Simulation Models of Pesticide Fate and Transport in Paddy Environment for Ecological Risk Assessment and Management

Abstract

Rice production is one of the major non-point sources of pesticide pollution in Japan. Monitoring of pesticide concentrations in river systems detected a number of herbicides commonly used in paddy fields, and these concentrations may appear to have adverse effects on the aquatic ecosystem. In this paper, two mathematical models developed in Japan, the PADDY and PCPF models for simulating the fate and transport of pesticides in a paddy environment are introduced. These models have been validated with observed data from laboratory experiments and field monitoring studies. In addition, the application of a mathematical model (RICEWQ) modified in Europe for high tier risk assessment in paddies is provided. We applied the PADDY and PCPF models to controlling pesticide runoff losses from paddy fields and to ecological risk assessment in the aquatic environment. The recommendation from model simulations for reducing pesticide runoff from paddy fields are 1) application of an intermittent irrigation scheme with a high drainage gate and 2) application of a longer water holding period after pesticide application. In order to establish a realistic assessment and management procedure for environmentally-friendly rice production, it is important to develop and validate mathematical models adapted to paddies in the Asian region. the PADDY and PCPF models to controlling pesticide runoff losses from paddy fields and to ecological risk assessment in the aquatic environment. Discipline: Agricultural chemicals

Risk assessment of pesticides used in rice-prawn concurrent systems in Bangladesh

“…To investigate the relevance of the pesticide exposure caused via water runoff events during the ricegrowing season we parameterised the PEARL model (Leistra et al, 2001) which was modified for applications in (flooded) paddy rice according to Ter Horst et al (2014). Although other models simulating pesticide fate in paddy rice exist (MED-Rice, 2003;Karpouzas et al, 2006;Inao et al, 2008;Inao and Kitamura, 1999;Watanabe et al, 2006;Young, 2012) the PEARL model was selected because it is a field scale model that simulates the runoff and pesticide concentrations in the runoff. Furthermore, the model is freely available and allows calibration without an extensive dataset being available (Ter Horst et al, 2014).…”

Characterization of the exchange of PBDEs in a subtropical paddy field of China: A significant inputs of PBDEs via air–foliage exchange

“…Although there are several models which estimate the environmental fate of POPs in paddy fields (Inao, 2003;Inao et al, 2008;Wei et al, 2008), few studies have assessed the in situ exchange fluxes and net inputs of POPs using simultaneous field measurements in multiple environmental compartments. In particular, polybrominated diphenyl ethers (PBDEs), of which commercial pentae and octaePBDEs have been banned for only 5 years, have not been investigated extensively.…”

Effects of insecticides on aquatic ecosystems in Bangladesh

“…Available mathematical models are not always flexible to represent the different scenarios and the required input data is not always available or can be produced. So, in order to establish a realistic assessment and management procedure for more sustainable rice production practices, it is important to develop and validate mathematical models adapted to the rice-prawn systems in Bangladesh and in other regions of south-east Asia (Inao et al, 2008).…”

“…To investigate the relevance of the pesticide exposure caused via water runoff events during the rice-growing season we parameterised the PEARL model (Leistra et al, 2001) which was modified for applications in (flooded) paddy rice according to Ter Horst et al (2014). Although other models simulating pesticide fate in paddy rice exist (MED- Rice, 2003;Karpouzas et al, 2006;Inao et al, 2008;Inao and Kitamura, 1999;Watanabe et al, 2006;Young, 2012) the PEARL model was selected because it is a field scale model that simulates the runoff and pesticide concentrations in the runoff. Furthermore, the model is freely available and allows calibration without an extensive dataset being available (Ter Horst et al, 2014).…”

“…The application of pesticides in rice production may lead to the contamination of the surrounding aquatic environments by several ways including spray drift, runoff, and leaching (Van den Brink, 2013;Van Wijngaarden et al, 2005;Capri and Karpouzas, 2008). Pesticides applied in rice-prawn concurrent systems may constitute a potential toxicological risk for the aquatic organisms that are cultured in the gher as well as for the maintenance of the aquatic communities that support the aquatic ecosystem of the gher, and herewith can make the whole system less profitable as it may eradicate organisms that are a food source for the cultured prawns (Huy Giap et al, 2005).…”