Ammonia-organic matter complexes

There is still some uncertainty as to the availability of the nitrogen in any ammonia-organic matter complexes formed in soils as a result of the addition under field conditions of anhydrous ammonia or ammonia solutions. Since ammonia that is added in these forms gives crop responses that differ little from those produced by other nitrogen sources, it seems unlikely that complex formation is an important factor in the practical use of these nitrogen sources. 

Armannsson [659] has described a procedure involving dithizone extraction and flame atomic absorption spectrometry for the determination of cadmium, zinc, lead, copper, nickel, cobalt, and silver in seawater. In this procedure 500 ml of seawater taken in a plastic container is exposed to a 1000 W mercury arc lamp for 5-15 h to break down metal organic complexes. The solution is adjusted to pH 8, and 10 ml of 0.2% dithizone in chloroform added. The 10 ml of chloroform is run off and after adjustment to pH 9.5 the aqueous phase is extracted with a further 10 ml of dithizone. The combined extracts are washed with 50 ml of dilute ammonia. To the organic phases is added 50 ml of 0.2 M-hydrochloric acid. The phases are separated and the aqueous portion washed with 5 ml of chloroform. The aqueous portion is evaporated to dryness and the residue dissolved in 5 ml of 2 M hydrochloric acid (solution A). Perchloric acid (3 ml) is added to the organic portion, evaporated to dryness, and a further 2 ml of 60% perchloric acid added to ensure that all organic matter has been... 

Analysis of Guano.—Guano is a very complex mixture, containing urate, oxalate, and phosphate of ammonia, earthy phosphates, soluble alkaline salts, and organic matter, The analysis of such a compound is attended with some labor. As the value of guanos, however, depends on the quantify of ammonia, phosphates, soluble and insoluble, and alkaline 6alts which they contain, a very simple analysis is quite sufficient for agricultural purposes.. 

Equation 8.9 shows that when NH3 is introduced to an acid solution, it reacts directly with the acid and produces the ammonium ion (NH4) (see Chapter 12). Concurrent with Equation 8.9, NH3 may associate itself with several water molecules (NH3nH20) without coordinating another H+. This hydrated NH3 is commonly referred to as unionized ammonia and is toxic to aquatic life forms at low concentrations. Because NH3 is a volatile gas, some of it may be lost directly to the atmosphere (volatilization) without dissolving in solution. On the other hand, the ammonium ion may undergo various reactions in the soil water that may alter its availability to plants and/or other organisms. These reactions include formation of metal-ammine complexes, adsorption on to mineral surfaces, and chemical reactions with organic matter. 

Any of these solution products can react with chemical species already present in the water, such as humic substances, metals, and metal complexes. As for the rest of the dissolved ammonia, while some will bind to sediments, suspended partieles, and organic matter available in the water, most will undergo nitrification by the Nitrosomonas and Nitrobacter bacteria species to yield nitrates that can be uptaken by aquatic plants and organisms. Many algae and phytoplankton have been found to utilize ammonia direetly as their source of nitrogen. Because of its low octanol/water partition coefficient, ammonia is not expected to adsorb strongly to sediments. 

Hydrolysis of urea is catalyzed by urease, an enzyme that can survive extracellularly in organic matter-clay soil complexes the reaction can proceed rapidly in warm, moist soils containing large amounts of the enzyme. Wider use of urease inhibitors (phosphoryl di- and triamides) may eventually reduce large ammonia volatilization losses see Byrnes, B. H., and... 

Humic matters are present in almost all natural waters. They are extracted from soil and peat. The solubility of the constituents of the soil humus depends on the type of soil, period of contact with water, pH of the water and its composition, and depending on such factors, the humic materials are present as either true or colloid solutions. In waters from peat moors the concentration of humic matters is usually tens of mg 1 . In some stationary waters as much as 500 mg 1 can be found. In waters from peat moors a low pH is typical (it can be lower than 4), high oxidation potential and the presence of iron, manganese and ammonia nitrogen (anaerobic processes). Iron and other metals are present in an organic complex form and they are difficult to remove [52, 53]. 

---