Sulfate water quality indicator

WA water quality labs by atomic absorption and autoanalyzer techniques. Charge balance calculations Indicated that all dissolved species of significance were analyzed. Comparison of filtered and unflltered aliquots suggested that un-lonlzed species were not present In appreciable quantities. Sampling and analysis uncertainties were determined by the operation of two co-located samplers for 16 weeks. The calcium and sulfate data were corrected for the Influence of sea salt to aid In the separation of the factors. This correction was calculated from bulk sea water composition and the chloride concentration In rainwater (11). Non seasalt sulfate and calcium are termed "excess" and flagged by a ... 

For this study, we consider four types of water non-impacted (arsenic below detection limit), low (greater than the detection limit and less than 10 pg/l As), moderate (10-100 p.g/1 As), and high (greater than 100 pg/1 As). Typical of water quality data, the data set is censored and as such, the concentrations reported for most constituents are not normally distributed (Gibbons, 1994). Because of this limitation, box plots (Fig. 6) are used to evaluate and compare the water quality results. The distributions of concentrations were compared for iron, sulfate, pH, alkalinity, nickel, zinc, manganese and specific conductance (SC). The box plots should be viewed with consideration of sample size, which is indicated on Fig. 6. 

The solubility of elements in freshwater is limited and the solubility of calcium and magnesium carbonates are of particular importance in freshwaters. The solubility of carbonates is inversely proportional to the temperature of the water. In other words, as the water temperature increases, calcium and magnesium carbonates become less soluble. If the solubility decreases sufficiently, carbonates will precipitate and form a scale on the surfaces of the system. This scale can provide a protective barrier to prevent corrosion of the metallic elements in a system. Excessive scale deposits can interfere with water flow and heat transfer. The quality of the scale is dependent on the quantity of calcium that can precipitate as well as water flow and the chloride and sulfate content of the water. The tendency of water to precipitate a carbonate scale is estimated from corrosion indices such as the Langelier Saturation Index (LSI) and Caldwell-Lawrence calculations [6-8] which use calcium, alkalinity, total dissolved solids, temperature and pH properties of the water. Other indices, such as the Ryznar Index... 

These considerations lead to the conclusion that to a first approximation the quantity and quality (with respect to sulfate reducers) of organic matter at each of the three stations is nearly the same. The rate of supply of organic material also cannot differ much if it is assumed that a constant proportion of the flux of organics hitting the interface at each station must remain as refractory residue and therefore is reflected in the standing crop. Taken at face value, these data indicate that FOAM, which has the greatest buildup of decomposition products in the pore water, is not necessarily the most productive of the three stations. Additional evidence for relative reaction rates at the three stations comes from solid-phase properties as discussed subsequently. 

The double bonds in the CPs (5) always react to some extent with sulfuric acid (or HF) to produce CP sulfates (or fluorides). The importance of CPs in the overall reaction sequence is indicated by the following information First, fresh sulfuric acid is a poor catalyst until a small amount of CPs is obtained (6). The best quality alkylates are produced with sulfuric acids containing 3-6% polymers (7,8). Although less information has been published when HFs are used as catalysts, the level of CPs in HF is also important. Phillips Petroleum Company (9) has developed a near-infrared technique to monitor the CP [or acid-soluble oil (ASO)] content of their HF phase. They report that in a refinery, the HF contained 10% by weight CPs but the acidity was about 84 85%. Since the HF contains about 0.2% water, about 4% was unreported. It is mainly alkyl fluorides. 

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