Flags: detection limits, holding time, shipping issues - USEPA/SuRGE GitHub Wiki

Every analyte will have an analyte_flag column (e.g. no3_flag). This column can be populated with zero or several flags reflecting different issues. Multiple flags will be separated by a space.

DETECTION LIMITS

• ND: Measured concentrations that are below the method detection limit (MDL) will be flagged as "ND" and reported as the value of the MDL.
• L: Values that exceed the method detection limit (MDL) but are less than the reporting limit (RL) will be flagged as "L". Procedures vary across labs for defining a RL. We assume equivalency between the terms "quantification limit" and "reporting limit". If neither value is reported by the lab, we assume the RL is equal to the lowest non-zero standard in the standard curve. Flags will be reported in analyte specific analyte_flag columns.

HOLDING TIME

• H: Holding time violations will be flagged with a H. The analyte_flag field is used to indicate when sample holding times have been violated (see holding times below).

analyte	holding time (days)
nh4	28
no2_3	28
no3	28
no2	28
tn	28
tp	28
op	28
doc	28
toc	28
fluoride	28
cl	28
br	28
so4	28
al	60
as	60
ba	60
be	60
ca	60
cd	60
cr	60
cu	60
fe	60
k	60
li	60
mg	60
mn	60
ni	60
pb	60
p	60
sb	60
sn	60
sr	60
s	60
v	60
microcystin	360

SHIPPING

• S: Samples that were compromised during shipping (e.g. were warm when received) will be flagged with an S.

COMMENTS

• Q: A Q flag indicates the presence of a comment associated with the sample. See the corresponding notes column for details.

FLAGS AND DUPLCATES

• In cases where duplicates have different flags, the aggregated value will have the flag associated with the higher concentration sample. For example, one duplicate is flagged "ND" and the other "L", the aggregated value is flagged "L" (see issue #12).