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Dynamic Sensing of Chemical Pollution Disasters and Predictive Modelling of Their Spread and Ecological Impact

Final Report Summary - ECODIS (Dynamic Sensing of Chemical Pollution Disasters and Predictive Modelling of Their Spread and Ecological Impact)

The ECODIS project developed sensor technologies for monitoring the physicochemical reactivity and biological impact of inorganic and organic pollutant species in aquatic systems. ECODIS also applied these technologies to the study of the short and long term chemical and biological status of aquatic ecosystems following a pollution disaster.

Key innovative objectives of ECODIS were:
(i) Development of sensors and in situ probes, covering a range of response times and spatial scales, for measuring (changes in) pollutant species concentrations, and to provide signals that were quantitatively linked to responses from the most appropriate biota over a wide range of concentrations.
(ii) Integration of short term conversion and transport processes (diffusion, changes in speciation (complexation, adsorption, biotransformation)) with macro-scale long term transport / hydrological models to achieve quantitative knowledge on pollutant spread upon disaster impact.
(iii) Analysis and modelling of the dynamic speciation and ensuing toxicity of pollutants with respect to their acute and chronic effects following a disaster event. A range of trophic levels would be studied to give insight into potential biodiversity impacts.
(iv) Creation of a new approach to ecotoxicological risk assessment that linked dynamic pollutant speciation (exposure) with toxicology in line with leading scientific understanding. The outcome of this approach would be compared with current practice, based on total concentrations, body burdens, bioassays, and field inventories.
(v) Production of a user friendly guide for crisis managers that outlined strategies for monitoring physicochemical and biological parameters on the site of a pollution disaster, handling and reporting of the ensuing data, and tools for ecological impact predictions for the impacted water body.

ECODIS tackled its objectives by an integrated approach comprised of the following four closely interlinked and interdependent sections of work:

Section I. Development and dedication of dynamic sensor technologies for pollutant speciation analysis and ecotoxicological effects
Dynamic sensor technologies were characterised and dedicated to speciation analysis of metal and organic pollutants under disaster conditions. A dynamic analytical sensor is characterised by its:
(i) response time, which is analogous to the effective time scale for bioavailability, and
(ii) accumulation time, tacc, i.e. the length of time over which pollutant species are accumulated in (loaded onto) the sensor prior to quantification.
The signal resulting from the accumulation step represents an integration over all exposure variations in the test medium during this time period, tacc, analogous to the concept of bioaccumulation. A multi-faceted approach was adopted for detection of ecotoxicological effects, namely hyperspectral imaging, a panel of bioassays, and genomic methods. Hyperspectral imaging emerged as a useful new technology for identifying ecotoxicological effects via detection of shifts in microbioal community composition. A panel of bioassays was developed for disaster conditions, including a new flash bioassay for rapid screening of acute toxicity.
Section II. Determination of the dynamic bioavailability and toxicological effects of pollutant species
Studies on biouptake encompassed characterising the role of biogels in pollutant accumulation, determination of uptake fluxes by algae from trace metal mixtures and the accumulation of polycyclic aromatic hydrocarbons (PAHs) by an aquatic worm. Biogels such as alginate and biofilms themselves are found to have a high capacity for sorption of Cd, Pb, and Cu. Most of the sorbed metal is bound to the biogel matrix and is nonlabile on the microelectrode timescale. The amount of metal sorbed is dependent on both the pH and the ionic strength of the exposure medium. Particular attention was paid to linking the temporal evolution of the pollutant speciation in the exposure medium to the dynamics of biouptake, including the ability of the organism's physiology to process the accumulated pollutant. Physiology-based biokinetic models were developed that allow estimation of the bioaccumulation potential in different types of biological tissue. Models for doseresponse relationships were developed that target different physiological endpoints. In particular, for pollution disaster situations it is useful to discriminate between:
(i) long-term effects and
(ii) short-term responses to increased exposure concentrations.
This differentiated approach involved consideration of two types of doseresponse relationships:
(a) relationship between mortality and morbidity indices and the total concentration of the toxicant in the aquatic organism, and
(b) relationship between mortality and morbidity indices and the biologically effective dose (BED) of the toxicant (including its metabolites) at the target tissue, which expresses the respective physiological response.
Section III. Modelling of the temporal spread of pollutants and risks in aquatic ecosystems
ECODIS generated new knowledge in understanding and predicting pollutant chemodynamics at the microscale, and in the coupling of these processes with macroscale flows in the water body. Sink/source functioning of sediments and biofilms was a process of key importance in this regard. The overall outcome was a model for the temporal spread of pollutants and risks in aquatic ecosystems at the catchment scale. At the microscale, the effect of protonation of ligand and metal species on metal complexation kinetics was quantified. Dissociation kinetics of complexes was found to be modified in mixtures of ligands; both enhancements and suppressions of the individual fluxes can occur depending on the composition of the mixture. Computer codes for computation of fluxes were developed.
Section IV. Measurement and management of disaster-site data and development of dynamic risk assessment
Field campaigns were conducted during which simultaneous chemical speciation, biouptake, and ecotoxicological measurements were made in situ. The results highlighted the utility of the multidisciplinary approach adopted in ECODIS for monitoring and interpretation of temporal and spatial pollutant chemodynamics coupled with biological impacts. The damage to the aquatic environment following an accidental spill of dangerous substances is determined by the intrinsic properties of the substance itself (aquatic toxicity, persistence, bioaccumulation, solubility in water, etc.), the fate of the substance in the aquatic environment (evaporation, sedimentation, dilution, chemical reactions, degradation, etc.), the physical conditions of the aquatic environment (flow rate, dimensions, physicochemical properties of the water, prior pollution, etc.), and the population and sensitivity of aquatic habitats. Exposure conditions experienced by organisms and the related ecological risk are defined by the temporal profiles of concentration and speciation of pollutants. These profiles need to be quantitatively linked to biological effects and finally, estimates of ecotoxicological risk. One of the major ECODIS goals was to develop a modelling framework that included predicted pollutant species distributions, and ensuing biological risks, in all compartments of the aquatic ecosystem as a function of time and space.

The ECODIS end results were broad in scope, encompassing fundamental scientific knowledge, technology for in situ monitoring, and a user-friendly guide for crisis managers. Specific results comprised:
- A suite of sensors and in situ probes, covering a range of response times and spatial scales, that measure the (changes in) pollutant species concentrations under disaster conditions. The speciation sensors were complemented by ecotoxicological sensors for generic and specific biological responses, as well as an in situ probe for measuring algal bioaccumulation fluxes.
- Theoretical concepts that quantitatively linked analytical signals from the speciation sensors to responses from the most appropriate biota over a wide range of pollutant species concentrations.
- Models, coupling micro- and macroscale processes that quantitatively described the pollutant spread in a water body upon disaster impact.
- An innovative approach to ecotoxicological risk assessment that linked dynamic pollutant exposure profiles with toxicology, resulting in sophisticated strategies for disaster management policies.
- A set of user-friendly guidelines for crisis managers that outlined strategies for monitoring, data management, and interpretation of pollution disasters.

Directly, the ECODIS results would be used by crisis managers on site of pollution disasters, both to direct actions in the immediate wake of the event, and to develop optimal responses based on their predicted spread and ecological impact. The scientific knowledge generated contributed to furthering multidisciplinary understanding of ecosystem functioning and response to pollutants.

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