Nitrogen limitation, phosphorus

Nutrients—Nutrients, such as nitrogen and phosphorus and other trace elements, are necessary for cell growth because they are key biological building blocks.52,53 Addition of nutrients as a supplement helps ensure that concentrations of nutrients do not become a limiting factor for bioremediation. 

McKee, K. L., Feller, I. C., Popp, M. and Wanek, W. (2002) Mangrove isotopic (81SN and 813C) fractionation across a nitrogen vs. phosphorus limitation gradient. Ecology 83, 1065 1075. 

Fig. 6.2 (a) Niche dimension of a habitat that is co-limited by nitrogen (N), phosphorus (P), and potassium (K), and (b) niche dimension of the same habitat after N addition. The different shapes indicate soil areas that are limited by N, P, or K. If one nutrient is added, e.g., N by N deposition, the total soil area with limiting amounts of one or more nutrients for plant growth becomes smaller. The habitat becomes more uniform and may offer less niches for plants to coexist... 

The nitrogen-phosphorus detector (NPD) is, as the name implies, preferentially sensitive to nitrogen and phosphorus atoms. The detector contains a ceramic bead formed with an alkali salt, such as rubidium or cesium. The bead is heated in the presence of hydrogen, but the flow of gas is limited so that no flame is present. As the column effluent passes around the bead, nitrogen- and phosphorus-containing compounds produce electronegative moieties, which are treated as an increase in current and recorded as peaks (Carlsson et al., 2001). 

Limiting concentrations of nitrogen and phosphorus (N and P) that are vital for maintenance of active microbial population in an activated sludge plant. 

---