Atmospheric concentrations and total deposition (wet+dry) of phosphorus were ... source of phosphorus for surface Mediterranean waters is tentatively assessed ...
Journal of Atmospheric Chemistry. 14: 501-513, 1992. © 1992 Kluwer Academic Publishers. Printedin the Netherlands.
SOURCE, TRANSPORT AND DEPOSITION OF ATMOSPHERIC PHOSPHORUS OVER THE NORTHWESTERN MEDITERRANEAN
G. BERGAME'I"rI, E. REMOUDAKI, R. LOSNO, E. STEINER, B. CHATENET Laboratoire de Physico-Chimie de l'Atrnosphdre, UA CNRS 1404, Universit6 Paris 7, 2, place Jussieu, 75251 Paris Cedex 05, France. P. BUAT-MENARD Centre des Faibles Radioactivitds, Laboratoire Mixte CNRS-CEA, 91198 Gif/Yvette Cedex, France.
ABSTRACT. Atmospheric concentrations and total deposition (wet+dry) of phosphorus were measured over the northwestern Mediterranean between april 1985 and march 1988. A seasonal cycle of both atmospheric concentrations and total deposition is observed, the higher values being recorded during the dry season. Air-mass trajectory analyses allow an identification of the major sources of atmospheric phosphorus: soil-derived dust from desert areas of north Africa and anthropogenic emissions from european countries. The impact of the atmospheric input as a source of phosphorus for surface Mediterranean waters is tentatively assessed on both annual and seasonal time scales. The results suggest that the atmospheric input of phosphorus could be significant to Mediterranean oligotrophic zones, especially during summer when phosphorus input from deeper waters into the photic layer is minimum.
1. Introduction Atmospheric transport of particulate matter from the continents to the oceans is now well recognized as a major pathway to supply open ocean surface waters with various trace elements. Of particular interest are the inputs of elements such as N, P, Fe which are essential elements for biological growth in marine environments. Duce (1986) has shown that in open ocean oligotrophic zones such as the Sargasso Sea and the North Pacific gyres, mean annual atmospheric inputs of N and Fe to surface waters are significant compared to fluxes from deeper waters, whereas atmospheric inputs of P seem to be of much lesser importance. However, he pointed out that during limited periods of time, the impact of short term pulses of material, for example major dust storms or high pollution episodes, could be much more significant. For the north-western Atlantic, Graham and Duce (1979) report atmospheric phosphorus concentrations ranging from 1.3 to 57 ng m-3. Higher concentrations have been observed in the
502
G. BERGAMETTI ET AL.
eastern North Atlantic (up to 80 ng m-3) during Saharan dust outbreaks (Graham and Duce, 1979), showing the importance of the soil-derived dusts emitted from arid regions as a source of atmospheric particulate phosphorus. Lower concentrations are observed far from continental sources over remote oceanic areas such as the central Pacific or southem Atlantic (less than 1 ng m-3), the major part of the atmospheric particulate phosphorus being from the sea due to the ejection of sea-salt particles enriched with phosphorus from the surface microlayer (Chen et al., 1985). Over continents, particulate phosphorus concentrations are significantly higher and average about 150 ng m-3. These high concentrations may be explained by both emissions from agricultural activities and industrial sources (Graham and Duce, 1979). The westem Mediterranean is a marine environment surrounded to the north by the industrial European countries and to the south by the large African arid and semi-arid regions. These various potential sources of atmospheric particulate phosphorus will probably be responsible for high concentration episodes when the airflow pattern will allow an efficient transport from these major source areas. Further, it has been shown that, over the open western Mediterranean, local precipitation is responsible for the sharpest decreases of the atmospheric elemental concentrations on a daily time scale (Bergametti et al., 1989a). Moreover, the processes occuring during transport and especially the sinks such as wet and dry deposition, also affect significantly the observed concentrations of particulate trace-elements. From a long time series of atmospheric concentrations and total deposition measurements, this paper attempts to test the hypothesis that, in the open westem Mediterranean and for defined time periods, the atmospheric phosphorus input may act as a "relay-source" to supply the photic zone with phosphorus. Indeed, this area could constitute an ideal case study because: a) high atmospheric inputs resulting from the strong anthropogenic and desert sources located on its coast lines are probable and b) a particularly well stratified surface layer is developed during summer, reducing the upward flux of nutrients from deeper waters.
