Periodic Reporting for period 1 - SoPla_Fate (Fate and impact of past, present and future consumer plastic on soil)
Periodo di rendicontazione: 2022-09-01 al 2024-08-31
Soil provides 98.8% of our food, making healthy soils vital for our food security. By 2050, we need to increase food production by 70% to meet the needs of a growing population. However, our soils have been under pressure and are degrading. One vital service soil provides is the contaminant sink and filtration to protect groundwater. However, this means that soil stores and potentially accumulates pollutants including microplastics.
The potential accumulation of microplastic in agricultural soil has recently raised concerns because of the increasing intentional use of plastics and unintentional entry of microplastics into soil due to farming practises. Practices like plastic mulching, where soil is covered with plastic to retain moisture and control weeds and the accidental introduction of plastics through biosolid applications, where composted biosolids are used as fertilizer, are contributing to microplastic entry into soil. Once the microplastic has been introduced into the soil they do not break down easily and can stay in the soil for many years. Based on this persistence, widespread use of plastic and recent results in soil eco toxicology and eco system effects, plastic has been proposed as driver of global change. However, even basic information such as plastic mass concentrations or its fate and impact on soil health are widely unknown.
Therefore, this project aimed to assess the significance of micro/plastic pollution in agricultural soil to understand its relevance to impact soil health through addressing the following specific objectives: (1) Quantify soil profile mass concentrations of plastic for their polymer type; (2) Develop/modify and validate a comprehensive analytical workflow additive fingerprinting/screening und potential identification employing LC and GC UHRMS systems; (3) Determine additive partitioning and leaching behaviour at different stages of polymer aging; (4) Quantification of plastic impact on vital soil processes.
Based on the findings of this project, it is evident that microplastics persist in the topsoil of all examined agricultural soils. However, the concentrations of microplastics detected were lower than anticipated, underscoring the importance of incorporating soil management practices into research methodologies and result interpretations. Further this highlights the need for standardized protocols to ensure comparability of results across studies.
These findings further highlight the impact of “best practice” and legislation covering soil management practices, such as fertilizer application control and quality control of organic fertilizers in protecting soil health and minimize microplastic contamination.
The potential accumulation of microplastic in agricultural soil has recently raised concerns because of the increasing intentional use of plastics and unintentional entry of microplastics into soil due to farming practises. Practices like plastic mulching, where soil is covered with plastic to retain moisture and control weeds and the accidental introduction of plastics through biosolid applications, where composted biosolids are used as fertilizer, are contributing to microplastic entry into soil. Once the microplastic has been introduced into the soil they do not break down easily and can stay in the soil for many years. Based on this persistence, widespread use of plastic and recent results in soil eco toxicology and eco system effects, plastic has been proposed as driver of global change. However, even basic information such as plastic mass concentrations or its fate and impact on soil health are widely unknown.
Therefore, this project aimed to assess the significance of micro/plastic pollution in agricultural soil to understand its relevance to impact soil health through addressing the following specific objectives: (1) Quantify soil profile mass concentrations of plastic for their polymer type; (2) Develop/modify and validate a comprehensive analytical workflow additive fingerprinting/screening und potential identification employing LC and GC UHRMS systems; (3) Determine additive partitioning and leaching behaviour at different stages of polymer aging; (4) Quantification of plastic impact on vital soil processes.
Based on the findings of this project, it is evident that microplastics persist in the topsoil of all examined agricultural soils. However, the concentrations of microplastics detected were lower than anticipated, underscoring the importance of incorporating soil management practices into research methodologies and result interpretations. Further this highlights the need for standardized protocols to ensure comparability of results across studies.
These findings further highlight the impact of “best practice” and legislation covering soil management practices, such as fertilizer application control and quality control of organic fertilizers in protecting soil health and minimize microplastic contamination.
At the start of the project I build a network of German farmers to facilitate the collection of undisturbed soil samples in Germany. The samples were prepared for long term storage at the Beneficiary as well as for transport to the partner laboratory in Australia. For the remainder of the project until termination I performed the project work at the partner institute in Australia.
My work focused on the time-consuming soil preparation to determine the microplastic concentrations in the different soil layers according to preselected size fractionations. The extraction method of the microplastic from soil was modified and validated to allow for larger volumes of soil to be extracted without hindering analysis by interferences. The optimization of the analytical method for soil samples was completed and validated to ensure high quality data output with a particular focus on polymer marker selection to exclude reporting of false positive polymer types and overestimated microplastic concentrations.
