1] Ground-based aerosol optical measurements were conducted within the framework of the Aerosol R... more 1] Ground-based aerosol optical measurements were conducted within the framework of the Aerosol Robotic Network (AERONET) program at the IMS-METU site at Erdemli (36°33 0 N, 34°15 0 E) along the Turkish coast of the northeastern Mediterranean from January 2000 to June 2001. The measurements were used to identify and define predominant regional aerosol optical properties, with an emphasis on mineral dust intrusion events. Dust storms affecting the region primarily originate from the central Sahara in spring, the eastern Sahara in summer, and the Middle East/Arabian peninsula in autumn. Summer and autumn dust intrusions usually occurred at higher altitudes (above 700 hPa), whereas urban-industrial aerosols from the north over the Balkan region, Ukraine, and Anatolia were transported to the region at lower altitudes. In addition to a drastic increase in the aerosol optical thickness, in some cases up to 1.8, the dust episodes were characterized by (1) a sharp drop in the Å ngstrom coefficient to values near zero, (2) a high-scattering with single-scattering albedo greater than 0.95 ± 0.03, and the real part of the refractive index around 1.5 ± 0.5, both of which acquire slightly higher values at longer wavelengths, (3) a lower absorption given by the imaginary part of the refractive index less than 0.002, and (4) an almost neutral spectral dependence of these parameters. Dust particles possessed a bimodal size distribution with typical volume mean radii of 2.2 mm and 0.08 mm for coarse and fine size fractions, respectively, and corresponding volume concentrations of about 1.0 and 0.1 mm 3 mm À2 of dust particles. It was apparent that the Saharan and Middle East desert dusts differ in their absorption index values (0.0015 and 0.0005, respectively). The difference is likely a result of their contrasting mineralogies. Citation: Kubilay, N., T. Cokacar, and T. Oguz, Optical properties of mineral dust outbreaks over the northeastern Mediterranean,
2) Institute of 1. INTRODUCION Pulses of mineral aerosols originating from North Africa reach the... more 2) Institute of 1. INTRODUCION Pulses of mineral aerosols originating from North Africa reach the Mediterranean region, and their micro-(such as Fe, Zn, Mn, Co, Ni) (Kubilay, 1996) and macro-nutrient (such as PO4 3− and NO3 −) content (Talbot et al., 1986; Bergametti et al., 1992; Migon and Sandroni, 1999; Herut et al., 1999) supposedly could contribute to marine biological production through time-dependent biogeochemical processes (Quetel et al.,1993). Among these nutrients, PO 4 3− is known to be the limiting nutrient for phytoplankton production in the Mediterranean and as a result of this limitation Eastern Mediterranean marine environment is characterised with a high N:P ratio near the sea surface (Krom et al., 1991). In order to estimate wet and dry deposition atmospheric fluxes of macro-nutrients into the eastern Mediterranean coastal waters, soluble inorganic phosphate (PO 4 3-), nitrate (NO 3 -) and nitrite (NO 2 -) concentrations in precipitation (from February 1996 to Jun...
Aerosol and rain samples were collected at a rural site located on the coastline of the Eastern M... more Aerosol and rain samples were collected at a rural site located on the coastline of the Eastern Mediterranean, Erdemli, Turkey between January 1999 and December 2007. Riverine sampling was carried out at five Rivers (Ceyhan, Seyhan, Göksu, Berdan and Lamas) draining into the Northeastern Levantine Basin (NLB) between March 2002 5 and July 2007. Samples were analyzed for macronutrients of phosphate, silicate, nitrate and ammonium (PO 3− 4 , Si diss , NO − 3 and NH + 4 ). Phosphate and silicate in aerosol and rainwater showed higher and larger variation during the transitional period (March-May, September) when air flows predominantly originate from North Africa and Middle East/Arabian Peninsula. Deficiency of alkaline material were found to be the main 10 reason of the acidic rain events whilst high pH values (>7) were associated with high Si diss concentrations due to sporadic dust events. In general, lowest nitrate and ammonium concentrations in aerosol and rainwater were associated with air flow from the Mediterranean Sea. Unlike NO − 3 and NH + 4 (Dissolved Inorganic Nitrogen, DIN), there were statistical differences for PO 3− 4 and Si diss solubilities in sea-water and pure-water.
