Update readme.md

data processing/readme.md

@@ -36,5 +36,8 @@ chlorophyll a | µg/L |	calculated chlorophyll concentration using [calibration
 potential density | kg/m3 |
 oxygen titrated | umol/kg | oxygen concebtration determined by Winkler titration on board
 turb_raw | | turbidity data raw from Wetlabs fluorometer
-NO3 | µM/L |	nitrate concentration, calibration solution was too low, so some samples are off scaleQF	NO2 corr. [µM/L]		PO4 [µM/L]		SiO2 [µM/L]	
+NO3 | µM/L |	nitrate concentration, calibration solution was too low, so some samples are off scale -> QF=3
+NO2 corr. | µM/L | nitrite concentration
+PO4 | µM/L| phospate concentration, calibration solution was too low, so some samples are off scale -> QF=3 
+SiO2 | µM/L | silicate concentration