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- Nakagawa, Kei, et al.
(författare)
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Use of sterols to monitor surface water quality change and nitrate pollution source
- 2019
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Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X. ; 107
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Tidskriftsartikel (refereegranskat)abstract
- Coprostanol was tested as ecological indicator to trace domestic and manure effluents and to investigate possible pollution sources in surface water. Pollution assessment was performed by analysing NO3 −, NO2 −, coprostanol (5β(H)-Cholestan-3β-ol), and cholestanol (5α(H)-Cholestan-3β-ol) in water samples from 42 sites along rivers in Shimabara and Unzen City, Japan. NO2-N concentration exceeded 0.04 mg L−1 at 2 sampling sites during winter and 6 sampling sites during summer. NO3 + NO2-N concentration exceeded 10 mg L−1 at 19 sampling sites during winter and 7 sampling sites during in summer. The highest concentration was 82.4 mg L−1 in summer. Detectable NO3-N concentration was observed in northern parts of the study area. Coprostanol concentration exceeded 700 ng L−1 (Australian Drinking Water Standard) at 8 sampling points during winter and 6 sampling sites during summer. At 10 and 5% of the sampling sites, both nitrate and coprostanol concentration exceeded drinking water standard during winter and summer, respectively. The percentage of sampling sites where either concentration was above drinking water standard was 45% during winter and 22% during summer season. However, depending on sampling site, the relationships between nitrate and coprostanol concentrations showed different patterns. The sterol ratio exceeded 0.5 at 17 sampling sites during winter and 14 sampling sites during summer. Thus, it was confirmed that fecal pollution is present in the studied surface water. A method to distinguish between principal pollution sources was developed by separating four areas in a nitrate concentration and sterol ratio plot. Results show that sampled data could be reasonably classified into appropriate polluted/non-polluted groups. Thus, coprostanol and sterol ratio can be used as indicators to distinguish between different nitrate pollution sources in surface water.
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| 2. |
- Rich, Evan A., et al.
(författare)
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Multi-epoch Direct Imaging and Time-variable Scattered Light Morphology of the HD 163296 Protoplanetary Disk
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 875:1
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Tidskriftsartikel (refereegranskat)abstract
- We present H-band polarized scattered light imagery and JHK high-contrast spectroscopy of the protoplanetary disk around HD 163296 observed with the High-Contrast Coronographic Imager for Adaptive Optics (HiCIAO) and Subaru Coronagraphic Extreme Adaptive Optics (SCExAO)/Coronagraphic High Angular Resolution Imaging Spectrograph (CHARTS) instruments at Subaru Observatory. The polarimetric imagery resolve a broken ring structure surrounding HD 163296 that peaks at a distance along the major axis of 0 ''.65 (66 au) and extends out to 0 ''.98 (100 au) along the major axis. Our 2011 H-band data exhibit clear axisymmetry, with the NW and SE side of the disk exhibiting similar intensities. Our data are clearly different from 2016 epoch H-band observations of the Very Large Telescope (VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), which found a strong 2.7 x asymmetry between the NW and SE side of the disk. Collectively, these results indicate the presence of time-variable, non-azimuthally symmetric illumination of the outer disk. While our SCExAO/CHARIS data are sensitive enough to recover the planet candidate identified from NIRC2 in the thermal infrared (IR), we fail to detect an object with JHK brightness nominally consistent with this object. This suggests that the candidate is either fainter in JHK bands than model predictions, possibly due to extinction from the disk or atmospheric dust/clouds, or that it is an artifact of the data set/data processing, such as a residual speckle or partially subtracted disk feature. Assuming standard hot-start evolutionary models and a system age of 5 Myr, we set new, direct mass limits for the inner (outer) Atacama Large Millimeter/submillimeter Array (ALMA)-predicted protoplanet candidate along the major (minor) disk axis of of 1.5 (2) M-J.
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