Marianne Stenrød

Head of Department/Head of Research

(+47) 482 97 607
marianne.stenrod@nibio.no

Place
Ås H7

Visiting address
Høgskoleveien 7, 1433 Ås

Biography

Key qualifications: Soil microbiology, Degradation of pesticides in soil – effects of cold climatic conditions, Pesticides in surface and ground water – occurrence, transport processes and sources of pollution.

Read more
To document

Abstract

Freezing and thawing have large effects on water flow in soils since ice may block a large part of the pore space and thereby prevent infiltration and flow through the soil. This, in turn, may have consequences for contaminant transport. For example, transport of solutes contained at or close to the soil surface can be rapidly transported through frozen soils in large pores that were air filled at the time of freezing. Accounting for freezing and thawing could potentially improve model predictions used for risk assessment of contaminant leaching. A few numerical models of water flow through soil accounts for freezing by coupling Richards’ equation and the heat flow equation using of the generalized Clapeyron equation, which relates the capillary pressure to temperature during phase change. However, these models are not applicable to macroporous soils. The objective of this study was to develop and evaluate a dual-permeability approach for simulating water flow in soil under freezing and thawing conditions. To achieve this we extended the widely used MACRO-model for water flow and solute transport in macroporous soil. Richards’ equation and the heat flow equation were loosely coupled using the Clapeyron equation for the soil micropore domain. In accordance with the original MACRO model, capillary forces were neglected for the macropore domain and conductive heat flow in the macropores was not accounted for. Freezing and thawing of macropore water, hence, were solely governed by heat exchange between the pore domains. This exchange included a first-order heat conduction term depending on the temperature difference between domains and the diffusion pathlength (a proxy variable related to the distance between macropores) and convective heat flow. As far as we know, there are no analytical solutions available for water flow during freezing and thawing and laboratory data is limited for evaluation of water flow through macropores. In order to evaluate the new model approach we therefore first compared simulation results of water flows during freezing for the micropore domain to existing literature data. Our model was shown to give similar results as other available models. We then compared the first-order conductive heat exchange during freezing to a full numerical solution of heat conduction. Finally, simulations were run for water flow through frozen soil with initially air-filled macropores for different boundary conditions. Simulation results were sensitive to parameters governing the heat exchange between pore domains for both test cases.

To document

Abstract

Limited knowledge and experimental data exist on pesticide leaching through partially frozen soil. The objective of this study was to better understand the complex processes of freezing and thawing and the effects these processes have on water flow and pesticide transport through soil. To achieve this we conducted a soil column irrigation experiment to quantify the transport of a non-reactive tracer and the herbicide MCPA in partially frozen soil. In total 40 intact topsoil and subsoil columns from two agricultural fields with contrasting soil types (silt and loam) in South-East Norway were used in this experiment. MCPA and bromide were applied on top of all columns. Half the columns were then frozen at −3 °C while the other half of the columns were stored at +4 °C. Columns were then subjected to repeated irrigation events at a rate of 5 mm artificial rainwater for 5 h at each event. Each irrigation was followed by 14-day periods of freezing or refrigeration. Percolate was collected and analysed for MCPA and bromide. The results show that nearly 100% more MCPA leached from frozen than unfrozen topsoil columns of Hov silt and Kroer loam soils. Leaching patterns of bromide and MCPA were very similar in frozen columns with high concentrations and clear peaks early in the irrigation process, and with lower concentrations leaching at later stages. Hardly any MCPA leached from unfrozen topsoil columns (0.4–0.5% of applied amount) and concentrations were very low. Bromide showed a different flow pattern indicating a more uniform advective-dispersive transport process in the unfrozen columns with higher con- centrations leaching but without clear concentration peaks. This study documents that pesticides can be pre- ferentially transported through soil macropores at relatively high concentrations in partially frozen soil. These findings indicate, that monitoring programs should include sampling during snow melt or early spring in areas were soil frost is common as this period could imply exposure peaks in groundwater or surface water.

