Mathematics – Logic
Scientific paper
Oct 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011gecoa..75.5367e&link_type=abstract
Geochimica et Cosmochimica Acta, Volume 75, Issue 19, p. 5367-5388.
Mathematics
Logic
Scientific paper
Activity concentrations of the naturally occurring, short-lived and highly particle-reactive radionuclide tracer 234 Th in the dissolved and particulate phase were determined at 7 shallow-water stations (maximum depths: 30 (S.1 and S.2), 65 (S.3), 97 (S.5), 105 (S.6) and 220 m (S.4 and S.7) in Saronikos Gulf and Elefsis Bay (central Aegean Sea, Greece) during 3 seasonal cruises (summer 2008, autumn 2008 and winter 2009) to assess the time scales of the dynamics and the depositional fate of particulate matter (POC, particulate 234 Th). For that reason, in situ filtrating systems were deployed in several depths of the water column consisting of GF/A disc prefilters to scavenge particulate fraction of 234 Th and organic carbon and impregnated cartridges to adsorb dissolved 234 Th. The obtained data showed average particulate 234 Th activity concentrations of 3.7 ± 0.4 Bq m -3 in summer, 2.1 ± 0.2 Bq m -3 in autumn and 2.4 ± 0.2 Bq m -3 in winter. The respective average dissolved 234 Th activity concentrations were 30.1 ± 2.8 Bq m -3 in summer, 30.2 ± 2.9 Bq m -3 in autumn and 27.4 ± 3.0 Bq m -3 in winter. The activity ratios of total 234 Th and its long-lived conservative parent 238 U were below unity in most of the stations indicating radioactive disequilibrium throughout the water column, thus very dynamic trace-metal scavenging and particle export from the water column. These profiles ( 234 Th and 238 U) were used to estimate the export fluxes and scavenging rates of 234 Th, as well as their residence times in the water column. The average cumulative export fluxes of particulate 234 Th were estimated to be 33 ± 4 Bq m -2 d -1 in summer, 35 ± 5 Bq m -2 d -1 in autumn and 45 ± 6 Bq m -2 d -1 in winter, whereas the respective average cumulative scavenging rates of dissolved 234 Th were 39 ± 5, 33 ± 5 and 50 ± 7 Bq m -2 d -1 . Moreover, the cumulative average residence times of 234 Th were 25 ± 4 d in summer, 45 ± 6 d in autumn and 64 ± 7 d in winter 2009 for the dissolved fraction and 4 ± 1, 3 ± 1 and 4 ± 1 d for the particulate one, respectively. POC/ A Th p ratio profiles decreased versus depth showing a variety of marine processes, such as loss of POC due to dissolution after biological activity, impact of minerals in particle sinking and microbial remineralization. Average cumulative export fluxes of POC were 162 ± 18 mmol m -2 d -1 in summer, 107 ± 19 mmol m -2 d -1 in autumn and 157 ± 25 mmol m -2 d -1 in winter 2009. The seasonal data of POC fluxes certified the existence of phytoplankton bloom in winter for Saronikos Gulf. In addition, after evaluating the maxima of POC fluxes in Elefsis Bay (a small embayment in northern Saronikos Gulf) during summer, potential bloom of phytoplankton also concluded; this approach is in agreement with previous data of the same area. Finally, the elevated POC concentrations and fluxes in the region certify that the Gulf is still one of the most organic polluted in the Mediterranean Sea.
Evangeliou Nikolaos
Florou Heleny
Scoullos Michael
No associations
LandOfFree
POC and particulate 234 Th export fluxes estimated using 234 Th/ 238 U disequilibrium in an enclosed Eastern Mediterranean region (Saronikos Gulf and Elefsis Bay, Greece) in seasonal scale does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with POC and particulate 234 Th export fluxes estimated using 234 Th/ 238 U disequilibrium in an enclosed Eastern Mediterranean region (Saronikos Gulf and Elefsis Bay, Greece) in seasonal scale, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and POC and particulate 234 Th export fluxes estimated using 234 Th/ 238 U disequilibrium in an enclosed Eastern Mediterranean region (Saronikos Gulf and Elefsis Bay, Greece) in seasonal scale will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1489074