In recent years the increasing use of organotin compounds in industry and agriculture, together w... more In recent years the increasing use of organotin compounds in industry and agriculture, together with the development of sensitive and precise analytical techniques for the quantitative speciation of organotin compounds at environmental levels, have created ...
Total and dissolved inorganic phosphorus (IP) was measured in both rainwater and aerosol samples ... more Total and dissolved inorganic phosphorus (IP) was measured in both rainwater and aerosol samples collected from two remote coastal areas: on the island of Crete (Greece) and at Erdemli (Turkey). Particle size distributions of P, as well as total deposition were also measured. Wet and dry deposition of dissolved inorganic phosphorus (DIP) from Crete are compared with simultaneously obtained dissolved inorganic nitrogen (DIN) and with productivity data from the literature. Our results indicate that (1) in both wet and dry deposition, the DIN/DIP molar ratio ranges between 63 and 349, exceeding by a factor of up to 22 the N/P ratio observed in seawater (ranging from 25 to 28) and (2) atmospheric deposition of DIP could reasonably account for a significant part of the new production (up to 38%) observed during the summer and autumn period (i.e., when water stratification is at its maximum).
1] Ground-based aerosol optical measurements were conducted within the framework of the Aerosol R... more 1] Ground-based aerosol optical measurements were conducted within the framework of the Aerosol Robotic Network (AERONET) program at the IMS-METU site at Erdemli (36°33 0 N, 34°15 0 E) along the Turkish coast of the northeastern Mediterranean from January 2000 to June 2001. The measurements were used to identify and define predominant regional aerosol optical properties, with an emphasis on mineral dust intrusion events. Dust storms affecting the region primarily originate from the central Sahara in spring, the eastern Sahara in summer, and the Middle East/Arabian peninsula in autumn. Summer and autumn dust intrusions usually occurred at higher altitudes (above 700 hPa), whereas urban-industrial aerosols from the north over the Balkan region, Ukraine, and Anatolia were transported to the region at lower altitudes. In addition to a drastic increase in the aerosol optical thickness, in some cases up to 1.8, the dust episodes were characterized by (1) a sharp drop in the Å ngstrom coefficient to values near zero, (2) a high-scattering with single-scattering albedo greater than 0.95 ± 0.03, and the real part of the refractive index around 1.5 ± 0.5, both of which acquire slightly higher values at longer wavelengths, (3) a lower absorption given by the imaginary part of the refractive index less than 0.002, and (4) an almost neutral spectral dependence of these parameters. Dust particles possessed a bimodal size distribution with typical volume mean radii of 2.2 mm and 0.08 mm for coarse and fine size fractions, respectively, and corresponding volume concentrations of about 1.0 and 0.1 mm 3 mm À2 of dust particles. It was apparent that the Saharan and Middle East desert dusts differ in their absorption index values (0.0015 and 0.0005, respectively). The difference is likely a result of their contrasting mineralogies. Citation: Kubilay, N., T. Cokacar, and T. Oguz, Optical properties of mineral dust outbreaks over the northeastern Mediterranean,
An established three stage sequential leach scheme was applied to a series of selected high volum... more An established three stage sequential leach scheme was applied to a series of selected high volume aerosol samples (n=35) collected from the Turkish Eastern Mediterranean coastline (Erdemli). Samples were selected according to their air mass back trajectory history to reflect the contrasting mixtures of aerosol material present in the Eastern Mediterranean marine aerosol. Two populations were adopted, those samples which were classed as "anthropogenic" and those which were "Saharan" dominated aerosol populations. Applying the three stage leach it was possible to define the proportion for each of the considered metals (Al, Fe, Cu, Pb, Cd, Zn and Mn) present in the (a) "exchangeable" (b) "carbonate / oxide" and (c) "refractory" phases, representing novel solid state aerosol speciation data for this marine system. Clear trends were established, conforming with data from previous studies with mainly crustal derived metals (Al and Fe) being present in the refractory phases (Al>88%; Fe>84%) and those influenced by anthropogenic sources being dominating in the exchangeable phase, although for these metals the variability was comparatively high (12-64%; 19-85%; 40-100% for Zn, Pb and Cd, respectively). For the majority, greater exchangeable fractions were present the lower the crustal source contribution to the aerosol population, whereas the "refractory" fraction exhibited contrasting behaviour. This was illustrated by the novel application of the mixing diagram, presenting each of the three speciation stages against the corresponding percent anthropogenic contribution to each collected sample. Zn, Pb and Cd all illustrated progressive decrease in the percent exchangeable with increasing crustal contribution to the aerosol population. The percent exchangeable was discussed in terms of its use to represent the upper limit of the bioavailable fraction of metal associated with the aerosol, post deposition. The mixing diagram approach enabled the prediction of the residual fractions for Cd, Pb and Zn (41±4%; 62±4% and 82±5%, respectively,) in Saharan end-member material.
