The study investigated the concentration and risk of some
heavy metals lead, cobalt, cadmium, nickel, chromium, arsenic, zinc and iron in
waterleaf (Talinum triangulare), fluted pumpkin (Telfairia occidentalis),
cassava tuber (Manihot esculenta crantz) and soil from the dumpsite in
Rumuolumeni, Port Harcourt. The result indicated that heavy metal contamination
was of the order
iron>zinc>chromium>nickel>lead>cobalt>cadmium>arsenic. The
highest values for soil were for iron (80.00±1.070 mg/Kg) and zinc (14.91±0.197
mg/Kg), while the least was arsenic (0.014±0.050 mg/Kg). Cassava tuber had
highest levels in iron (61.80±2.038 mg/Kg) and zinc (11.03±0.107 mg/kg), with
the lowest levels in arsenic (0.004±0.005 mg/Kg). In fluted pumpkin, iron
(43.15±0.881 mg/Kg) and zinc (8.979±0.193 mg/Kg) were highest but cobalt and
cadmium were not detected. Iron (37.72±1.962 mg/Kg) and zinc (6.797±0.208
mg/Kg) had the highest concentration in waterleaf but arsenic was not detected.
Zinc, chromium, and nickel were higher than the WHO permissible limit. The
transfer factor from soil to plants was as high as 75-90%, especially for
cassava tuber. The enrichment factor revealed that the contamination is of
anthropogenic sources except for arsenic, cobalt and lead in some samples. The
non-carcinogenic risk showed that the highest risk was for chromium and iron,
while cobalt and lead pose risk for cassava tubers. The risks due to soil
ingestion were relatively high for carcinogenic metals like lead (1.2E-4),
cadmium (1.2E-4), nickel (2.6E-2) and chromium (1.2E-2). These values are
higher than the benchmark of 10-4- 10-6 set for management decisions by USEPA
for carcinogenic substances in the environment. The other heavy metals with
high carcinogenic risk are nickel and chromium in waterleaf, fluted pumpkin,
and cassava with estimated values ranging from 3.7E-3 to 2.3E-2. From the
findings, the risks associated with consuming food planted within the dumpsite
environment are high and should be stopped.
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