Behavior of paddy pesticides and major metabolites in the Sakura River, Ibaraki, Japan

Abstract

Thirty-nine paddy pesticides and 11 of their metabolites were monitored in the Sakura River during the rice cultivation season in 2007 and 2008. Pesticide concentrations in the river water depended on the timing of pesticide application. Herbicides that were shipped to Ibaraki Prefecture in large amounts or had high water solubility, a low soil adsorption constant value, or large usage rates were detected at high peak concentrations. The concentrations of nursery-box-applied fungicides and insecticides peaked immediately after transplanting. The concentrations of pesticide metabolites, such as bromobutide-desbromo, cafenstrol-descarbamoyl, clomeprop-propionic acid, carbofuran, and fenthion-sulfoxide depended on the degradation rates and metabolic pathways of the parent compounds and on the stability of the metabolites in water and soil. Clomeprop-propionic acid, carbofuran, and fenthion-sulfoxide, which were formed from rapidly degradable pesticides, were detected at much higher peak concentrations than the parent compounds. © Pesticide Science Society of Japan Keywords: paddy pesticide, application timing, river water, physicochemical property, metabolic pathway, environmental fate. Original Articlefield area is under rice cultivation. After soil puddling and land leveling in late April, rice seedlings are transplanted in early May. Intermittent irrigation starts in mid-June and continues throughout the growing period, except during the midsummer drainage period from late June to mid-July. Generally, heading occurs from late July to early August, and harvest starts in early September, after drainage of the paddy water in late August. 15)Early-mid-season herbicides are applied within 2 weeks after transplanting (early to mid-May), and mid-season herbicides are applied 2-3 weeks after transplanting (late May to early June). Depending on the emergence of weeds, a lateseason herbicide might be used in June.16) Fungicides and insecticides are used on rice seedlings in nursery boxes before transplanting and for direct application to paddy fields before heading or harvest. Recently, nursery-box application has become increasing popular in the Sakura River basin. Aerial spraying of paddy pesticides was not conducted in the basin in 2007 and 2008 (Japan Agricultural Aviation Association: private communication; unpublished data). Analyzed compoundsTwenty-nine herbicides, 2 fungicides, and 8 insecticides were selected for analysis (Table 1), in consideration of the amounts of paddy pesticides shipped to Ibaraki Prefecture recently. We selected 11 metabolites of the herbicides and insecticides in accord with previous studies 11,14,17,18) as a reference. All analytical standards were purchased from Wako Pure Chemicals Industries (Japan), Hayashi Pure Chemicals Industries (Japan), or Kanto Chemicals (Japan). Sample collection and analysisThe sampling site (Kimijima Bridge) is located midway along the course of the Sakura River (Fig. 1). Water samples (approximately 3000 ml per sample) were collected once a week on Monday fr...

Ecological effect assessment by species sensitivity distribution for 68 pesticides used in Japanese paddy fields

“…Although carbofuran has not been registered in Japan, it was included in analyses because it is a main metabolite of carbosulfan and benfuracarb and is often detected in river water. 21) The MoAs (Tables 1-3) were derived from the Insecticide Resistance Action Committee, 22) the Fungicide Resistance Action Committee, 23) and the Herbicide Resistance Action Committee. 24) However, other literature was used to derive the MoAs of propyrisulfuron, 25) pyrimisulfan, 26) tefuryltrione, 27) and indanofan.…”

Determining the suitability of a polar organic chemical integrated sampler (POCIS) for the detection of pesticide residue in the Ishikawa River and its tributary in Osaka, Japan

“…The conventional sampling method for aquatic pesticides has been grab sampling. [3][4][5] Grab sampling is a method in which a single sample is collected at a particular time.…”

Behavior of isoprothiolane and fipronil in paddy water, soil, and rice plants after nursery-box or submerged applications

“…Many rice pesticides and their metabolites have been detected at high frequencies and concentrations in river water during the cultivation season. [1][2][3][4][5][6][7][8][9] The metabolites of some pesticides (e.g., organophosphorus insecticides) may be more toxic to aquatic organisms than the parent compound. Clear peaks of some nurserybox-applied pesticides and their main metabolites have been also observed annually at rice-transplanting time.…”

“…Clear peaks of some nurserybox-applied pesticides and their main metabolites have been also observed annually at rice-transplanting time. 7,9) Thus, for assessing and managing the ecological risks of the pesticides in river systems, it is important to evaluate the behavior of rice pesticides, including nursery-box-applied pesticides, and their metabolites in paddy fields.…”