1] A worldwide compilation of atmospheric total phosphorus (TP) and phosphate (PO 4 ) concentrati... more 1] A worldwide compilation of atmospheric total phosphorus (TP) and phosphate (PO 4 ) concentration and deposition flux observations are combined with transport model simulations to derive the global distribution of concentrations and deposition fluxes of TP and PO 4 . Our results suggest that mineral aerosols are the dominant source of TP on a global scale (82%), with primary biogenic particles (12%) and combustion sources (5%) important in nondusty regions. Globally averaged anthropogenic inputs are estimated to be $5 and 15% for TP and PO 4 , respectively, and may contribute as much as 50% to the deposition over the oligotrophic ocean where productivity may be phosphorus-limited. There is a net loss of TP from many (but not all) land ecosystems and a net gain of TP by the oceans (560 Gg P a À1 ). More measurements of atmospheric TP and PO 4 will assist in reducing uncertainties in our understanding of the role that atmospheric phosphorus may play in global biogeochemistry. Citation: Mahowald, N., et al. (2008), Global distribution of atmospheric phosphorus sources, concentrations and deposition rates, and anthropogenic impacts, Global Biogeochem. Cycles, 22, GB4026,
1] Since iron is an important micronutrient, deposition of iron in mineral aerosols can impact th... more 1] Since iron is an important micronutrient, deposition of iron in mineral aerosols can impact the carbon cycle and atmospheric CO 2 . This paper reviews our current understanding of the global dust cycle and identifies future research needs. The global distribution of desert dust is estimated from a combination of observations of dust from in situ concentration, optical depth, and deposition data; observations from satellite; and global atmospheric models. The anthropogenically influenced portion of atmospheric desert dust flux is thought to be smaller than the natural portion, but is difficult to quantify due to the poorly understood response of desert dust to changes in climate, land use, and water use. The iron content of aerosols is thought to vary by a factor of 2, while the uncertainty in dust deposition is at least a factor of 10 in some regions due to the high spatial and temporal variability and limited observations. Importantly, we have a limited understanding of the processes by which relatively insoluble soil iron (typically $0.5% is soluble) becomes more soluble (1-80%) during atmospheric transport, but these processes could be impacted by anthropogenic emissions of sulfur or organic acids. In order to understand how humans will impact future iron deposition to the oceans, we need to improve our understanding of: iron deposition to remote oceans, iron chemistry in aerosols, how desert dust sources will respond to climate change, and how humans will impact the transport of bioavailable fraction of iron to the oceans.
1] Methanesulfonate (MSA) and non-sea-salt (nss) sulfate concentrations were measured in bulk aer... more 1] Methanesulfonate (MSA) and non-sea-salt (nss) sulfate concentrations were measured in bulk aerosol samples collected during January 1996 to December 1999 at two stations along the Turkish and Cretan coastline of the eastern Mediterranean. The data set enabled the origin and variability of biogenically derived sulfate concentrations in the eastern Mediterranean atmosphere to be defined. Although similar seasonal patterns of MSA and nss-sulfate concentrations for both stations were detected, the mean concentrations at Erdemli (Turkey) over the sampling period (42 ± 52 ng m À3 MSA, and 6.8 ± 5.2 mg m À3 nss sulfate) were found to be almost twice that of those measured at Finokalia, Crete (25.8 ± 14.9 ng m À3 MSA and 3.9 ± 1.7 mg m À3 nss sulfate). Analysis of the air mass back trajectory and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data suggests that the majority of the biogenic contribution at Erdemli is originated from summer coccolithophorid Emiliania huxleyi blooms developed in the Black Sea. The data further points to a significant relationship between Saharan dust transport events and local oceanic production of MSA through occasional fertilization of the eastern Mediterranean during wet deposition events. This process accounts for episodic, strong weekly changes in MSA concentrations during the spring months. Considering that Erdemli and Finokalia are approximately 1000 km apart from each other geographically, large differences in their MSA and nss-sulfate concentrations indicates a considerable role of regional mesoscale atmospheric transport processes on the spatial structure of biogenically produced atmospheric sulfur aerosols.