2. Sampling and Analysis 2.1. SAMPLING PROCEDURES The samples were collected at Capo Cavallo (42°31N, 8°40E) on the north-western coast of Corsica Island (Bergametti et al., 1989a). Aerosol samples were collected dally by bulk filtration on 0.4 ~m porosity Nuclepore filters at the top of a 10-m high meteorological tower between february 1985 and april 1988. Sampling duration was 24 hours with a nominal airflow of 1 m3 h-1. Fifty-seven total (wet+dry) atmospheric deposition samples were collected at the same site, between february 1985 and october 1987. The sampling duration was about 15 days. Details on the total atmospheric deposition sampling can be found elsewhere (Remoudaki et al., 1990a). In order to evaluate the partitioning between dissolved and particulate phosphorus in precipitation, eight rain events were collected in ultra clean conditions during field campaigns at Capo Cavallo (Losno, 1989). The rainwater samples were filtered immediatly after collection on Nuclepore 0.4 lam porosity filters to stop the possible exchanges between particulate and dissolved phosphorus.
503
SOURCE, TRANSPORT AND DEPOSITION ng.m-3 100
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Figure 1. Daily atmospheric concentrations (in ng.m-3 on a logarithmic scale) of particulate phosphorus (from february 1985 to october 1988) at Capo Cavallo, Corsica Island.
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Figure 2. Seasonal geometric mean concentrations of atmospheric particulate phosphorus concentrations (in ng.m-3) and geometric standard deviation at Capo Cavallo, Corsica Island.
504
G. BERGAMETTIET AL.
2.2. ANALYSIS Atmospheric particulate concentrations of phosphorus were determined by wavelength dispersivc X-ray fluorescence spectrometry according to the method described by Losno et al. (1987). The mean relative errors have been estimated to be 6% for phosphorus. Results concerning the concentrations of other elements have been presented in a previous paper (Bergametti et al., 1989a). At the laboratory, total atmospheric deposition samples were filtered on Nuclepore filters (0.4 tam pore size) to separate the particulate from the dissolved fraction. Since these samples were pre-acidified, this treatment serves only analytical purposes for the elements which exist in both dissolved and particulate fractions (i.e. Al, Si, Fe, Mn, P). For both rainwater and total deposition samples, the concentrations of P in the particulate fraction have been determined by wavelength dispersive X-ray fluorescence spectrometry. The analysis of the dissolved fraction of phosphorus was performed by a colorimetric method (Murphy and Riley, 1962). Hence, the results conceming the total atmospheric deposition were expressed as the sum of the dissolved and particulate phosphorus. The mean relative errors arc less than 15 %.
