Uptake of pesticides from water by curly waterweed Lagarosiphon major and lesser duckweed Lemna minor

Abstract

The uptake of pesticides from water by two aquatic plants, the submersed Lagarosiphon major (Ridley) Moss and the floating duckweed Lemna minor L., was measured over periods of up to 72 h. Twelve non-ionised pesticides and analogues, chosen to span a wide range of physicochemical properties, and one analogue (3,5-D) of the phenoxyacetic acid herbicide 2,4-D were studied. Concentrations of the parent compound were determined in the plants following extraction and separation by chromatography. Quantification was by liquid scintillation counting for the (14)C-labelled compounds and by high-performance liquid chromatography for the four non-radiolabelled commercial pesticides. Uptake for all compound and plant combinations had reached equilibrium by 24 h. Accumulation of compound in the plant could be described well for most non-ionised compounds by equilibration into the aqueous phase in the plant cells together with partitioning onto the plant solids, this latter process becoming dominant in Lagarosiphon for compounds with log K(ow) > 1 and in Lemna for compounds with log K(ow) > 1.8. Lipophilic compounds with log K(ow) > 4 were concentrated more than 100-fold on a fresh-weight basis. However, the uptake of isoproturon and chlorotoluron was up to threefold less than expected from their K(ow) values, and their behaviour was better explained using solvation descriptors. Uptake of the acid 3,5-D was dependent on solution pH, this compound being strongly taken up at lower pH by the process of ion trapping, as previously observed in barley roots. Aquatic vegetation can thus rapidly accumulate pesticides, and could be an important sink especially for lipophilic pesticides reaching well-vegetated waters.

Safety of Novel Protein Sources (Insects, Microalgae, Seaweed, Duckweed, and Rapeseed) and Legislative Aspects for Their Application in Food and Feed Production

“…Duckweed species are also capable to uptake and transform phenols (Fujisawa and others ) and pesticides, including organophosphorus pesticides (malathion, demeton‐S‐methyl, and crufomate) (Gao and others ), lipophilic compounds (De Carvalho and others ), 3‐methyl‐4‐nitrophenol, 3,5‐dichloroaniline, 3‐phenoxybenzoic acid (Fujisawa and others ), dimethomorph (Olette and others ; Dosnon‐Olette and others ), copper sulphate and flazasulfuron (Olette and others ), and xenobiotics (chlorophenols) (Day and Saunders ).…”

Optimal choice of pH for toxicity and bioaccumulation studies of ionizing organic chemicals

“…The effect of the ion trap is illustrated with several calculation approaches, using two phenoxyacetic acids (POA) as examples: 2,4‐Cl POA (p K a 2.98, K OW 2.43 12) and 3,5‐Cl POA (p K a 2.98, K OW 2.38 12). The measured data were derived from three studies and for three different plants, namely, for barley (2,4‐Cl POA and 3,5‐Cl POA 35), for Ricinus communis (3,5‐Cl POA 37), and for water weed (2,4‐Cl POA 67). For all three species, and for both compounds, the measured BCF is higher at lower pH (Fig.…”

Endothall behavior in Myriophyllum spicatum and Hydrilla verticillata

“…Based on log K ow values fluridone should accumulate more than endothall, so the fact that endothall accumulates in EWM and the two hydrilla biotypes significantly above the concentration in the treatment solution is notable. De Carvalho et al found that log K ow values are not reliable predictors of herbicide accumulation in aquatic plants when those values are <2.…”

“…In addition to nonlinear regression analyses, for absorption and translocation data, the percentage of total herbicide present in aboveground and belowground plant parts was calculated to determine translocation and the plant concentration factor (PCF) was calculated to determine herbicide bioconcentration. The equation used to calculate PCF was presented in Vassios et al as adapted from de Carvalho et al and was defined as: …”