In soils, metals associate with organic matter and with iron and manganese oxide coatings, which reduces their bioavailability. For example, large portions of the agricultural soils of the USA, Australia and other countries have trace element deficiencies, particularly of zinc. The effectiveness of fertilizer additions depends on the form of the added metal. With time, the added zinc becomes less available as it is incorporated by the soil. Most soils, natural waters and sediments contain a large fraction of metals in non-bioavailable forms.
All chemical analyses tend to overestimate the concentration of metal that is bioavailable.
To obtain better estimates of the bioavailable metal in environmental samples, scientists are relying on analytical procedures other than total metal for the purposes of risk assessment and regulatory compliance. Because only a fraction of the total metal in any given environmental medium is bioavailable, it is important that appropriate chemistry and biology be considered in regulatory programs, such as risk assessments. From 1983 to 1989, he was Director of the Environmental Studies Institute and Professor of Chemistry at Drexel University in Philadelphia. His research has been primarily concerned with the fate and effects of trace metals and organic chemicals in aquatic and soil environments. He has authored more than 130 technical publications, edited five books and prepared numerous reports.