Hirozumi Watanabe

Wash off of imidacloprid and fipronil from turf and concrete surfaces using simulated rainfall

The surface runoff of imidacloprid granular product (GR) from turf surfaces, and imidacloprid emulsifiable concentrate (EC), fipronil suspension concentrate (SC) products and fipronil byproducts from concrete surfaces was investigated during 1h rainfall simulations at 50 mm/h or 25 mm/h with product incubation times of 1.5 h, 1 d, 7 d, and 14 d. About 57.3% of the applied mass of imidacloprid, corresponding to an event mean concentration of 392.0 μg/L, was washed off from the concrete surfaces after 1.5h of incubation. After 1 d, 7 d, and 14 d of incubation on either turf or concrete surfaces, up to 5.9% of the applied mass of pesticide was removed in each of the run-off events. The maximum concentrations of pesticides were observed in the initial fraction of the runoff collected in the first rainfall event. They were 157.8, 3267.8 and 143.3 μg/L for imidacloprid GR, imidacloprid EC and fipronil SC, respectively. Imidacloprid was not persistent on concrete surfaces, with run-off concentrations below detection limits in 7d incubation experiments. The cumulative mass losses of imidacloprid from turf and fipronil from concrete had a linear relation with cumulative surface run-off depth, while cumulative mass losses of imidacloprid from concrete surfaces were better fit by a power function of the cumulative surface run-off depth. The concentrations of fipronil in the runoff from the third rainfall event at 14 d incubation time were still relatively high and ranged from 12.0 to 31.0 μg/L. A toxicity unit approach was also employed to evaluate the potential acute toxicity of fipronil and its byproducts to aquatic organisms.

Pesticide exposure assessment in rice paddy areas: A Japanese perspective

This chapter provides an overview of the Japanese regulatory issues regarding pesticide use in rice paddies and an introduction of the new pesticide registration program. In addition, the experience of the environmental monitoring of pesticides and the modeling approaches used for the calculation of predicted environmental concentrations (PECs) in surface water and ground water systems adjacent to rice paddies in Japan are also discussed. Japan has been one of the major pesticide users in the world. Although having a long history in rice cultivation, the pesticide exposure assessment for paddy rice production received less attention compared with EU and US. Applications of up-to-date techniques and the development of realistic assessment procedures under specific climatic conditions as well as mitigation management practices for controlling pesticide contamination are important for an environmental-friendly rice production. Through the international cooperation and research exchanges, advances in pesticide risk assessment for rice paddies in Asian region and other rice-growing areas in the world would contribute to sustainable rice production. Transplanting of rice seedlings grows almost all rice paddies in Japan. The land preparation starts around April and June, and the harvest season lasts from August to October depending on the region and the rice varieties. Most of the rice paddies are treated with herbicides and other crop protection products, such as fungicides and insecticides that are applied during the crop season accordingly. Newly developed insecticides and fungicides are also applied during seedbed preparation.

Exposure risk assessment and evaluation of the best management practice for controlling pesticide runoff from paddy fields. Part 2: Model simulation for the herbicide pretilachlor

BACKGROUND Monitoring studies revealed high concentrations of pesticides in the drainage canal of paddy fields. It is important to have a way to predict these concentrations in different management scenarios as an assessment tool. A simulation model for predicting the pesticide concentration in a paddy block (PCPF-B) was evaluated and then used to assess the effect of water management practices for controlling pesticide runoff from paddy fields. RESULTS The PCPF-B model achieved an acceptable performance. The model was applied to a constrained probabilistic approach using the Monte Carlo technique to evaluate the best management practices for reducing runoff of pretilachlor into the canal. The probabilistic model predictions using actual data of pesticide use and hydrological data in the canal showed that the water holding period (WHP) and the excess water storage depth (EWSD) effectively reduced the loss and concentration of pretilachlor from paddy fields to the drainage canal. The WHP also reduced the timespan of pesticide exposure in the drainage canal. CONCLUSIONS It is recommended that: (1) the WHP be applied for as long as possible, but for at least 7 days, depending on the pesticide and field conditions; (2) an EWSD greater than 2 cm be maintained to store substantial rainfall in order to prevent paddy runoff, especially during the WHP.

