Staff scientist Gulf General Atomic Company, San Diego, 1970-1971. Director Research and Development Ouachita Industries, Inc., Monroe, Louisiana, 1971-1972. Assistant professor chemical oceanography Rosenstiel School Marine & Atmospheric Science, University Miami, Florida, 1972-1976.
Physical scientist National Oceanographic and Atmospheric Administration, Washington, 1976-1978. Member professional staff & congressional liaison National Advisory Commission on Oceans and Atmosphere, 1978-1980. Partner Mattson & Pave, Washington, Miami, Key Largo, 1980-1986, Mattson & Tobin, Key Largo, 1987-2000.
Founder/Chief Executive Officer Great House of Wine, Inc, Fort Lauderdale, Florida and Napa, California, 1997—2003. Sole practitioner Key Largo, Florida, since 2000. Adjunct professor law University Miami, 1983-1993.
Consultant Alaska Department Environmental Conservation, 1981-1991, consultant oil and hazardous material spills, natural research damage assessment.
- Bar: District of Columbia 1979, Florida 1983, United States District Court District of Columbia 1979, United States District Court (southern district) Florida 1984, United States Court Appeals (District of Columbia circuit) 1979, United States Court Claims 1985, Supreme Court of the United States Court 1985, United States Court Appeals (11th circuit) 1985, United States Court Appeals (5th circuit) 1987, United States Court Appeals (federal circuit) 1990.
- Water quality measurement : the modern analytical techniques
- Lang:- eng, Vol:- 1, Pages 473.
- Activated carbon: surface chemistry and adsorption from solution,
- Book by Mattson, James S
- Water Quality Measurement: Volume 1: The Modern Analytical Techniques (Pollution Engineering & Technology)
- Book by Mark, H.
Author: (with H.B. Mark) Activated Carbon: Surface Chemistry and Adsorption from Solution, 1971. Editor (with others): Computers in Chemistry and Instrumentation, 8 vols., 1972-1976.
(with P.L. Grose) The Argo Merchant Oil Spill: A Preliminary Scientific Report, 1977, (with H.B. Mark) Water Quality Measurement: Modern Analytical Techniques, 1981. Contributor articles to professional journals.