Microplastic contamination is an emergent threat that is still only little researched and understood. At the University, we have supervised a number of Bachelor and master students that have examined the distribution of microplastics from different sources, in the aquatic environment.
Currently, we are about to embark on a project to investigate the distribution, concentration, origin and potential impact of microplastics downstream in the Nissan River. As the image below illustrates most of the plastics found in river sediment are of a particular shape and size. We hypothesize that these are of point-source origin.
During a dry period in summer 2021 we are planning to sample the river, its reservoir, Jakobssjö, and its delta at Halmstad with the help of MSc Environmental Toxicology student Matyas Baan. During the 2021/22 academic year first phase of the project will focus on assessing the microplastic contamination of these water bodies while the subsequent stages will investigate the potential impact of this through studies on fish and invertebrates.
For more information on the project contact Matyas Baan at matyasbaan@ymail.com.
UPDATE SEPTEMBER 2021
Students involved: Matyas Baan and Stig Willett (supervised by David Green, Antonia Liess and Per Magnus Ehde)
Field survey: The concentration and distribution of macro- and microplastic particles in the Nissan and Lagan water systems were investigated in June and August 2021 (Figure 1).
Figure 1: A) Nissan river system with sampling locations indicated as blue pins. B) Lagan river system with sampling locations indicates as blue pins.
Field methods: Water column, bottom sediments and shore sediments were taken at impoundments upstream of Hyltebruk and downstream of Hyltebruk in the Jakobs sjö reservoir, as well as in 2 more impoundments along the Nissan River (Figure 1a).
Figure 2: A) Equipment - Ekmangrab and metal tray - for bottom sediment sampling B) Water sediment sample being filtered through plankton nets of different sizes for particle size fractionation C) Metal buckets and glass sampling containers are used for sampling to avoid contamination by plastic.
Samples from the Lagan river system provide current background MP contamination. Samples were collected in quadruplicate according to a nested design. Water samples were collected with plankton nets (see figure 2b and c). Bottom sediments were collected by boat (figure 3), using an Ekmangrab (figure 2a).
Figure 3: Sampling Jacobs sjö by boat.
Shore sediment samples were taken from shore deposits, using rectangles of a defined area and a metal spoon (se figure 4a and b). Larger microplastics are visible by eye (red arrows e.g. figure 4c).
Figure 4: A) Sampling frames of different sizes used for shore sediments. B) Sampling frame, spoon, and glass container. C) Microplastics trapped in shore sediments (red arrow here and in a and b).
Sample preparation in the laboratory: Sediment samples were size fractionated using sieves of different mesh sizes. Of the largest size fraction all samples are analysed and the proportion of plastic by weight and number in relation to the remaining detritus has been recorded.
Smaller MPs will be isolated from bulk samples using a density separation method, which will also help identify MPs composition. MPs will be identified microscopically according to standard methods (Johansen et al. 2019). We are also currently experimenting with different methods for marking and counting smaller microplastics, where a staining method using Nile red seems promising (see figure 5).
Figure 5: Microscopic slides under the microscope using staining with Nile red. The bright fragments are microplastics, whereas the dark particles are natural organic materials.
TIME PLAN:
The filed work has been conducted in July to August 2021.
Shore sample size fractionation using sieves was conducted in August 2021.
The largest size fraction of all 32 shore sediment samples was separated, counted and weight in August 2021.
The remaining laboratory work will be conducted September to December 2021.
References
Johansen, M. P. et al. (2019) ‘Biofilm-enhanced adsorption of strong and weak cations onto different microplastic sample types: Use of spectroscopy, microscopy and radiotracer methods’ Water Research 158, 392-400