scholarly journals Chemical characterization of ambient aerosol collected during the northeast monsoon season over the Arabian Sea: Labile-Fe(II) and other trace metals

2003 ◽  
Vol 108 (D14) ◽  
Author(s):  
Anne M. Johansen
Keyword(s):  
Trace Metals ◽  
Arabian Sea ◽  
Monsoon Season ◽  
Chemical Characterization ◽  
Northeast Monsoon ◽  
Ambient Aerosol

scholarly journals Physico-chemical Characterization of Gosainkunda Lake

2013 ◽  
Vol 13 (1) ◽  
pp. 107-114 ◽  
Author(s):  
Rosha Raut ◽  
Subodh Sharma ◽  
Rosha M Bajracharya ◽  
Chhatra Mani Sharma ◽  
Smriti Gurung
Keyword(s):  
High Altitude ◽  
Monsoon Season ◽  
Chemical Characterization ◽  
Small Catchment ◽  
Major Cations ◽  
Physico Chemical ◽  
Bedrock Weathering ◽  
Post Monsoon Season ◽  
Cation Type

High altitude lakes are very sensitive to climate change due to their small catchment area, limited vegetation cover, surface water with low nutrients, and thin soil and low bedrock weathering rates. The present study was focused on high altitude Himalayan Lake Gosainkunda, situated at an elevation of 4300 m in the Langtang National Park, and carried out during the post- monsoon season (October) in 2010. The main aim of the study was to assess the water quality quantitatively considering the anthropogenic as well as natural impacts in the lake. The water samples were collected at six different sites to represent entirely the quality of the lake. The sampling sites were systematically designated as the inlet, outlet, human influence site, littoral zone, middle (central) and the deepest part of the lake. Some major cations (Ca++, Mg++, Na+ & K+) and anions (Cl-, SO4 — & HCO3 -) were analyzed; the cation type is dominated by Ca++ (64%) while the anions are dominated by Cl- (49%). Among the trace elements (Al, Fe, Mn, Zn, Cu, Cd, Cr, Ni, Pb & As), except for Al and Fe, all others were found below the detection limit. Nepal Journal of Science and Technology Vol. 13, No. 1 (2012) 107-114 DOI: http://dx.doi.org/10.3126/njst.v13i1.7449

scholarly journals Chemical characterization of wintertime aerosols over the Arabian Sea: Impact of marine sources and long-range transport

2020 ◽  
Vol 239 ◽  
pp. 117749
Author(s):  
Poonam Bikkina ◽  
V.V.S.S. Sarma ◽  
Kimitaka Kawamura ◽  
Srinivas Bikkina ◽  
Bhagawati Kunwar ◽  
...  
Keyword(s):  
Long Range ◽  
Arabian Sea ◽  
Chemical Characterization ◽  
Long Range Transport ◽  
Range Transport

scholarly journals Oxygen minimum zone of the open Arabian Sea: variability of oxygen and nitrite from daily to decadal time scales

2013 ◽  
Vol 10 (9) ◽  
pp. 15455-15517 ◽  
Author(s):  
K. Banse ◽  
S. W. A. Naqvi ◽  
P. V. Narvekar ◽  
J. R. Postel ◽  
D. A. Jayakumar
Keyword(s):  
Arabian Sea ◽  
Monsoon Season ◽  
Temporal Trends ◽  
Southwest Monsoon ◽  
Oxygen Minimum Zone ◽  
Northeast Monsoon ◽  
Endpoint Detection ◽  
N2o Production ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. The oxygen minimum zone (OMZ) of the Arabian Sea is the thickest of the three oceanic OMZs, which is of global biogeochemical significance because of denitrification in the upper part leading to N2 and N2O production. The residence time of the OMZ water is believed to be less than a decade. The upper few hundred meters of this zone are nearly anoxic but non-sulfidic and still support animal (metazoan) pelagic life, possibly as a result of episodic injections of O2 by physical processes. The very low O2 values obtained with the new STOX sensor in the eastern tropical South Pacific probably also characterize the Arabian Sea OMZ, but there is no apparent reason as to why the temporal trends of the historic data should not hold. We report on discrete measurements of dissolved O2 and NO2-, besides temperature and salinity, made between 1959 and 2004 well below the tops of the sharp pycno- and oxyclines near 150, 200, 300, 400, and 500 m depth. We assemble nearly all O2 determinations (originally, 849 values, 695 in the OMZ) by the visual endpoint detection of the iodometric Winkler procedure, which in our data base yields about 0.04 mL L−1 (∼2 μM) O2 above the endpoint from modern automated titration methods. We find 632 values acceptable (480 from 150 stations in the OMZ). The data are grouped in zonally-paired boxes of 1° lat. and 2° long. centered at 8°, 10°, 12°, 15°, 18°, 20°, and 21° N along 65° E and 67° E. The latitudes of 8–12° N, outside the OMZ, are only treated in passing. The principal results are as follows: (1) an O2 climatology for the upper OMZ reveals a marked seasonality at 200 to 500 m depth with O2 levels during the northeast monsoon and spring intermonsoon season elevated over those during the southwest monsoon season (median difference, 0.08 mL L−1 [3.5 μM]). The medians of the slopes of the seasonal regressions of O2 on year for the NE and SW monsoon seasons are −0.0043 and −0.0019 mL L−1 a−1, respectively (−0.19 and −0.08 μM a−1; n = 10 and 12, differing at p = 0.01); (2) four decades of statistically significant decreases of O2 between 15° and 20° N but a trend to a similar increase near 21° N are observed. The balance of the mechanisms that more or less annually maintain the O2 levels are still uncertain. At least between 300 and 500 m the annual reconstitution of the decrease is inferred to be due to lateral, isopycnal re-supply of O2, while at 200 (250?) m it is diapycnal, most likely by eddies. Similarly, recent models show large vertical advection of O2 well below the pycno-cum-oxycline. The spatial (within drift stations) and temporal (daily) variability in hydrography and chemistry is large also below the principal pycnocline. The seasonal change of hydrography is considerable even at 500 m. There is no trend in the redox environment for a quarter of a century at a GEOSECS station near 20° N. In the entire OMZ the slopes on year within seasons for the quite variable NO2- (taken as an indicator of active denitrification) do not show a clear pattern. Also, future O2 or nutrient budgets for the OMZ should not be based on single cruises or sections obtained during one season only. Steady state cannot be assumed any longer for the intermediate layers of the central Arabian Sea.

