To study the distribution of Ni emission to air from the myriad of point and diffuse sources within a plant site is a complex sampling and analysis problem. However, it provides important underlying information for source abatement. At a Ni refinery in Southern Norway such sampling of Ni in air in close proximity to sources with subsequent analysis of content or particle structures by various methods has always been a complicated endeavour with no or inconclusive results. The main difficulty lies in obtaining both a representative and a large enough sample size to achieve quality results within a reasonable cost budget.

Normally a filter sample of dust used for the chemical analysis of Ni in air is collected with fairly expensive reference instrumentation. If more than one filter sample is needed, e.g. several copies of a specific sampling period and location, several co-located instruments should be used, or one filter is cut into several pieces for post-analysis. Cutting a filter in pieces will compromise the sample and chemical analysis and most reference PM samplers are not easily or cheaply operated and transportable. Thus, a novel in-house sampling device that delivers 3 independent and parallel filters simultaneously was constructed. The goal was to obtain triplet sample sets from many locations inside the plant area. The sample sets could be screened for Ni levels and provide filter copies for advanced chemical analysis when needed. Comparisons of individual samples in sets of varying Ni content showed satisfactory equivalence.

The sampling device is continuously used in a pilot Ni ambient distribution study within the plant site. The triplet sampler has been rotated at more than 10 sites since 2015. The sites varied between being on the ground and on roof tops of buildings. Some locations were near potential sources that give diffuse emissions of nickel dust. Results have been used to understand the Ni variation spatially and to identify important contributing sources to the total Ni emissions that potentially is emitted to the surrounding airshed. Parallel samples have been sent for more advanced post-analysis for periods with known elevated nickel concentration. The results have yielded more defensible abatement plans and more effective abatement measures.