Agriculture Reference
In-Depth Information
Water quality of irrigation canals
Twenty-five water samples were collected in both October 2004 and March
2005 in Carapongo for HM and FC analysis. Additionally, 20 water samples
were collected in Huachipa and Nieverı´ a in September 2005 for FC. Sampling
sites included main and lateral irrigation canals, water gates and proximity to
populated places. Criteria included samples taken during both the dry and the
wet seasons.
Water samples for HM were preserved with nitric acid for subsequent
laboratory analysis. Water samples for FC were collected in sterilized glassware
containers. Each sample was geo-referenced by a GPS location. To assess the
contamination status of water, the General Water Law of Peru was consulted
(MINAG, 1969, 1976) and the indexes displayed in Table 7.1 were used to
classify all maps.
Quality of vegetables
Vegetables represent the main crop around Carapongo, Nieverı´ a and
Huachipa. In total, 57 vegetable samples were collected and sampled.
Carapongo was divided in five agricultural zones to allocate samples
proportionally (Campo Sol, Guadalupe, Huancayo, Nuevo Horizonte and
Tulipanes). Five vegetable samples within each zone were collected in
December 2004 (FC analysis) and April 2005 (FC and HM analysis). Crops
included were those noted in previous surveys conducted in the area (Lozano,
2004): huacatay (Tagetes minuta L., used as seasoning or as a condiment in
Peruvian foods), lettuce (Lactuca sativa L.), radish (Raphanus sativus L.),
turnip (Brassica rapa L. var. rapa) and the common beet (Beta vulgaris L. var.
crassa). An additional seven samples were collected in Nieverı´ a and Huachipa
in March 2006 for FC analysis. Selected crops were turnip, common beet,
huacatay, celery (Apium graveolens L.) and grass (Lolium perennial L.).
Five to six sub-samples were taken for each vegetable sample during
harvest season. For the assessment of HM, vegetables were classified in
accordance with their edible parts: roots (turnip, radish and common beet)
and foliage (lettuce, huacatay and celery). In addition, vegetables were
collected before and after washing for FC assessment.
The freshly harvested vegetables were brought to the laboratory and
washed, initially with running water to remove the soil particles, followed by
three washings with distilled water. Samples were cut into small pieces before
being oven-dried at 1058C to constant weight. The samples were then
pulverized with a mortar and subjected to wet digestion in the conical flask
with HNO
3
and HClO
4
(2 :1) to extract total HM (AOAC, 1984). Then 10ml
of HCl was added to dissolve inorganic salts and oxides. Care was taken to
prevent contamination in all steps of the process. HM in all samples were
determined with atomic absorption spectroscopy (AAS) for Cd and Cr,
AAS
þ
graphite furnace for Pb, and AAS
þ
hydride generation for As.
Guidelines for HM in vegetables were taken from several sources
including the 1995 Chinese National Standards Analytical Methods (Zhou
et al, 2000) and Codex Alimentarius (2006). The guidelines for HM were set
