The International Humic Substances Society (IHSS) as a Link Between Geology, Hydrology and Soil Science through Organic Matter Studies: A Historical Perspective.

Organic matter in general and humic substances (HS) in particular, are involved in many processes in soils, sediments, rocks and natural waters: e.g., rock weathering, plant nutrition, pH buffering, trace metal mobility and toxicity, bioavailability, degradation and transport of hydrophobic organic chemicals, formation of disinfection by-products during water treatment, heterotrophic production in blackwater ecosystems and, more generally, the global carbon cycle.
Before the 1970s’ natural organic matter (NOM) of different ecosystem pools (i.e., soils, sediments, and natural waters) was often studied in isolation, although many similarities exist between them. This is particularly so for HS. In this historical context, a need appeared to bring together environmental chemists, soil scientists, hydrologists, and geologists who are interested in HS, aiming to provide opportunities for them to exchange ideas.

The IHSS (http://www.ihss.gatech.edu) was founded in Denver, Colorado (USA) in 1981 with the motto: "To Advance the Knowledge and Research of Natural Organic Matter in Soil and Water".

This presentation will be comprised of three sections: (i) a brief historical retrospective on studies of NOM over the last two centuries; (ii) the state of NOM chemical studies in the 1960-70s’ and the developing interest in the employment of physical approaches to OM fractionation; (iii) the emergence of IHSS, and the realization of its objectives, including forming connections between geology, hydrology and soil science through OM studies. On this last point, a rapid inventory of the publications done at the IHSS International Congresses from 1995 to 2006 demonstrates the integration of these disciplines, when considering publications with titles referring strictly to water soluble OM (31 % of the total), to soil or soil-plant system OM (47 %) and to sediment, rock or mineral-associated OM (22 %).