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IMPASSE has studied the impacts of microplastics in agroSystems and stream environment. The project is now finished. 

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Project period
Contact person
Luca Nizzetto

About the project

Microplastics are increasingly seen as an environmental problem of global proportions. While the focus to date has been on microplastics in the ocean and their effects on marine life, microplastics in soils have largely been overlooked. Lack of knowledge regarding potential consequences of microplastics in agricultural landscapes from application of sewage sludge are of great concern.

Fertilizer based on sludge contains valuable nutrients, but sustainable use requires that the levels of undesirable substances in the sludge is kept under control. Wastewater treatment plants receive large amounts of microplastics emitted from households, industry and surface runoff in urban areas. Most of these microplastics accumulate in the sewage sludge.

In many countries large amounts of sludge from municipal sewage treatment plants are applied to agricultural soils to recover value organic matter and nutrients. These applications are generally well regulated as sludge might contain hazardous substances of different sorts. Microplastics are however not currently on the regulatory agenda for the use of sludge in agriculture. The potential consequences for agricultural sustainability and food security have not been adequately analyzed.

IMPASSE is the first international research project, funded through the Water Joint Programming initiative (JPI) investigating the loads, fluxes and impacts of microplastics in farmlands.

Involved partners are:

  • Norwegian Institute for Water Research (NIVA, Norway)
  • Imdea Water (Spain). 
  • The Swedish University of Agriculture (SLU, Sweden)
  • Vrije University Amsterdam (VU, the Netherlands). 
  • Windsor and Trent University (Canada). 
  • University of Ljubljana (Slovenia)

We carry out seminar work on the development of new and validated methods to measure microplastics in complex samples such as soil and sediments. We collect and analyze samples of sewage sludge, fertilizers, soil, sediments, stream water and wastewater. We are working in further developing and validating decision and risk assessment support tools, such as soil and stream model of microplastic fate and transport. We are also conducting seminar toxicological tests with terrestrial and freshwater organisms (Macroinvertebrates).

Our goal is to serve the scientific community, stakeholders and the public sector to understand the implication of plastic in farming and freshwater environment and design perspective for a sustainable future and utilization of biofertilizers.

Impasse is a project funded by EU, funding agencies in Norway, Sweden, Spain, Netherland and Canada. The project received support in the frame of the the ERA-NET WaterWorks2015 Cofunded Call. This ERA-NET is an integral part of the 2016 Joint Activities developed by the Water Challenges for a Changing World Joint Programme Initiative (Water JPI).

Work packages:

Exposure and distribution of Microplastics (WP1)

We have conducted two intensive monitoring campaigns in farming case studies in Canada and Spain, collecting several hundreds of samples, including sludge (used as soil amending agent), soil, sediments, fresh water, and runoff samples. We have characterized different potential sources including wastewater effluents.

In Spain we focused on assessing emissions of microplastics (MPs) and exposure in surface waters in the watershed of Henares River (Province of Madrid). Close collaboration with international partners (IMDEA, NIVA, Trent University and Windsor University) ensured consistent sampling techniques (mesh sizes, sampling depths, etc.) between case studies.

Three sampling stations for river water and sediments were selected, representative of different levels of human impact:

i) low impact from all sources;
ii) high agricultural impact;
iii) high mixed impact (urban, agricultural, industrial) at the watershed outlet.

In addition, a runoff experiment was performed to evaluate the contribution of MPs from runoff on agricultural soils. Special devices for runoff collection were placed on three plots with comparable soil characteristics but different MPs treatments:

(i) soil never treated with sludge (control),
(ii) soil treated with sludge in the past (in 2013), and
(iii) soil treated with sludge at the start of the experiment (in November 2017). Sludge was applied according to standard agricultural practices.

In Canada, monitoring of MPs was undertaken in three catchments within Lake Simcoe; Beaverton and Orillia, which have a history of biosolids applications on agricultural lands, and a control site within the Innisfil region. The aim was to assess contributions of MPs from a range of sources (wastewater, biosolids, stormwater), their transport (via runoff, soil erosion, and stream flow), and fate (in soils and stream sediment).

Over 3000 samples were collected throughout the catchments. Samples were taken before, during and after the application of biosolids to soils, with higher frequency sampling conducted during heavy rainfall events. Runoff plots were constructed to analyse MP transport from soils into streams during rainfall events.

Samples collected in Spain and Canada were transferred to NIVA in Norway for the MP analysis. The lack of validated methods for the analysis of MPs in soil, sediments and sludge samples, called for an urgent and significant effort to fill this gap. We have developed the first full validation study of a method for this type of analysis and published it in one of the top journals in the field.

This study includes, for the first time, a direct assessment of analytical recovery for different type of MPs with results that enormously increase credibility and trust on the data we are delivering.