> Microplastic concentration and distribution in the collected soils have been quantified.
The second task I focused on was the extraction of plastic additives from microplastics and subsequent analysis. The method development for the extraction of a diverse range of additives is ongoing with the aim to combine different methods to safe time and resources. Employing a set of extraction methods, additives from consumer plastics were extracted and analysed employing high resolution liquid and gas mass spectrometry. The analytical methods I employed were available at the Australian partner laboratory and were found to be suitable for the selected products covering a wide range of plastic additives including phthalates, UV filter and stabilizer. This allowed to establish the baseline of type and quantity of additives I found in consumer plastics. This allows to later compare the additive profiles to the weathered plastic to identify changes in the composition.
Furthermore, the plastic weathering experiment was set up at employing the weathering chamber located at the Polymer Translational Research Group. The consumer plastic analysed for its additives was placed into the chamber and samples have been taken at pre-determined times to understand the impact of UV light on the degradation of consumer plastics and impact of additives.
> Additive concentrations and types have been identified and quantified for different types of pristine consumer plastic.
The results on the microplastic concentrations and distribution in soil have been disseminated to the participating farmers and further through the established networks, to the scientific community as well as regulators through the participation in two international conferences. Also, a seminar at the Australian partner was held for collaborators and the wider School focusing on the additive quantification. Results have also been disseminated to the general public though outreach events such as “Pint of Science” and the “World Science Festival Brisbane”.
My work focused on the time-consuming soil preparation to determine the microplastic concentrations in the different soil layers according to preselected size fractionations. The extraction method of the microplastic from soil was modified and validated to allow for larger volumes of soil to be extracted without hindering analysis by interferences. The optimization of the analytical method for soil samples was completed and validated to ensure high quality data output with a particular focus on polymer marker selection to exclude reporting of false positive polymer types and overestimated microplastic concentrations.
> Microplastic concentration and distribution in the collected soils have been quantified.
The second task I focused on was the extraction of plastic additives from microplastics and subsequent analysis. The method development for the extraction of a diverse range of additives is ongoing with the aim to combine different methods to safe time and resources. Employing a set of extraction methods, additives from consumer plastics were extracted and analysed employing high resolution liquid and gas mass spectrometry. The analytical methods I employed were available at the Australian partner laboratory and were found to be suitable for the selected products covering a wide range of plastic additives including phthalates, UV filter and stabilizer. This allowed to establish the baseline of type and quantity of additives I found in consumer plastics. This allows to later compare the additive profiles to the weathered plastic to identify changes in the composition.
Furthermore, the plastic weathering experiment was set up at employing the weathering chamber located at the Polymer Translational Research Group. The consumer plastic analysed for its additives was placed into the chamber and samples have been taken at pre-determined times to understand the impact of UV light on the degradation of consumer plastics and impact of additives.
> Additive concentrations and types have been identified and quantified for different types of pristine consumer plastic.
The results on the microplastic concentrations and distribution in soil have been disseminated to the participating farmers and further through the established networks, to the scientific community as well as regulators through the participation in two international conferences. Also, a seminar at the Australian partner was held for collaborators and the wider School focusing on the additive quantification. Results have also been disseminated to the general public though outreach events such as “Pint of Science” and the “World Science Festival Brisbane”.
Quantification of environmentally relevant concentrations of microplastics in the terrestrial environment is scarce. This is one of the first studies quantifying polymer type and microplastic concentrations on a mass basis rather than particle counts in different soil types allowing for comparison between studies. Further, only very limited studies have conducted research into the distribution of microplastics in soil. The results of this study show the immobility of microplastics in the soil matrix informing future sampling protocols.
The results on the pollution level of agricultural soils with microplastics is valuable for guidance of policy makers. In Germany as well as in Australia regulations and legislations around soil amendments with organic waste are in place containing threshold values of certain pollutants. This may be extended to microplastics to prevent their entry and accumulation into soils.
The new knowledge should benefit the health of agricultural soils in Germany and Australia and thus secure its vital functions for the environment and agriculture.
The results on the pollution level of agricultural soils with microplastics is valuable for guidance of policy makers. In Germany as well as in Australia regulations and legislations around soil amendments with organic waste are in place containing threshold values of certain pollutants. This may be extended to microplastics to prevent their entry and accumulation into soils.
The new knowledge should benefit the health of agricultural soils in Germany and Australia and thus secure its vital functions for the environment and agriculture.