• Energy Research

Abstract The ecological environment of the Loess Plateau in Northern Shaanxi is fragile, and the soil pollution caused by the development of coal resources can not be ignored. in this study, Shigetai Coal Mine in the Loess Plateau of Northern Shaanxi was selected for field investigation and sampling, the content of heavy metals in soil was analyzed, the environmental pollution status in the study area was evaluated by single factor pollution index method, comprehensive pollution index method and potential ecological risk index method, and the spatial distribution characteristics of heavy metals were discussed by geostatistics method. The results show that the average contents of heavy metals Hg, Cd, Pb and Cr are 2.03, 1.36, 1.11 and 1.23 times of the soil background value of Shaanxi Province, respectively. The average contents of other heavy metals are lower than the soil background value of Shaanxi Province. Hg and Cd show medium variation, as, Pb, Cr, Zn, Ni and Cu show strong variation. The skewness coefficient and kurtosis coefficient of soil Cd, as and Cu in the study area are high, In cumulative state. Single factor pollution index (Pi) and potential ecological risk index (E) show that heavy metal Hg is the main pollution factor, mainly concentrated in the East and north of the study area. The comprehensive index of potential ecological risk (RI) in the study area is 1336.49, showing a very high ecological risk, and its distribution characteristics are consistent with the distribution of potential ecological risk index (E) of Hg. The ecological risk early warning results show that Hg is in the light warning situation, Cd, Pb and Cr are in the early warning situation, the high value area of ecological risk early warning in the study area is mainly distributed in the East and North, and the whole study area presents an obvious zonal distribution law. In the process of coal mining, the soil is greatly disturbed. The ecological management of the mining area should be combined with the local natural conditions and regional environmental characteristics, and according to the principle of "adjusting measures to local conditions and implementing measures by classification". Adopt an environmentally sustainable approach to governance to achieve eco-environmental protection and high-quality development of coal resources.

Abstract We present 294 pulsars found in GeV data from the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope. Another 33 millisecond pulsars (MSPs) discovered in deep radio searches of LAT sources will likely reveal pulsations once phase-connected rotation ephemerides are achieved. A further dozen optical and/or X-ray binary systems colocated with LAT sources also likely harbor gamma-ray MSPs. This catalog thus reports roughly 340 gamma-ray pulsars and candidates, 10% of all known pulsars, compared to ≤11 known before Fermi. Half of the gamma-ray pulsars are young. Of these, the half that are undetected in radio have a broader Galactic latitude distribution than the young radio-loud pulsars. The others are MSPs, with six undetected in radio. Overall, ≥236 are bright enough above 50 MeV to fit the pulse profile, the energy spectrum, or both. For the common two-peaked profiles, the gamma-ray peak closest to the magnetic pole crossing generally has a softer spectrum. The spectral energy distributions tend to narrow as the spindown power E ̇ decreases to its observed minimum near 1033 erg s−1, approaching the shape for synchrotron radiation from monoenergetic electrons. We calculate gamma-ray luminosities when distances are available. Our all-sky gamma-ray sensitivity map is useful for population syntheses. The electronic catalog version provides gamma-ray pulsar ephemerides, properties, and fit results to guide and be compared with modeling results.