Tebuthiuron Movement via Leaching and Runoff from Grazed Vertisol and Alfisol Soils in the Brigalow Belt Bioregion of Central Queensland, Australia

Abstract

Tebuthiuron is one of five priority herbicides identified as a water pollutant entering the Great Barrier Reef. A review of tebuthiuron research in Australia found 13 papers, 6 of which focused on water quality at the basin scale (>10,000 km(2)) with little focus on process understanding. This study examined the movement of tebuthiuron in soil and runoff at the plot (1.7 m(2)) and small catchment (12.7 ha) scales. The greatest concentration and mass in soil occurred from 0 to 0.05 m depth 30-57 days after application. Concentrations at all depths tended to decrease after 55-104 days. Runoff at the small catchment scale contained high concentrations of tebuthiuron (average = 103 μg/L) 100 days after application, being 0.05% of the amount applied. Tebuthiuron concentrations in runoff declined over time with the majority of the chemical in the dissolved phase.

Suspect and Nontarget Screening for Contaminants of Emerging Concern in an Urban Estuary

“…Tebuthiuron (50−110 ng/L) was consistently detected at site 15 in dry sampling dates. It can be transported to receiving waters >100 days after application, 60 although its environmental fate remains unclear. The occurrence of three features (m/z 215.0980, 172.0905, and 158.0741), each with putative thiadiazole substructures, was correlated with the occurrence of tebuthiuron at site 15.…”

Pesticide Behavior, Fate, and Effects in the Tropics: An Overview of the Current State of Knowledge

“…67 Studies in this special issue have investigated the leaching, surface runoff, and sorption potential of various pesticides including the insecticides chlorpyrifos and endosulfan 38 and the herbicide tebuthiuron. 68 Dores et al 38 found that volatilization was likely a key loss pathway for chlorpyrifos and endosulfan, although considerable amounts could be leached through preferential flow sites as well as lost through surface runoff. Soil dissipation rates for these insecticides were found to be much faster than rates reported for temperate locations, although sorption was similar to that measured elsewhere.…”

“…Soil dissipation rates for these insecticides were found to be much faster than rates reported for temperate locations, although sorption was similar to that measured elsewhere. Thornton and Elledge 68 examined the persistence and movement of tebuthiuron in two Australian soils with two different chemical formulations (granular and dry flowable). They found that tebuthiuron was transported largely in the dissolved phase and had the ability to leach in the soil profile and that high concentrations (relative to guideline values) could be lost in surface runoff.…”

“…On the one hand, some level of chemical persistence is desirable to kill/suppress pests, but longer than necessary persistence may result in losses from sites of application through leaching, drift/volatilization, or surface runoff, especially under the tropical warm, humid, and heavy rainfall conditions. Several studies, including those in this special issue, have shown that although only a small percentage (<3%) of most applied pesticides leave a paddock in most trials, the offsite concentrations can still reach levels that are likely to cause negative effects to nontarget aquatic organisms. ,, Indeed, monitoring of aquatic environments downstream of agricultural lands reveals that a suite of several relatively polar pesticides reach concentrations that are considered of concern across ecologically important locations in Australia, Brazil, and other tropical locations. ,,,, These findings have led to criticisms of pesticide regulation authorities including the lengthy, ad hoc, and case by case review processes and the use of unreliable modeling platforms to assess offsite risk. , …”

Leichhardt, land clearing and livestock: the legacy of European agriculture in the Brigalow Belt bioregion of central Queensland, Australia

“…Woody weed control was undertaken in 2011 by aerial application of 12.5 kg/ha of granular tebuthiuron, which contained 200 g/kg of active ingredient. The method and rate of application were reflective of commercial practice within the central Queensland grazing industry (Thornton and Elledge 2016).…”