|Chromium in the southern California marine environment|
Mearns, A.J.; Young, D.R. (1977). Chromium in the southern California marine environment, in: Giam, C.S. (Ed.) Pollutant effects on marine organisms. pp. 125-142
In: Giam, C.S. (Ed.) (1977). Pollutant effects on marine organisms. Lexington Books: Lexington. ISBN 0-669-01518-0. XI, 215 pp., more
|Authors|| || Top |
The Southern Califomia Coastal Water Research Project, a local govemment agency for marine ecological research, has been conducting an interdisiplinary study of the sources, distribution, and fate of chromium and other trace elements in coastal waters. Marine life in coastal waters of southern Califomia is naturally exposed to about 0.2 micrograms per liter dissolved chromium, composed of 0.15 micrograms per liter hexavalent and 0.05 micrograms per liter trivalent. Uncontaminated local sediments contain about 40,000 micrograms per kg dry weight. Municipal wastewaters (1.4 billion cu m per year) are a dominate source of chromium in southem Califomia. Most chromium (90%) is bound to wastewater particulates which contaminate sediments adjacent to outfalls by a factor of 20. In contrast, ambient dissolved levels in seawater are only enhanced by a factor of 1 to 5 in the mixing zone of outfan diffusers; most of this is due to the trivalent form. Toxicity experiments confirm that hexavalent chromium is the most toxic form and can produce detrimental biological effects (inhibition of reproductive success) at 12.5 micrograms per liter (about 85 times ambient) and probably lower concentrations. In contrast, trivalent chromium is not toxic to marine animals, perhaps owing to its relative insolubility at the normal pH of seawater . Fish can accumulate chromium during long-term exposure at levels as low as 16 micrograms per liter (hexavalent). In the field, most tissues of marine fish remain at ambient levels despite exposure to highly contaminated sediments. However, there is some evidence for a twofold increase in gonads. Adductor muscle of scanops demonstrate a tenfold enhancement of chromium in response to wastewater discharge. Review of other data suggest that chromium levels in marine organisms may be inversely related to size or trophic status. More information on long-term biological effects of chromium at near-ambient levels (5-50X) is needed before safe levels can be set. Levels in muscle tissues of fish require a more careful diagnosis since many reports are below limits of detectability for tissues ( often 0.2 micrograms per kg). New criteria might be proposed for trivalent and hexavalent separately. However, factors contributing to the possible conversion of trivalent to hexavalent chromium in the sea should be explored. Cultures of annelids may be quite useful in determining effects of long-term exposures at or near ambient.