Oxidative damage to plasmid DNA induced by airborne PM10 （particulate matter with an aerodynamic diameter of 10 μm or less） is caused by the bioavailable （i.e., soluble） heavy metals on the particle surface. However, quantitative analyses of the links between PM10 and oxidative damage are limited. In this study, plasmid DNA assay and ICP-MS were applied to study oxidative capacity and trace element compositions, respectively, of summer and winter PM10 samples collected at several sites （Sun Yat Sen Municipal Park （SYSP） and Av. de Horta e Costa （AHC） on the Macao peninsula and Macao University on Tai- pa Island （TI）） in Macao. At AHC and TI, the oxidative capacity of PM10 collected in winter was higher than that collected in summer, for both the whole sample and the water-soluble fraction. In contrast, no seasonal variation was noted at SYSP. PMI0 exhibited the highest oxidative capacity at SYSP and lowest oxidative capacity at TI in both seasons, demonstrating that the PMl0 collected on the Macao peninsula had a higher toxicity than that from Taipa Island. ICP-MS analyses revealed that the concentrations of total analyzed trace elements and their water-soluble components in PMI0 from TI and AHC were higher in winter than in summer, whereas SYSP displayed the opposite trend. The extents of oxidative damage induced by the wa- ter-soluble fractions and intact whole particles were generally similar, implying that the oxidative damage caused by particles in Macao resulted mainly from the water-soluble fraction. The oxidative capacities of PM10 were positively correlated with both whole and soluble Zn at the 95% confidence level, indicating that Zn was the major element responsible for the oxidative damage caused by particles in Macao. Other heavy metals, such as Cr, Cu, Cd, Ni, As, and Pb, also exhibited elevated concen- trations, and the potential health impacts of these metals should be considered.
The sequence stratigraphy of the Jurassic coal measures of northwestern China has been studied based on data from outcrop and borehole sections. Because of the geological background and the diversity of basin types, such as isochronisms of coal seams and recognition of key sequence boundaries, it is rare to summarize and correlate sequence structure and framework. The types and recognition characteristics of the sequence boundaries of the Jurassic coal measures are revealed by comparing climatic characteristics, structural styles and the base level cycle. A total of five third-order sequences and 15 systems tracts have been subdivided and the sequence stratigraphic framework has been reconstructed confirming that the thick coals accumulated in the late stage of transgression system tracts of sequence I （SQ I） and sequence III （SQ III）. This idea is of important academic significance for instructing coal resources exploration, and enhancing geological effects of prospecting engineering. It is also of practical significance for guaranteeing construction of the large-scale coal production base in northwestern China, accelerating the westward development of the coal industry stratagem.
Based on an extensive borehole survey of the Middle Jurassic coat-bearing sequences in the Saishiteng coalfield, northern Qaidam Basin （NQB）, a total of 20 rock types and 5 sedimentary facies were identified, including braided river, meandering river, braided delta, meandering river delta, and lacustrine facies. The distribution of rock types and sedimentary facies contributed to the reconstruction of three periods＇ sedimentary facies maps of the Middle Jurassic in the Saishiteng coalfield, namely, the Dameigou age, the early Shimengou age and the late Shimengou age. That also provided the basis for the development of a three-stage depositional model of the Middle Jurassic in the NQB, indicating the lacustrine basin of the NQB in the Dameigou age and early Shimengou age were corresponding to an overfill basin, and that in the late Shimengou age was related to a balanced-fill basin. The analysis of the stability and structure of coat seams based on sedimentary facies maps showed that the preferred coal-forming facies in the Saishiteng coalfield were inter-delta bay and interdistributary bay of lower delta plain in the Dameigou age. In particular, the swamps that developed on the subaqueous pataeohigh favored the development of thick coat seams. Thus, ruinable coal seams may also be found along the Pingtai pataeohigh in the western part of the Saishiteng coalfield.
Meng LiLong- Yi ShaoLei LiuJing LuBaruch SpiroHuai-Jun WenYong-Hong Li
