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Zusammenfassung:
Laboratory investigations on the limiting factors in aquatic environments have revealed the nitrite sensitivity of some macroinvertebrate species, e.g. the larvae of Chironomus piger and C. riparius, the embryos of Ancylus fluviatilis, and the early stages of sponges (KAHLERT & NEUMANN 1997, NEUMANN et al. unpublished data). In contrast, the alevins of Salmo trutta dwelling in the interstices of running waters proved not to be sensitive towards naturally occurring nitrite concentrations (BARTLETT & NEUMANN 1998). Aside from this, surface and ground waters still exhibit increasing concentrations of nitrate which may act as a precursor of nitrite during microbial denitrification and/or nitrate ammonification. Aquatic sediments meet the basic requirements for these two heterotrophic processes: absence of oxygen, availability of electron donors, and biofilms attached to particle surfaces. The question arises as to whether aquatic sediments (a) exposed to naturally occurring nitrate concentrations in the water column or (b) perfused by nitrate-polluted groundwater may function as a compartment of nitrite formation (STIEF & NEUMANN 1998). Knowledge of the factors controlling the interstitial nitrite formation and of its spatial distribution within the sediments is important for assessing the risk to aquatic organisms.