The analytical effort in analyzing MP has been so far tremendous. We have individually identified and chemically analyzed 5988 individual particles across all analyzed samples. MPs detection is a laborious, and to a large extent still manual, operation.

Impacts of microplastics in agricultural environments (WP2)

We are conducting toxicological tests on individual populations of terrestrial organisms using different types of MPs. Concerning soil organisms we have studied:

i) The effects of polyester (PET) fibers in two size classes on different soil invertebrates (earthworms, enchytraeids, oribatid mites, springtails and isopods);
ii)The effects and accumulation (ingestion and egestion) of polyester (PET) fibers in earthworms (Eisenia andrei);
iii) The effects of polyethylene (PE) microbeads on enchytraeid worms (Enchytraeus crypticus) and springtails (Folsomia candida);
iv) The effects of car tyre debris on soil invertebrates (earthworms, enchytraeids and springtails).

Enchytraeid worms (Enchytraeus crypticus) and springtails (Folsomia candida) were exposed to polyester fibers of two size classes via soil and via food. The shorter fibers were produced from longer fibers by milling. The length of the long fibers was 700 – 11 500 µm, of the shorter fibers 15 – 1 300 µm.

We collected evidences of both ingestion and effects on some toxicological endpoints  by some of the tested organisms. We will disseminate our results through this site with greater details after they are published in peer-reviewed scientific journals.

Concerning fresh water organisms, we are studying the acute and chronic effects of fibers and tyre particles for invertebrate species with different habitat preferences and feeding strategies (Daphnia magna, Asellus aquaticus, Hyalella azteca and Lumbriculus variegatus). According to their different habitats, the test organisms were exposed to MPs in the water phase (Daphnia, Hyalella) or mixed into sediment (Asellus, Hyalella and Lumbriculus). A range of concentrations was tested, including environmental relevant concentrations (water exposure: 0, 0.00015, 0.0015, 0.015, 0.15 g/L; sediment exposure: 0, 0.002, 0.02, 0.2, 2 g/kg). For acute exposure, ingestion and immobility or mortality was assessed, while for chronic exposure also reproduction and growth were assessed. All test organisms ingested fibers and tyres, except for Daphnia which only ingested tyre debris.  

Modelling MPs fate and transport (WP3)

Work at SLU (Sweden), Windsor University (Canada) and NIVA (Norway) has focused on model development. We are working on INCA-Microplastics, a catchment-based, hydrologically driven model of sediments and microplastic transport. This is the first of its kind.

Necessary input data including GIS layers describing land coverage and flow and water quality observations for model calibration have been obtained from the Spanish partner and Canadian partner. The hydrological components of the model have been setup and calibrated against streamflow observations from three sites in the catchment. In 2019, the MP transport routines will be calibrated as soon as data are available from WP1.

Similarly at Windsor University, the MP transport model was set up to run simulation for the Beaverton and Orillia sites in Canada. Tests are being conducted on model’s optimal spatial complexity within each basin.  

Engagement with stakeholders (WP4)

Throughout this phase of the project, we have maintained a continuous and intense interaction with different stakeholders.

We have organized a stakeholder meeting involving the head representatives of the National Norwegian Water Industry organization and Norwegian Farmer organization.

We participated in a national workshop on MPs organized by the Swedish water industry association, held in Malmø 7th November 2018. We contributed in delivering a perspective over MP research needs.

NIVA researchers have undertaken important interactions with stakeholders at European level. We were invited by the European Chemical Agency (ECHA) to attend the workshop on the Restriction of Intentionally-Added Microplastics under REACH on the 30-31st May 2018. The plenary group received a presentation on the IMPASSE project. Within the meeting, we presented and participated in the discussion in the Agriculture sub-group, providing an overview on existing works related to MPs in agricultural systems.

Moreover, we are collaborating with the British Royal Society to prepare a synthesis document on MPs for policy makers in UK. This document will feed in to the UK Government Strategy on MPs and will be part of a broader initiative called Living Landscapes. Within this interactions we released phone interviews and provided written documentations and scientific review to the British Royal Society officers.

We have actively participated in the International Water Association (IWA) world congress in Tokyo in September 2018, where we organized two workshops on MPs (one as co-organizers and the second as main organizers and chairs (Through IMDEA team)). We presented our preliminary results and provided our perspective for the future and needs of research in this field.

In addition, we were invited to present the project and the preliminary results to European Sustainable Phosphorus Platform (ESPP). This organization brings together industry, R&D and regions/cities to promote sustainable management of phosphorus. The meeting included the organization members, invited experts and key stakeholders, and was conceived to enable a dialogue between scientists, industry and farmers at European level.

These are just a few of our on-going dialogues with stake holders.