An Application of Calpuff Dispersion Model to a Non-standard Problem

Pulp and paper mill situated in the complex terrain of northern Slovakia, in the close vicinity of the city of Ružomberok, continuously releases to atmosphere 30 kg of water vapor per second. Impressive clouds above the industrial complex have given rise to concerns from the side of local citizens, suspecting the emissions to be responsible for the local increase in precipitation. Therefore, a complex study has been initiated, including model simulation of the dispersion of water vapor from the paper mill focused on the domain of 8 x 7 km in close vicinity of the paper mill. Phase conversions of water vapor in the atmosphere are a complex thermodynamic process involving many factors. However, we found out that for some practical applications a simplified approach is sufficient to assess the magnitude of the above mentioned effects. A combination of CALMET-CALPUFF models were applied to compute hourly concentrations of water vapor added to the atmosphere by emissions from the paper mill; these were compared to the hourly absolute humidity values as measured by the meteorological stations in the region, which are not supposed to be affected by the paper mill. The interest was focused on those hours in which the “background” absolute humidity was below saturation value, but additional vapor from the paper mill would bring the value to or above the saturation point. Winter periods of two years (2005, 2006) were modeled and analyzed, during which 66 hours occurred when the additional water from the paper mill caused the humidity to exceed the saturation point, compared to 478 hours with 100% background relative humidity, when the additional vapor from the mill could possibly strengthen the icing effect which would occur anyway. The study concludes that the contribution of the paper mill to total precipitation is negligible even in the close vicinity of the factory. However, in certain cases it can cause icings on a nearby E50 road communication; although these cases are not frequent, they can lead to fatal outcomes. The uncertainties associated with the study method are also discussed.