Historical (1850-2010) mercury stable isotope inventory from anthropogenic sources to the atmosphere

Mercury (Hg) stable isotopes provide a new tool to trace the biogeochemical cycle of Hg. An inventory of the isotopic composition of historical anthropogenic Hg emissions is important to understand sources and post-emission transformations of Hg. We build on existing global inventories of anthropogenic Hg -emissions to the atmosphere to develop the first corresponding historical Hg isotope inventories for total Hg (THg) and three Hg species: gaseous elemental Hg (GEM), gaseous oxidized Hg (GOM) and particulate-bound Hg (PBM). We compile delta Hg-202 and Delta Hg-199 of major Hg emissions source materials. Where possible, delta Hg-202 and Delta Hg-199 values in emissions are corrected for the mass dependent Hg isotope fractionation -during industrial processing. The framework and Hg isotope inventories can be updated and improved as new data become available. Simulated THg emissions from all sectors between 1850s and 2010s generally show an increasing trend (-1.1 parts per thousand to -0.7 parts per thousand) for delta Hg-202, and a stable trend (-0.02% to -0.04%) for Delta Hg-199. Delta Hg-200 are -near-zero in source materials and therefore emissions. The delta Hg-202 trend generally reflects a shift of -historically -dominant Hg emissions from 19th century Hg mining and liquid Hg0 uses in Au/Ag refining to 20th century coal combustion and non-ferrous metal production. The historical delta Hg-202 and Delta Hg-199 curves of GEM closely follow those of THg. The delta Hg-202 curves of GOM and PBM show no trends. Delta Hg-199 values for both GOM and PBM decrease from the 1850s to 1950s by similar to 0.1%, and then gradually rebound towards the 2010s. Our updated delta Hg-202 values (-0.76 +/- 0.11 %, 1SD, n= 9) of bulk emissions from passively degassing volcanoes overlap with delta Hg-202 of present-day anthropogenic THg emissions.