Environmental quality issues in the perspectives of risk assessment and management in the Venice lagoon

In the framework of the European Water Framework Directive (European Union, 2000), the definition of environmental quality of waters (i.e. surface water, groundwater) refers to the concept of ecological, physical, chemical and biological integrity of environmental resources. The measurement of ecological quality requires a reference area, which is a nonaltered habitat of high ecological status. Accordingly, the environmental quality should be assessed by hydro-geo-morphological (tides, currents, sediment fluxes, etc.), physico-chemical (e.g. oxygenation, light, salinity, temperature, nutrient concentrations), and biological integrity (e.g. community health, species richness, individual abundance and dominance) parameters, as well as by the concentration of priority pollutants in biotic and abiotic environmental media (i.e. water, sediment, particulate matter and organism tissues). Until recently, the estimation of water quality focussed mainly on nutrients and chemicals, assessing the environmental quality by using water quality criteria, and water quality standards. According to the US Clean Water Act (Public Law 92-500), a quality criterion is defined as a ‘numeric or narrative expression that specifies concentrations of water (or sediment, [particulate matter, organic tissues]) constituents (such as toxic chemicals or heavy metals) which, if not exceed, are expected to support an ecosystem suitable for protecting life’. Environmental quality criteria are generally derived by applying different approaches: (1) Effects or weight-of-evidence database from laboratory or field exposures to contaminated media, for example, screening level concentrations for sediment (effect range approach, Long and Morgan, 1990); threshold effect level (MacDonald et al., 1996); (2) Equilibrium partitioning approach (e.g. derivation of sediment quality criteria from water quality criteria, Jones et al., 1996); (3) Background levels, or some multiple of background levels, in the affected region (Oslo and Paris Commissions, 1993); (4) Bioaccumulation and biomagnification- based guidelines, based on bioconcentration factors (Van der Kooij et al., 1991); (5) Biotic indices based on the presence-absence of target taxa (Occhipinti and Ferni, 2003). Amore suitable and integrated approach to evaluate environmental quality and to obtain environmental quality criteria is the risk-based approach, which takes into account the site-specificity of ecosystem, different exposure and effect measurements, and provides monitoring and management decision options by the involvement of stakeholders (ANZECC and ARMCANZ, 2000). The risk-based approach, using the weight of evidence method, is consistent with the most recent concept of environmental quality, such as adopted by the European Water Framework Directive (EU, 2000). In this chapter a summary of issues concerning the environmental quality for the lagoon of Venice is presented.