Agriculture Reference
In-Depth Information
contaminated. The integration of spatial-temporal data on water quality in a
GIS model proved to be a useful tool to evaluate pollution trends for different
contaminants flowing through a watershed and downstream into a coastal
city, and the associated risks of contamination of vegetable-growing areas.
The project demonstrated the usefulness of participatory mapping (GIS) as an
effective approach to dissemination of environmental pollution information
and risk reduction strategies. These methods also will help the development of
appropriate information dissemination packages for the communities who
depend for their livelihood upon these ecosystems.
Vegetables grown in areas contaminated by water from the Rı´ mac River
had high levels of As and Pb, although a reduction in As has been observed
over the last two years due to improvements in the Ministry of Energy and
Mines' regulatory systems. Regulations now exist which involve obligatory
programmes of environmental adequacy as well as environmental impact
assessments (MINEM, 1993). Despite the high levels of Pb found in the river
water, the content found in soils and crops does not pose a significant health
risk. However, significant levels of As and Cd were found in soil, and these
could be harmful. Investigation of the Cd and As levels in vegetables showed
that there was more accumulation in foliage than in roots. The indigenous
aromatic plant huacatay contains Cd and As concentrations that are above
those permitted by Peruvian law. Contamination of irrigation water with
pathogens was a more serious problem for vegetable production. FC were
found to reach levels higher than permitted by Peruvian law: more than 97 per
cent of water samples from irrigation canals contained five million MPN/
100ml, which is beyond the maximum permitted limits for FC bacteria.
Analysis of lettuce and radish samples showed 17 per cent and 31 per cent of
the samples having bacterial loads that are above permitted limits. The
practice of washing vegetables using water from the irrigation canals further
contaminated these vegetables: 57 per cent of clean vegetables were
contaminated during the rinsing process.
To complement the chemical and biological data collection, the study
sought to understand how farmers perceive environmental risks. Not
surprisingly, farmers tended to depend on observed phenomenon rather than
hearsay references to mining risks. Almost three-quarters associated domestic
sewage and other urban solid wastes in the irrigation channels, with only 11
per cent mentioning mining. Provision of correct information about the
sources of pollution in the environment would go a long way to enhancing
awareness of such risks to the community.
The high levels of microbiological contamination raises the need for
measures to be applied which would make it possible to improve the quality
of water used for irrigation and washing in the study area. While the ideal
scenario would be to prevent untreated domestic sewage from entering the
river through sewerage, this is not realistic at the moment. Consequently,
other mechanisms that permit in situ quality improvement should be
considered, such as the use of washtubs of clean water for vegetables or the
implementation of reservoirs so as to treat irrigation water.
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