Assessment of hydrogeochemical hazard and risk in the urbanized territories

Analysis, assessment and management of different kinds of risk are the basic elements of providing of sustainable development. Hydrogeochemical risk assessment should take into account both risk of groundwater pollution (so called "the risk of exposure") and risk of impact of polluted groundwater on the population and objects of an infrastructure (so called "the risk after exposure"). The conceptual model of hydrogeochemical risk in the urbanized territories is presented. The main ideas concerning stages of formation of hazard and risk in the system "decision maker - source of pollution - groundwater - human" underlie the model. The conceptual model framework contains the model of formation of hazardous hydrogeochemical conditions and the model of influence of hazardous hydrogeochemical situation on human directly or via human related objects - buildings, food, water, etc. In the first model the probability of occurrence of hazardous hydrogeochemical situation is determined in a result of multiplying probabilities of several occurrences. These are the probability of impact of source on groundwater and the probability of object location in the zone of impact and the probability of formation of cumulative effect above maximum allowed value and the probability of groundwater instability occurrence. In the second model the hydrogeochemical risk for recipient is estimated. Risk assessment takes into account estimation of the probability of hazardous hydrogeochemical state, the probability of contact of under consideration recipient with component of environment, the probability of occurrence of recipient vulnerability and estimation of damage value. The conceptual model allows following stages of hazard and risk formation and estimate probabilities of each component of the hydrogeochemical risk beginning from projecting through construction activity and exploitation to reconstruction and closing down. The conceptual model can be used for estimation of geochemical hazard and risk in soils, surface water and groundwater and for development of principles of management by geochemical risk. This approach was used for risk assessment of groundwater contamination under disposal fields in Moscow. Contaminated vadoze zone supplies groundwater with heavy metals and ammonium during more than 100 years. Stochastic - deterministic approach was used for risk forecast. The deterministic model of contaminants migration takes into account the migration in vadoze zone and in groundwater. Stochastic elements represented in this model relate with features of geological structure and features of vadoze zone contamination. Results of the multiple forecasts have allowed estimating probability of groundwater pollution for different sites. Estimation of damage considered expenses on soils reclaiming, groundwater remediation and development of environmental monitoring.