Spatial Risk Mapping Research Articles

A probabilistic methodology to assess the risk of groundwater quality degradation.

An approach to assess the risk of groundwater quality degradation with regard to fixed standards. based on Disjunctive Kriging (DK) is presented. The DK allows one to evaluate the Conditional Probability (CP) of overriding a given threshold of concentration of a pollutant at a given time, and at a generic point in a considered groundwater system. The result of such investigation over the considered area can be plotted in form of maps of spatial risk. By repeating this analysis at different times, several spatial risk maps will be produced, one for each considered time. By means of non-parametric statistics, the temporal trend of the CPs can be evaluated at every point of the considered area. The trend index, assessed by means of a sort of classification of the trend values obtained as described above, can be superimposed on the most recent values of the spatial risk (i.e.: the most recent values of probability). Consequently a classification of the risk of groundwater quality degradation results with which to weigh both the spatial distribution and the temporal behaviour of the probability to exceed a given standard threshold. The methodology has been applied to values of nitrate concentration sampled in the monitoring well network of the Modena plain, northern Italy. This area is characterised by intensive agricultural exploitation and hog breeding along with industrial and civil developments. The influence of agriculture on groundwater results in a high nitrate pollution that limits its use for potable purposes.

Spatial Characterization of the Occurrence of Road Salts and Their Environmental Concentrations as Chlorides in Canadian Surface Waters and Benthic Sediments

Abstract Increased concern over the contamination of surface waters by road salts and their adverse effects on the freshwater organisms led to the inclusion of “road salts” on the second Priority Substances List (PSL2) under the Canadian Environmental Protection Act The list identifies substances that must be assessed on a priority basis to characterize the nature and extent of the risk they pose to the environment or human health. This paper adds to the collection of several reports which constitute “supporting documentation” for the environmental risk assessment of the priority substance “road salts”. It reviews the physical-chemical properties of inorganic salts commonly used for road maintenance and their fate and transport in surface waters and sediments, together with the environmental concentrations of road salt constituents in the context of watershed geology and other environmental factors governing their concentrations. The paper also provides a spatial map of chloride concentrations as a basis for developing an understanding of a spatially based, ecological risk assessment for surface water systems and relates the spatial risk map to observed concentrations of chlorides. The data suggest that the surface waters most sensitive to road salts impacts are small ponds and streams draining large urbanized areas. Environment Canada is presently considering several alternatives for dealing with road salts.