Spatial and Temporal Variability of Persistent Organic Pollutants

Concentrations of persistent organic pollutants (POPs) in air and water do show a remarkable spatial and temporal variability. Part of this variability is obviously associated to proximity to sources. On the other hand, there are a myriad of processes and variables in the biosphere that drive variability of POP concentrations in the environment. In fact, these processes can lead to change of concentrations of more than one order of magnitude. When assessing the risk associated to POPs, and their role as a driver of changes in ecosystems, it is important to have the information available on the sources of this variability, and the kind of variability they produce(seasonal, pulse, diurnal, spatial trends, vertical profiles, etc). Therefore the objective of this deliverable is to provide a review of the different kind of variability that has been found in the environment and comment on the potential processes driving this variability. For temporal variability, and since POPs are semi-volatile organic compounds, temperature is identified as an important driver of atmospheric concentrations due to its influence on air-water partitioning. Furthermore there is an important variability at daily and diurnal scale due to several factors, such varying air masses, influence of carbon cycle on dissolved-phase POP concentrations etc. However, it is shown, that an important fraction of this variability at short time is currently not well understood. State of the art models, however, show that atmospheric inputs can induce ten-fold variability in POP concentrations in surface waters. Concerning spatial variability, in addition to proximity to sources, there is also other variables that lead to an important spatial variability. Atmospheric sources such as diffusive uptakes and dry deposition are strongly enhanced at high wind speeds. Furthermore, since POPs are hydrophobic pollutants they can present a patchy distribution due to the influence of organic carbon cycle. Models for the European seas also show that there is a high variability in atmospheric inputs of POPs. The review of literature reported concentrations of PCBs, PAHs and PBDEs confirm this important variability The identified spatio-temporal trends in POP concentrations and the identifications of some of the drives of these sources of variability provide important information that may eventually be useful in order to define the POPs impact that can lead to points of no return in ecosystems and identify thresholds.

DACHS Jordi;  JURADO Elena;  MARINOV Dimitar;  MACIEL Helena;  ZALDIVAR COMENGES Jose'; 

2006-11-08

Joint Research Centre

JRC33814

https://publications.jrc.ec.europa.eu/repository/handle/JRC33814,