Need for clean water and recirculation to reduce emissions of plant protection products from soilless cultivation

Abstract

Soilless cultivation suggests a closed system of water flows, of which (drip) irrigation, evaporation andin more high-tech systemscondensation water are the main flows. However, in practice growers discharge water during the process of filter cleaning and actively discharge water due to high levels of sodium or contamination with chemical or biological components. On average in the Dutch greenhouse situation 2-5% of the annual irrigated water is discharged, spread over the year. These discharges lead to pollution of surface water with nutrients as well as (residues of) plant protection products (PPPs). This awareness led in 2008 to the start of a working group that aimed to develop an risk evaluation tool for pesticide authorisation in Europe. The evaluation tool consists of a modelled approach for determining expected concentrations in surface water based on a reference scenario per crop i.e. a description of an actual situation including the technical layout of the glasshouse, the climatological year and the receiving ditch.

Environmental Indicator Crop Protection (EICP) : documentation of calculation rules

“…the Greenhouse emission model (GEM). These methods are extensively documented (Kruijne et al, 2012;Vermeulen et al, 2010;Wipfler et al 2015). For the EICP documentation in the following, we have repeated most relevant and critical elements but refer for details to the respective original documentation.…”

“…Discharge of recirculation water is the major emission route towards surface water in these cases. The driving forces behind these discharge events are the sodium content in the recirculated nutrient solution and the sodium tolerance of the greenhouse crop (Vermeulen et al, 2010). Hence, the quality of the irrigation water has a large effect on the total emitted mass of pesticides to surface water.…”

Guidance on the assessment of exposure of operators, workers, residents and bystanders in risk assessment of plant protection products

“…Where experimentally determined DFR data are not available, the initial DFR (DFR0 is the DFR just after application, assuming that no dissipation has taken place at this time point) in a first‐tier assessment should be assumed to be 3 (μg active substance/cm 2 of foliage)/(kg a.s. applied/ha). This value is regarded as highly conservative (van Hemmen et al, 2002; Lewis and Tzilivakis, 2017a). Yet, as the DFR value depends upon multiple parameters and none of them could be estimated as a sole or most critical driver for the worst‐case DFR0 level, no refinement of the default value can be currently proposed.…”

“…The indicative TC values reported in Table 10 are adapted from EUROPOEM II (van Hemmen et al, 2002), with due consideration of US EPA values (Appendix F) and new experimental data for bolting beet and harvesting peaches (Appendices G and H); they apply to both outdoor and indoor scenarios. Up to four sets of TC values are given per crop group, according to whether or not it can be assumed that the worker will wear clothing that covers the arms, body and legs.…”

“…Four indicative inhalation task‐specific factors (TSF) have been estimated for a small set of exposure data for harvesting and re‐entry in ornamental greenhouse (van Hemmen et al, 2002), as set out in Table 11.…”