A new “high-resolution” computer simulator to predict future environmental pollution scenarios

Where do chemical pollutants go after they have been emitted to the environment? For how long will these dangerous substances be present in air, water, soil and sediments? Can we assess in advance whether they will reach concentrations capable of causing adverse effects on plants, animals, and humans?

An international team lead by NIVA (Norwegian institute for Water Research) researchers in Oslo has developed a new sophisticated computer simulator capable of predicting and forecasting current and future distribution of pollutants in realistic environments as a function of climate, human activities, and of pollutant properties.

Everyday use causes emission

Chemical industry is a fundamental asset of European economy representing a significant fraction of the GDP and 7% of the total industrial production of the “old world”. Synthetic chemicals are used in virtually all human activities including agriculture and food production and processing, industrial production, transport etc.

- Recent advances in analytical chemistry showed that not only the step production is causing pollution but also the use of products during everyday life activities, Luca Nizzetto, Research Scientist at NIVA, says.

This includes emission of several house care and personal care products, additives used in product of large distribution (such as for example plasticizers and flame retardants in e-products), and also pharmaceuticals.

- If the emission of contaminants in a given areas is closely linked to human activities, their fate in the environment and eventually their potential for impacting it, largely depends on natural processes such as the water cycle and the cycle of nutrients and organic matter. These processes are in turn influenced by climate and, of course, human intervention. It is clear that analyzing such a “circular” frame requires sophisticated tools and “integrative” reasoning, Nizzetto says.

INCA - a new tool

With the introduction of the new European regulation on chemicals (REACH) the European Industry had placed investment ramping up to billions of Euros in order to fulfil registration requirements and chemical risk assessment. Unfortunately, the available tools for predicting contaminant distribution and accumulation in the environment, and forecasting the associated risk for human and biota, are still generally extremely simplistic.

For example, existing models are not site-specific (i.e. they do not reflect a real environment but a generic “hypothetical” geographical scenario) and they provide a very simplified description of environmental processes. Using these tools to assess climate and human activity influence on environmental pollution may therefore lead to inaccurate results or information hardly usable when it comes to analyze the situation of real scenarios and specific locations.

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INCA-Contaminant is a high resolution simulator built upon the existing water quality model family of integrated catchment model “INCA”, developed during the last 15 years and devoted to the high-resolution simulation of hydrology and biogeochemical cycles in specific environments. As previous INCA models, INCA-Contaminants can be applied to real river catchment and currently represent the highest achieved level of multidiscipline integration in the area of water quality models.

- INCA-Contaminants is a truly multidisciplinary tool capable of analyzing and simulating hydrology, organic matter cycle, soil erosion, sediment transport and contaminant fate in realistic scenarios, Nizzetto explains.

 - For example, during the three-years development period the model was configured to simulate contaminant fate and distribution in the Sandvikselva catchment - a small boreal forest catchment in the vicinity of Oslo, the Morava river catchment - a large tributary of the Danube flowing between Czech Republic , Austria and Slovakia, the Thames in the UK, and the Ganges in India.  INCA-contaminants is built upon thousands of equations that describes the process listed above, interdependently and as a function of climate and human intervention in the environment.

Figure 1
INCA-Contaminants simulating contaminant fate and distribution in the Morava river catchment - a large tributary of the Danube flowing between Czech Republic , Austria and Slovakia. (Graphics: Luca Nizzetto, NIVA).  



Integrated simulation

The simulator is fed with numeric information describing the area of interest’s characteristics. These are for example: land elevation, river network structure, soil characteristics, fraction of land occupied by agriculture, residential, industrial, or forest areas. In order to run realistic simulations INCA-Contaminants uses climate data of rain and snow deposition, air temperature and wind speed. Finally a number of parameters are introduced describing fundamental properties of the chemical substances to be simulated including also data on their emissions to soil or water, air concentrations and atmospheric deposition fluxes. Using this information INCA-contaminants runs simulation delivering information on concentration and transport of the selected pollutants in soil, water and sediments, on a daily base, and in arbitrary points in the catchment and river course.

- One of the interesting features of INCA-Contaminants is that it can simulate an arbitrary number of substances simultaneously, and these substances can be linked in a way that one substance can result from the transformation of another parental substance, Nizzetto says, who emphasizes that this is a useful and important function, since contaminants in the environment can undergo chemical reactions producing degradation products that can be even more toxic and persistent than the original parental molecule.

PCBlast from the past

- We already run a few applications with our new simulator and demonstrated that INCA-Contaminants works well and provides solid results that could be validated against experimental data, Luca Nizzetto says.

The model has been used in the different applications where different types of questions were addressed. For example, during the application in the Sandvikselva and the Thames rivers, INCA-Contaminants successfully predicted the concentration and temporal trends in water and sediments of several persistent organic pollutants (such as the Polychlorinated Byphenyls - PCBs) historically accumulated in the catchment soils.

- In these applications we could also analyze, for the first time in quantitative terms, the sensitivity of results to changing soil organic matter turnover, sediment transport patterns and climate. Traditional contaminant models present numerous drawbacks when used to perform this type of analysis, the NIVA-researcher added.

During the application with the Morava river, the scientists used the model to simulate observed pattern on DDT long term trend in the soils of central Europe. They could for example reply to questions such as: how long will DDT represent a problem for the environment in this region, and which are the mechanisms driving its very slow dissipation, and again, what will be the effect of land use change on the future of the environmental burden of DDT.

Morava_river_Wikimedia Commons_KarlGruber
During the application with the Morava river catchment - a large tributary of the Danube - the scientists used the model to simulate observed pattern on DDT long term trend in the soils of central Europe. (Photo: Wikimedia Commons / Karl Gruber).

Contaminants of emerging concern

Finally, in the application with the Ganges river, the scientists focused on a group of contaminants of emerging concern: a set of perfluoroalkyl substances (PFAS) used in industrial processes as surfactants or to coat textile and other products to give waterproof and “non-stick” properties.

- We asked INCA-Contaminants to help us estimating the expected emission of PFAS to the Ganges waters that could justify the experimentally observed concentration data. Thanks to the model we could perform a catchment-wide assessment and highlight an interesting relationship between the intensity of emissions of these pollutants and the percentage of urban population in the different areas of Northern India, Nizzetto concludes.

Reference:

Nizzetto, L., Butterfield, D., Futter, M., Lin, Y., Allan, I., Larssen, T., 2016. Assessment of contaminant fate in catchments using a novel integrated hydrobiogeochemical-multimedia fate model. Science of the Total Environment 544, 553-563.

Sharma, B.M., Bharat, G.K., Tayal, S., Larssen, T., Bečanová, J., Karásková, P., Whitehead, P.G., Futter, M.N., Butterfield, D., Nizzetto, L., 2016. Perfluoroalkyl substances (PFAS) in river and ground/drinking water of the Ganges River basin: Emissions and implications for human exposure. Environmental Pollution 208, Part B, 704-713.

Lu, Q., Futter, M.N., Nizzetto, L., Bussi, M.D., Jurgens, M.D., Whitehead, P.G., 2016. Fate and Transport of Polychlorinated Biphenyls (PCBs) in the River Thames Catchment – Insights from a Coupled Multimedia Fate and Hydrobiogeochemical Transport Model. Science of the Total Environment In review.

Sanka, O., Kalina, J., Lin, Y., Deutsher, J., Futter, M.N., Butterfield, D., Brabec, K., Nizzetto, L., 2016. Modeling hydrological and biogeochemical controls of the dissipation of p,p’-DDT from soils. Environmental Science and Technology In review.

Last updated 27.06.2016