Rapid　on-site　analysis　of　airborne　trace　metals　has　been　heavily　favored　over　traditional　methodologies　because　air　pollutants　can　be　altered　by　environmental,　behavioral,　and　social　patterns　at　any　given　time　and　location.　However,　existing　portable　approaches　are　either　not　capable　of　performing　integrated　on-site　analysis　or　not　yet　practically　applicable.　Exploiting　graphene　oxide　(GO)　in　enhancing　the　analytical　performance　of　paper-based　colorimetric　detection,　for　the　first　time,　this　paper　reports　the　development　of　a　practically　useful　portable　system　for　accurate,　sensitive　on-site　characterization　of　trace　metals　in　ambient　particulate　matter　(PM).　The　system　consists　of　GO-nanosheet-coated　paper　devices,　unmanned　aerial　vehicle　multiaxial　sampling,　and　cellphone-based　colorimetric　detection.　The　increased　specific　surface　area　and　the　homogeneity　of　color　distribution　from　the　coating　of　GO　improves　the　accuracy　and　sensitivity　of　the　assays.　Additionally,　by　leveraging　a　Wi-Fi　camera,　a　self-developed　app　and　a　sample　pretreatment　cartridge,　metal　in　PM　samples　can　be　readily　processed　and　characterized　on-site　within　30　min.　The　effects　of　chip　geometric　design,　pH,　reaction　volume,　and　metal　interference　on　detection　results　have　been　studied.　The　detection　limits　of　the　system　were　calibrated　to　be　16.6,　5.1,　and　9.9　ng　for　metals　Fe,　Cu,　and　Ni,　respectively,　which　are　comparable　to　the　detection　limits　of　commercial　inductively　coupled　plasma　(ICP)　instruments,　thus　making　our　portable　system　practically　useful.　Finally,　the　system　was　used　for　airborne　trace-metal　study　at　6　locations　in　Fuzhou　City　(China),　and　the　results　obtained　using　our　system　demonstrated　good　agreement　with　those　obtained　by　the　ICP.　The　significance　of　our　system　in　supplementing　air　pollution　study　and　furthering　research　on　rapid,　accurate,　on-site　air　toxicity　assessment　was　demonstrated.　©　2019,　The　Author(s).