3. Temporal Variability of the Atmospheric Particulate Phosphorus Concentrations Figure 1 presents the daily phosphorus atmospheric concentrations for the period february 1985march 1988. We observe a seasonal pattem of phosphorus atmospheric concentrations in the Westem Mediterranean atmosphere. Mediterranean summers are characterized by higher mean concentrations while winters are characterized by lower mean concentrations. This pattern is inversely related to that of precipitation. The low concentration periods correspond to the rainy seasons (i.e. winters) in the Westem Mediterranean and, the high concentration periods correspond to the "dry" seasons (i.e. summers) (figure 2). This seasonal cycle is observed whatever the origin of the elements: crustal origin A1 or Si (Bergametti et al., 1989b), anthropogenic origin Pb or Cu (Remoudaki et al., 1990a) and mixed origin as Mn (Remoudaki et al., 1990b). Strong increases in atmospheric phosphorus concentrations appear episodically during the sampling period: for example, the atmospheric phosphorus concentration increases by a factor of 100 in less than 48 hours between December 28 and 30, 1985. Based on three-dimensional air mass trajectories, these strong increases are attributed to dust transport events from the arid or semi arid African regions. This soil-derived dust origin is also confirmed by simultaneous increases in concentrations of Al and Si (Bergametti et al., 1989b) and by no significant changes in concentrations of particulate pollutants such as Pb or Cu (Remoudaki et al., 1990a). Twenty saharan dust events were identified during the first year of measurements (Bergametti et al., 1989b) indicating a relatively high occurence of these saharan inputs. Although phosphorus is an element of mixed origin, when such events occur, the predominance of the soft-derived phosphorus in the Mediterranean atmosphere is clearly established. The relative annual mean contribution of the crustal source to the measured phosphorus atmospheric concentrations can be shown by the low geometric mean enrichment factor (about 3) calculated using data covering the whole sampling period. As indicated above, three-dimensional air mass trajectories analysis has been performed for the first year of measurements (april 1985-april 1986) in order to connect changes in concentrations
505
SOURCE, TRANSPORT AND DEPOSITION
with the origin of the sampled air-mass. For the mid-sampling period (i.e each day), a four-day backward air mass trajectory was computed to end at the 925 hPa barometric level, using the wind fields from the European Center for Medium Range Weather Forecasts (Reading, U.K) (Martin et al., 1990). The model of trajectory calculation reports also the forecasted precipitation events greater than 0.1 mm h-1. To classify the samples with respect to the origin of the air masses, we have not made an "a priori" hypothesis concerning the various source-regions of phosphorus for the western Mediterranean atmosphere. We have divided a wind rose into 16 sectors of 22°5, and each sample was classified in the 22°5 sector corresponding to the position of the air mass 2 days before its arrival over the sampling site. However, in some cases, low wind speeds occured and the some trajectories were too short to assign a precise source region. Thus, we defined a seventeenth sector for these particular trajectories. As previously mentioned, local precipitation may strongly change atmospheric phosphorus concentrations on a short time scale. Thus we have not considered the samples collected when local precipitation occurred. Moreover, because the mean reloading time of the local atmosphere with continental aerosols following a local rain event has been estimated to be about 2 days (Bergametti et al., 1989a), the samples for which a local precipitation occurred 2 days or less before sampling were also excluded. Further, to eliminate the influence of rains during transport and so to point out only the effect of the emission strength in the source regions, we have used the precipitation events forecasted by the trajectory model. Only the samples not affected by a precipitation event occurring during the last 2 days of transport have been considered in this treament. For each sector, we calculated the geometric mean aerosol concentration and we grouped together adjacent sectors when the mean concentrations were found to be similar (Remoudaki et al., 1990a). The results of the classification of the daily atmospheric phosphorus concentrations in relation to the origin of the sampled air-masses are given in table 1.
Table 1. Phosphorus atmospheric mean concentrations (in ng/m3) and mean P/A1 ratio over the Mediterranean Sea according to the origins of the air masses (mg: geometric mean, Sg: geometric standard deviation). P
Northeast sector Northwest sector South sector
P/A1
mg
Sg
mg
Sg
19.4 10.2 17.8
1.8 1.9 1.5
0.07 0.05 0.03
1.5 1.4 1.2
The highest concentrations are associated with transport cases from northeast (19.4 ng m -3) and south (17.8 ng m-3). In contrast, the northwest sector exhibits the lowest concentrations of particulate phosphorus (10.2 ng m-3). As discussed above, three major source-types can be responsible for the observed particulate phosphorus: emissions from sea water, soU-derived dusts
