不同变形失稳模式下隧道围岩稳定性判据研究的进展

计算机模拟隧道围岩失稳研究的困难在于失稳模型不清楚、失稳判据不明确。本文综合分析了目前国内外应用的隧道稳定性判别方法,总结了不同变形失稳机制下的计算模型及其量化的破坏判据,分析了各种方法的研究进展和存在局限,为围岩稳定性数值模拟提供快速、合理、可操作的判据。     

Photoirradiation of polycyclic aromatic hydrocarbon diones by UVA light leading to lipid peroxidation

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous genotoxic environmental pollutants and potentially pose a health risk to humans. In most if not all cases, PAHs in the environment can be oxidized into their corresponding PAH-diones. This process is considered a detoxification pathway with regard to tumorigenicity. Nevertheless, photo-induced toxicological activity of PAH-diones has not been systematically investigated. In this study, we show that 27 potential environmental PAH-diones induced lipid peroxidation, in a dose (light) response manner, when irradiated with UVA at 7 and 21 J cm⁻². Photoirradiation in the presence of sodium azide, deuterated methanol, or superoxide dismutase revealed that lipid peroxidation is mediated by reactive oxygen species. Electron spin resonance (ESR) spin trapping studies supported this observation. These results suggest that UVA photoirradiation of PAH-diones generates reactive oxygen species and induces lipid peroxidation.     

Representative measurement of two-dimensional reactive phosphate distributions and co-distributed iron(II) and sulfide in seagrass sediment porewaters

The high degree of heterogeneity within sediments can make interpreting one-dimensional measurements difficult. The recent development and use of in situ techniques that measure two-dimensional distributions of porewater solutes have facilitated investigation of the role of spatial heterogeneity in sediment biogeochemistry. A colourimetric diffusive equilibration in thin films method has been developed that allows two-dimensional, high-resolution measurement of reactive phosphate in sediment porewaters. A method detection limit of 0.22 μM, an effective upper limit of ∼1000 μM and relative standard deviations typically below 5% were achieved. This method was evaluated by deployment in seagrass (Zostera capricorni) colonised sediments, as part of combined probes with similar colourimetric methods for sulfide and iron(II). The two-dimensional, high resolution distributions obtained provide a highly representative measurement of the co-distributions of porewater solutes, allowing heterogeneous features and biogeochemical processes to be observed and interpreted. Microniches of high phosphate concentration >100 μM were observed throughout the distributions and were interpreted to be due to localised zones of rapid organic matter mineralisation, possibly using electron acceptors other than iron(III) oxyhydroxides (e.g. aerobic respiration) as often they did not correspond with microniches of higher Fe(II) concentration.     

The ratio of clay content to total organic carbon content is a useful parameter to predict adsorption of the herbicide butachlor in soils

Thirteen soils collected from 11 provinces in eastern China were used to investigate the butachlor adsorption. The results indicated that the total organic carbon (TOC) content, clay content, amorphous Fe2O3 content, silt content, CEC, and pH had a combined effect on the butachlor sorption on soil. Combination of the data obtained from the 13 soils in the present study with other 23 soil samples reported by other researchers in the literature showed that Koc would be a poor predictive parameter for butachlor adsorption on soils with TOC content higher than 4.0% and lower than 0.2%. The soils with the ratio of clay content to TOC content (RCO) values less than 60 adsorbed butachlor mainly by the partition into soil organic matter matrix. The soils with RCO values higher than 60 apparently adsorbed butachlor by the combination of the partition into soil organic matter matrix and adsorption on clay surface.     

