Daily Total Column Ozone (TCO) measurements compiled from Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instruments (OMI) were used to analyze the global and hemispherical TCO interannual variations. Two periods of TCO measurements were analyzed separately covering full years. For the 1978-1994 period, the TCO showed a global decade decrease rate of 13.45 DU (about −4.3%). For the Northern Hemisphere(NH) the decade decrease rate was of 12.96 DU (−4.0%), while in the Southern Hemisphere (SH) was of 13.57 DU (−4.5%). These decreases in ozone trends, using the totality of TOMS and OMI satellite measurements, are greater than those reported in literature. The 1998-2014 period global TCO decade decrease rate was of 1.56 DU, corresponding 0.94 DU and 0.138 DU for the NH and SH, respectively. The global TCO variations must show a double annual periodicity, the first one with maxima in March due to the Northern Hemisphere (NH) and the second one during September due to the Southern Hemisphere (SH). However, the maxima due to SH TCO interannual variations have gradually vanished. A disturbance in the SH TCO interannual variations has appeared since 1980; graphically the periodicity brakes down and transforms to a double peak from 1985 and on. This effect can be attributed to the hemispheric impact of the ozone hole at the South Pole. Between October 1, 2004 and December 14, 2005 TOMS and OMI have recorded this disturbance unequivocally. We conclude that the disturbance in SH TCO has an irreversible character.
Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument OMI Version 8 data, from November 1978 to February 2013, have been used to retrieve the shape and amplitude of the daily mean of the total column ozone (TCO) and their associated dispersion over eleven selected 1°-wide latitude bands. Their inter-annual variation at 44.5° S, 23.5° S, 23.5° N, 44.5° N and 59.5° N shows a quasi-regular periodic behavior. However, Polar Regions exhibit abrupt changes, whereas at the Equator a complex perturbation of periodicity is highlighted, which could be associated to the effect of the quasi-biennial oscillation (QBO). The discrete 1°-wide latitude bands show a stabilization of TCO levels from the late nineties, but they do not display a generalized recovery. Indeed, at the Equator, between 1997 and 2013, a 1.4% per decade decrease in the total column ozone is exhibited, which may be significant given that during the 1987-1994 period the decrease was only of 0.5%. Additionally, the discrete bands reveal the appearance of a perturbation of the inter-annual ozone variations at 59.5º S, in contrast to regular behavior in the Northern Hemisphere and at other latitudes. The perturbation apparently begins in the 1980-1984 time series and is clear and systematic after 1998.
There exist potential health risks due to the presence of some elements in groundwater. This study presents measurements of gross alpha and beta activity and chemical concentrations (fluorides and nitrates) in 25 water wells in Aldama municipality, Chihuahua, Mexico. Total alpha and beta emitter analyses were performed at the Academic Unit of Nuclear Studies at the Autonomous University of Zacatecas. Radioactive elements were concentrated by total evaporation. All samples were measured with a Wallac-Oy 1411 liquid scintillate with a pulse separation option (Pulse Shape Analysis) for 6 h. Fluorine and nitrate analyses were performed at the Faculty of Engineering of the Autonomous University of Chihuahua by flow injection-hydride generation collection-atomic absorption spectrometry. Exposure levels were calculated for each well and found to exceed maximum limits allowed under Mexican law in terms of 1) gross alpha and beta activity; and 2) fluoride and nitrate concentrations. Gross alpha activity in two wells exceeded the reference value of 0.56 Bq•L −1. Fluorides and nitrates were found in 40% and 48% of water wells, respectively. Fluoride values were higher than 1.5 mg•L −1 , and the exposure doses for adults and children exceeded the reference value of 0.06 mg•kg −1 •d −1. Children are the most vulnerable, since their intake doses are near or above of 0.12 mg•kg −1 •d −1 of the minimum level of risk for the development of skeletal fluorosis or bone fractures. On the other hand, while nitrate concentrations in water wells exceeded the drinking water limit of 10 mg•L −1 , this does not represent a serious health risk, since the calculated exposure doses for adults and children are below the chronic reference level of 1.6 mg•kg −1 •d −1 established by the USEPA.
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