Silver Membrane Filters for Oceanography Applications

Oceanography is the scientific study of the oceans involving marine biology and the exploration of deep-sea areas and their properties such as depth, temperature, salinity, and resources. It is especially important today as climate change, pollution, and other factors are threatening the ocean and its marine life.

Marine biology and Oceanography organizations have long used a variety of filter media to assist with their research. While the ways in which filtration supplies can be used are as diverse as the life forms that live under the waves, here we highlight some of these applications that have previously been mentioned in published papers to give you an idea about some ways filters can be purposed in marine research.

One of the aspects of marine research has focused on the presence and impact of Microplastic pollution on the marine environment and organisms as millions of tons of plastic waste are released into the marine water every year.  Microplastics are small pieces of plastic that are less than 5 mm in size and can pose potential risks to human health and ecosystems. Microplastic analysis using silver membrane is a method of detecting and identifying microplastic particles in environmental samples, such as water or sediment. The Silver membrane filters are composed of metallic silver and have several advantages for microplastic analysis, such as:

They have a smooth and reflective surface, which makes them compatible with Raman imaging and other optical techniques. [1]
They have a low affinity for organic molecules, which reduces the interference from non-plastic particulates. [2]
They have a high thermal stability, which allows them to withstand oxidative digestion methods. [2]

Another oceanographic use for filtration materials comes from the study of zooplankton that live deep in the Pacific Ocean[3]. The silver membrane filters (1.2 Micron) were used to pre-filter samples of plankton waste prior to nitrogen content analysis via a high temperature combustion technique.

Also using silver membrane filters (1.2 Micron, 25 mm) was an experiment by the Woods Hole Oceanographic Institution which used them as part of a study to see if the growth of marine phytoplankton in certain areas leads to organic carbon being exported [4]. Here the membranes were used to collect and prepare particles from deep water samples for further analysis.

The conclusion of each study was the efficacy of using the silver membranes for various filtration applications, especially for sampling and analyzing particulate contaminants in air, water, or soil.

References:

1. Cunsolo, S., Williams, J., Hale, M. et al. Optimizing sample preparation for FTIR-based microplastic analysis in wastewater and sludge samples: multiple digestions.  Anal. Bioanal Chem 413, 3789-3799 (2021)
2. Razeghi, N., Hamidiam, A.H., MirzaJani, A. et al. Sample preparation methods for the analysis of microplastics in freshwater ecosystems: a review. Environ Chem Lett 20, 417-443 (2022)
3. Wilson E,  Steinberg D.K. , Buesseler K.O. Changes in fecal pellet characteristics with depth as indicators of zooplankton repackaging of particles in the mesopelagic zone of the subtropical and subarctic North Pacific Ocean. Deep-Sea Research II 55, 1636-1647 (2008)
4. McDonnell A.M.P., Buesseler K.O. A new method for the estimation of sinking particle fluxes from measurements of the particle size distribution, average sinking velocity, and carbon content. Limnol. Oceanogr.: Methods 10, 329-346 (2012)