Comparison of Nutrient Concentrations in USA Estuaries: Meeting Comments and Sampling Procedure
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Presentation Transcript
AMQAW Meeting Comments on Mainstem Replicate Sampling Procedure June 2006
NUTRIENT CONCENTRATIONS • Comparisons Among Estuaries • Data assembled by NASL staff • Summary developed by Jerry Frank • Very large range in concentrations in USA estuaries • Generally highest in winter and lowest in fall • Generally highest in oligohaline areas and lowest in lagoons
NH4 before Field Technique Changes 20% error 7uM
NH4 after Field Technique Changes • Wear gloves • cup rims not touched • rinsing of cups and caps • cup arrangement in rack 20% line 7 uM
SAV Criteria Way out there 0.014 mg/l 0.14 mg/l
DIN Criteria • SAV DIN Criteria = 11 uM (0.15 mg/l) • MDLs for NH4 range from 0.6 to 0.9uM • Detection is great relative to criteria • Main interest is with higher values (bad WQ for SAV) where replicate variability is low (<5%)
Summary • Changes in field procedures have helped • Basic advantage of in-field stabilization, esp for NH4 which is very reactive • Most replicate variability at very low concentrations (occasionally a lot of very little) • Replicate variability does not seem to influence several uses of monitoring data • Continue emphasis in careful field and lab procedures
