Synthesis of HNO3 from organic matter and its influence on nutrient replenishment in forest soils.
Chemical analyses during a decade of bulk precipitation, throughfall, humus water and soil water in forest plots ranging from sand to silt of Pleistocene origin in Flanders (N-Belgium) prove that previous and present weathering is predominantly due to synthesis of HNO3 from soil organic matter. The HNO3 reacts with silicates and possibly PO4(3-) species, releasing Al, Fe, nutrient base cations and H2PO4-, and is transformed into NO3-. In all soils solubilized Al3+ is predominantly associated with NO3- and with some organic bases in the coarse-textured soils with undisturbed or previously plowed spodic B horizon. The amounts of ions leached, especially Al3+ and NO3-, are much higher in the sandy than in the silty soils as a result of a stronger neutralization of acidity in the silty soils. Nutrients, leached from the soil, have to be replenished in some way for a sustained forest growth. N- and S-species must come from the atmosphere. Basic cations and P-species have to be supplied out of the solid phase. The concentrations of NO3- in the soil water show that the liberation of these elements from the solid phase is performed by HNO3. Especially in the coarse-textured soils the need for NO3- is high. Therefore, instead of being a real hazard for the forest ecological system, supplementary addition of HNO3 or NH3 can be beneficial.
Van Ranst
Eric
E
Laboratory of Soil Science, Ghent University, Ghent, Belgium. eric.vanranst@ugent.ac.be
De Coninck
Frans
F
Van Rompaey
Kurt
K
D001530:Belgium; D001673:Biodegradation, Environmental; D011232:Chemical Precipitation; D004784:Environmental Monitoring; D006863:Hydrogen-Ion Concentration; D008903:Minerals / Q000032:analysis* / Q000737:chemistry; D009566:Nitrates / Q000032:analysis; D017942:Nitric Acid / Q000737:chemistry*; D012987:Soil; D014197:Trees; D014867:Water / Q000032:analysis / Q000737:chemistry*; D014872:Water Movements
D008903:Minerals; D009566:Nitrates; D012987:Soil; D014867:Water; D017942:Nitric Acid