pesticide residues in soil, water and crops
TRANSCRIPT
8/2/2019 Pesticide Residues in Soil, Water and Crops
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Motivation
Outlook
First results of pesticide analyses
soil
water
crops
insects
Pesticide residues in soil, water and crops
resulting from cash crop cultivation
in Benin and Burkina FasoY. Bonzi Coulibaly1, H. Tapsoba1, C. Stechert2, M. Kolb2, M. Bahadir 2
1Laboratoire de Chimie Organique: Structure & Réactivité , Université de Ouagadougou, Burkina Faso; [email protected]
2Institute of Ecological Chemistry and Waste Analysis, Technische Universitaet Braunschweig, Germany
or cash crop cultivation, especially in cotton cultures in Benin and Burkina
aso imported insecticides are used, that are mostly toxic. For example,
he organo-chlorinated endosulfan – banned in many countries – is still in
se in both Western African countries. One consequence of pesticide
pplication is the formation of residues in soil, water, and crops.
hese two countries have important natural reserves in proximity to cotton
arms as Pama Reserve Parc in the East of Burkina Faso and Parc
National de la Pendjari in the North of Benin. Thus, contamination of soils
nd water especially in those areas is important for their key function asabitat media for a great number of non-target organisms (e.g. arthropods,
mphibians and bats) that fullfill important ecosystem functions (Fig. 1).
esticide residues in soil and water at BIOTA biodiversity observatories of
hese areas and at vicinal agricultural areas are monitored in order to
valuate the pollution levels.
0
200
400
600
800
1000
1200
1400
1600
1800
K O S C B
K O S C B M B S
S O S S
B S C
V S C
O S C K S
C
N S C C
M a t e r i
c o n c
. i n µ g / k g s o i l d m
α-endosulfan
β-endosulfan
endosulfan sulfate
Biocotton BF Sesam BF Conventional Cotton BF / Benin
Fig. 2: Endosulfan residues in agricultural soils from sampling sites in Benin
(cotton field in Materi near Pendjari Park in October 2007) and Burkina
Faso (BF) in November 2007
Sampling sites
ig. 1: Interaction of non-target organisms with environmental compartments
he sampling sites are selected on cash crop farmland of Burkina Faso
nd Benin (disturbed areas) and in the undisturbed area of the Pendjari
National Park in Benin in cooperation with zoologists that sample the non-
arget organisms at the same sites in Benin. Sampling strategy is matchinghe climatic conditions by considering the two seasons: dry (November to
April) and wet (May to October) and the crop growing season, especially of
otton.
Residue analyses of soil and water samples were performed for typically
applied insecticides in cotton like organochlorines, organophosphates and
pyrethroides. Residues of endosulfan isomers and their main metabolite
endosulfan sulfate were detected (Fig. 2 and Tab. 1).
Endosulfan is a non systemic organochlorine insecticide with a DT50 valueof about 50 days (time for the disappearance of 50 % of the applied
insecticide). It is known to be carcinogenic, teratogenic, and neurotoxic as
well as toxic to aquatic organisms.
In soil samples from the beginning of the dry season (end of October /
November) the applied insecticide mixture of endosulfan (α- and β-isomer
in ratios of 2:1 or 7:3) was degraded for a major part (50 to 80 %) to the
metabolite endosulfan sulfate that is more persistent and similar toxic than
its parent compounds. The residues levels in soil of conventional cotton
growing were relatively high in a range of 160 µ g/kg to 2300 µ g/kg (sum of
all three substances). Even in soil from a bio-cotton field low
concentrations of endosulfan were found but with an untypical domination
of the α-isomer. This might be due to a contamination with the volatile
isomer α-endosulfan via evapotranspiration and atmospheric transport
from treated fields in the neighborhood.
Samplinglocation
Benin Burkina Faso
PendjariPark
Huntingzone
Cotton area Cotton area
BaliI
BaliII
BatiaI
BatiaII
Taya-couI
Taya-couII
MateriI
Kiki-deni
Natia-bouani
Conc. of α-, β- endosulfan,endosulfan sulfatein µg/L n.d. n.d. 0.02 0.02 n.d. <0.02
0.03 < 0.02
0.05
Tab. 1: Endosulfan residues in pond water from sampling sites in Benin andBurkina Faso
n.d.: not detected
Information on pesticide products and their application pattern used in
cash crop cultivation in the two countries will be supplemented. Sampling
of soil, water and crops will be continued in 2008 and 2009. Analytical data
will provide an overview of the environmental contamination state due to
cotton cultivation and thus complete the data of pesticide residues in non-
target organisms to evaluate possible influences of pesticides on bio-
diversity.
Sampling sites in the vicinity of Biodiversity
Observatories (NSCC, KOSCB, KOSCBM
Kikideni, Natiabouani in Burkina Faso;Tayacou, Materi, Batia, Bali in Benin)
Additional cotton sites of conventional
cotton in Burkina Faso
(BSC, VSC, OSC, KSC)
Pama reserve parc
Parc National de la Pendjari