It was previously reported that fDOM values (Water Quality data product, DP1.20288.001), measured using older model sensor probes, were artificially low. NEON has retired these probes and replaced them with newer models in which the defect has been corrected. It therefore should not occur in any data collected after June 1st, 2022.
Note that this issue does not affect all data collected before June 1st, 2022, only data collected by probes manufactured prior to June 2017. After talking with the sensor manufacturer, we believe it may be possible to post-correct measurements which were low, but still positive. Based on information provided by the manufacturer, negative measurements cannot be quantitatively corrected because they correspond to two alternative “true” values. In a qualitative sense, it can still be said they are very low, less than 3 RFU or 15 ppb QSU according to the manufacturer.
NEON’s new IS data processing pipeline will be implemented in 2023 and will include flags for impacted data and corrected values, where possible, for this data product. An update will be made when this is complete.
For more detailed information on the problem please use the Contact Us form. Select DP1.20288.001 in the Data Product dropdown list and include the term “INC0052659” in the body of your request.