Dichlobenil and 2,6-dichlorobenzamide (BAM) dissipation in topsoil and deposits from groundwater environment within the boreal region in southern Finland

Abstract

BAM (2,6-dichlorobenzamide) is a metabolite of pesticide dichlobenil and a common groundwater contaminant. Dichlobenil and BAM half-lives were determined in five Finnish subsurface deposits and in topsoil. Aerobic and anaerobic conditions with sterilized controls were included in this 1.4-year incubation experiment. In subsurface deposits, dichlobenil half-life varied from 157 days to no degradation and that of BAM from 314 days to no degradation. Microbes and oxygen enhanced dichlobenil and BAM dissipation rates in some deposits. However, dichlobenil and BAM concentrations were most significantly affected by deposit characteristics, especially carbon and nitrogen amounts. Also low pH, cadmium, iron, zinc, manganese and lead correlated with low dichlobenil and/or BAM concentrations. In mineral topsoil, dissipation was faster with half-lives of 41-54 days for dichlobenil, and 182-261 days for BAM. Dichlobenil was depleted completely in surface soil, but BAM was not dissipated below 55-81 % of the initial concentration. Generally, dichlobenil and BAM dissipation in samples from the northern boreal region was similar to that reported for the temperate region. BAM was persistent in topsoil and subsurface deposits, indicating long-term persistence problems in groundwater also within the northern boreal region.

Influence of organic matter, nutrients, and cyclodextrin on microbial and chemical herbicide and degradate dissipation in subsurface sediment slurries

“…At the end of the first experiment, the above liquid samples from the peat-amended slurries on day 78 were evaporated to dryness under a nitrogen flow, the residue was solubilized in 0.5 mL acetone, and analyzed by gas chromatography-mass spectrometry (GC-MS), as presented below. At the end of the second experiment, the pesticides adsorbed to the sediments were extracted three times with methanol : water (3:1 vol vol -1 ) as presented in Pukkila and Kontro (2014), except that 9.96 µg of propazine in 100 µL of methanol : water (3:1, vol vol -1 ) were used as an internal standard. The pooled extracts were evaporated to dryness, the herbicides were solubilized in acetone, and analyzed, using a Shimadzu GCMS-QP-2010Ultra GC-MS equipped with an AOC-20i+s autosampler and a ZB-5MS capillary column (29 m, 0.25 mm, 0.25 µm), using selected ion monitoring, as described in .…”

“…The herbicides atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine), simazine (2,4-bis(ethylamino)-6-chloro-1,3,5-triazine), hexazinone (3-cyclohexyl-6dimethylamino-1-methyl-1,3,5-triazine-2,4-dione), and dichlobenil (2,6-dichlorobenzonitrile), and their degradation products desethylatrazine (2-amino-4-chloro-6-isopropylamino-1,3,5-triazine, DEA), deisopropylatrazine (6-chloro-2-N-ethyl-1,3,5-triazine-2,4-diamine, DIA), desethyldeisopropylatrazine (2-chloro-4,6-amino-1,3,5-triazine, DEDIA), and 2,6dichlorobenzamide (BAM) have been found in groundwater, some commonly (Li et al, 2001;Hildebrandt et al, 2007;Vuorimaa et al, 2007;Holtze et al, 2008;Talja et al, 2008;Pukkila et al, 2009). For instance, atrazine, dichlobenil, and BAM dissipation in groundwater deposits has mostly been slow or nonexistent (Johnson et al, 2003;Talja et al, 2008; Pukkila and Kontro, 2014).…”

“…Among the factors associated with slow herbicide dissipation in deep groundwater are the microbial community composition and activity, and the low organic matter, nutrient and oxygen concentrations (Kruger et al, 1993; Issa and Wood, 1999; Pukkila and Kontro, 2014;Mattsson et al, 2015).…”

“…ADP. The applicability of peat and CPS in the remediation of a wider group of groundwater contaminants was further studied with the herbicides atrazine, simazine, hexazinone, and dichlobenil, and with the degradation product BAM, which are the most common contaminants in groundwater in Finland (Vuorimaa et al, 2007; Pukkila and Kontro, 2014;Mattsson et al, 2015). Sterilized controls were included to separate microbial degradation from the abiotic effects of the additives.…”

Sonication Effects on Atrazine Dissipation in Vadose Zone Sediment Slurries

“…For comparison, pesticide dichlobenil dissipated in subsurface deposit slurries to the low concentration of 1.0-6.3 mg·L −1 , and its degradation product BAM to 3.0-11.3 mg·L −1 [30]. Atrazine forms strong complexes in a solution with organic and inorganic sediment colloids [31,32].…”