PNNL

Abstract

A better understanding of soil organic matter (SOM) biogeochemisty and associated biogeochemical reactions and processes in soils is critical to meeting the environmental challenges that we face currently with the changing climate. Humic substances obtained from alkaline extractions of soils have played a predominant role in developing our knowledge of soil organic matter chemistry and behavior during the 20th century. Recently, there has been new important developments, and research efforts conducted to inspect and interrogate soil organic matter using molecular, nano and micron-scale state-of-the-art techniques have produced evidence that, according to some researchers, may be used to argue against the existence of the humic subtances in soils, as they are presently defined. A debate on the definition and continued use of the term “humic substances” has been taking place at conferences and in the scientific literature. However, because a consensus has not been reached on this important topic, the use of the term “humic substances” in this special issue is conform to the current existing definition of this term. This special issue of the Journal of Environmental Quality includes ten papers on the subject of ‘Alkaline Extraction of Soils and Natural Waters to Understand Environmental Processes’, and contributes to the on-going assessment of the role of humic substances in current and future environmental and ecological studies. The contributed papers are grouped into three broad subject headings: (i) chemistry of humic substances, (ii) humic substances in environmental processes, and (iii) case studies and reviews of humic substances. Continued progress in understanding soil organic matter and C biogeochemistry is essential to achieve long-term ecological, environmental, and agriculture sustainability.