506
G. BERGAMETTI ET AL.
and anthropogenic emissions. In the westem Mediterranean, we can eliminate the sea salt emissions: by using Na concentrations measured on the same samples (Bergametti et al., 1989a) and by using a P enrichment of 150 in the surface microlayer (Graham et al., 1979) relatively either to the mean surface seawater composition (Quinby-Hunt and Turekian, 1983; 0.08 lamol/kg) or to the western Mediterranean surface layer (Bdthoux et al., 1990; 0.067 ~mol/kg), we can estimate that marine P does not account for more than 5 % of the total particulate phosphorus concentrations. In order to distinguish between soil-derived phosphorus and anthropogenic phosphorus, we have computed for each sector the P/AI ratios (table 1). This ratio is significantly greater for northwest (0.05) and northeast (0.07) sectors than for the south sector (0.03). This result is in agreement with expected larger anthropogenic inputs of phosphorus from European countries than from Africa. However, the P/A1 ratio observed for transports from arid and semi-arid regions of the African continent corresponds to a phosphorus content in soilderived dust higher than the mean ratio for the overall crustal abundance of phosphorus (0.1% corresponding to P/AI=0.013, Mason, 1966). This may be explained by the presence of large apatite deposits in western North Africa which could raise up to 0.2% the average phosphorus content of the dusts emitted from these desert regions (Graham and Duce, 1979). Hence, atmospheric phosphorus concentrations observed for transports from the African continent may be attributed to P-rich soil-derived dust. For non-desert areas such as the north European continent, we can assume that the abundance of phosphorus in soils is close to that of the overall crustal material and thus, the high P/Al ratios strongly suggest that large contributions from industrial and agricultural emissions of phosphorus are superimposed on the European crustal source. Moreover, it has been recently pointed out that emissions from continental biogenJc sources and biomass buming are characterized by particulate emissions significantly enriched with phosphorus (Leslie, 1981; Artaxo et al., 1990). In the Mediterranean region and especially in France, Spain, Italy and Greece, forest fires often occur during summer and thus may constitute a sporadic source of particulate phosphorus over the Mediterranean basin which is, however, difficult to estimate quantitatively.
4. Inputs of Atmospheric Phosphorus into the Western Mediterranean Surface Waters 4.1 TOTAL ATMOSPHERIC DEPOSITION Figure 3 reports the total atmospheric deposition (wet+dry) of phosphorus and the corresponding mean dally precipitation rate (mdp) over the sampling period . The mean annual flux of atmospheric phosphorus is 0.011 lag/cm2/d. We also observe a seasonal pattem of the atmospheric phosphorus total deposition, higher fluxes occuring during the dry mediterranean summer (i.e. when mdp is low) and lower fluxes during the wet mediterranean winter (higher mdp) (table 2). Such a pattern has also been observed for elements as Pb (Remoudaki et al., 1990a) and Cu and Mn (Remoudaki et al., 1990b). It has been shown that during winter, the high frequency of precipitation leads to a scavenging of aerosol particles emitted by continental sources very close to the coast line, thus limiting the capability of the atmospheric particulate matter to reach the open sea. Although the frequency of precipitation (which is the more efficient deposition process for the particulate matter in this marine area (Bergametti, 1987)) is also high over the open sea at this time, these winter rain events are inefficient in term of mass deposited since there is little atmospheric particulate matter to be scavenged in the atmosphere. On the
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Figure 4. Phosphorus and aluminium atmospheric deposition (in pg/cm2/d) at Capo Cavallo, Corsica Island for the period february 1985- october 1987.
508
G. BERGAMETTI ET AL.
contrary, during summer, rain events are more scarse and the residence time of atmospheric particles is increased, allowing them to be long-range transported over the sea. In this case, the few rain events occuring over the open sea are more efficient since they wash a highly loaded atmosphere.
