3 research outputs found
Relationship between geomorphology and contamination with weathered hydrocarbons in an old river levee/marsh association
A site evaluation was made for a low-lying property in an old river
levee/marsh association, used marginally for cattle raising, which was
contaminated due to historical practices. Contamination was related to
geomorphology: the lowest areas contained 79 % of the contaminated
samples. Other contaminated samples were all rear access roads
(probable intentional dumping). There were no samples in the higher,
levee areas away from roads with hydrocarbon concentrations above 3,000
mg/kg. Medium and high impact levels, corresponding to average
hydrocarbon concentrations of 13,400 mg/kg and 109,700 mg/kg,
respectively, were found in 28 % and 27 % of the property area. The
medium impact level was predicted to have a reduced pasture production
potential of ~ 50 % while at the high impact level practically no
pasture production was predicted. Toxicological risk to cattle is
present in only 12 % of the sample points although almost all of these
are in very marshy areas not apt for cattle raising. Because the
hydrocarbons at this tropical site are very weathered, acute toxicity
was not related to hydrocarbon concentration. Although slightly more
than half of the property has hydrocarbon concentrations above the
permissible limit, only about one-third of the contaminated area is apt
for cattle raising. This study, based on hydrocarbon distribution
related to site geomorphology, soil toxicity bioassay, risk assessment
to cattle and evaluation of pasture production allowed to made a more
accurate assessment and definition of future use of the site. These
criteria could be used for diagnostic studies of sites with similar
tropical conditions