Environmental Engineering Reference
In-Depth Information
indicator that lead existed in the sediments of the soil in which the crawfish lived and ate.
The concentration found ranged from 0.25 to 0.40 micrograms of lead per gram of crawfish.
They recommended purging of the crawfish prior to human consumption to reduce the
possibility of lead consumption.
Approximately ten years later this laboratory embarked on several major projects in the
determination and interpretation of metals in crawfish. Initial work involved an
undergraduate chemistry major project to determine copper, iron and zinc in the crawfish
from Southwest Louisiana (Hagen and Sneddon, 2009). The results showed no significant
differences in these metal concentrations between male and female crawfish, and no
significant differences between crawfish from a pristine area and near a major highway. The
concentrations of iron in the meat compared to the whole crawfish was about four times
higher and was assumed to be due to the shell of the crawfish containing high levels of iron.
In early 2007 and through 2010, two major field trials were initiated (Richert and Sneddon,
2008b and Moss et al., 2010). Six metals (cadmium, copper, nickel, lead , iron and zinc) were
determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) in
both tail (meat) and whole body of the crawfish and also in the soil in a four-month season
(February through May) 2007 in Southwest Louisiana (Richert and Sneddon, 2008b).
Cadmium or lead were not found in the meat or the while body. Nickel was found in some
samples of the meat but mostly in the April and May samples. Copper, iron and zinc were
found in both tail and whole body of the crawfish. Limited soil sampling showed no
cadmium, nickel, or copper but levels or concentrations of iron, lead and zinc were found in
the soils. Moss et al, (Moss et al., 2010) provided a mini-review of crawfish aquaculture and
determined the following concentrations (microgram of metal per gram of dried sample of
metal0, 95 % confidence interval and range from February through May 2009 as follows:
cadmium, 0.49 +/- 0.14, 0.34-0.79, copper, 34.9 +/- 5.3, 23.8-44.2, nickel, 1.83 +/- 0.54, 1.08-
3.39, lead, 18.0 +/- 4.0, 9.9-23, zinc , 47.4 +/- 4.63, 41.3-55.8 were relatively constant with a
slight increase in iron, 620.4 +/- 205.8, 328.8-1072.8 over the four months. The temperature
of the crawfish ponds were monitored weekly but had no noticeable effect on the metal
concentrations. Also sampled were the soil the crawfish lived in with copper and zinc
concentrations decreasing with increasing water temperature and noticeable effect with the
other four metals. A comparison to the study by Richert and Sneddon (Richert and Sneddon,
2008b) showed no significant differences in the six metal concentrations from one season to
the next.
Two projects were undertake in the laboratory for controlled studies for the uptake of
copper, lead and zinc in crawfish (Neelam et al, 2010) and selenium-lead interactions (White
et al., 2012). Ten gallon aquarium tanks were spiked with up to 100 part per million (ppm)
of the three metals and the crawfish introduced into the tanks. Not surprisingly all three
metals were absorbed by the crawfish. Copper showed the highest absorption by the
crawfish. Lead showed a constant increase in absorption with increased spiked of lead. It
was noted that there was no obvious correlation between the metal absorbed and the
amount of metal in the aquarium. It was noted that higher amount of lead were absorbed
compared to copper and zinc. White et al. (White et al., 2012) determined whether the
relationship between selenium and lead is one of an antagonistic or synergistic nature.
Experiments were conducted on the freshwater crustacean crawfish (Procambarus clarkii).
Crawfish were exposed to a known concentration of lead, dissected then analyzed to
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