Table 2. Seasonal fluxes of atmospheric phosphorus over the western Mediterranean Sea (in lag/cm2/d). dry season 1985 wet season 1986 dry season 1986 wet season 1987 dry season 1987
0.010 0.008 0.013 0.009 0.014
(+ (+ (+ (+ (+
0.00009) 0.00007) 0.0001) 0.00008) 0.0001)
Although this seasonal pattern is the major factor controlling the variability of the phosphorus atmospheric deposition fluxes, the sporadic dust transport events strongly influence the amount of deposited phosphorus since the highest phosphorus fluxes are observed simultaneously with aluminium peaks (figure 4). A rough apportionment can be made between soil-derived, marine and excess phosphorus in these deposition samples. Classically, soil-derived phosphorus (Pc) is computed by using A1 as a tracer and the ratio P/A1 in a crustal model (Mason, 1966). The marine component (Pm) is evaluated as indicated previously for aerosols (enrichment of phosphorus = 150 comparatively to the mean surface seawater (Quinby-Hunt and Turekian, 1983) and using Na as a tracer of the marine source). The difference between measured phosphorus and the sum Pc +Pm is considered as excess phosphorus (Pe). The results (figure 5) clearly show that recycled phosphorus from the marine sources only account for a small part (less than 2%) of the total atmospheric phosphorus fluxes. The soil-derived dusts contribute on an annual time scale for about 23% of the atmospheric input of phosphorus but can represent episodically (i.e. when saharan events occur) more than 50% of the total phosphorus. Taking into account the slight enrichment of phosphorus in desert dust compared to the mean crustal abundance, it is likely that we have underestimate the soil-derived phosphorus input which could represent up to an average of 40% of the total atmospheric phosphorus deposition. Despite this uncertainty, excess phosphorus is, on an annual time scale, the larger contributor to the total atmospheric deposition of phosphorus (58 to 75%). As a first approximation, this excess phosphorus may result primarily from anthropogenic activities, industrial (phosphate industry and stationary combustion sources, Graham and Duce, 1979; ) and agricultural (mainly fertilizers). 4.2. RELEASE OF DISSOLVED PHOSPHORUS TO MEDITERRANEAN WATER
It is generally postulated that only dissolved phosphorus can be easily available as a nutrient for biological growth. The precise fraction of the atmospheric phosphorus which can be dissolved in marine water is difficult to evaluate since it depends on, among many factors, the relative abundance of the various particulate phosphorus species present in the air and on the ability of marine microorganisms to dissolve them.
SOURCE, TRANSPORTAND DEPOSITION
509
Previous work by Lepple (1975) indicates that no more than 8% of phosphorus present in saharan dust can be released in seawater. Graham and Duce (1982) report that 36% (_+15%) of phosphorus contained in aerosols collected at Narragansett (Rhode Island) is released in seawater over a 12 h period. As rain events can be considered as the major deposition pathway for atmospheric phosphorus in the westem Mediterranean, it is of a great interest to focus on the partitioning between dissolved and particulate phosphorus in rainwater. The individual rain samples collected at Capo Cavallo (Losno et al., 1987) suggest that a strong difference in solubility exists between soilderived and excess phosphorus. In figure 6, we have reported the soluble phosphorus as a function of non crustal phosphorus. The percentage of dissolved phosphorus is close to or greater than the percentage of non crustal phosphorus, suggesting that the non crustal phosphorus is completly soluble in rainwater. On the contrary, the crustal phosphorus seems to be only poorly soluble in agreement with Lepple (1975). Two problems remains to obtain a precise evaluation of the net atmospheric input of dissolved phosphorus to the sea: what is the fate of the phosphorus dissolved in rainwater when it is mixing with seawater? and what is the ability of microorganisms to extract phosphorus from the paniculate matter? Taking into account these uncertainties, we can only evaluate a probable range of dissolved phosphorus entering seawater by assuming that 8% of soil-derived phosphorus is soluble in seawater and that the solubility of excess (non-crustal, non-marine) atmospheric phosphorus ranges from 40% to 100%. Table 3 gives the estimates of the input of dissolved phosphorus from the atmosphere to Mediterranean surface water.