1] Nutrients are supplied to the mixed layer of the open ocean by either atmospheric deposition o... more 1] Nutrients are supplied to the mixed layer of the open ocean by either atmospheric deposition or mixing from deeper waters, and these nutrients drive nitrogen and carbon fixation. To evaluate the importance of atmospheric deposition, we estimate marine nitrogen and carbon fixation from present-day simulations of atmospheric deposition of nitrogen, phosphorus, and iron. These are compared with observed rates of marine nitrogen and carbon fixation. We find that Fe deposition is more important than P deposition in supporting N fixation. Estimated rates of atmospherically supported carbon fixation are considerably lower than rates of marine carbon fixation derived from remote sensing, indicating the subsidiary role atmospheric deposition plays in total C uptake by the oceans. Nonetheless, in high-nutrient, low-chlorophyll areas, the contribution of atmospheric deposition of Fe to the surface ocean could account for about 50% of C fixation. In marine areas typically thought to be N limited, potential C fixation supported by atmospheric deposition of N is only ∼1%-2% of observed rates. Although these systems are N-limited, the amount of N supplied from below appears to be much larger than that deposited from above. Atmospheric deposition of Fe has the potential to augment atmospherically supported rates of C fixation in N-limited areas. In these areas, atmospheric Fe relieves the Fe limitation of diazotrophic organisms, thus contributing to the rate of N fixation. The most important uncertainties in understanding the relative importance of different atmospheric nutrients are poorly understood speciation and solubility of Fe as well as the N:Fe ratio of diazotrophic organisms.
1] Multiyear daily surface aerosol aluminum (Al) concentration and sunphotometer measurements at ... more 1] Multiyear daily surface aerosol aluminum (Al) concentration and sunphotometer measurements at Erdemli (Turkey) sampling station were used to assess the performance of Absorbing Aerosol Index (AAI) and Aerosol Optical Thickness (AOT) retrieved from the daily Total Ozone Mapping Spectrometer (TOMS) over the northeastern Mediterranean. A total of 98 moderate-to-high intensity dust events with durations from 1 day to 1 week were identified by aerosol Al concentrations and/or TOMS-AAI above their threshold values of 1.0 mg m À3 and 0.5, respectively. Only 15 events were found to bring appreciable dust load into the northeastern Mediterranean, predominantly below the 850-hPa pressure level, and therefore were not detected effectively by TOMS. Eight of these events corresponded to short-range high intensity intrusions (Al > 3.0 mg m À3 ) from nearby dust sources of the Middle East and Arabian deserts, the rest (seven events) represented moderate-to-high intensity (Al > 1.0 mg m À3 ) long-range transport from North Africa. Given the highly complex dynamics of the region, the use of TOMS-AAI data is justified for monitoring Saharan dust transport characteristics in the northeastern Mediterranean. Moreover, the TOMS-AOT data were found to covary linearly with its counterpart obtained by the ground-based measurements (correlation coefficient 0.86, significant at <0.001), which lies within the range of estimates suggested by earlier studies. Citation: Kubilay, N., T. Oguz, M. Koçak, and O. Torres (2005), Ground-based assessment of Total Ozone Mapping Spectrometer (TOMS) data for dust transport over the northeastern Mediterranean, Global Biogeochem. Cycles, 19, GB1022,
... 15, 2001 Structure of Emiliania huxleyi blooms in the Black Sea surface waters as detected by... more ... 15, 2001 Structure of Emiliania huxleyi blooms in the Black Sea surface waters as detected by SeaWIFS imagery Tulay Cokacar, Nilgun Kubilay, and ... Since the first invasion of E. huxleyi into the Black Sea about 2000 years ago, high carbonate content in sediment cores [Hay ...
