Alkalinity ground water

Ortho-phosphate dose range (mg/i P) Percentage of high alkalinity ground waters Percentage of high alkalinity surface waters Percentage of low alkalinity surface waters... 

Biodegradation results from the pH drop such a detergent polymer experiences as it leaves the alkaline laundry environment (pH ca 10) and enters the sewage or ground water environment (pH close to neutral) the polymer (now a polyacid rather than a salt) is unstable and hydrolyzes to monomer which rapidly biodegrades. The chemistry has been reported ia many patents (186) and several pubHcations (187,188). 

The influence that variations of temperature and levels of atmospheric CO2 and O2 have on chemical weathering are more subtle. Temperature appears to have a direct effect on weathering rate (White and Blum, 1995). The silica concentration of rivers (Meybeck, 1979, 1987) and the alkalinity of ground waters in carbonate terrains (Harmon et al., 1975) are both positively correlated with temperature variations. It is not clear, however, whether temperature-related variations in weathering rates are largely due to variations in vegetational activity that parallel temperature variations. 

Fig. 3. Schoeller diagrams, with pH (inset), showing the average compositions for ground water and surface water from sites 1 (A) and 2 (B). Abbreviations Aik - alkalinity AGW -Atikokan ground water.

Hatva, T. (1989) Iron and manganese in ground-water in Finland Occurrence of glacifluvial aquifers and removal by biofiltration. Publ. Water environmental research institute. Nat. Board Waters Envir., Finland, No. 4, 99 p. Haupt, S. Strehlow, H.H. (1987) Corrosion layer formation and oxide reduction of passive iron in alkaline solution A combined electrochemical and surface analytical study. Langmuir 3 837-885... 

Abnormally low pH values (acidic conditions) of surface or ground-water have little or no effect on human activities. Excess acidity (or, much less commonly, excess alkalinity) may have quite serious effects on aquatic life, however. As described in chapter 3, fish eggs, fry and immature fish, and some species of mature fish are especially susceptible to pH values of less than about 4.0 (or more than about pH 9.0). 

An alkaline aquatic work-up with KOH precipitates dipotassium l,l -dinitrami-no-5,5 -bistetrazolate. The products of the individual stages can be purified by recrystallization, or used as obtained. No column chromatography must be used. Fortunately K2DNABT shows low water solubility, which (i) facilitates its isolation and purification and (ii) avoids future toxicity problems due to potential ground water pollution. 

In soils, F can be found in four major fractions (1) dissolved in soil solution (2) sorbed to Al, Fe, and Mn oxides and hydroxides and carbonates (3) solid phases, such as fluorite and fluorophlogopite and (4) associated with organic compounds. The solubility of F in soil solution is variable and is affected by pH, speciation, adsorption and desorption reactions, and dissolution and precipitation reactions (Luther et al., 1996). Acidic conditions and low calcium carbonate content are favorable to F solubility and can therefore enhance both root uptake (Weinstein and Alscher-Herman, 1982) and migration to surface and ground water (Smith, 1983). These conditions can lead to human, plant, and animal health issues. Soils that do contain appreciable amounts of calcium carbonate and are neutral to slightly alkaline conditions can fix F as insoluble calcium fluoride (CaF2), and reduce its bioavailability and mobility (Kubota et al., 1982 Tracy et al., 1984 Reddy et al., 1993 Poulsen and Dudas, 1998). 

An amperometric immunosensor using sequential injection analysis techniques to detect the herbicide 2,4-D in water was described by Wilmer and Trau [102,103]. This rapid competitive EIA used an alkaline phosphatase-labelled monoclonal antibody directed against the herbicide and an immunoreactor with 2,4-D immobilized via BSA, either to Eupergit in a column or directly to the surface of a glass capillary. A detection limit of the immunosensor at 0.1 (jLg 2,4-D 1, without enrichment of the analyte, pointed to the feasibility of making automatic measurements of 2,4-D in drinking and ground water. 

Ground-water samples were collected from four wells in the study area. Data for these sites, along with previously collected water-quality data, are given in Table 1 and locations are shown on Fig. 1. Measurements of temperature, pH, and dissolved oxygen were made in a flow-through chamber. Field meters were calibrated using appropriate pH standards (Wilde and Radtke, 1998). Alkalinity was determined on-site by incremental titration of filtered water with sulfuric acid (Wilde and Radtke, 1998). 

Carbonic acid is the most abundant acid in natural water systems and is the acid most responsible for rock weathering. Bicarbonate ion is generally the dominant anion in fresh surface- and ground-waters. Bicarbonate and carbonate ions are also the chief contributors to total alkalinity in natural waters (see below). For such reasons we will consider carbonate-solution chemistry in some detail. 

Residue persistence in groundwater appears to be associated with low pH and alkalinity. Groundwater pH and alkalinity increase with depth in the aquifer. High CO2 contents in the groundwater, especially in summer, tend to increase water contents of Ca and Mg by dissolution of dolomitic limestone residues from the aquifer sediments, increasing pH and alkalinity above laboratory-determined values Such conditions apparently promote chemical hydrolysis of aldicarb residues, reducing their persistence in deeper ground-water. 

---