Simulating the dissipation of two herbicides using micro paddy lysimeters.

A set of packed micro paddy lysimeters, placed in a greenhouse, was used to simulate the dissipation of two herbicides, simetryn and thiobencarb, in a controlled environment. Data from a field monitoring study in 2003, including the soil condition and water balances, were used in the simulation. The herbicides were applied and monitored over a period of 21 d. The water balances under two water management scenarios, intermittent irrigation management (AI) and continuous irrigation management (CI), were simulated. In the AI scenario, the pattern of herbicide dissipation in the surface water of the field were simulated, following the first-order kinetics. In the CI scenario, similarity was observed in most lysimeter and field concentrations, but there were differences in some data points. Dissipation curves of both herbicides in the surface water of the two simulated scenarios were not significantly different (P>0.05) from the field data except for intercept of the thiobencarb curve in the CI scenario. The distribution of simetryn and thiobencarb in the soil profile after simulation were also similar to the field data. The highest concentrations of both herbicides were found on the topsoil layer at 0-2.5 cm depth. Only a small amount of herbicides moved down to the deeper soil layers. Micro paddy lysimeters are thus a good alternative for the dissipation study of pesticides in the paddy environment.

Biomass burning in Indo-China peninsula and its impacts on regional air quality and global climate change-a review

Although, many biomass burning (BB) emissions products (particulate matter and trace gases) are believed to be trans-boundary pollutants that originates from India and China (the two most populous countries in Asia), the information about BB emission and related contents is limited for Indo-China Peninsula (ICP) region. This motivated us to review this region pertaining to BB emission. The main objective of the review is to document the current status of BB emission in ICP region. In order to highlight the impact of BB on regional air quality and global climate change, the role of BB emission in ICP region is also discussed. Based on the available literature and modeling simulations studies, it is evidenced that ICP is one of the hotspot regional source for aerosols in terms of BB emissions. In addition, regional emissions through BB have significant implications for regional air quality especially in the neighboring countries such as China, Taiwan and India. Our assessment highlight that there is still a general lack of reliable data and research studies addressing BB related issues in context of environmental and human health. There is therefore a critical need to improve the current knowledge base, which should build upon the research experience and further research into these issues is considered vital to help inform future policies/control strategies.

Determination of imidacloprid in paddy water and soil by liquid chromatography electrospray ionization-tandem mass spectrometry

A method for the determination of imidacloprid in paddy water and soil was developed using liquid chromatography electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS). Separation of imidacloprid was carried out on a Shimadzu C18 column (150 mm × 4.6 mm, 4.6 μm) with an acetonitrile-water (50: 50, v/v) mobile phase containing 0.1% of acetic acid. The flow rate was 0.3 mL/min in isocratic mode. The product ion at 209 m/z was selected for quantification in multiple-reaction monitoring scan mode. Imidacloprid residues in soil were extracted by a solid-liquid extraction method with acetonitrile. Water samples were filtered and directly injected for analysis without extraction. Detection limits of 0.5 μg/kg and 0.3 μg/L were achieved for soil and water samples, respectively. The method had recoveries of 90 ± 2% (n = 4) for soil samples and 100 ± 2% (n = 4) for water samples. A linear relationship was observed throughout the investigated range of concentrations (1–200 μg/L), with the correlation coefficients ranging from 0.999 to 1.000.

Degradation profile and safety evaluation of methomyl residues in tomato and soil

Summary A high performance liquid chromatography with the photodiode array detector (HPLCDAD) analytical method was developed to determine the residue levels and investigate the dissipation pattern and safety use of methomyl in tomato and soil. Methomyl residues were extracted from tomato and soil samples with ethyl acetate. The extract was cleaned up with the QuEChERS method. The results showed that the average recoveries were in the range of 87.1-94.5%, with RSD of 6.9-11.2%. Limits of detection (LOD) and quantification (LOQ) were 0.005 and 0.007 mg/kg, respectively. The residue levels of methomyl were best described to first order rate kinetics and half-lives ranged from 1.34 to 1.8 days in tomato and soil, respectively. The theoretical maximum residue contributions for methomyl on tomato were found to be less than the maximum permissible intake values even on zero days, therefore consumer health risks are minimal at the recommended dose on tomato.