scholarly journals Oxygen minimum zone of the open Arabian Sea: variability of oxygen and nitrite from daily to decadal timescales

2014 ◽  
Vol 11 (8) ◽  
pp. 2237-2261 ◽  
Author(s):  
K. Banse ◽  
S. W. A. Naqvi ◽  
P. V. Narvekar ◽  
J. R. Postel ◽  
D. A. Jayakumar
Keyword(s):  
Arabian Sea ◽  
Oxygen Sensor ◽  
Monsoon Season ◽  
Temporal Trends ◽  
Southwest Monsoon ◽  
Oxygen Minimum Zone ◽  
Northeast Monsoon ◽  
N2o Production ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. The oxygen minimum zone (OMZ) of the Arabian Sea is the thickest of the three oceanic OMZ. It is of global biogeochemical significance because of denitrification in the upper part leading to N2 and N2O production. The residence time of OMZ water is believed to be less than a decade. The upper few hundred meters of this zone are nearly anoxic but non-sulfidic and still support animal (metazoan) pelagic life, possibly as a result of episodic injections of O2 by physical processes. We report on discrete measurements of dissolved O2 and NO2–, temperature and salinity made between 1959 and 2004 well below the tops of the sharp pycnocline and oxycline near 150, 200, 300, 400, and 500 m depth. We assemble nearly all O2 determinations (originally there were 849 values, 695 of which came from the OMZ) by the visual endpoint detection of the iodometric Winkler procedure, which in our data base yields about 0.04 mL L−1 (~ 2 μM) O2 above the endpoint from modern automated titration methods. We acknowledge that much lower (nanomolar) O2 values have been measured recently with the STOX (Switchable Trace amount OXygen) sensor in the eastern tropical South Pacific, and that similar conditions may also prevail in the Arabian Sea OMZ. In spite of the error in O2 measurements at vanishingly low levels, we argue that the temporal trends of the historic data should still hold. We find 632 values acceptable (480 from 150 stations in the OMZ). The data are grouped in zonally paired boxes of 1° lat. and 2° long. centered at 8, 10, 12, 15, 18, 20, and 21° N along 65 and 67° E. The latitudes of 8–12° N, outside the OMZ, are treated in passing. The principal results are as follows: (1) an O2 climatology for the upper OMZ reveals a marked seasonality at 200 to 500 m depth with O2 levels during the northeast monsoon and spring intermonsoon seasons elevated over those during the southwest monsoon season (median difference, 0.08 mL L−1 [~ 3.5 μM]). The medians of the slopes of the seasonal regressions of O2 on year for each of the NE and SW monsoon seasons are −0.0043 and −0.0019 mL L−1 a−1, respectively (−0.19 and −0.08 μM a−1; n = 10 and 12, differing at p = 0.01); (2) four decades of statistically significant decreases of O2 between 15 and 20° N but an opposing trend toward an increase near 21° N are observed. The mechanisms of the balance that more or less annually maintain the O2 levels are still uncertain. At least between 300 and 500 m, the replenishment is inferred to be due to isopycnal re-supply of O2, while at 200 (or 250?) m it is diapycnal, most likely by eddies. Similarly, recent models show large vertical advection of O2 well below the pycnoclines and oxyclines. The NO2– distribution, taken as an indicator of active NO3– reduction, does not show a trend in the redox environment for a quarter of a century at a GEOSECS station near 20° N. In the entire OMZ, the regression slopes on year within seasons for the rather variable NO2– do not present a clear pattern but by other measures tended to an increase of NO2–. Vertical net hauls collect resident animal (metazoan) pelagic life in the NO2– maximum of the OMZ at O2 levels well below the lower limit of the Winkler titration; the extremely low O2 content is inferred from the presence of NO2– believed to be produced through microbial NO3– reduction. Instead of the difficult measurement by the STOX sensor, the relation between the very low O2 inferred from presence of NO2– and mesozooplankton should be studied with 100 to 150 L bottles rather than nets. The spatial (within drift stations) and temporal (daily) variability in hydrography and chemistry is large also below the principal pycnocline. The seasonal change of hydrography is considerable even at 500 m depth. Future O2 or nutrient budgets for the OMZ must not be based on single cruises or sections obtained during one season only. Steady state cannot be assumed any longer for the intermediate layers of the central Arabian Sea.

Olfactory and Chemical Characterization of Indoor Air-Towards a Psychophysical Model for Air Quality

1981 ◽  
Author(s):  
Birgitta Berglund ◽  
Ulf Berglund ◽  
Thomas Lindvall ◽  
Helene Nicander-Bredberg
Keyword(s):  
Air Quality ◽  
Indoor Air ◽  
Chemical Characterization
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