Table 3. Atmospheric input of dissolved phosphorus to the western Mediterranean (lag/m2/d). A: solubility of soil-derived phosphorus: 8% and solubility of excess phosphorus: 40%; B: solubility of soil-derived phosphorus: 8% and solubility of excess phosphorus: 100%. A
B
annual time scale
36
70
summer situation
40
85
4.3. ESTIMATE OF THE IMPACT OF ATMOSPHERIC PHOSPHORUS ON THE NEW PRODUCTION Briefly, the biological production in the photic layer of open marine areas results from the regenerated production by recycling nutrients, produced by animals and heterotrophic microorganisms metabolism, and from the new production which is supported by nutrients coming from external sources (mainly vertical transport of deeper nutrient rich water and the atmosphere). According to Eppley and Peterson (1979) and assuming a steady-state for the
510
G. BERGAME'I~I ET AI.
100%
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Summer 86
Summer 87
Figure 5. Apportionment of phosphorus sources in atmospheric deposition at Capo CavaUo, Corsica Island for the period february 1985- october 1987. 100
80
60 % of non crustal
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20
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SOURCE, TRANSPORT AND DEPOSITION
511
photic layer, the new production is equivalent to a first approximation to the export flux of material from the photic zone to deep waters.
Table 4. Budget of phosphorus in the photic layer of the westem Mediterranean Sea (lag/m2/d). Estimates are a: From 14C measurements (Minas et al., 1988) and using C/P Redfield ratio (106); b: From the C particulate flux out of the photic zone as measured by sediment traps at 200 m depth (J.C Micquel and S. Fowler, personal communication) and using P/C Redfield ratio; * lower than the armual mean but not precisely known.
annual
summer
primary production
3000-5300a
*
new production
680-1500a
70b
36-70
40-85
Phosnhoms reouired to suooort :
Atmosoheric innut of dissolved phosphorus
It is possible to establish such a chemical mass balance for the open westem Mediterranean water both on an annual scale and for the specific summer situation. These two budgets are summarized in table 4. On an annual scale, the vertical transport of deeper water provides the larger input of dissolved phosphorus (Minas et al., 1988) to the mediterranean photic zone and allows significant new production. In this case, the atmospheric dissolved phosphorus source only represents 2 to 10% of the phosphorus used for the new production, in agreement with Graham and Duce (1979) who estimated, on a global scale, that the input of the dissolved atmospheric phosphorus represented about 10% of the input of dissolved phosphorus to the oceans by rivers. During summer, the situation is quite different. A strong stratification is developed in the western Mediterranean Sea, the photic layer is only about 50m depth and the exchanges with deeper nutrient rich water are strongly limited. So, since the input of nutrients decreases, the new production, deduced from sediment traps measurements, strongly decreases to represent less than 10% of the mean annual new production. Our results strongly suggest that, during this period, the atmospheric input of dissolved phosphorus represent a large part of the phosphorus exported from the photic zone. Thus, the atmospheric source may be considered, in this steady-state hypothesis, as the major source of phosphorus inputs during summer, acting as a substitute to deeper nutrient rich water. Acknowledgements. We thank the staff of the signal station of Capo Cavallo for their logistical support during the field experiments and the french national navy for the free access to
