A. Gaudry

The composition of precipitation on Amsterdam Island, Indian Ocean

Abstract This paper discusses 1. (1) the composition of precipitation on Amsterdam Island, in the central Indian Ocean, 2. (2) the processes controlling the precipitation composition and (3) the acids responsible for the observed acidity. The data set comprises 66 rain events collected over a 30 month period and analyzed for SO42−, NO3−, Cl−, CH3COO−, HCOO−, Na+, Mg2+ , K+ , Ca2+, H+, strong acidity and total acidity. Supporting data used in data analysis include 222Rn and meteorological parameters. Precipitation on Amsterdam Island has two components, seawater and acid. Using Mg2+ as the seawater tracer, there is no significant difference between the K + Mg 2+ , Cl − Mg 2+ , Na + Mg 2+ and Ca 2+ Mg 2+ ratios of the rain and those of seawater. The SO 4 2− Mg 2+ ratio is significantly larger than the seawater ratio. The acid component is substantially smaller than the seasalt component. The volume weighted pH of the precipitation samples is 5.06 with primary proton donors being H2SO4, organic acids (HCOOH and CH3COOH) and HNO3. The maximum contributions of these acids to precipitation acidity are 30, 25 and 15%, respectively. There is an interaction between the alkaline seawater component and the acidic component. Specifically, using Mg2+ as a tracer of seawater alkalinity, there is, on the average, a loss of 10 % of the original free acidity due to neutralization. Specific samples ranged from 222Rn was used as a tracer to estimate the influence of the long range transport of marine and continental material on the composition of Amsterdam Island precipitation. A comparison of the SO42−∗, NO3−, H+ and CH3COO− and HCOO− concentrations between events with a continental source area and those with a marine source area revealed a possible continental influence on NO3− only.

Covariations in oceanic dimethyl sulfide, its oxidation products and rain acidity at Amsterdam Island in the Southern Indian Ocean

Simultaneous measurements of rain acidity and dimethyl sulfide (DMS) at the ocean surface and in the atmosphere were performed at Amsterdam Island over a 4 year period. During the last 2 years, measurements of sulfur dioxide (SO2) in the atmosphere and of methane sulfonic acid (MSA) and non-sea-salt-sulfate (nss-SO42-) in rainwater were also performed. Covariations are observed between the oceanic and atmospheric DMS concentrations, atmospheric SO2 concentrations, wet deposition of MSA, nss-SO42-, and rain acidity. A comparable summer to winter ratio of DMS and SO2 in the atmosphere and MSA in precipitation were also observed. From the chemical composition of precipitation we estimate that DMS oxidation products contribute approximately 40% of the rain acidity. If we consider the acidity in excess, then DMS oxidation products contribute about 55%.

Precipitation composition and its variability in the southern Indian Ocean: Amsterdam Island, 1980–1987

Event precipitation samples have been collected on Amsterdam Island (37° 47′ S, 77° 31′ E) from May 1980 through January 1987 and analyzed for SO4=, NO3−, Cl−, Na+, Mg++, K+, Ca++, H+, HCOOt, and CH3COOt. The objective of this paper is to assess the processes which influence variability in the chemical composition of precipitation at this remote marine site. Back trajectories and gas phase 222Rn measurements were used to identify source regions and their relative contributions to precipitation composition. The technique of cluster analysis was applied to trajectory data as a method for determining to what degree different atmospheric flow patterns influence variability in the observed composition. The dominant source regions for chemical deposition were found to be Madagascar and/or S.E. Africa and the ocean region north and east of Amsterdam Island. A strong seasonal signal in the precipitation composition is illustrated. Processes which influence variability in the chemical composition include the following: seasonality in the source strength of biogenic precursors for non-sea-salt (nss) SO4=, NH4+ and carboxylic acids; seasonality in biomass-burning continental sources for the concentration of NO3− and a portion of nss Cl−; and variations in source region driven by daily changes in meteorology, as well as seasonal and annual differences in transport and removal patterns. In addition, interannual differences in nss SO4= concentration appear to be related to fluctuations in large-scale circulation patterns as defined by the Southern Oscillation.

