Residue and Dissipation Kinetics of Metsulfuron-Methyl Herbicide in Soil: A Field Assessment at an Oil Palm Plantation

Agrochemical inputs to managed oil palm plantations are a probable risk to ecosystems: Results from a screening level risk assessment

Palm oil is a high value crop widely grown in the tropics. The management of palm oil is characterised by widespread agrochemical use. Here we report the results of a screening level risk assessment conducted from the available literature on the environmental concentration of agrochemicals in surface waters and soils in palm oil growing areas. To date, only a small number of published studies have measured pollutant concentrations in and around palm oil plantations. To identify potential high-risk contaminants, a standard SSD based risk assessment, establishing risk quotients for detected contaminants, was conducted in relation to available species sensitivity distributions. A probabilistic SSD based risk assessment, calculating potential risk distributions, was also conducted for contaminants with the required number of data points available. Metals were the most commonly detected (and measured) substances and also presented the greatest risk, especially copper and zinc, but also nickel, lead and cadmium. For these metals, environmental concentrations overlapped levels found to cause effects in toxicity studies, indicating the potential for adverse outcomes from exposure. To fully understand the extent of this risk, more detailed studies are needed that assess metal speciation states and bioavailability under the prevailing soil and water chemistry conditions in palm oil plots. Limited studies have measured pesticide concentrations in palm oil systems. In these few cases, only a few active substances have been measured. From the limited information available, potential risks are indicated due to the presence of some insecticides. However, fungicides are also widely used for palm oil disease management, but little data studies are available to assess both exposure and potential effects. To further assess the potential chemical footprint of different palm oil management practices, studies are needed that systematically assess pollutant levels across a range of chemical groups to consider effects within a mixture context.

Evaluation on persistence and mobility of metsulfuron-methyl at oil palm plantation: residue field trial experiment versus VARLEACH model

The present paper discussed the comparison of the persistence and mobility of metsulfuron-methyl from a residue field trial experiment and simulation using a VARLEACH model. The residue field trial experiment was performed at Sungai Buloh Oil Palm Estate, Selangor. The plots were treated with metsulfuron-methyl at two treatment rates of 15 g a.i ha^-1 (T1) and 30 g a.i ha^-1 (T2). Soil samples were collected at 0, 1, 3, 7, 14, 21, 30, 60 and 90 days after treatment (DAT) and analysed subsequently by HPLC-UV. The results show that metsulfuron-methyl degraded rapidly in the soil with the half-life (t½) of 6.3 days in T1 and 7.9 days in T2. The simulation of VARLEACH model gave similar pattern of persistence and mobility of metsulfuron-methyl in the soil profile. However, total residues and the mobility of the metsulfuron-methyl were poorly simulated by the VARLEACH model due to consistent overestimation of the quantified residues. Results indicated that the metsulfuron-methyl lost more rapidly than the prediction values from VARLEACH model. In this case, simulation models which use transformation routines similar and which include additional degraded processes such as leaching, volatilisation, plant uptake or runoff could be considered. Albeit, overestimated values on the concentrations of metsulfuron-methyl are reported using VARLEACH model, the model still can be used as rapid and fast approach to predict the behaviour of pesticide at minimum cost.