Rivers, nitrate content

In contrast, during the low flow season (June-October) important nutrient loads from both point and non-point sources are relevant. Summer irrigation drives nitrate inputs to stream waters [38], The lower dilution capacity of the river causes higher concentrations of nitrate and DOC, as well as an increase in phosphate content with... 

Content of nitrates in river water (t/km3) Arid regions Densely populated regions Temperate climate forests 1.45 25 0.4... 

The amount of carbon present in soil is closely related to the CO2 content of the atmosphere. But atmospheric CO2 is regulated mainly by the ocean rather than by soil (see Section 2). The amount of nitrogen in the soil also does not influence the N pool in the atmosphere because the atmosphere is a huge reservoir regulated mainly by the ocean (Butcher efal, 1992). Nevertheless, the soil has a tremendous influence on the nitrate load of the rivers (see Section 3). 

As is known, fixed nitrogen is present in seas and lakes in several forms. Nitrates produce the greatest influence on biotic productivity. They, similar to phosphates, are present in the Aral Sea in very low concentrations. Thus, the nitrate nitrogen content in the open part of the Large Sea never exceeded 5 mg m and only in the mouth areas of rivers was it somewhat higher. The nitrate values in the Small Sea were higher. Their content in the surface waters varied from 7.0 to 15.0 mg m and in the bottom layer - from 1.0 to 3.0 mg m . ... 

Figure 6 displays the evolution of UV spectra along the river. As usual, nitrate ion is present in most of the samples, and the organic matter content is rather low. The study of normalised spectra (see Chapter 2) shows the existence of two isosbestic points related... 

It was found out that for selected area of the river flow there is no full mix of nitrate pollutant up to receipt of homogeneous solution. The flow consists of stream with high and low content of pollutant. 

Silicate is a very important nutrient in the ocean. Unlike other major nutrients such as phosphate and nitrate or ammonium, which are needed by almost all marine plankton, silicate is an essential chemical only for certain biota such as diatoms, radiolarian, sihcoflageUates, and siliceous sponges. However, this biology is one of the most important producers in marine. The estimation shows that diatoms contribute more than 40% of the entire primary production. Therefore, silicate cycling has received significant scientific attention in recent years and many scientists have studied silicate behavior in marine environments. Biogenic silicate is the amorphous content extracted by chemical methods, which is named as biogenic opal or opal in brief. The concentration of dissolved silicate in the world ocean is about 70.6 pmol/L and the net input of dissolved silicate from land to ocean is (6.1 2.0)x 10 mol (calculated by Si) every year, and the primary contribution (about 80%) comes from river. 

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