Atrazine and Metolachlor Contamination in Surface and Ground Water in the Zomba/Bvumbwe Region in Malawi

Abstract

A snapshot survey was conducted to assess ground and surface water contamination by atrazine and metolachlor in the Zomba/Bvumbwe region. Ground and surface water samples were collected and their atrazine and metolachlor were extracted using ethyl acetate. The extracts were cleaned up using florisil, concentrated on a rotary evaporator and detected using thin layer chromatography. No herbicide residue was detected in the groundwater samples. In surface water samples atrazine was detected in 38 % and metolachlor was detected in 15 % of the samples. The concentrations of the herbicides were at their highest soon after the first run off event after herbicide application. The concentrations, however were generally below the World Health Organization's (WHO's) recommended maximum guideline values (2 μg/ml atrazine and 10 μg/ml) metolachlor. Following the first run off event concentrations of herbicides steadily decreased with time, decreasing to zero within eight weeks of herbicide application at 37 % of the water sampling points that had herbicide contamination. Light soaking rains, higher clay content, flat land, longer distance between agricultural land and surface water body (filtering area), lower herbicide application rates and herbicide incorporation seemed to reduce herbicide export to surface water. Based on the study it is recommended that regular monitoring of pesticides in water should be done and that quantification of the pesticides should be done more accurately using a gas or liquid chromatograph with appropriate detectors. It is also recommended to follow good land husbandry practices to reduce export of pesticides to surface water bodies.

A Critical Review of the Status of Pesticide Exposure Management in Malawi

“…Therefore, there are particular concerns for communities that utilize untreated drinking water from shallow wells located in agricultural areas. For example, atrazine and metolachlor were detected in surface water samples from Zomba and Bvumbwe areas in southern Malawi, especially with peak concentrations occurring in the first run-off event after pesticide application [42]. Exposure from spray drift, run-off and percolation is expected to be significant in large commercial farms that utilize large amounts of pesticides using aeroplanes, booms and tractors.…”

Herbicide Residues in Water Resources: A Scoping Review

“…Herbicides are extensively used in most countries for killing weeds. New herbicide families have recently been introduced to agricultural producers due to their numerous advantages, including low utilization per hectare, low toxicity to mammals, and the absorption of water through branches and roots (18,29). Agricultural growth and diversity of pests have increased the number of pesticides, contaminating water resources with herbicides.…”

Review of advances in the thin layer chromatography of pesticides: 2012–2014

“…The separated zones were visualized after exposure to UV light. [56] A semiquantitative HPTLC method based on visual comparison of zone diameters between standards and samples was reported for cypermethrin, CPF, and imidacloprid residues in 10 kinds of vegetables. Samples were extracted with ethyl acetate, extracts were cleaned up on a charcoal column, methanol-ammonia mobile phase was used with silica gel plates, and potassium iodide and o-tolidine were applied to detect yellowish-brown zones of the pesticides.…”