A 10-year trajectory flow climatology for Amsterdam Island, 1980–1989

Abstract This paper documents the meteorology and flow climatology of Amsterdam Island, a World Meteorological Organization baseline observatory located in the southern Indian Ocean. The island is strongly influenced by two meteorological systems: the subtropical anticyclone and the westerlies, known as the roaring forties. Westerly surface winds dominate ground-level flow on the island, which receives an annual average precipitation of 1100 mm. A 10-year back air trajectory climatology at 850 hPa to the island showed the same predominant westerly-southwesterly flow (55% of the period). Special emphasis was placed on trajectories that had their origin on the African continent because this was the predominant nonmarine source of trace materials that could be transported to Amsterdam Island. This transport, most frequent in the winter and early spring, coincided with the winter peak of continental radon. A comparison of trajectories and 12-h precipitation amounts on the island showed that most of the rain coincided with southwesterly flow, but many large individual events were frequently associated with northerly and westerly flow regimes. Meteorological information about local conditions and flow climatology is necessary to aid in the interpretation of atmospheric chemistry measurements made at global stations such as Amsterdam Island.

Sensitivity of biomonitors and local variations of element concentrations in air pollution biomonitoring

In this work, we compare the concentrations of trace elements for fourty samples of lichens, mosses and tree barks used as biomonitors in an air pollution biomonitoring study in Morocco. This comparison concerns six types of biomonitors: the lichens Xanthoria parietina, Parmelia sulcata and Evernia prunastri; the moss Hylocomium splendens and barks of cedar and cork oak. The complementarity of three analytical methods was used in order to increase the number of determined elements. These techniques are: 14 MeV neutron activation analysis, thermal neutron activation analysis using the k0-quasi-absolute method and X-ray fluorescence analysis. The results enabled us to compare the element accumulation sensitivity for the six biomonitors used and to study the local concentration variations versus biomonitors sizes and the height above ground of their collecting point.

Relationship of Atmospheric Pollution Characterized by gas (NO2) and particles (PM10) to Microbial Communities Living in Bryophytes at Three Differently Polluted Sites (Rural, Urban and Industrial).

Atmospheric pollution has become a major problem for modern societies owing to its fatal effects on both human health and ecosystems. We studied the relationships of nitrogen dioxide atmospheric pollution and metal trace elements contained in atmospheric particles which were accumulated in bryophytes to microbial communities of bryophytes at three differently polluted sites in France (rural, urban, and industrial) over an 8-month period. The analysis of bryophytes showed an accumulation of Cr and Fe at the rural site; Cr, Fe, Zn, Cu, Al, and Pb at the urban site; and Fe, Cr, Pb, Al, Sr, Cu, and Zn at the industrial site. During this study, the structure of the microbial communities which is characterized by biomasses of microbial groups evolved differently according to the site. Microalgae, bacteria, rotifers, and testate amoebae biomasses were significantly higher in the rural site. Cyanobacteria biomass was significantly higher at the industrial site. Fungal and ciliate biomasses were significantly higher at the urban and industrial sites for the winter period and higher at the rural site for the spring period. The redundancy analysis showed that the physico-chemical variables ([NO2], relative humidity, temperature, and site) and the trace elements which were accumulated in bryophytes ([Cu], [Sr], [Pb]) explained 69.3% of the variance in the microbial community data. Moreover, our results suggest that microbial communities are potential biomonitors of atmospheric pollution. Further research is needed to understand the causal relationship underlined by the observed patterns.

Air pollution biomonitoring survey in Morocco using k0-INAA

Abstract Environmental monitoring is an essential step in any economical and social development policy. The atmospheric pollution study is a principal task due to the importance of atmospheric transfer of pollutants. Geographically, Morocco is characterized by different micro-climates influencing, on one hand, the transfer range of trace elements and, on the other hand, the availability of biological organisms that can be used in trace element air pollution biodetection study. Tree-barks, lichens and mosses were used in this study to evaluate trace elements bioavailability in different regions of Morocco. Those organisms were analyzed using the multi-elemental k 0 -INAA technique. The quality control of the results was performed by the analysis of reference materials. The analysis results were interpreted in the form of enrichment factors reflecting the atmospheric availability of anthropogenic pollutant elements such as Cl, V, Cr, Zn, As, Se and Sr.