Hazard assessment of the neonicotinoid insecticide thiamethoxam residues in tomato: a prelude to risk assessment profile

A minor modification to the QuEChERS (quick, easy, cheap, effective, rugged and safe) method was carried out for the analysis of thiamethoxam in tomato using high performance liquid chromatography equipped with a diode array detector (HPLC-DAD). The method showed a good linearity with a determination coefficient (R2) of 0.999 for the 0.02–5 mg/L concentration range. The method was validated using a blank tomato spiked at 0.05, 0.1 and 0.5 mg/kg, and the average recovery rate was 96%–99%. The limits of detection and quantification were 0.02 and 0.05 mg/kg, respectively. In this study, dissipation and residual levels of thiamethoxam in tomato under open field conditions were investigated. Thiamethoxam residues tend to dissipate following first-order rate kinetics with a half-life of 2.34 days. At harvest time, the remaining residues of thiamethoxam were below the European Union (EU) maximum residue level of 0.2 mg/kg when measured 14 days after the final application. Exposure of thiamethoxam was determined and compared to acceptable daily intake (ADI). The assessment of consumer exposure was based upon the estimated daily intake (EDI) which was compared to ADI and expressed as percentage. Based upon tomato consumption, the EDI of thiamethoxam ranged from 8.82 × 10−6 to 3.38 × 10−4 mg/kg b.w./day, which corresponds to 0.08% and 3.3% of ADI, respectively. Since the dietary exposure never exceeded 4% ADI, the tomato fruit may be considered safe for human consumption after application of the recommended dose of thiamethoxam.

Numerical modeling of diazinon transport through inter-row vegetative filter strips

A numerical simulation model of pesticide runoff through vegetative filer strips (PRVFS) was developed as a tool for investigating the effects of pesticide transport mechanisms on VFS design in dormant-sprayed orchard. The PRVFS model was developed applying existing theories such as kinematic wave theory and mixing zone theory for pesticide transport in the bare soil area. For VFS area, the model performs flow routing by simple mass accounting in sequential segments and the pesticide mass balance by considering pesticide washoff and adsorption processes on the leaf, vegetative litter, root zone and soil. Model sensitivity analysis indicated that pesticide transfer from surface soil to overland flow and pesticide washoff from the VFS were important mechanisms affecting diazinon transport. The VFS cover ratio and rainfall intensity can be important design parameters for controlling diazinon runoff using inter-row VFS in orchard. The PRVFS model was validated using micro-ecosystem simulation of diazinon transport for 0, 50 and 100% VFS cover conditions. The PRVFS model is shown to be a beneficial tool for evaluating and analyzing possible best management practices for controlling offsite runoff of dormant-sprayed diazinon in orchards during the rainy season.

Simulating the fate and transport of nursery-box-applied pesticide in rice paddy fields

BACKGROUND The Pesticide Concentration in a Paddy Field model (PCPF-1) was modified by adding a root zone compartment to simulate nursery-box-applied (NB-applied) pesticide. The PCPF-NB model was validated for predicting the concentrations of NB-applied fipronil and imidacloprid in rice paddy fields using two treatment methods: before transplanting (BT) and at sowing (AS). Uncertainty and sensitivity analyses were used to evaluate the robustness of the concentrations predicted by the model. RESULTS The hourly predicted concentrations of imidacloprid and fipronil were accurate in both paddy water and 1 cm deep paddy soil. The coefficient of determination and Nash-Sutcliffe model efficiency were greater than 0.87 and 0.60 respectively. The 95th percentiles of the predicted concentrations of fipronil and imidacloprid indicated that the influence of input uncertainty was minor in paddy water but important in paddy soil. The pesticide deposition rate and the desorption rate from the root zone were identified to be the major contributors to the variation in the predicted concentrations in paddy water and soil. CONCLUSION The PCPF-NB model was validated for predicting the fate and transport of NB-applied fipronil and imidacloprid using the BT and AS treatment methods.