Eight polycyclic aromatic compounds (PACs) were tested for their toxic effect on the soil nitrification process, bacterial genetic diversity, and the total number of protozoans (naked amoebae and heterotrophic flagellates). After four weeks of exposure in a well-characterized agricultural soil, toxic effects were evaluated by comparison to uncontaminated control soils. All PACs affected the nit...

Dissolved oxygen (O2) was measured with microelectrodes in shallow subsurface microsites in a prairie stream and related to rates of nitrification determined in the laboratory using the nitrapyrin method. Substrata sampled included diatom mats, leaves and wood (coarse benthic organic matter, CBOM), filamentous green algae, bryophytes, and fine benthic organic matter (FBOM). Significant differen...

Nitrification, the microbial oxidation of ammonium (NH4 ), is one of the key nitrogen transformation processes. It is performed under oxic conditions by 2 groups of bacteria, one group that oxidizes ammonium to nitrite (NO2 ) and a second group that further oxidizes nitrite to nitrate (NO − 3 ). Nitrification links organic matter mineralization (ammonification) and nitrogen removal through deni...

an airlift-type activated sludge reactor using a sponge support medium was fed with wastewater containing 500 mg-n/l of nh4 +-n. in order to establish partial nitrification, the reactor was kept at 35°c. moreover, the reactor was started up with the nahco3 solution as an alkali agent to supply inorganic carbon for enhancement of partial nitrification. the partial nitrification was established d...

In order to examine how fundamental soil N cycling processes are affected by elevated N inputs to temperate forest ecosystems, we made concurrent laboratory measurements of gross rates of nitrogen (N) mineralization, nitrification, nitrate (NO3 ) consumption, ammonium (NH4 þ) immobilization, nitrous oxide (N2O) and nitric oxide (NO) production, and NO consumption in soils from the Harvard Fores...

Shifts in nitrogen (N) mineralization and nitrification rates due to global changes can influence nutrient availability, which can affect terrestrial productivity and climate change feedbacks. While many single-factor studies have examined the effects of environmental changes on N mineralization and nitrification, few have examined these effects in a multifactor context or recorded how these ef...

Most studies on soil N2O emissions have focused either on the quantifying of agricultural N2O fluxes or on the effect of environmental factors on N2O emissions. However, very limited information is available on how land-use will affect N2O production, and nitrifiers involved in N2O emissions in agricultural soil ecosystems. Therefore, this study aimed at evaluating the relative importance of ni...

In addition to N load, cold weather nitrification is an important consideration for stabilized performance of biological processes applied to continuous animal production systems. A winter simulation experiment was conducted in the laboratory to evaluate performance of immobilized bacteria for treatment of swine wastewater under cold weather conditions. Bench fluidized reactors (1.2 L) containi...

Potential nitrogen mineralization and nitrification were measured in soils from a primary successional sequence developed on sand dunes and from a secondary successional sequence on old fields. Potential nitrogen mineralization in soils from the primary sere increased through the first five stages and then leveled off. Nitrogen mineralization was relatively constant in soils from the secondary ...