Every day known and unknown pollutants are discharged in the aquatic and atmospheric environment and they can impact even remote areas, very far from the emission sources. The pollutants released into the environment undergo a complex series of processes, including chemical reactions and interactions with mineral particles, organic matter and living organisms, which affect their diffusion, potential effects and final fate. The study of pollutant circulation is necessary in order to interpret field monitoring data and develop transport and ecological models. Assessment of the potential effects of pollutant mixtures should take into account also their additive, synergistic or antagonistic toxicity. The finding of biomarkers which highlight the biological response to specific classes of contaminants and the development of analytical methods for the determination of trace pollutants in different matrices are necessary tools to follow the environmental dynamics and the possible effects of chemicals on biota.
Sources, distribution and mechanisms of transformation of organic and inorganic pollutants
Conventional pollutants (nutrients, metals, organic matter), emerging pollutants (endocrine disruption, polybromodiphenyl ethers, perfluorinated, pharmaceuticals and personal care compounds, nanoparticles, trace metals), “obsolete” pollutants (compounds used in the past or abandoned without too many precautions following their call by trade) end up degrading the quality of water resources, thereby limiting the uses and endangering aquatic life.
The identification of the sources, the study of mechanisms of diffusion and transformation of elements and substances are different aspects, strongly interrelated, involved in the assessment of the ecological risk caused by environmental contamination, because they influence persistence, mode of transport and fate of pollutants.
Studies were carried out at IRSA on rivers, lakes and aquifers to determine environmental critities situation, to estimate transported load and identify management solutions at the basin scale. That's the case of transport and accumulation of metals in the methylated form (e.g. methyl-mercury) or the formation of metabolites of herbicides (eg demethyl-terbuthylazine), insecticides (eg p, p'DDE op, p'DDD) or surfactants (eg nonylphenol and their precursors, NPE1O, NPE2O).
Relevant cases of contamination, such as those from DDT in the river basins of the Toce and Ticino, respectively tributary and outlet of Lake Maggiore, those from metals, herbicides and endocrine disruptors in the River Lambro and Po and from perfluorinated compounds in the River Bormida, have seen the involvement of IRSA. The presence of endocrine disrupters is one of the major criticities identified in the different river systems investigated (Lambro, Po, Tiber). Marked effects on fish by endocrine disrupters have been reported in the Po.
Geographical areas that are farthest from urban, industrial and agricultural sources of pollutant emissions represent the most suitable place to understand the long-range transport phenomena and verify the impact of environmental contamination at global scale. Through these studies it is possible to obtain information on the “assimilation/sink” of pollutants by the terrestrial ecosystem.
Since over two decades, IRSA has been developing investigations in the remote areas of the Earth, with particular continuity in the high elevated areas of the Himalaya and the Karakorum chains. These activities were carried out within the collaboration with the Ev-K2-CNR Committee, with the objective to contribute to understand the importance of global pressures on the structure and functioning of remote ecosystems. Activities concerned particularly the study of:
- snow contamination, contributing to underline the dominant role of monsoons in the pollutants circulation,
- numerous lake environments and running waters at altitude between 4500 and 5500 m, where the limnological aspects were integrated with hydromorphological, climatic and glaciological investigations.
Studies also deal with alpine and subalpine remote environments, characterized by extreme climatic conditions, shallow soils, steep terrain, and for these reason very sensitive to global change. Since more than ten years IRSA carries out researches focusing on long term trends of main chemical species in atmospheric deposition, in the soil solution and runoff. The aim of such investigations is to explore the long-term potential effects of nitrogen (N) deposition on the aquatic and terrestrial ecosystems, where chronic N inputs exceeding the N assimilation capacity of biological processes can lead to the phenomenon of “N saturation”.
Contaminant partitioning, bioavailability and bioaccumulation
The study of contaminant partitioning among the various environmental matrices: water/colloids/particulate matter/sediment, soil/soil solution, air/water, air/soil plays a central role in understanding their environmental behaviour. The modes of partitioning affect the diffusion of pollutants in surface waters, their bioavailability and bioaccumulation, thus their capacity to interact with biota and, finally, their ability to migrate through the insature layer to reach groundwaters. Water sample fractionation by using filtration and tangential flow ultrafiltration, passive sampling devices (e.g., SPMDs and DGTs) capable of selectively accumulate truly dissolved contaminants, procedures for selectively extract organic and inorganic compounds from biological matrices (fishes, macroinverterbrates, algae), speciation techniques, chemical and biological models, such as Minteq and Biotic Ligand Model, are applied for these purposes. IRSA activities in this context include:
- the quali/quantitative characterization of dissolved, colloidal and particulate organic matter in the northern basin of the Adriatic Sea, in relation to massive mucilaginous occurrences that affected that ecosystem;
- the analysis of distribution of persistent and hazardous contaminants (endocrine disrupters, PAHs, pharmaceutical compounds, PCBs, heavy metals) in different matrices of surface water bodies (Po, Lambro and Tiber rivers, Lake Maggiore);
- the uptake and bioaccumulation processes of pollutants in test organisms (e.g. Lumbriculus variegatus) in order to understand the modes of transmission of contamination through the trophic chain and the possible effects on biota.
Toxicity and effects of contaminants
Aquatic organisms are exposed to complex mixtures of contaminants, which, generally, are present at very low concentrations, yet capable of exerting detrimental effects. This is due to an additive mechanism of toxic contributions that has been demonstrated in more occasions. Some of these chemicals can also affect the endocrine system of fish and, in general, of wildlife. Despite the fact that multiple toxic mechanisms may be involved, the effects of toxic chemicals are always modulated by the trophic status of aquatic ecosystems, as IRSA has demonstrated in several recent studies undertaken in the area of confluence of the River Lambro with the River Po.
Short- and long-term toxicity tests conducted on several species of aquatic organisms (bacteria, algae, crustaceans and fish), various stages of their life-cycles and different environmental matrixes (water, sediment, extracts etc.) are some examples of the tools commonly used in laboratory and field studies. Investigating the processes of bioconcentration and bioaccumulation of pollutants as well as the responses of a multiplicity of biomarkers, are additional research subjects that, related to the alterations and effects induced by chemicals, can be studied at IRSA. According to the new European regulation of REACH, a database named DESC collecting and organizing eco-toxicological data for a high number of chemicals has been developed by IRSA and made available to Administrators and stakeholders.
Advanced analytical methods and real time monitoring systems
In order to study the occurrence and fate of emerging substances and to achieve the low detection limits required by recent Directives (WFD 2000/60/EC, 2008/105/EC) the development of new measurement methods and technologies is needed.
In order to achieve these goals new analytical methods based on the hyphenation of mass spectrometry with chromatography have been developed for the determination of polybromodiphenylethers (PBDE), perfluorinated compounds, endocrine disrupters, disinfection by-products (DBP) and algal (eso- and endo-cellular) microcystins. Among the advanced preparation techniques Molecularly Imprinted Polymers (MIP), as an innovative sorbent for the solid extraction of herbicides, insecticides and PAH in water samples, have been designed and experimented. In the field of trace metals analysis in aquatic environments special focus has been devoted to the speciation of metals and to the optimization of current methods of extraction and preconcentration.
A further field of research at IRSA is the development of real time monitoring system which can be employed as tool for the in situ monitoring of concentration and processes or as early warning systems. Such a system was developed and tested for the determination of physico-chemical and ecological variables in lakes, while an on-line system, consisting of an automated station of sample extraction connected to a HPLC-MS system, was designed and built for the determination of polar compounds in drinking water treatment plant.