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根据重力场非潮汐变化的波长特征讨论了由重复重力测量结果中提取地震前兆场信息的可能性。文中提出并应用场论理论中重力梯度场变化的二维散度可突出与地震有比较直接关系的孕震信息。通过对北祁连河西地区几次强震的分析研究,认为重力散度较好地反映了地震发生前震源区的孕震特征,是一种值得进一步研究的方法。 相似文献
855.
Knowledge of historical trends in heavy metal deposition can aid the study and impact prediction of contemporary pollution.
For this purpose, analysis of ombrotrophic peat cores has proved a valuable complement to other sedimentary analyses. However,
doubts still remain concerning the mobility of heavy metals in peat. The debate cannot be resolved until the behaviour of
these elements in peat is better understood.
Peat cores were collected from hollows and hummocks on Ringinglow Bog in the southern Pennines. The cores were sliced into
contiguous 1-cm slices. Samples were analysed for total concentrations of major elements (Al, Ca, K, Mg, Na) and trace metals
(Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) using atomic absorption spectrophotometry. Multivariate statistical analysis was conducted
on the data.
Preliminary results indicate relatively high concentrations of Cd, Cu, Fe, Pb and Zn reflecting the influence of industrial
activities in Sheffield and Manchester. As aluminium, cadmium, copper, lead and zinc exhibit similar profiles they may be
suitable surrogates for monitoring historical pollution. However, other elements (e.g. Fe, K, Mn, Na) are clearly influenced
by bog hydrology or plant translocation and would be inappropriate monitors. 相似文献
856.
亚热带小区域水平上土壤质量时空变化的定量化评价 总被引:4,自引:0,他引:4
亚热带小区域水平上土壤质量时空变化的定量化评价王效举,龚子同(中国科学院南京土壤研究所,南京210008)QuantitativeEvaluationofSoilQualityChangesinTimeandSpaceataSmallAreaLeve... 相似文献
857.
Dielectric barrier discharges (DBD) have been used in the degradation of dioxins due to the large number of excimers and free radicals produced in discharge process. In this article, the density functional theory (DFT) is used to study the degradation mechanism of octachlorinated dibenzo-p-dioxin (OCDD) with the atomic oxygen O(3P) in DBD reactor. The reactants, intermediates, transition states and products are optimized at the MPWB1K/6- 31 + G(d,p) level. The vibrational frequencies have been calculated at the same level. The reaction pathways and mechanisms are analyzed in detail. The effect of removing the chlorine atom on environment also has been discussed. 相似文献
858.
Chlorine dioxide(ClO_2) is a widely used alternative disinfectant due to its high biocidal efficiency and low-level formation of trihalomethanes and haloacetic acids. A major portion of total organic halogen(TOX), a collective parameter for all halogenated DBPs, formed in ClO_2-treated drinking water is still unknown. A commonly used pretreatment method for analyzing halogenated DBPs in drinking water is one-time liquid–liquid extraction(LLE), which may lead to a substantial loss of DBPs prior to analysis. In this study, characterization and identification of polar halogenated DBPs in a ClO_2-treated drinking water sample were conducted by pretreating the sample with multiple extractions. Compared to one-time LLE, the combined four-time LLEs improved the recovery of TOX by 2.3 times. The developmental toxicity of the drinking water sample pretreated with the combined four-time LLEs was 1.67 times higher than that pretreated with one-time LLE.With the aid of ultra-performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry, a new group of polar halogenated DBPs, trihalomethanols,were detected in the drinking water sample pretreated with multiple extractions; two of them,trichloromethanol and bromodichloromethanol, were identified with synthesized standard compounds. Moreover, these trihalomethanols were found to be the transformation products of trihalomethanes formed during ClO_2disinfection. The results indicate that multiple LLEs can significantly improve extraction efficiencies of polar halogenated DBPs and is a better pretreatment method for characterizing and identifying new polar halogenated DBPs in drinking water. 相似文献
859.
针对最新实施工业污染物排放标准,目前常规治理VOCs的工艺方法已不能达到新国标要求,中国石化安全工程研究院设计制造出针对炼化、码头和油库的油气回收的低温催化氧化中试装置,并利用此装置进行了几种典型VOCs气体的催化氧化实验,分析得到低温催化氧化中试装置对苯、二甲苯和汽油油气的治理效果理想,为实际工况下催化氧化VOCs工艺包设置提供数据支持,为低温催化氧化治理VOCs气体的工业推广应用打下了基础。 相似文献
860.
双酚A暴露对斑马鱼胚胎期代谢作用的影响 总被引:1,自引:1,他引:0
端正花 朱琳 赵娜 卜文俊 Lam Siew Hong Gong Zhiyuan 邹莉 李巍 Ong Eng Shi Ong Choon Nam 《中国环境科学》2009,29(12):1318-1322
运用基于GC/MS的代谢组学方法,以受精卵在双酚A(BPA)中暴露4d后的斑马鱼胚胎为对象,研究了其体内挥发性和半挥发性代谢组分变化.暴露浓度设定为0,0.5,1.5,4.5mg/L,包括US EPA假定的“安全水平”(1.5mg/L).结果表明,1.5mg/L BPA暴露能使斑马鱼体内花生四烯酸和胆固醇的相对百分含量极显著降低,饱和脂肪酸、氨基酸、葡萄糖和肌糖的相对百分含量显著升高.因此,1.5mg/L BPA能干扰斑马鱼胚胎期的正常代谢. 相似文献