To document

Abstract

This project evaluated whether the principles of combined toxicity assessment (CTA) and cumulative risk assessment (CRA) can be used to predict the toxicity of ecologically-relevant mixtures of plant protection products (PPPs) in surface waters receiving run-off from Norwegian agricultural areas. A combination of testing solid phase extracts (SPE), whole surface water and a synthetic mixture in an algal bioassay and predicting combined toxicity using CTA models were conducted on selected samples from the Heia catchment (Råde, Norway). The results demonstrated that designing and testing synthetic mixtures on the basis of measured concentrations of PPPs was the best method for the accurate determination of combined toxicity due to confounding factors introduced by whole water and SPE testing. Combined toxicity models based on Concentration Addition (CA) successfully predicted the toxicity of the complex synthetic mixture and verified that a mixture of PPPs acted in an additive manner. Tiered assessment of the cumulative risk of active PPP substances and PPP formulations proposed by the European Food Safety Authority (EFSA) were considered applicable also for the CRA of complex environmental mixtures and could potentially aid the identification of relevant mixtures, risk drivers and susceptible species as input to the assessment and approval of PPPs.

To document

Abstract

This project was performed to improve the environmental cumulative risk assessment (CRA) of mixtures of plant protection products detected by the Norwegian Agricultural Environmental Monitoring Programme (JOVA) in Norwegian surface waters. Existing ecotoxicity data were compiled and reduced the assessment uncertainty compared to previous risk assessments. Ecotoxicity tests verified that the cumulative toxicity of ecologically-relevant environmental mixtures was fairly well predicted for algae, daphnia and aquatic plants. The results from the ecotoxicity tests were used to evaluate the assessment factor used in the risk assessment, and the improved data used in the CRA of plant protection products in the JOVA monitoring performed in 2013. Three of the six investigated sites had risk quotients indicative of environmental risk. Mitigation measures based on the identification of the main risk drivers were discussed and include consideration of no-spray zones, grassed buffer strips, reduced doses and patch spraying, and pesticide risk maps.

Abstract

In Europe there is an on-going process on implementing regulations aimed at reducing pollution from agricultural production systems, i.e. the Water Framework Directive and the Framework Directive for Sustainable Use of Pesticides. At the same time, there is an increasing focus on food security possibly leading to continued intensification of agricultural production with increased use of external inputs, such as pesticides and fertilizers. Application of sustainable production systems can only be achieved if they balance conflicting environmental and economic effects. In Norway, cereal production is of large importance for food security and reduction of soil and phosphorus losses, as well as pesticide use and leaching/runoff in the cereal production are of special concern. Therefore, we need to determine the most sustainable and effective strategies to reduce loss of top soil, phosphorus and pesticides while maintaining cereal yields. A three-year research project, STRAPP, is addressing these concerns. A catchment area dominated by cereal production is our common research arena within STRAPP. Since 1992 a database (JOVA) with data for soil erosion, nutrient and pesticide leaching/runoff (i.e. concentrations in stream water), yield, and agricultural management practices (fertilization, use of pesticides, soil tillage and rotations) has been established for this catchment allowing us to compare a unique diversity in cropping strategies in a defined location. An important part of STRAPP focuses on developing ‘best plant protection strategies’ for cereal fields in the study area, based on field inventories (manual and sensor based) of weeds and common diseases, available forecast systems, and pesticide leaching risk maps. The results of field studies during the growing seasons of 2013 and 2014 will be presented, with a focus on possible integrated pest management (IPM) strategies for weeds and fungal diseases in cereal production. We will also present the project concept and methods for coupling optimized plant protection strategies to (i) modelling of phosphorus and pesticide leaching/runoff, as well as soil loss, and (ii) farm-economic impacts and adaptations. Further, methods for balancing the conflicting environmental and economic effects of the above practices, and the evaluation of instruments for increased adoption of desirable management practices will be outlined.