Xiaomei Yang in Chinese Loess Soil A Case Study of Glyphosate Fate Pesticide Use and Off-site Risk Assessment Pesticide Use and Off-site Risk Assessment: A Case Study of Glyphosate in Chinese Loess Soil Xiaomei Yang Pesticide use and off-site risk assessment: a case study of glyphosate fate in Chinese Loess soil Xiaomei Yang Thesis committee Promotors Prof. Dr Coen J. Ritsema Professor of Soil Physics and Land Management Wageningen University Prof. Dr Violette Geissen Privatdozent at INRES, University of Bonn, Germany Co-promotors Dr Hans G.J. Mol Group leader, Natural Toxins and Pesticides RIKILT, Wageningen UR Dr Fei Wang Associate professor of the Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, China Other members Prof. Dr Bart Koelmans, Wageningen UR Prof. Dr Celeste Coelho, University of Aveiro, Portugal Prof. Dr Thilo Streck, University of Hohenheim, Germany Dr Celia Dias-Ferreira, Centro de Estudos de Recursos Naturais, Ambiente e Sociedade, Coimbra, Portugal This research was conducted under the auspices of the Research School for Socio- Economic and Natural Sciences of the Environment (SENSE) Pesticide use and off-site risk assessment: a case study of glyphosate fate in Chinese Loess soil Xiaomei Yang Thesis submitted in fulfilment of the requirements for the degree of doctor at Wageningen University by the authority of the Rector Magnificus Prof. Dr A.P.J. Mol in the presence of the Thesis Committee appointed by the Academic Board to be defended in public on Monday 9 May 2016 at 11 a.m. in the Aula. Xiaomei Yang Pesticide use and off-site risk assessment: a case study of glyphosate fate in Chinese Loess soil, 154 pages. PhD thesis, Wageningen University, Wageningen, NL (2016) With references, with summaries in English and Dutch ISBN: 978-94-6257-675-9 Table of contents Chapter 1 General introduction ................................................................................. 7 Chapter 2 Farmer and retailer knowledge and awareness of the risks from pesticide use: a case study in the Wei River catchment, China ............ 19 Chapter 3 Short-term transport of glyphosate with erosion in Chinese loess soil – a flume experiment .................................................................................. 39 Chapter 4 Decay characteristics and erosion-related transport of glyphosate in Chinese loess soil under field conditions .............................................. 61 Chapter 5 Integration of transport concepts for risk assessment of pesticide with erosion ................................................................................................... 81 Chapter 6 Synthesis ................................................................................................. 99 Literature cited ..................................................................................................... 115 English summary ................................................................................................... 137 Nederlandse samenvatting................................................................................... 141 Acknowledgements .............................................................................................. 145 Curriculum Vitae ................................................................................................... 149 General introduction 1 General introduction 7 Chapter 1 1.1 Fate and risks of pesticides in the environment Pesticides are compounds that protect crops from pests, diseases and weeds in an effort to reduce or avoid yield losses while maintaining high product quality. Depending on the specific target, the word pesticides can refer to herbicides, insecticides, fungicides as well as many others (e.g. nematicides, fumigants, etc.). The demand for increased production has led to an approximate 30-40% increase in the use of pesticides in farming. This trend is predicted to continue to increase substantially in the coming decades (Liu et al., 2015b). Although the use of pesticides has obvious benefits, such as protecting crops and increasing yields, the consequences of its use have widely influenced both the environment and human health (Ecobichon, 2003; Enserink et al., 2013). Considering both the increasing use of pesticide and the rising concerns surrounding its use, the ability to accurately determine and eventually reduce the overall risk of a pesticide - beyond the information on the label - is essential and unfortunately lacking. The fate of pesticides in the environment can follow different processes depending on a pesticide’s properties: uptake by plants, drifting, volatilization, interception, infiltration/leaching, runoff and transport in sediment, adsorption/desorption and decay (Figure 1.1). After