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In recent years, Beijing has been shown to suffer one of the most serious air pollution problems of any major world city. The concentrations of particulate matter (PM) pollutants, PM 2.5–10 and PM 2.5 , are commonly used as air pollution indexes. We conducted a detailed environmental magnetism study to investigate possible sources of air pollution in Beijing, China, using 283 pairs of the PM 2.5 and PM 2.5–10 samples collected daily from July 2010 to June 2011. Rock magnetic measurements, including magnetic susceptibility, anhysteretic remanent magnetization, isothermal remanent magnetization, saturation isothermal remanent magnetization, hysteresis loops, first-order reversal curves (FORCs), and thermomagnetism, indicate that the main magnetic mineral is low-coercivity pseudo-single domain (PSD) magnetite. Scanning electron microscope (SEM) observations and energy dispersive X-ray spectroscopy (EDS) analyses on the PM indicate that the major magnetic phase is coarse-grained magnetite, which is most likely from automobile exhausts and braking system debris. Magnetic parameters of PM 2.5 and PM 2.5–10 show significant seasonal patterns that may be attributed to domestic heating enhancing magnetization of the PM during late autumn to early spring. Power spectral analyses and box–whisker plots indicate that the magnetic parameters have strong weekly variations that may be due to traffic emissions. These results indicate that magnetic parameters can be used as efficient proxies for monitoring Beijing's air pollution, and that the atmospheric environment may be improved by controlling vehicle emissions. [ABSTRACT FROM AUTHOR]

In contrast with its decrease in western China deserts, the dust storm event in eastern China, Korea, and Japan shows an increase in frequency. Although the drylands in northeastern China have been recognized as an important dust source, the relative contributions of dust transport from the drylands and deserts are inconclusive, thus the quantification of dust storm sources in downwind area remains a challenge. We measured the 14 C and 13 C contents in carbonates of dust samples from six sites in China, which were collected for the duration of dust storm events in drylands, deserts, and urban areas. The δ 13 C of the dryland dust samples considerably varied in a range of − 9.7 to − 5.0‰, which partly overlapped the desert dust carbonate δ 13 C ranges. The 14 C content of the dryland dust carbonates showed a narrow range of 60.9 ± 4.0 (as an average and 1 SD of five samples) percent modern carbon (pMC), indicating the enrichment of modern carbonate. Dust samples in desert regions contained relatively aged carbonates with the depleting 14 C showing of 28.8 ± 3.3 pMC. After the long-range transport of the western China desert dust plume, the carbonates collected at the southern China remained the depletion of 14 C (33.5 ± 5.3 pMC) as in the desert regions. On the other hand, the samples of dust storm events at the urban areas of eastern China showed an enrichment of 14 C contents (46.2 ± 5.0 pMC, n = 7), which might be explained by the stronger contribution of modern-carbonate-rich dryland dust. [ABSTRACT FROM AUTHOR]

The Ocean Drilling Program (ODP) Leg 184 recovered a continuous sedimentary sequence since Miocene at Site 1148 in the northern South China Sea (SCS), which provided a unique record for better understanding the tectonic, environmental and climatic evolution of the SCS. In this study, we report a detailed paleomagnetic study on 881 discrete samples from the upper 460 m cores of Hole 1148A through stepwise alternating field demagnetization (AF) or thermal demagnetization (TD). Rock magnetic results from isothermal remanent magnetization (IRM) acquisition, temperature dependence magnetic susceptibility (κ-T) and hysteresis loop parameters of representative samples indicate that the main magnetic mineral is low coercivity pseudo-single domain magnetite. The characteristic remanent magnetization (ChRM) with moderate downward or upward inclinations was identified after removing a low-stability drilling-induced remanence with steep downward inclinations. A new 23 Myr magnetostratigraphic time framework was established by correlating the magnetic polarity sequence to the Geomagnetic Polarity Time Scale 2012 (GPTS 2012; Ogg, 2012 ) in combination with biostratigraphic data. The mean sediment accumulation rates for lithostratigraphic Units V and IV, Unit III and lower Unit II, upper Unit II, Unit IB and Unit IA are calculated as ∼20.8 m/Myr, ∼15–17 m/Myr, 24.18 m/Myr, 17.07 m/Myr and 49.01 m/Myr, respectively. [ABSTRACT FROM AUTHOR]