ࡱ > g i f Y R bjbjWW = = N ] | | ( $ | ` h X $ @Le e > Data Quality Notes for the Lake Pontchartrain Sediment Database Annotations based on quality screening techniques are provided in the qualifier field to the right of each chemical attribute column as illustrated here. Abbreviations and codes at the beginning of a qualifier field (for example, AG_Q) are explained below. Ratios with zinc provide the main discriminant function for metals and inorganic constituents. Other appropriate normalizing constituents can be used for organic compounds (see Manheim and others, 1998). Values exceeding the indicated ratios are regarded as anomalous. Alert level calls attention to unusual concentration levels. It does not necessarily imply data quality problems. High alert levels are normally due to presence of contaminants. Low alert levels may signify sediment mineralogy that is naturally low in trace metals, or a leachate procedure designed to recover contaminants but not more refractory trace elements in unpolluted sediments. Table B1. Codes used in quality control field of sediment database [in consolidated table as well as full database, appendixes C and D] CodeExplanation