Wildfire is the major disturbance in Mediterranean forests, posing an important threat to life, human goods, and natural resources in fire-prone forest areas. In the case of Portugal, wildfires devastate in the last decade an average of 140 000 ha per year. Fire frequency in Portugal is also not expected to decrease in the foreseeable future, not just because of the likely increase in fire-propitious meteorological conditions due to climate change but also because of the nature of the country’s forestry activities.

A key environmental concern in relation to wildfires is that they constitute a diffuse source of contamination of the aquatic systems affecting the water quality, namely through the production and subsequent exportation of deleterious pyrolytic substances, such as polycyclic aromatic hydrocarbons (PAHs), and also through the input of metals associated to ash/soil loads. Concern about PAHs relates to their toxicity, carcinogenicity, environmental persistence, and tendency to bioaccumulate. Contamination of water bodies by postfire inputs of various metals may constitute also an environmental problem, as some of them are poisonous at high concentrations, are persistence in the environment and tend to bioaccumulate.

A substantial part of the PAHs and metals can end up in downstream aquatic habitats, since wildfires can also enhance greatly runoff generation and the associated transport of sediments. In fact, preliminary results yielded by the proponent team showed the presence of distinct PAHs in runoff and water samples from a burnt area and concerning toxic effects in organisms exposed to them (Campos et al, in press), which emphasizes the urgently needed to provide a sound scientific basis for assessing, monitoring and predicting the risks of surface water pollution by recently burnt areas. Moreover, both PAHs and metals constitute a concerning risk to human health, either by direct consumption of water with concentrations exceeding guideline values, or by use of water for recreational activities as fishing and swimming. Whilst the effects of wildfire on hydrological and erosion processes have received considerably research attention (including in Portugal by members of the proponent), the information on post-fire exports of PAHs and metals from recently burnt areas has been poorly studied so far. Also the toxic effects of this ash-loaded runoff on aquatic biota and human health remain an important research gap.

The present FIRETOX proposal addresses this urgent need for a better understanding of the toxic effects that wildfires can cause in downstream aquatic ecosystems. It therefore aims at:

• assessing the production and exportation of PAHs and metals by runoff in burnt areas at plot-to- catchment scale (task 2);

•determining the toxicity of runoff and sediment samples from burnt areas on aquatic organisms from different trophic/functional groups, and relate it to the samples’ PAH and metal contents (task 3);

• evaluating the potential of fire-produced PAHs and metals for bio-amplification and bio-accumulation in aquatic biota (pelagic and benthic organisms) (task 4);

• developing and testing in-situ assays for field validation in additional burnt areas (task 5);

• elaborating a protocol that uses one or more of parameters studied by for a rapid and reliable assessment of the potential risks that recently burnt areas pose for aquatic biota and human health due to pollution of downstream surface water bodies with PAHs and metals (task 6).

The knowledge gap that FIRETOX addresses is of special and urgent importance for the implementation of the Water Frame Directive (WFD). Namely, the WFD established the obligation to characterize the various sources of point and diffuse pollution of water bodies. In this context, also FIRETOX’s contribution to the knowledge about the eco-toxicological response of pelagic and benthic species to runoff from burnt slopes and catchments deserves special mention. This knowledge is fundamental for the type of integrated assessment that the WDF demands, in this specific case of the off-site effects of wildfires on surface water quality. The FIRETOX protocol is envisaged as an important contribution to such an integrated assessment for future wildfires. Therefore, it will be duly divulged to authorities with responsibilities in implementing and upholding the WFD in Portugal.

The topic of the FIRETOX proposal has a strongly multi-disciplinary character. These three distinct fields of expertise - i.e. field hydrology, aquatic eco-toxicology and environmental organic chemistry – are duly covered by the FIRETOX team.

CESAM members on this project

Bruno André Fernandes de Jesus da Silva Nunes

Dalila do Rosário Encarnação Serpa
Researcher

Isabel Maria Alves Natividade Campos

Joana Luísa Pereira

Nelson J. Cabaços Abrantes
Principal Investigator

Patrícia A. Oliveira Pereira Kowalski