Extracellular antimutagenic activities of selected probiotic Bifidobacterium and Lactobacillus spp. as a function of growth phase

The capabilities of selected strains from genera Lactobacillus and Bifidobacterium to produce extracellular bioactive compounds with antimutagenic properties against benzo[a]pyrene (BaP) and sodium azide (SA) were tested as a function of growth phase. The bacterial supernatants from exponential and stationary phases were characterized with different patterns of antimutagenic activity against the two mutagens. All lactobacilli exhibited either no effect or low antimutagenicity against BaP during exponential growth. Higher antimutagenic activities of lactobacilli supernatants were observed in the stationary phase against SA as well. An exception was Lactobacillus sakei 23K which expressed a relatively low percent of inhibition of mutagenesis (PI = 28.14 ± 7.41) in the exponential phase and no antimutagenic activity in the stationary phase. Of the bifidobacteria, only Bifidobacterium adoleascentis ATCC 15703 exhibited higher antimutagenecity against BaP in the exponential phase. The same bacterial supernatants however, did not possess any antimutagenicity against SA in either the exponential or stationary phases. B. bifidum ATCC 11863 did not express any significant differences in its activity against either BaP or SA in the exponential or stationary phases. Only B. breve ATCC 15700 expressed a high antimutagenic effect against SA in the stationary phase but exhibited no effect during exponential growth. Overall, bacterial antimutagenic responses were associated with growth phase and type of mutagen.     

Brassinosteroid alleviates phenanthrene and pyrene phytotoxicity by increasing detoxification activity and photosynthesis in tomato

The present study was carried out to investigate the effects of exogenously applied 24-epibrassinolide (BR) on growth, gas exchange, chlorophyll fluorescence characteristics, lipid peroxidation and antioxidant systems of tomato seedlings grown under different levels (0, 10, 30, 100 and 300 μM) of phenanthrene (PHE) and pyrene (PYR) in hydroponics. A concentration-dependent decrease in growth, photosynthetic pigment contents, net photosynthetic rate (Pn), stomatal conductance (Gs), maximal quantum yield of PSII (Fv/Fm), effective quantum yield of PSII (Φ_PSII), photochemical quenching coefficient (qP) has been observed following PHE and PYR exposure. By contrast, non-photochemical quenching coefficient (NPQ) was increased. PHE was found to induce higher stress than PYR. However, foliar or root application of BR (50 nM and 5 nM, respectively) alleviated all those depressions with a sharp improvement in the activity of photosynthetic machinery. The activities of guaicol peroxidase (GPOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) as well as content of malondialdehyde (MDA) were increased in a dose-dependent manner under PHE or PYR treatments. Compared with control the highest increments of GPOD, CAT, APX, GR and MDA by PHE/PYR alone treatments were observed following 300 μM concentration, which were 67%, 87%, 53%, 95% and 74% by PHE and 42%, 53%, 30%, 86% and 62% by PYR, respectively. In addition, both reduced glutathione (GSH) and oxidized glutathione (GSSG) were induced by PHE or PYR. Interestingly, BR application in either form further increased enzymatic and non enzymatic antioxidants in tomato roots treated with PHE or PYR. Our results suggest that BR has an anti-stress effect on tomato seedlings contaminated with PHE or PYR and this effect is mainly attributed by increased detoxification activity.     

Benzo[a]pyrene exposure influences the cardiac development and the expression of cardiovascular relative genes in zebrafish (Danio rerio) embryos

It is reported that the most abundant polycyclic aromatic hydrocarbons (PAHs) in weathered crude oils are cardiotoxic. However, the action mechanism of PAHs on vertebrate cardiovascular development and disease is unclear. In the present study, the cardiac morphology and functioning of zebrafish embryos exposed to benzo[a]pyrene [B(a)P], as a high-ring PAHs, for 72 h were observed and determined. The results showed that B(a)P exposure resulted in cardiac developmental defects in zebrafish embryos. Significant changes in expression level of multiple genes potentially critical for regulating the B(a)P-induced cardiovascular developmental defects were also found. A gene network regulating cardiac development perturbed by B(a)P exposure was identified and established by computational analysis and employment of some databases. The information from the network could provide a clue for further mechanistic studies explaining molecular events regulating B(a)P-mediated cardiovascular defects and consequences.     

