Assessing Glyphosate and Fluridone Concentrations in Water Column and Sediment Leachate

Abstract

Purpose: In recreational water bodies, herbicides are widely used for controlling unwanted weeds, and impacts of herbicide residues on health risks to aquatic ecosystem is a serious concern. This study was aimed to improve the existing understanding of the deposition of herbicides from water column to bed sediment and leachate of herbicides from bed sediment to water column. We investigated the attachment of two herbicides with sediment and release from sediment: (1) Glyphosate; and (2) Fluridone. The goal of this study was to determine the deposition and release of Glyphosate and Fluridone in bed sediment of the Sacramento-San Joaquin River Delta.Materials and Methods: Field sampling was performed to collect water and sediment samples from Sacramento-San Joaquin River Delta. Bottom dredge sampler was used for collecting sediment samples and horizontal water bottle sampler was used for collecting water samples. A series of experiments were conducted to determine the attachment and release of Fluridone and Glyphosate from sediment at a different level of initial concentrations. For analyzing Fluridone and Glyphosate in sediment leachate and water, samples were processed using enzyme-linked immunosorbent assay (ELISA) based method.Results and Discussion: Observations showed that proportions of Glyphosate concentrations in water were higher than Fluridone concentrations in water, when both herbicides were inoculated in water in same quantity. On the contrary, the concentrations of Fluridone in sediment-bound leachate were higher than Glyphosate concentrations in sediment-bound leachate, regardless of the initial concentrations. Fluridone and Glyphosate concentrations in water column samples differed significantly (p < 0.05) over the time even initial concentrations of these herbicides were kept similar, which indicates that Fluridone interaction with water column was considerably different than the interaction of Glyphosate with the water column. Pandey et al. Herbicide Concentration in Water and Sediment LeachateConclusions: Bed sediment can be an important sink and source for release of Fluridone and Glyphosate from bed sediment to the water column of an ambient water body. Significant concentrations of herbicides were deposited in bed sediment of Sacramento-San Joaquin Delta, and eventually the high concentrations of herbicides were observed in sediment leachate. Improved understanding of this important release pathway can provide much needed information to adequately address the impacts of particle attached herbicides on aquatic and ecological environment of a water body.Keywords: fluridone and glyphosate in ambient water, particle attached herbicides, herbicides leachate from sediment, sediment and water column interaction, deposition and resuspension

Invasive Aquatic Vegetation in the Sacramento–San Joaquin Delta and Suisun Marsh: The History and Science of Control Efforts and Recommendations for the Path Forward

“…Field assessments have revealed elevated sediment concentrations of fluridone and diquat compared to the water, by up to an order of magnitude (Hosea 2005), and similar results for fluridone have been observed in recent monitoring at both treated and untreated Delta sites (Rasmussen et al 2020). These field observations are consistent with laboratory evaluations that compare fluridone and glyphosate concentrations in sediment leachate: glyphosate concentrations in sediment diminish rapidly after initial washes; fluridone concentrations remain high after consecutive washes (Pandey et al 2019). Further study has shown that degradation of sediment-bound fluridone is faster with increasing exposure to ultra-violet light, increasing temperature (greater than 20 °C), and higher clay content in the sediment matrix (Wickham et al 2020).…”

Herbicides in Water Sources: Communicating Potential Risks to the Population of Mangaung Metropolitan Municipality, South Africa

“…Herbicides are predominantly utilised in agricultural activities, but substantial quantities are also utilised in forestry, industrial areas, public areas, parks, golf courts, and sports grounds for weed control and maintenance [ 5 , 6 ]. Pandey et al [ 45 ] also stated that these herbicides can be used to control invasive plants in water. As a result, the presence of these herbicides in dams/reservoirs may be attributed to their use to control aquatic weeds, such as algae and submerged weeds.…”

Herbicide Exposure and Toxicity to Aquatic Primary Producers

“…For phytoplankton and free-living submerged aquatic plants, water is the main medium through which they are exposed to dissolved herbicides. Resuspension of sediments contaminated with herbicides can result in the release of herbicides into the water column (Pandey et al 2019). Resuspension can therefore also expose phytoplankton and free-living aquatic plants indirectly to herbicides accumulated in the sediment.…”

“…Many herbicides interact with the dissolved and particulate organic matter in the water, resulting in the adsorption of active herbicides (Voice and Weber 1983;Chefetz et al 2004;Pandey et al 2019). These aggregates may sink to the bottom causing the transport of herbicides from the water column to the sediment.…”