1] Ground-based aerosol optical measurements were conducted within the framework of the Aerosol R... more 1] Ground-based aerosol optical measurements were conducted within the framework of the Aerosol Robotic Network (AERONET) program at the IMS-METU site at Erdemli (36°33 0 N, 34°15 0 E) along the Turkish coast of the northeastern Mediterranean from January 2000 to June 2001. The measurements were used to identify and define predominant regional aerosol optical properties, with an emphasis on mineral dust intrusion events. Dust storms affecting the region primarily originate from the central Sahara in spring, the eastern Sahara in summer, and the Middle East/Arabian peninsula in autumn. Summer and autumn dust intrusions usually occurred at higher altitudes (above 700 hPa), whereas urban-industrial aerosols from the north over the Balkan region, Ukraine, and Anatolia were transported to the region at lower altitudes. In addition to a drastic increase in the aerosol optical thickness, in some cases up to 1.8, the dust episodes were characterized by (1) a sharp drop in the Å ngstrom coefficient to values near zero, (2) a high-scattering with single-scattering albedo greater than 0.95 ± 0.03, and the real part of the refractive index around 1.5 ± 0.5, both of which acquire slightly higher values at longer wavelengths, (3) a lower absorption given by the imaginary part of the refractive index less than 0.002, and (4) an almost neutral spectral dependence of these parameters. Dust particles possessed a bimodal size distribution with typical volume mean radii of 2.2 mm and 0.08 mm for coarse and fine size fractions, respectively, and corresponding volume concentrations of about 1.0 and 0.1 mm 3 mm À2 of dust particles. It was apparent that the Saharan and Middle East desert dusts differ in their absorption index values (0.0015 and 0.0005, respectively). The difference is likely a result of their contrasting mineralogies. Citation: Kubilay, N., T. Cokacar, and T. Oguz, Optical properties of mineral dust outbreaks over the northeastern Mediterranean,
2) Institute of 1. INTRODUCION Pulses of mineral aerosols originating from North Africa reach the... more 2) Institute of 1. INTRODUCION Pulses of mineral aerosols originating from North Africa reach the Mediterranean region, and their micro-(such as Fe, Zn, Mn, Co, Ni) (Kubilay, 1996) and macro-nutrient (such as PO4 3− and NO3 −) content (Talbot et al., 1986; Bergametti et al., 1992; Migon and Sandroni, 1999; Herut et al., 1999) supposedly could contribute to marine biological production through time-dependent biogeochemical processes (Quetel et al.,1993). Among these nutrients, PO 4 3− is known to be the limiting nutrient for phytoplankton production in the Mediterranean and as a result of this limitation Eastern Mediterranean marine environment is characterised with a high N:P ratio near the sea surface (Krom et al., 1991). In order to estimate wet and dry deposition atmospheric fluxes of macro-nutrients into the eastern Mediterranean coastal waters, soluble inorganic phosphate (PO 4 3-), nitrate (NO 3 -) and nitrite (NO 2 -) concentrations in precipitation (from February 1996 to Jun...
Aerosol and rain samples were collected at a rural site located on the coastline of the Eastern M... more Aerosol and rain samples were collected at a rural site located on the coastline of the Eastern Mediterranean, Erdemli, Turkey between January 1999 and December 2007. Riverine sampling was carried out at five Rivers (Ceyhan, Seyhan, Göksu, Berdan and Lamas) draining into the Northeastern Levantine Basin (NLB) between March 2002 5 and July 2007. Samples were analyzed for macronutrients of phosphate, silicate, nitrate and ammonium (PO 3− 4 , Si diss , NO − 3 and NH + 4 ). Phosphate and silicate in aerosol and rainwater showed higher and larger variation during the transitional period (March-May, September) when air flows predominantly originate from North Africa and Middle East/Arabian Peninsula. Deficiency of alkaline material were found to be the main 10 reason of the acidic rain events whilst high pH values (>7) were associated with high Si diss concentrations due to sporadic dust events. In general, lowest nitrate and ammonium concentrations in aerosol and rainwater were associated with air flow from the Mediterranean Sea. Unlike NO − 3 and NH + 4 (Dissolved Inorganic Nitrogen, DIN), there were statistical differences for PO 3− 4 and Si diss solubilities in sea-water and pure-water.
