accounted for large parts of total values of DOC and ions. Correspondingly, DOC of LHG accounted for small part (only 5%), because LHG was located at north China and intensively influenced by natural mineral dust, which caused high concentrations of Ca2+ (the highest value could reach 5299.18 microg x L(-1)) and consequently low percentage of DOC of snowpit samples. Correlation and PCA analyses were used to study the sources of DOC. DOC was significantly correlated with Ca2+, Mg2+, K+ and SO4(2-). Additionally, PCA further indicated that the main potential source of DOC was the natural source of mineral dust. Meanwhile, anthropogenic pollutants (e.g., biomass, fossil combustion and agricultural related pollutants) could also not be ignored. Moreover, the carbon depositional fluxes of three snowpits were roughly estimated, and the values of LHG, TGL and ZF snowpits were 189.23, 132.76 and 128.44 mg (m2 x a)(-1), respectively, which played a significant role in the carbon cycle in this region and was also helpful for the study of glaciers fluctuation.

[Chemical speciation and risk assessment of heavy metals in the middle part of Yarlung Zangbo surface sediments].

Nine heavy metals (Cd, Co, Ni, Cu, Zn, Pb, Cs, As, Cr) of surface sediments collected from the Middle Part of the Yarlung Zangbo River were analyzed by BCR sequential extraction procedure. Based on speciation distributions of these metals, ecological risk of heavy metals was assessed with methods of risk assessment code (RAC) and sediment quality guideline quotient (SQG-Q). The results show that: (1) Large part of Cr and As belong to residual fraction(87%-96%). Ni, Cu, Co and Cs have similar distribution characteristics (non-residual part accounts for approximate 20%). Correspondingly, mass fraction of Cd exists mainly in acid soluble and reducible faction (65% ) , indicating high ecological risk level. (2) Based on calculation of RAC method, Cd is of high risk to the environment (37. 38%). Accordingly, Co, Ni, Cu and Zn are of low risk, and Pb, Cs, As and Cr pose extreme low risk to the environment. According to evaluation of heavy metal speciation distributions, the potential ecological risk of heavy metals is in the descending order of Cd > Co > Ni > Cu > Zn > Pb > Cs > As > Cr. (3) The SQG index of sediments is 0. 804, indicating that studied river sediment has a moderate potential biological toxicity effect. Given most of heavy metals exists in residual fraction, the sediments of this region pose a low ecological risk to the environment.

[Study on soil element background values of the Hoh Xil area in north Tibet].

Hoh Xil locates at northern part of the Tibetan Plateau. Twenty five surface soil samples were collected from this area in 2007 and 32 elements were analyzed and compared to the element contents of Yarlung Zangbo river sediment, background element value of the Tibetan surface soil and the Chinese Continental crust contents. The results showed that the element contents of the < 20 microm fraction were higher than those of bulk samples; Contents of many elements of this study were similar to those of the Tibetan soil. Meanwhile, contents of Ca and As of the studied area were higher than those of Chinese continental crust, resulting mainly from local alpine arid climate and widely distributed the rocks that enriched in As, respectively. The EOF analysis of the contents of bulk soil samples revealed the sources and chemical properties of studied elements: many elements such as Al, Fe, Ga inherit the characteristics of the parent rocks of this region. Meanwhile, elements with an active chemical property and the element Zr that specially existed in the heavy minerals also had a certain contribution to the contents. The contents of B and Cs revealed contribution of hot springs to the soil of studied area.

The effect of the structure of polychlorinated biphenyls on their hydroxylation, oxidation, and glutathionyl conjugation reactions / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To compare the nature of the metabolites formed from the phase I metabolism (hydroxylation and oxidation) and phase II metabolism (glutathionyl conjugation) of PCBs that have different chlorine substitution patterns. To discuss the structure-activity relationships and metabolic mechanisms of PCBs.</p><p><b>METHODS</b>4-Cl-biphenyl (PCB3), 4,4'-Cl-biphenyl (PCB15), 3,4,3',4'-Cl-biphenyl (PCB77) were used for in vitro metabolic study. LC/MS and UV-Vis studies were performed for metabolites identification.</p><p><b>RESULTS</b>The cytochrome P-450 catalyzed hydroxylation rate decreased as the number of chlorine substitutions increased. In this reaction, PCB3 was fully metabolized, approximately half of the PCB15 was metabolized and PCB77 was not metabolized at all. The oxidation rate of PCB15-HQ was higher than that of PCB3-HQ under various oxidation conditions. The LC/MS and UV-Vis data suggest that in the conjugation reaction of PCB15-Q and GSH, the Michael addition reaction occurs preferentially over the displacement reaction.</p><p><b>CONCLUSION</b>The metabolic profiles of polychlorinated biphenyls (PCBs) are dramatically affected by chlorine substitution patterns. It is suggested that the metabolic profiles of PCBs are related to their chlorine substitution patterns, which may have implications for the toxicity of PCB exposure.</p>

[Indoor air pollution in the Nam Co and Ando Regions in the Tibetan Plateau].

Concentrations and variations of fine particulate matter (PM2.5) and carbon monoxide (CO) within tents from the Nam Co and Ando regions were observed at summer 2009, in order to understand the concentrations and variations of PM2.5 and CO in these tents (or in rooms) and their main affect factors, as well as the exposure of different residents. The result indicates that the twenty-four hour average concentrations of PM2.5 and CO (V/V) in the tents without chimney are 1.272 mg x m(-3) and 5.035 x 10(-6), which are significantly higher than those of tents installed chimneys (0.097 mg x m(-3) and 0.089 x 10(-6)). Diurnal variations of PM2.5 and CO are similar and show multiple peaks, which is different with those in the eastern rural areas of China and closely connected with the behaviors of the residents within the tents. Generally, women and children spend three or four hours longer in tents than other family members every day. Children have the highest exposure of 0.972 mg x m(-3) and 0.132 x 10(-6) for PM2.5 and CO, respectively. Therefore, although the outdoor air in the Tibetan Plateau is very clean, the air of the Tibetan tents are seriously polluted and mainly caused by yak dung combustion.