512
G. BERGAMETTIET AL.
the signal station. We are grateful to D. Martin, B. Strauss and J.M. Gros who have computed the air mass trajectories. This work was supported in part by the Ministate de rEnvironnement, by UNEP/WMO (Medpol Program) and by the ATP "A6rosols D6sertiques" (CNRS-PIREN). We also acknowledge the European Economic Communities for the doctoral fellowship contract N°B/87000259 (E. Remoudaki). 5. References Artaxo, P., Maenhaut, W., Storms, H., and Van Grieken, R. (1990) 'Aerosol Characteristics and sources for the Amazon basin during the wet season', J. Geophys. Res., 95, 16971-16985. Bergametti, G., Dutot, A.L., Buat-M6nard, P., Losno, R., and Remoudaki, E., (1989a) 'Seasonal variability of the elemental composition of atmospheric aerosol particles over the northwestern Mediterranean', Tellus, 41B, 353-361. Bergametti, G., Gomes, L., Remoudaki, E., Desbois, M., Martin, D., and Buat-M6nard, P. (1989b) 'Present transport and deposition pattems of African dusts to the northwestern Mediterranean' in M. Leinen and M. Samthein (eds.), Paleoclimatology and Paleometeorology: Modern and past Patterns of Global Atmospheric Transport, Kluwer Academic Publishers, Dordrecht, pp 227-252. B6thoux, J.P., Courau, P., Nicolas, E., and Ruiz-Pino, D. (1990) 'Trace metal pollution in the Mediterranean Sea', Oceanol. Acta, 13, 4, 481-488. Chen, L., Arimoto, R., and Duce, R.A. (1985) 'The sources and forms of phosphorus in marine aerosol particles and rain from northern New Zealand', Atmos. Environ., 19, 779-787. Duce, R.A. (1986) 'The impact of atmospheric nitrogen, phosphorus, and iron species on marine biological productivity', in P. Buat-M6nard (ed.), The Role of Air-Sea Exchange in Geochemical Cycling, Kluwer Academic Publishers, Reidel Publishing Company, Dordrecht, pp 497-529. Eppley, R.W., and Peterson, B.J. (1979) 'Particulate organic matter flux and planktonic new production in thedeep ocean', Nature, 282, 677-680. Graham, W.F., and Duce, R.A. (1979) 'Atmospheric pathways of the phosphorus cycle', Geochim. Cosmochim. Acta, 43, 1195-1208. Graham, W.F., Piotrowicz, S.R., and Duce, R.A. (1979) 'The sea as a source of atmospheric phosphorus', Mar. Chem., 7, 325-342. Graham, W.F., and Duce, R.A. (1982) 'The atmospheric transport of phosphorus to the westem Norlh Atlantic', Atmos. Environ., 16, 1089-1097. Lepple, F.K. (1971) 'Eolian dust over the North Atlantic Ocean', Ph D thesis, University of Delaware. Leslie, A.C.D. (1981) 'Aerosol emissions from forest and grassland burning in the southern Amazon basin and Central Brazil', Nucl. Instrum. Meth., 181,345-351. Losno, R. (1989) 'Chimie d'616ments min6raux en trace dans les pluies m6diterran6ennes', Th~se de Sciences, Universit6 Paris 7. Losno, R., Bergametti, G., and Mouvier, G. (1987) 'Determination of optima conditions for atmospheric aerosols analyses by X-Ray fluorescence', Environ. Tech. Letters, 8, 77-87. Losno, R., Bergametti, G., and Buat-M6nard, P. (1988) 'Zinc partitioning in Mediterranean rainwater', Geophys. R es. Letters, 15, 1389-1392. Martin, D., Bergametti, G., and Strauss, B. (1990) 'On the use of the synoptic vertical velocity in trajectory model: validation by geochemical tracers', Atmos. Environ., 24A, 2059-2069.
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Mason, B. (1966) 'Principles of geochemistry', Wiley and Sons eds., New-York. Minas, H.J., Minas, M., Coste, B., Gostan, J., Nival, P., and Bonin, M.C. (1988) 'Production de base et de recyclage; une revue de la probl6matique en M6diterran6e nord-occidentale', Oceanol. Acta, N ° SP, 155-162. Murphy, J., and Riley, J.P. (1962) 'A modified single solution method for the determination of phosphate in natural waters', Analytica Chimica Acta, 27, 31-36. Quinby-Hunt, M.S., and Turekian, K.K. (1983) 'Distribution of elements in sea water', EOS, 64, 130-132. Remoudaki, E., Bergametti, G., and Buat-M6nard, P. (1990a) 'Temporal variability of atmospheric lead concentrations and fluxes over the northwestern Mediterranean Sea', J. Geophys. Res., in press. Remoudaki, E., Bergametti, G., and Losno, R. (1990b) 'On the dynamic of the atmospheric input of copper and manganese into the northwestern Mediterranean Sea', Atmos. Environ., in press.
