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Beschrijving van de DEPAC module : Droge depositie modellering met DEPAC_GCN2010

Description of the DEPAC module : Dry deposition modelling with DEPAC_GCN2010

Synopsis

The process of dry deposition represents the coming down of air components like ammonia on vegetation and soils. Since dry deposition measurements are difficult and expensive, dry deposition estimates are mainly computed through modelling. New insights have led to an update of the description of the dry deposition process. This report presents a detailed description of the revised software-module DEPAC, which simulates the dry deposition process of ammonia. Dry deposition influences the concentration of a component in the air and is an important source of components for the receiving surface. Thus it is important to estimate the amount of total nitrogen deposited on nature. When too much nitrogen is deposited, biodiversity is harmed since nitrogen-thrifty vegetation is replaced with more common species like grasses and brambles. Dry deposition of ammonia represents the largest amount of the total nitrogen deposition. Ammonia enters the air predominantly through the process of evaporation from manure in animal stables and when liquid manure is spread over the land. Earlier versions of the DEPAC module ignored the ammonia concentration in vegetation and soils. The current version assumes that ammonia is present in vegetation, water surfaces and soils. Thus surfaces not only adsorb ammonia but also are able to emit it under certain atmospheric conditions. Further included in the update are an improved description of the light fall in woods and other high vegetation and an improved description of the yearly cycle of the amount of leaf area of plants and trees.
 

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