Nitrate seasonal changes

Diatoms are autotrophic and, as such, form the basis of food chains in many aquatic ecosystems (e.g. Austin et al. 2005). Their requirements of light and so-called biolimiting nutrients (e.g. silica, nitrates, phosphates and iron), mean that the seasonal changes in diatom abundance in the surface ocean tend to be marked, often... 

Figure 6a presents a seasonal change in the TN contents and those after the HCl treatment of aerosol samples. By the HCl fume treatment, 7-70% (av. 40%) of nitrogen was removed. Removed nitrogen is present as nitrate. This is supported by the positive correlation (r = 0.92) obtained between NOJ and removed N with the slope close to unity and intercept of nearly... 

The deposition amount of nitrate ion is shown in Fig. 4a. The amount was high at Tokyo and Osaka, which are the highly populated and industrialized areas with heavy traffic. The values of nitrate in the summer season, however, should be treated with much care, because some microbiological change of nitrate to ammonium ions may have occurred during the sampling period of one month (5). It is of interest to mention, however, that the annual deposition amounts of nitrate at the stations on the Japan Sea side were fairly constant around the value of 1.3 g/nry which is comparable to the amount reported by EML for the polluted area of the east coast of the United States (6). 

Kendall C., Campbell D. H., Burns D. A., Shanley J. B., Silva S. R., and Chang C. C. Y. (1995b) Tracing sources of nitrate in snowmelt runoff using the oxygen and nitrogen isotopic compositions of nitrate. In Biogeochemistry of Seasonally Snow-covered Catchments, Proc., July 3-14, 1995 (eds. 

King D. and Nedwell D. B. (1984) Changes in nitrate-reducing community of an anaerobic salt marsh sediment in response to seasonal selection by temperature. J. Gen. Microbiol. 130, 2935-2941. 

In order to identify the role of ozone in the transformation process of nitrogen and sulphur oxides into sulphates and nitrates, we used long-term data to construet seasonal graphs of the dynamics of change of the ozone concentrations by month, as well as seasonal graphs for sulphates and nitrates. 

As aerosols in the atmosphere originate from multiple sources, the composition of nutrients changes considerably over the four seasons. Nitrate, NOJ, and NHJ are defined as secondary aerosol-associated species and are not associated with primary aerosols. The combustion of fossil fuels is a significant source of NO, whereas NHj may originate from anthropogenic emissions such as animal waste and the application of chemical fertilizers. 

It is also important to note that, while the C record followed that of the N isotopes at lOka, it did not register a corresponding rise at 3.3ka. A return to deeper, probably seasonal mixing at this time had dramatic consequences for the phytoplankton flora, allowing the N-fixers to be replaced by forms adapted to assimilating dissolved nitrate and ammonium, but carbon assimilation by the two groups is similar, hence the lack of change in... 

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