application, a pesticide can be taken up by a plant and thus enters the plant’s physiological processes. Although part of the pesticide volatilizes into the atmosphere (Burrows et al., 2002) or is assimilated by plants, most of it ultimately reaches the soil and becomes involved in soil physiochemical processes, such as dissolution, adsorption, desorption, and decay (Ahuja et al., 2000; Gavrilescu, 2005; Laitinen et al., 2007). There is a consensus that pesticide fate depends primarily on its pesticide physiochemical characteristics (Báez et al., 2015) as well as the climate conditions (Chen, 2007) which lead to different decay mechanisms, adsorption-desorption behaviour and half-life times in the soil matrix (FOCUS, 2000; Kalam et al., 2004). Additionally, a pesticide can be transported together with surface water and be susceptible to erosion processes, infiltrate and move into deeper soil layers via soil macropores (Styczen et al., 2011a), or leach into groundwater (Vereecken, 2005). Inappropriate farming practices and overuse of pesticides on cultivated land has resulted in not only on-site pollution but also off-site problems (Damalas, 2009; Enserink et al., 2013; Hao et al., 2014; Yadav et al., 2015). Continuous application of a pesticide can lead to serious degradation of soil (Brunet et al., 2009) as well as affect the quality of surface and groundwater (Geissen et al., 2010; Kalita et al., 2006; Malaguerra et al., 2013; Ongley et al., 2010), drinking water (Chau et al., 2015; Fuscoletti et al., 2015), and even 8 General introduction commercially available mineral water and soft drinks (Johnson et al., 2006). Studies have reported that pesticides from agricultural systems, together with surface runoff, contribute more chemical loading to water bodies than pollutants from industrial discharges (Wang et al., 2015a). In some hotspots, especially in high erosion areas, the off- site transport of pesticides has become the main source of pollutants aggravating aquatic ecosystems (Rabalais, 2002; Slaninová et al., 2009; Sun et al., 2012), challenging food security, and threatening human health via the aquatic food chain (Liu et al., 2015a; Perry et al., 2014). Therefore, pesticide in the soil-water system has become a global environmental concern often coupled with the increasing demand for food (Damalas and Eleftherohorinos, 2011; Guo et al., 2014; Rashid et al., 2010; Sinha et al., 2011; Wang et al., 2015a). Figure 1.1 The fate of pesticide after spraying Reducing pesticide use is an important way to mitigate the effects of pesticides on the environment. However, the accurate assessment of risks and how to effectively reduce use is a challenge. The pesticide users as well as the related stakeholders who are responsible for pesticide production, safety and use are all participants in this issue 9 Chapter 1 (Pedlowski et al., 2012). Although pesticides are developed and regulated by strict laws to minimize the impact on human health and the environment (FOCUS, 2000; Handford et al., 2015), serious concerns have been raised about health risks resulting from occupational exposure (Damalas and Eleftherohorinos, 2011; Dasgupta et al., 2007; El- Zaemey et al., 2013; Yang et al., 2014b). Occupational exposure to pesticides occurs mainly to agricultural workers in fields and greenhouses (El-Zaemey et al., 2013; Enserink et al., 2013; Hvistendahl, 2013; Karunamoorthi et al., 2012). The lack of knowledge, low education level, and insufficient facilities make it difficult for farmers and agricultural workers to use pesticide properly and safely. This leads to serious poisoning and acute or chronic diseases (Chen et al., 1998; Dasgupta et al., 2007; Eddleston et al., 2002; Hvistendahl, 2013; Recena et al., 2006; Zhou et al., 2011). In addition, overuse or mixing of pesticides increases the risk to both human health and the environment (Pedlowski et al., 2012; Zhang et al., 2015). The adverse effects of pesticides on the environment and human health, depend on multiple factors including the toxicity of the pesticide, dosage applied, application practices, fate of the pesticide in the soil (including its half-life and persistent metabolites), climate conditions after application and people’s awareness levels regarding pesticide use (Enserink et al., 2013; Fan et al., 2015; Matthews, 2008). All of these factors make it difficult to fully assess pesticide risk either on human health or on the environment, particularly when the cultivation system, conventional practices and local climate are taken into account (Damalas and Eleftherohorinos, 2011). China has a long history of cultivation. It also has the world’s highest application, exportation, and production of pesticides (Zhang et al., 2011b).