Trace metal geochemistry of peat under a sanitary landfill-a reconnaissance     

W. H. Mathews  R. M. Bustin 《Environmental Geology》1994,23(1):14-22

Core samples were taken at two sites from a peat deposit buried by a sanitary landfill operated by the city of Vancouver since the 1960s and from a third site where the same peat bed is not covered by landfill. Twenty-nine subsamples from the three cores were analyzed by a variety of techniques to determine the concentration of as many as 34 constituents. The content of heavy metals, the principal object of this investigation, is highest in the lower part of the peat succession, in which there is a significant amount of interbedded inorganic sediment, rather than in the upper clean bog peat. Individual layers as little as 2.5 cm thick can hold concentrations of heavy metals ten times that of the nearby layers. The heavy metal contents show a high positive correlation with those of iron and manganese and a very low correlation with sulfur. Iron from the landfill has been transported by downward percolating groundwater in solution or colloidal suspension into the lower layers of peat deposit where the passing heavy metals were sorbed. A comparison of the amounts of heavy metals stored in the peat alone with the amount leaving the whole landfill annually suggests that some metals, notably lead and arsenic, might be retained in the peat for very long periods, whereas other metals such as zinc and mercury might be quickly lost.  相似文献   

Effect of refraction of sound on bistatic doppler sodar measurements of wind profiles     

T. Mathews  D.A. Bohlender  D. Smith 《Atmospheric Research》1986,20(2-4)

Comparisons of wind profiles measured with bistatic Doppler sodars below 100 m with in-situ measurements have shown that these sodars underestimate the winds. The possibility of refracted sound contaminating the scattered signals has been investigated both experimentally and theoretically. It was found that it is unlikely that refraction of the initial sound burst is the cause of the underestimation of winds at low levels.  相似文献   

Late Pleistocene chronology and environment of the “ice-free corridor” of northwestern Alberta     

James M. White  Rolf W. Mathewes  W.H. Mathews 《Quaternary Research》1985,24(2):173-186

Pollen and macrofossil analyses of two radiocarbon-dated lake sediment cores in the upper Peace River district were used to investigate the controversial late-glacial geochronology of the “ice-free corridor.” The basal mineral-rich sediments contain reworked, radiogenically “dead” palynomorphs, as well as intrusive “modern” carbon. Analyses of the basal sediments from Boone Lake show that two ¹⁴C ages greater than 12,000 yr B.P. are spuriously old due to contamination by organic matter of Cretaceous age. The data support occlusion or near occlusion of Laurentide and Cordilleran ice in the Peace River area during the late Wisconsinan period. The sediment record began around 12.000 yr B.P. in the ice-dammed and enlarged Boone Lake. An initially open, sedge-dominated cover was invaded by sage, willow, grass, and poplar by 11,700 yr B.P., suggesting that a habitable landscape has existed in the area for at least 12 millennia. The data, however, do not support the ice-free corridor arguments of B. O. K. Reeves (1973, Arctic and Alpine Research5,1–16; 1983, In “Quaternary Coastlines and Marine Archaeology: Towards the Prehistory of Land Bridges and Continental Shelves” (P. M. Masters and N. C. Fleming, Eds.), pp. 389–411. Academic Press. New York), who suggests that ice occlusion did not occur in the Peace River Valley during the last 55,000 yr.  相似文献   

Eroding islands of Gulf of Mannar,Southeast India: a consequence of long-term impact of coral mining and climate change     

Asir  N. Gladwin Gnana  Kumar  P. Dinesh  Arasamuthu  A.  Mathews  G.  Raj  K. Diraviya  Kumar  T. K. Ashok  Bilgi  Deepak S.  Edward  J. K. Patterson 《Natural Hazards》2020,101(1):103-124

Natural Hazards - Lightning is one of the most widespread and deadly hazards in Bangladesh. Bangladesh has among the highest death rates of any country. The main objective of this study is to...  相似文献   

Range-Doppler Mapping of Space-Based Targets Using the JRO 50 MHz Radar     

S. Kesaraju  J. D. Mathews  M. Milla  J. Vierinen 《Earth, Moon, and Planets》2017,120(3):169-188

The Jicamarca Radio Observatory (JRO) two-dimensional square array radar system operating at ~ 6-m wavelength was used to study the Moon and low Earth orbit satellites using the Range-Doppler inverse synthetic aperture radar technique also known as Delay-Doppler imaging. The radar data was collected on Oct 21, 2015. A circularly polarized coded pulse was transmitted from a quarter-array antenna segment during lunar transit over JRO. Dual-linear polarization receive systems were employed on two quarter-array segments and on two 1/64th array modules giving the longest possible baselines across the transit path. A Range-Doppler mapping technique that uses the rotational motion of the targets and an autofocusing motion and ionospheric delay compensation technique has been implemented to generate the two-dimensional maps of the point-target (Satellite) and range-spread target (Moon). A review of our technique and the maps obtained from these observations is presented herein. Range-Doppler maps of the Moon and satellites are instructive with regards to possible further improvement of the technique, especially regarding ionospheric compensation.  相似文献   

