Climate Change and the European Water Dimension - Agri ...

Climate Change and Global POPs
VI.F.4. Persistent Organic Pollutants (POPs)
POPs are described in the UNECE Convention on Long-Range Transboundary Air
Pollution (CLRTAP) as ‘…organic compounds that: i). possess toxic characteristics;
ii). are persistent; iii). are liable to bioaccumulate; iv). are prone to long-range
atmospheric transport (LRAT) and deposition; and v). can result in adverse
environmental and human health effects at locations near and far from their sources’.
They represent a small percentage of the chemicals of commerce, and many are
already strictly regulated or not currently in production. International agreements to
reduce or eliminate POPs are designed to reduce the risks to regional and global
environments (www.unece.org/env/lrtap). On May 2001, 151 Governments adopted
the Stockholm Convention on POPs, targeting the 12 chemicals/groups listed in
Table 1. The Convention contains provision for other compound classes with similar
properties to become the subject of the Convention and international controls in the
future. Examples of such “new or candidate POPs” include the polychlorinated
naphthalenes (PCNs) and polybrominated diphenyl ethers (PBDEs). The 2001
Stockholm Convention became legally binding on May 17 2004
(http://www.pops.int/documents/press/pr2-04SC.pdf) (UNECE, 1998; UNEP, 1998).
VI.F.5. The role of the atmosphere and the global re-distribution of POPs
The atmosphere is the ‘conduit’ through which POPs can move from atmospheric
emission sources via deposition to terrestrial and aquatic ecosystems (Klecka et al.,
2000). Indeed, the combination of POP semi-volatility and persistence means that
they can undergo Long Range Atmospheric Transport (LRAT), moving from source
regions to more remote locations, so that they have been detected in biota from
regions of the world where they were neither used nor produced. Their global
transport and distribution is extremely complex (see Figure VI.F.3). For example, it is
influenced by:
• the location of primary (i.e. fresh/new) emission/source areas;
• an array of emission and atmospheric transport and fate processes;
• the potential for repeated air-surface exchange;
• the physico-chemical properties of the substance in question.
These vary spatially and temporally, and ultimately influence the global fate/sinks of
POPs and their entry into food chains.
The complexity of the processes leading to the releases of POPs and the
environmental systems in which POPs circulate cause considerable gaps in our
understanding of their environmental fate and global budget. In many cases,
knowledge of the spatial and temporal pattern of primary emissions of POPs over the
last decades is poorly known. Uncertainty over the sources impedes the
interpretation of measured concentrations, because: i). it is difficult to determine
whether a certain concentration in the environment represents a recent or local signal
or whether it is the residue of a long-lasting emission/degradation processes; ii).
understanding of the pathways and sinks in the environment is incomplete. For
example, the importance of export to the deep ocean has only recently been studied
quantitatively.
The process of POP transfer to remote regions occurs in three stages. First, the
chemical is emitted to the atmosphere in source regions (e.g. by combustion,
incineration, pesticide spraying, volatilisation from pesticide treated soils or landfills).
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