Ammonium anthropogenic influences

We focus on temperate shelf seas because these are not only best studied, but also most subject to anthropogenic influence. Most of our examples are taken from studies in northwest European waters, because it is these that we know best. The aim of this chapter is to review recent improvements in knowledge of the sources and sinks of nutrients in the shelf seas of northwest Europe, and to consider, especially, the influence of ratios of nutrient elements on the floristic composition of the phytoplankton in these seas. We deal mainly with the macronutrient elements nitrogen, phosphorus and silicon, and to some extent with iron. The acronym DAIN (Dissolved Available /norganic Mtrogen) is a convenient way to refer to nitrate, nitrite and ammonium, excluding di-nitrogen which is not available to most phytoplankters. 

The first three components suggest regional sources of acidic anthropogenic aerosol, the marker elements of a copper smelter, and seasalt, respectively. The fourth component or the ammonium In component three do not provide a ready Interpretation of a known emission or meteorological source of variability. The negative correlation of nitrate with component two Is consistent with separate Influences of the copper smelter and automobile emissions. 

In addition, a distinction between organic sulphur particles and ammonium sulphate, previously all characterised as sulphur-rich, could be made. It was then also possible to identify organic and biogenic (higher relative phosphorus or potassium content) particles, of which the highest relative abundances were found in the continentally influenced samples (indicative of anthropogenic sources such as traffic, industrial processes, biomass burning, etc.). 

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