GIS&T pedagogies and instructional challenges in higher education: A survey of educators     

Adam J. Mathews  Thomas A. Wikle 《Transactions in GIS》2019,23(5):892-907

Anyone involved in teaching the principles and applications of geographic information science and technology (GIS&T) understands the challenges of effective instruction within an environment subject to nearly constant change. Indeed, the dynamic nature of GIS&T introduces both new paradigms and increasingly powerful tools for exploring spatial relationships. However, while past efforts among educators and practitioners have identified knowledge and competencies important to GIS&T learning, less attention has been directed at methods used to teach GIS&T. For example, while some instructors employ traditional approaches such as lectures and structured laboratory exercises, others have shifted to active learning strategies such as “flipped classrooms” and collaborative, project‐oriented assignments. In this article, we assess the pedagogical approaches used to teach GIS&T courses through an Internet‐based survey of 318 college and university faculty. Our findings demonstrate that active learning pedagogies are becoming more firmly established, supplementing or replacing traditional teaching approaches. Contrary to our assumptions, age and teaching experience are not factors that influence the adoption of active learning strategies. Along with assessing instructional approaches, our survey identifies the challenges associated with teaching GIS&T, as identified by survey respondents.  相似文献   

Arecibo ALFA Array Observations in Search of Lunar Meteoroid-Strike EMPs     

Kesaraju  Saiveena  Mathews  John D.  Perillat  Phil 《Earth, Moon, and Planets》2019,122(3-4):95-114

Earth, Moon, and Planets - We present the preliminary results of a search for transient Electromagnetic Pulses (EMP) associated with the impact of meteoroids on the lunar surface as observed with...  相似文献   

r-Process abundance universality and actinide cosmochronology     

Kaori Otsuki  Grant J. Mathews  Toshitaka Kajino   《New Astronomy》2003,8(8):240-776

We review recent observational and theoretical results concerning the presence of actinide nuclei on the surfaces of old halo stars and their use as an age determinant. We present model calculations which show that the observed universality of abundances for 56<Z<75 elements in these stars does not necessarily imply a unique astrophysical site for the r-process. Neither does it imply a universality of abundances of nuclei outside of this range. In particular, we show that a variety of astrophysical r-process models can be constructed which reproduce the same observed universal r-process curve for 56<Z<75 nuclei, yet have vastly different abundances for Z≥75 and possibly Z<56 as well. This introduces an uncertainty into the use of the Th/Eu chronometer as a means to estimate the ages of the metal deficient stars. We do find, however, that the U/Th ratio is a robust chronometer. This is because the initial production ratio of U to Th is almost independent of the astrophysical nucleosynthesis environment. The largest remaining uncertainties in the U/Th initial production ratio are due to the input nuclear physics models.  相似文献   

RETRACTED ARTICLE: Aspect Sensitivity Considerations in Interpreting Radar Meteor Range-Spread Trail Echo Durations     

Malhotra  Akshay  Mathews  John D.  Urbina  Julio 《Earth, Moon, and Planets》2007,124(1):1-1

Earth, Moon, and Planets -  相似文献   

Cooling Flow Star Formation and the Apparent Stellar Ages of Elliptical Galaxies     

Mathews WG  Brighenti F 《The Astrophysical journal》1999,527(1):L31-L34

Simple theoretical arguments indicate that cooled interstellar gas in bright elliptical galaxies forms into a young stellar population having a bottom-heavy but optically luminous initial mass function extending to approximately 2 M middle dot in circle. When the colors and spectral features of this young population are combined with those of the underlying old stellar population, the apparent ages are significantly reduced, similar to the relatively young apparent ages observed in many elliptical galaxies. Galactic mergers are not required to resupply young stars. The sensitivity of continuous star formation to LB and LX&solm0;LB is likely to account for the observed spread in apparent ages among elliptical galaxies. Local star formation is accompanied by enhanced stellar Hbeta equivalent widths, stronger optical emission lines, more thermal X-ray emission, and lower apparent temperatures in the hot gas. The young stars should cause M&solm0;L to vary with galactic radius, perturbing the fundamental plane of the old stars alone.  相似文献