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Colloids and aggregates accumulate chemical constituents well above concentrations <br /> present in the aqueous solution, and stabilize these chemicals in soils and aquifer materials <br /> (McCarthy, 2004). As a result, groundwater total chemical concentrations can be highly <br /> variable depending on the accumulated sediment in monitoring wells,total suspended load, <br /> perturbation during sampling, seasonal response to water influx, and changes in turbidity. <br /> As a result, total concentrations are not commonly used for water quality assessment of <br /> groundwater, as most colloids and aggregates are filtered by aquifer materials outside of <br /> the influence of the monitoring well, and compliance is thus,typically based on dissolved <br /> concentrations. <br /> To assess groundwater chemistry in a uniform and consistent way, at least three well <br /> volumes are purged prior to sampling to draw fresh aquifer water into the well, then <br /> samples are filtered through 0.45 lam membrane filters to obtain the dissolved fraction. <br /> This "best-practice" sampling method reduces colloidal material content that may have <br /> accumulated in the wells and better represents chemical concentrations in the aquifer(i.e. <br /> formation water). Nitrate and fluoride are reported as total concentrations; however,these <br /> anions do not form colloids and are effectively the dissolved concentration. Both dissolved <br /> and total chemical concentrations have been reported in the summary water quality tables. <br /> The contrast between dissolved and total concentrations for abundant earth metals (e.g., <br /> aluminum,potassium from clay minerals,silica is another good indicator)shows that initial <br /> samples contained sediments and colloids. The decrease over time in total concentrations <br /> of these metals shows the wells "cleaned up" and produced less sediments as they were <br /> pumped and developed through sampling. <br /> Laboratory analyses of chemical concentrations in water samples depend on internal <br /> standards and spiked additions to develop standard curves from which water sample <br /> concentrations are calculated. Deviations from the standard curves are common, and labs <br /> report analytical deviations in a quality assurance (QA) report, as required by the EPA's <br /> Laboratory Documentation Required for Data Evaluation, guidance document <br /> R9QA/400.2. Laboratories report a range of acceptable recoveries for both internal <br /> Loveland Ready-Mix Concrete 10 December 2019 <br /> 20200407_1muvii basclint,aicrymlinsummer%docx TELESTO <br />