In recent years the increasing use of organotin compounds in industry and agriculture, together w... more In recent years the increasing use of organotin compounds in industry and agriculture, together with the development of sensitive and precise analytical techniques for the quantitative speciation of organotin compounds at environmental levels, have created ...
Total and dissolved inorganic phosphorus (IP) was measured in both rainwater and aerosol samples ... more Total and dissolved inorganic phosphorus (IP) was measured in both rainwater and aerosol samples collected from two remote coastal areas: on the island of Crete (Greece) and at Erdemli (Turkey). Particle size distributions of P, as well as total deposition were also measured. Wet and dry deposition of dissolved inorganic phosphorus (DIP) from Crete are compared with simultaneously obtained dissolved inorganic nitrogen (DIN) and with productivity data from the literature. Our results indicate that (1) in both wet and dry deposition, the DIN/DIP molar ratio ranges between 63 and 349, exceeding by a factor of up to 22 the N/P ratio observed in seawater (ranging from 25 to 28) and (2) atmospheric deposition of DIP could reasonably account for a significant part of the new production (up to 38%) observed during the summer and autumn period (i.e., when water stratification is at its maximum).
1] Ground-based aerosol optical measurements were conducted within the framework of the Aerosol R... more 1] Ground-based aerosol optical measurements were conducted within the framework of the Aerosol Robotic Network (AERONET) program at the IMS-METU site at Erdemli (36°33 0 N, 34°15 0 E) along the Turkish coast of the northeastern Mediterranean from January 2000 to June 2001. The measurements were used to identify and define predominant regional aerosol optical properties, with an emphasis on mineral dust intrusion events. Dust storms affecting the region primarily originate from the central Sahara in spring, the eastern Sahara in summer, and the Middle East/Arabian peninsula in autumn. Summer and autumn dust intrusions usually occurred at higher altitudes (above 700 hPa), whereas urban-industrial aerosols from the north over the Balkan region, Ukraine, and Anatolia were transported to the region at lower altitudes. In addition to a drastic increase in the aerosol optical thickness, in some cases up to 1.8, the dust episodes were characterized by (1) a sharp drop in the Å ngstrom coefficient to values near zero, (2) a high-scattering with single-scattering albedo greater than 0.95 ± 0.03, and the real part of the refractive index around 1.5 ± 0.5, both of which acquire slightly higher values at longer wavelengths, (3) a lower absorption given by the imaginary part of the refractive index less than 0.002, and (4) an almost neutral spectral dependence of these parameters. Dust particles possessed a bimodal size distribution with typical volume mean radii of 2.2 mm and 0.08 mm for coarse and fine size fractions, respectively, and corresponding volume concentrations of about 1.0 and 0.1 mm 3 mm À2 of dust particles. It was apparent that the Saharan and Middle East desert dusts differ in their absorption index values (0.0015 and 0.0005, respectively). The difference is likely a result of their contrasting mineralogies. Citation: Kubilay, N., T. Cokacar, and T. Oguz, Optical properties of mineral dust outbreaks over the northeastern Mediterranean,
An established three stage sequential leach scheme was applied to a series of selected high volum... more An established three stage sequential leach scheme was applied to a series of selected high volume aerosol samples (n=35) collected from the Turkish Eastern Mediterranean coastline (Erdemli). Samples were selected according to their air mass back trajectory history to reflect the contrasting mixtures of aerosol material present in the Eastern Mediterranean marine aerosol. Two populations were adopted, those samples which were classed as "anthropogenic" and those which were "Saharan" dominated aerosol populations. Applying the three stage leach it was possible to define the proportion for each of the considered metals (Al, Fe, Cu, Pb, Cd, Zn and Mn) present in the (a) "exchangeable" (b) "carbonate / oxide" and (c) "refractory" phases, representing novel solid state aerosol speciation data for this marine system. Clear trends were established, conforming with data from previous studies with mainly crustal derived metals (Al and Fe) being present in the refractory phases (Al>88%; Fe>84%) and those influenced by anthropogenic sources being dominating in the exchangeable phase, although for these metals the variability was comparatively high (12-64%; 19-85%; 40-100% for Zn, Pb and Cd, respectively). For the majority, greater exchangeable fractions were present the lower the crustal source contribution to the aerosol population, whereas the "refractory" fraction exhibited contrasting behaviour. This was illustrated by the novel application of the mixing diagram, presenting each of the three speciation stages against the corresponding percent anthropogenic contribution to each collected sample. Zn, Pb and Cd all illustrated progressive decrease in the percent exchangeable with increasing crustal contribution to the aerosol population. The percent exchangeable was discussed in terms of its use to represent the upper limit of the bioavailable fraction of metal associated with the aerosol, post deposition. The mixing diagram approach enabled the prediction of the residual fractions for Cd, Pb and Zn (41±4%; 62±4% and 82±5%, respectively,) in Saharan end-member material.
