Complementary methods to distinguish organic and mineral matter in atmospheric particulate deposition and their respective nutrient inputs to temperate forest ecosystems

Sampling atmospheric particulate deposition (APD) in forest ecosystems highlights the need for methods to measure and analyze its organic and mineral repartition. We validated an organo-mineral repartition model of APD composition in open fields and below canopy with a mineral fraction, named mineral dust deposition (MDD), and particulate organic matter (POM). MDD is subdivided into soluble (S-MDD) and hardly soluble (H-MDD) fractions. To (i) monitor APD and its nutrient fluxes in forest ecosystems in the north of France and (ii) quantify the relative contribution of POM and MDD to APD, we adapted sampling materials and preparation methods that were developed for regions close to mineral dust sources. We have also compared two protocols. The “APD” protocol led to quick results for APD rates and POM contents. The “H-MDD” protocol is a treatment for soil samples that uses hydrogen peroxide, which solubilized both POM and S-MDD, and allowed detailed analyses of H-MDD. Both protocols induced a mass loss that was a maximum for the “H-MDD” protocol (31 ± 3%). The contribution of POM in APD in open fields (49 ± 10%) was lower than below the canopy (at least 66 ± 6%). H-MDD accounted for approximately 80% of the MDD mass and contained the largest portion of low-solubility elements (Si, Al and Fe). The fractions S-MDD and POM contained the largest portion of Ca and P (more than 70%). The two protocols were complementary and may be used successively to accurately describe APD.