PM(10)-bound polycyclic aromatic hydrocarbons: biological indicators, lung cancer risk of realistic receptors and 'source-exposure-effect relationship' under different source scenarios

Cancer has become a critical health issue in the world heritage city Kandy, Sri Lanka. Polycyclic aromatic hydrocarbons (PAHs), one of persistent organic pollutants, in the atmosphere may be a major etiological factor in lung carcinogenicity. Over the very high concentrations of ambient air PAHs reported in Kandy, this paper is focused on setting priorities to control human exposure to PAHs in prevention of cancer.On re-appraisal of the classical indicator benzo(a)pyrene (B[a]P) for atmospheric PAHs-related carcinogenicity, B[a]P failed to reflect the toxicity completely and may not be the sole indicator for risk assessment studies in complex multi-sourced urban environments. The excess lifetime lung cancer risks of atmospheric PAHs with ‘less than lifetime exposure’ were assessed based on both ‘B[a]P toxic equivalents’ and ‘B[a]P surrogate epidemiological’ approach of risk quantification, over emissions characterized urban, suburban, and rural areas of Kandy. In urban heavy traffic areas, PAH-related additional cancer burden has been 942 million⁻¹ over 30 y of exposure. Over the whole study area, ∑p-PAHs show strong correlation (r = 0.8) to the predicted risk levels. While the urban and suburban predicted cancer risk levels could not show significant correlation to their emission sources indicating the real complexity in mega urban environments, the rural lung cancer risk levels correlated perfectly with the source, firewood combustion.Policy decisions on environment and health could be based on established correlations among ‘emission sources-exposures-health effects’. The priority for “analysis of options and policy formulation to reduce inhalation PAHs exposure of population in Kandy” was considered “moderate to high”.     

4-壬基酚对拟柱胞藻生长、抗氧化酶和光合作用的影响及机理

为探究4-壬基酚对入侵水华蓝藻拟柱胞藻的影响,对不同浓度(0.00、0.05、0.10、0.50、1.00、2.00 mg·L~(-1)) 4-壬基酚处理96 h后的拟柱胞藻叶绿素a、抗氧化酶和光合作用进行测定。结果表明,4-壬基酚对拟柱胞藻96 h半数效应浓度(96 h-EC_(50))为0.457 mg·L~(-1)。高浓度处理(0.50 mg·L~(-1))时,拟柱胞藻叶绿素a含量、最大光合效率(F_v/F_m)、光合效率(α)、最大相对电子传递速率(rE TRmax)、半饱和光强(Ik)、RC/Cs0、ET0/RC、ΦP0、ΦE0、ψ0和Sm/t(F_m)均显著下降被显著抑制,而光合系统Ⅱ中ABS/RC、DI0/RC和TR0/RC均显著增加,同时超氧化物歧化酶(SOD)、过氧化氢酶(CAT)的活性随着浓度增加明显上升。而低浓度处理下(0.10 mg·L~(-1)),拟柱胞藻的叶绿素a含量、光合效率、最大相对电子传递速率和半饱和光强增加。这些结果表明高浓度4-壬基酚处理下,拟柱胞藻的叶绿素合成受阻,光合色素减少,光合反应中心结构受损,Q-A大量累积,光合效率下降,抑制藻细胞的光合作用,导致了拟柱胞藻生长受到阻碍,而低浓度壬基酚处理下,则可能表现出低剂量毒物兴奋效应。     

用尿中1-羟基芘评价人体暴露PAHs的肺癌风险

 采集并分析了100名不吸烟成人24h呼吸的空气样品和尿液样品,建立了人尿中1-羟基芘(1-OH-Py)浓度与苯并(a)芘(BaP)、芘(Py)等14种多环芳烃(PAHs)呼吸暴露浓度的定量关系.参考现有关于BaP空气污染浓度与肺癌死亡率的剂量-反应关系模型,推导出用尿中1-OH-Py预测人体呼吸暴露PAHs的肺癌风险模型.用建立的模型对100名受试者进行了肺癌风险评价,结果表明,一般人群BaP暴露的肺癌风险约为11/10万,焦炉工人约为160/10万;若同时考虑14种PAHs的BaP当量毒性,则其相应肺癌风险要高出约0.5倍.一般人群的尿中1-OH-Py的生物暴露限值为0.11μmol/mol肌酐,焦炉工人为1.90μmol/mol肌酐.