Variables: concentration Keywords: trace analytics stream pesticides pyrethroids Substances: Chlorpyrifos (SBPBAQFWLVIOKP-UHFFFAOYSA-N) Allethrin (ZCVAOQKBXKSDMS-UHFFFAOYSA-N) Chlorpyrifos-methyl (HRBKVYFZANMGRE-UHFFFAOYSA-N)