1] A worldwide compilation of atmospheric total phosphorus (TP) and phosphate (PO 4 ) concentrati... more 1] A worldwide compilation of atmospheric total phosphorus (TP) and phosphate (PO 4 ) concentration and deposition flux observations are combined with transport model simulations to derive the global distribution of concentrations and deposition fluxes of TP and PO 4 . Our results suggest that mineral aerosols are the dominant source of TP on a global scale (82%), with primary biogenic particles (12%) and combustion sources (5%) important in nondusty regions. Globally averaged anthropogenic inputs are estimated to be $5 and 15% for TP and PO 4 , respectively, and may contribute as much as 50% to the deposition over the oligotrophic ocean where productivity may be phosphorus-limited. There is a net loss of TP from many (but not all) land ecosystems and a net gain of TP by the oceans (560 Gg P a À1 ). More measurements of atmospheric TP and PO 4 will assist in reducing uncertainties in our understanding of the role that atmospheric phosphorus may play in global biogeochemistry. Citation: Mahowald, N., et al. (2008), Global distribution of atmospheric phosphorus sources, concentrations and deposition rates, and anthropogenic impacts, Global Biogeochem. Cycles, 22, GB4026,
1] Since iron is an important micronutrient, deposition of iron in mineral aerosols can impact th... more 1] Since iron is an important micronutrient, deposition of iron in mineral aerosols can impact the carbon cycle and atmospheric CO 2 . This paper reviews our current understanding of the global dust cycle and identifies future research needs. The global distribution of desert dust is estimated from a combination of observations of dust from in situ concentration, optical depth, and deposition data; observations from satellite; and global atmospheric models. The anthropogenically influenced portion of atmospheric desert dust flux is thought to be smaller than the natural portion, but is difficult to quantify due to the poorly understood response of desert dust to changes in climate, land use, and water use. The iron content of aerosols is thought to vary by a factor of 2, while the uncertainty in dust deposition is at least a factor of 10 in some regions due to the high spatial and temporal variability and limited observations. Importantly, we have a limited understanding of the processes by which relatively insoluble soil iron (typically $0.5% is soluble) becomes more soluble (1-80%) during atmospheric transport, but these processes could be impacted by anthropogenic emissions of sulfur or organic acids. In order to understand how humans will impact future iron deposition to the oceans, we need to improve our understanding of: iron deposition to remote oceans, iron chemistry in aerosols, how desert dust sources will respond to climate change, and how humans will impact the transport of bioavailable fraction of iron to the oceans.
1] Methanesulfonate (MSA) and non-sea-salt (nss) sulfate concentrations were measured in bulk aer... more 1] Methanesulfonate (MSA) and non-sea-salt (nss) sulfate concentrations were measured in bulk aerosol samples collected during January 1996 to December 1999 at two stations along the Turkish and Cretan coastline of the eastern Mediterranean. The data set enabled the origin and variability of biogenically derived sulfate concentrations in the eastern Mediterranean atmosphere to be defined. Although similar seasonal patterns of MSA and nss-sulfate concentrations for both stations were detected, the mean concentrations at Erdemli (Turkey) over the sampling period (42 ± 52 ng m À3 MSA, and 6.8 ± 5.2 mg m À3 nss sulfate) were found to be almost twice that of those measured at Finokalia, Crete (25.8 ± 14.9 ng m À3 MSA and 3.9 ± 1.7 mg m À3 nss sulfate). Analysis of the air mass back trajectory and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data suggests that the majority of the biogenic contribution at Erdemli is originated from summer coccolithophorid Emiliania huxleyi blooms developed in the Black Sea. The data further points to a significant relationship between Saharan dust transport events and local oceanic production of MSA through occasional fertilization of the eastern Mediterranean during wet deposition events. This process accounts for episodic, strong weekly changes in MSA concentrations during the spring months. Considering that Erdemli and Finokalia are approximately 1000 km apart from each other geographically, large differences in their MSA and nss-sulfate concentrations indicates a considerable role of regional mesoscale atmospheric transport processes on the spatial structure of biogenically produced atmospheric sulfur aerosols.
