Elucidating the fundamental chemistry of soils: past and recent achievements and future frontiers

Contributions in the field of soil chemistry have immensely benefited humankind, including enhanced agricultural production and the quality of our environment. This review focuses on research breakthroughs since the mid-1970s and delineates frontiers in soil chemistry for the upcoming decade. However, early contributions in ion exchange, sorption phenomena, and soil acidity are highlighted. Beginning in the 1970s, soil chemistry paradigms shifted from the chemistry of plant nutrient reactionsrprocesses in soils to studies on environmental soil chemistry. The latter included research on: acid rain effects on soils and waters; trace metalrmetalloid, environmentally important plant nutrient, radionuclide, and organic chemical reaction mechanisms and retention; speciation of soil contaminants using chemical extraction and molecular scale analytical techniques; facilitated colloid transport of metals and organic chemicals; humic substance structure; kinetics of soil chemical processes; redox transformations of contaminants in soils; modeling of soil chemical reactions; and soil remediation. Frontiers in soil chemistry over the next decade will undoubtedly involve the use of advanced in situ technologies in combination with interdisciplinary research efforts to unlock important information on: speciation of contaminants in soils; cycling of trace elements and nutrients and impacts on global climate change; development of models to accurately predict the rate, fate, and transport of contaminants in the subsurface environment; elucidation of mechanisms for microbial transformations of contaminants; unraveling the precise structure of soil organic matter; and enhanced understanding of rhizosphere chemistry. In summary, the future of soil chemistry is bright for the 21st century. q 2001 Elsevier Science B.V. All rights reserved.