Phosphorus Compounds in the Environment

Abiotic Degradation of Organic Phosphorus Compounds in the Environment... 

There are two principal pathways for the abiotic degradation of organic phosphorus compounds in the environment hydrolytic reactions and photolytic reactions. The importance of either mechanism depends to a substantial degree both on the nature of the particular compound of interest (Fig. 4.1), and on its location in the environment. Some compounds, such as the phosphorodithionate pesticide malathion, are readily broken down (malathion has a half-life of about 11 h in alkaline solution ... 

OTHER TECHNIQUES A number of other techniques have been used to determine specific organic phosphorus compounds in the environment, including a firefly luciferase assay for adenosine di- and triphosphate (Kaplan and Bott, 1985), a protein assay for cyclic adenosine monophosphate (Francko and Wetzel, 1982) and cetryltrimethylammonium bromide precipitation of dissolved RNA and DNA in marine and freshwaters (Karl and Bailiff, 1989). However, none of these are regularly used in studies of organic phosphorus dynamics in aquatic ecosystems. 

Detailed investigation of mechanisms by which organisms access organic phosphorus compounds in the environment, which is critical to understanding almost all the key issues involving organic phosphorus dynamics. 

Give two reasons why biodegradation of phosphorus compounds in the environment is important. 

Eutrophication is the rapid depletion of dissolved oxygen in a body of water because of an increase in biological productivity. It is connected to the excess presence of plant nutrients in the environment, mainly nitrates and phosphorus. These compounds are connected to the excessive use or production of fertilizers. 

Organic constituents that may be found in ppb levels in WP/F smoke include methane, ethylene, carbonyl sulfide, acetylene, 1,4-dicyanobenzene, 1,3-dicyanobenzene, 1,2-dicyanobenzene, acetonitrile, and acrylonitrile (Tolle et al. 1988). Since white phosphorus contains boron, silicon, calcium, aluminum, iron, and arsenic in excess of 10 ppm as impurities (Berkowitz et al. 1981), WP/F smoke also contains these elements and possibly their oxidation products. The physical properties of a few major compounds that may be important for determining the fate of WP/F smoke in the environment are given in Table 3-3. 

The nature of alkyl halide and the environment of the phosphorus atom make a substantial contribution to the direction of the reaction. Thus, cyclic phosphites [108], like trialkyl phosphites [110], react with preservation of the coordination of the P(III) phosphorus atom (126-132 ppm). If the alkoxyl group is substituted by amide, alkyl, or aryl, the nucleophilicity of the phosphorus atom in the corresponding amidophosphite (phosphonite) increases in comparison with the trialkyl phosphite. This probably promotes attack by 1 -haloalkyl-2-pyrrolidone at the phosphorus atom and not the oxygen, and this was confirmed experimentally. As a result of the investigated reactions amidophosphonates or ethyl phenyl phosphinates llOa-c were isolated compounds with P(III) were not detected in these cases. 

EDCs in the environment are often analyzed using GC or LC based instrumental techniques. GC coupled with an electron capture detector (BCD), a nitrogen-phosphorus detector (NPD), or mass spectrometry (MS) has been the preferred method due to its excellent sensitivity and separation capability on a capillary column. High performance liquid chromatography (HPLC) with various detectors such as ultraviolet detection (UV), fluorescence detection (FLD), MS, and more recently tandem MS (MS/MS) has also been used for analysis of some EDCs, especially for the polar compounds. Analytical techniques for each class of EDCs will be discussed in the following section. 

Notwithstanding the impressive enhancement in the rates of hydrolysis of many organic phosphorus compounds by dissolved metal ions, because of the generally low concentration of most dissolved metal ions in the environment, homogeneous catalysis will only be an important pathway for organic phosphorus breakdown in unusual circumstances (Smolen and Stone, 1997). 

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