Talk by Louise Foan, University of Toulouse – Niels Bohr Institute - University of Copenhagen

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Talk by Louise Foan, University of Toulouse

Can mosses be used to monitor atmospheric deposition of organic pollutants?

Regulation of persistent organic pollutants (POPs) emissions and reliable monitoring of POP concentrations in ambient air is of paramount importance because of their slow rates of degradation, toxicity and potential for both long-range transport and bioaccumulation in living organisms (Aarhus protocol, 1998). Polycyclic aromatic hydrocarbons (PAHs) in particular have shown carcinogenic, mutagenic and immunotoxic effects detrimental to health and appear to be ubiquitous in the environment. Indeed, these compounds are released through combustion of fossil fuels in power plants, domestic heating, waste incineration, industrial processes and, most importantly, motor vehicle exhaust.

Despite recent effort to investigate PAH distribution and fate in air, water and soil, few studies provide extensive information on spatial and temporal trends of PAH atmospheric deposition, due to high investment and running costs of the technical devices. An alternative consists in resorting an integrative technique able to assess the environment contamination; technique based on observations and studies of the reactions of living organisms exposed to pollution episodes. Biological monitoring has been used for the last three decades, the principal applications mainly concerning the study of pollutants such as heavy metals, sulphur and phosphorous compounds, NO2, ozone and radionuclides. Bryophytes, more commonly called mosses, are particularly used for biomonitoring air quality because these terrestrial plants are excellent bioaccumulators of airborne pollutants. However, few studies have been developed in relation with persistent organic pollutants (POPs) such as organochlorine pesticides (OCPs), polychlorobiphenyles (PCBs) or polycyclic aromatic hydrocarbons (PAHs). In this context, my thesis aimed to validate bryophytes as tools for biomonitoring atmospheric deposition of PAHs on various space-time scales:

-       A historical study of the contamination of a Spanish Natural Park with herbarium
        mosses collected between 1879 and 2007.

-       An annual study of atmospheric deposition at the Spanish Natural Park, using moss
         transplants, rainwater and particulate samples.

-       A pilot project at a European scale with mosses sampled in situ in France, Switzerland
        and Spain.

To further investigate the quantitative importance of different sources of deposition, the use of stable isotopes at natural abundance levels in mosses provides a powerful approach for understanding environmental interactions. Isotopic composition of elements, such as carbon and nitrogen, changes in predictable ways during their course through the biosphere, which makes them ideal tracers of the pathways and origins of these elements.

PAH concentrations and isotopic ratio (δ13C and δ15N) data was submitted to multivariate analysis with site-specific and regional data, such as the elevation of the sampling sites, pluviometry and soil occupation data, to identify the parameters of influence on pollutant content in mosses. Moreover, correlation tests were carried out with other moss data (heavy metals content) and air pollution data (NH3, NO2, PM10) to observe possible common trends between pollutants and identify common atmospheric emission sources.