The advantages of the field-portable, handheld XRF instrument and technique are demonstrated via case studies in the toxic metal polluted area of Gyöngyösoroszi, Toka watershed (North-East Hungary). The possibilities and advantages of in situ metal detection using field-portable XRF instrument are demonstrated herein in various applications: 1) delineation of point sources, 2) high resolution mapping, 3) diffuse toxic metal pollution mapping, 4) pollution transport route identification, 5) pre-remediation assessment, 6) directed sampling.