Agriculture Reference
In-Depth Information
100 known PAHs, however only 16 have environmental and toxicological importance
(Environment Protection Agency [EPA], 1986). These compounds are able to react, directly
or after undergoing metabolic transformations,
with
the
DNA,
becoming
potential
carcinogens and efficient mutagens.
Soil receives considerable amounts of PAHs that, because of the complexity of their
chemical structure, low solubility in water and strong sorption tendency into the soil,
become recalcitrant and remain for long periods in the environment, enhancing the
probability of exposure of humans and animals to these compounds (Jacques et al., 2007).
When present in the environment they can be transferred to invertebrates by ingestion of
soil and plant material contaminated or by cuticle (Achazi & Van Gestel, 2003).
In order to reduce the negative impact of these compounds in the soil, petroleum refineries
use a bioremediation system called landfarming. The technique has been used for the
treatment of soils contaminated with hydrocarbons for 100 years and, the petroleum
industry for at least 25 years (Riser-Roberts, 1998). Currently, other types of industry started
to employ this technique, such as textile and food industries and treatment of effluents.
Souza et al. (2009) carried out bioassays with
A. cepa
in order to assess landfarming soil
samples before and after biodegradation of hydrocarbons. Before biodegradation, the
landfarming had 13.5 g/Kg of Total Petroleum Hydrocarbons (TPH) and caused strong
clastogenic and mutagenic effects. After 108 days of biodegradation, the concentration of
TPH decreased 27% with significant reduce of mitotic and chromosome abnormalities,
micronuclei and nuclear buds.
Using the diplopod
R. padbergi
exposed to different concentrations of industrial soil
contaminated with PAHs, Souza et al. (2011) and Souza and Fontanetti (2011) analyzed the
perivisceral fat body and midtgut of the animals and verified that there were several
alterations in these two tissues.
2.4 Dioxins
Seven dibenzo-p-dioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs) and 12
polychlorinated biphenyls (PCBs) are called dioxins (Word Health Organizatrion [WHO],
2010; United States Environmental Protection Agency [USEPA], 2000, 2003), being released
into the environment as a byproduct of chemical processes and through the combustion of
industrial and municipal wastes (Stephens et al., 1995). According to Schlatter (1994), since
the accident in Seveso, Italy, they became the symbol of threat caused by toxic chemicals. As
a result of widespread fear, dioxins are a matter of real concern in relation to environmental
contamination.
Among the isomers of PCDDs, the most toxic is 2,3,7,8 - tetrachloro-dibenzo-para-dioxin
(2,3,7,8-TCDD) (Eisler, 1986). There is little information in literature on the effects of PCDDs
on terrestrial invertebrates. Reinecke and Nash (1984) reported that two species of
earthworms (
Allolobophophora caliginosa
and
Lumbricus rubellus
) showed no adverse effects
when exposed for 85 days in soil with 5 ppm of 2,3,7,8-TCDD, but both species died at 10
ppm. Studies involving plants and PCBs have been made, since these organisms are less
sensitive to PCBs and thus may be a possible route of biomagnification in various food
chains (Sinkkonen et al., 1995).
2.5 Agrochemicals
The use of fertilizers and pesticides has become a common practice due to population
growth, food crisis and consequent need for the increase in the agriculture production.