Atmospheric trace compounds at a European coastal site—application to CO2, CH4 and COS flux determinations

Abstract The variations of CO2, CH4, COS, and NMHC concentrations, and of 222Rn activity were studied simultaneously in the boundary layer in a littoral site in Brittany, France. Various meteorological conditions occurred during the experiment allowing determination of trace gas concentrations characteristic of air masses having either dominant continental or oceanic influence. The relative NMHC concentration of the air reflects the origin of the air masses. Oceanic air is characterized by high proportions of alkenes, whereas the alkanes concentration is higher in continental air masses. In 1986 alternate sea- and land-breeze conditions allowed measurement of the evolution of the composition of an oceanic air mass under continental influence. By using the variabilities of 222Rn activities measured during the experiment, as well as the estimation of its mean flux over continents, we deduced the mean regional fluxes of CO2, CH4 and COS to be 5.8, 0.07 and −36 × 10−6 m mol m−2 h−1, respectively.

Heavy metal bioaccumulation by the bryophyte Scleropodium purum at three French sites under various influences: rural conditions, traffic, and industry

An active biomonitoring of the heavy metals pollution experiment was undertaken by means of the bryophyte species Scleropodium purum transplanted at three different sites exposed to rural, traffic, or industrial influences. Concentrations of about 40 elements in S. purum were determined by instrumental neutron activation analysis and inductively coupled plasma mass spectrometry. Accumulation rates of heavy metals were determined in the three sites. These accumulation rates in polluted sites were matched together and also to those recorded at the rural site. The changes of the accumulation rate of heavy metals in S. purum versus their concentrations in PM10 particles simultaneously collected above show some different accumulation properties of S. purum according to elements and sites. S. purum has a weak efficiency in the three sites to accumulate elements like V, Cr, Cu, Zn, As, Se, Sb, and Pb originating from atmospheric hot sources generally enriched in particulates matter (PM10), whereas it is particularly high for Br, Th, and Rb. For other elements, Co, La, Ce, and Hf, and rare earth elements, Fe, Sr, Nb, Ti, Al, and Sc, the collection efficiency by S. purum is intermediate. In the industrial site Dunkerque, a magnification of the collection efficiency by S. purum for elements originating from steel and aluminum productions and petroleum refinement suggests that these metals could be enriched in coarse particles with a better accumulation by the bryophyte with respect to PM10.

A PIXE and ICP-MS Analysis of Metallic Atmospheric Contaminants in Tree Bark Tissues, A Basis for Biomonitoring Uses∗

The qualitative and quantitative metallic content of tree barks of Argania spinosa (L.) Skeels were studied. Argania spinosa is an endemic species in Morocco. This tree is adapted to semi-arid climates and exposed to specific conditions of relative humidity, temperature, wind, and particle transport. Three sites were sampled in Morocco: the large town of Rabat, the harbor of Agadir, and Aït Baha, a countryside location exposed to continuous desert wind. The methodologies included (1) in situ microanalysis with proton-induced X-ray emission (PIXE) and (2) trace element determinations by mass spectrometry with inductively coupled plasma (ICP-MS) associated with extraction procedures. Both methods allowed detection of elements coming from different bark compartments. The profile of airborne contaminants in the barks was typical of the sampling sites. The level of lead in barks sampled in Rabat reached 100 ng cm−2, or higher, while it varied between 3 and 35 ng cm−2 in Aït Baha. The in situ study of the microscopic structure of the bark provided the location of major and minor elements at various depths inside the bark. A differential between free deposit on the bark surface and penetrated content was found for the major and trace elements. The free deposit on the bark surface was suspected to be mostly the result of recent contamination. Part of the contaminants spread out on the surface penetrated the superficial suber. This long-term accumulation affected mostly Pb. In deeper levels, airborne elements at low concentrations and elements resulting from root uptake were concurrently present and resulted in a complex situation, as noted for zinc.