1] Nutrients are supplied to the mixed layer of the open ocean by either atmospheric deposition o... more 1] Nutrients are supplied to the mixed layer of the open ocean by either atmospheric deposition or mixing from deeper waters, and these nutrients drive nitrogen and carbon fixation. To evaluate the importance of atmospheric deposition, we estimate marine nitrogen and carbon fixation from present-day simulations of atmospheric deposition of nitrogen, phosphorus, and iron. These are compared with observed rates of marine nitrogen and carbon fixation. We find that Fe deposition is more important than P deposition in supporting N fixation. Estimated rates of atmospherically supported carbon fixation are considerably lower than rates of marine carbon fixation derived from remote sensing, indicating the subsidiary role atmospheric deposition plays in total C uptake by the oceans. Nonetheless, in high-nutrient, low-chlorophyll areas, the contribution of atmospheric deposition of Fe to the surface ocean could account for about 50% of C fixation. In marine areas typically thought to be N limited, potential C fixation supported by atmospheric deposition of N is only ∼1%-2% of observed rates. Although these systems are N-limited, the amount of N supplied from below appears to be much larger than that deposited from above. Atmospheric deposition of Fe has the potential to augment atmospherically supported rates of C fixation in N-limited areas. In these areas, atmospheric Fe relieves the Fe limitation of diazotrophic organisms, thus contributing to the rate of N fixation. The most important uncertainties in understanding the relative importance of different atmospheric nutrients are poorly understood speciation and solubility of Fe as well as the N:Fe ratio of diazotrophic organisms.
1] Multiyear daily surface aerosol aluminum (Al) concentration and sunphotometer measurements at ... more 1] Multiyear daily surface aerosol aluminum (Al) concentration and sunphotometer measurements at Erdemli (Turkey) sampling station were used to assess the performance of Absorbing Aerosol Index (AAI) and Aerosol Optical Thickness (AOT) retrieved from the daily Total Ozone Mapping Spectrometer (TOMS) over the northeastern Mediterranean. A total of 98 moderate-to-high intensity dust events with durations from 1 day to 1 week were identified by aerosol Al concentrations and/or TOMS-AAI above their threshold values of 1.0 mg m À3 and 0.5, respectively. Only 15 events were found to bring appreciable dust load into the northeastern Mediterranean, predominantly below the 850-hPa pressure level, and therefore were not detected effectively by TOMS. Eight of these events corresponded to short-range high intensity intrusions (Al > 3.0 mg m À3 ) from nearby dust sources of the Middle East and Arabian deserts, the rest (seven events) represented moderate-to-high intensity (Al > 1.0 mg m À3 ) long-range transport from North Africa. Given the highly complex dynamics of the region, the use of TOMS-AAI data is justified for monitoring Saharan dust transport characteristics in the northeastern Mediterranean. Moreover, the TOMS-AOT data were found to covary linearly with its counterpart obtained by the ground-based measurements (correlation coefficient 0.86, significant at <0.001), which lies within the range of estimates suggested by earlier studies. Citation: Kubilay, N., T. Oguz, M. Koçak, and O. Torres (2005), Ground-based assessment of Total Ozone Mapping Spectrometer (TOMS) data for dust transport over the northeastern Mediterranean, Global Biogeochem. Cycles, 19, GB1022,
... 15, 2001 Structure of Emiliania huxleyi blooms in the Black Sea surface waters as detected by... more ... 15, 2001 Structure of Emiliania huxleyi blooms in the Black Sea surface waters as detected by SeaWIFS imagery Tulay Cokacar, Nilgun Kubilay, and ... Since the first invasion of E. huxleyi into the Black Sea about 2000 years ago, high carbonate content in sediment cores [Hay ...
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