Writer: Ecrin Tekeş
Introduction
Urbanization refers to the intensification of the human population in distinct areas. This intensification leads to the conversion of land for residential, commercial, industrial, and transportation purposes. It tends to include densely populated centers as well as their adjacent periurban or suburban fringes (EPA, 2024)
Urbanization, particularly in industrial countries, often follows a structured and sustainable path aligned with industrial growth. However, in many developing nations, the rapid pace of urbanization often outstrips sustainable industrial and social development, leading to significant environmental, economic, and social challenges. When urban expansion does not adhere to principles of sustainable development, issues such as air and water pollution, inadequate infrastructure, and overpopulation arise, placing strain on essential resources like education, transportation, clean air, and potable water. This unchecked growth, particularly in large cities, creates a host of negative consequences, from environmental degradation to economic instability. In developing countries, such as Iran, the lack of careful consideration of urbanization’s side effects has led to notable challenges over recent decades (Kalhor K. et al, 2015)
Urbanization and the Rise of Microplastic Pollution
Plastic is the most common type of marine litter found in our ocean and the Great Lakes. Plastic litter comes in all shapes and sizes, but those shorter than five millimeters (or the size of a pencil eraser) are called “microplastics”. As an emerging field of study, not much is yet known about microplastics and their impacts. Microplastics come from a variety of sources, including larger plastic debris that breaks down into smaller and smaller pieces. In addition, microbeads, a type of microplastic, are very small pieces of manufactured polyethylene plastic that are added as exfoliants to health and beauty products such as some cleansers and toothpaste. These tiny particles easily pass through water filtration systems and reach the ocean and the Great Lakes, posing a potential threat to aquatic life (National Ocean Service, 2024).
Microplastic pollution varies significantly across different geographic regions, with its abundance and distribution largely influenced by both environmental and human (anthropogenic) factors. However, environmental elements such as ocean currents, wind patterns, tides, and river dynamics often have a greater impact on the spread of microplastics than human activities. Areas where these environmental factors are more intense tend to have higher concentrations of microplastics. On the other hand, human activities like improper waste disposal contribute to the accumulation of plastic in the environment. The concentration of microplastics is measured using various units, making it necessary to standardize the reporting of their global distribution and abundance (Shahul Hamid et al, 2018).
Lakes serve as primary sinks for microplastics in freshwater systems. As rivers flow into lakes, they transport coastal pollutants, allowing microplastics to accumulate in sediment layers. Analyzing sediment cores from estuaries enables the assessment of historical microplastic pollution in incoming rivers and the evaluation of urbanization’s impact on the river basins. The Aha Lake basin, located in southwestern China (a major developing country and the largest producer and consumer of plastics), has a relatively small area of 180.2 km². With three main inflowing rivers at different stages of urbanization, Aha Lake offers a valuable opportunity to understand the effects of urbanization on microplastic pollution.
This study considers microplastics of various sizes, colors, shapes, and polymer types as distinct “microplastic communities.” A systematic investigation was conducted to assess the abundance and characteristics of these microplastic communities in the sediments of Aha Lake. The objectives of this research are: (1) to determine the vertical distribution and abundance of microplastic communities in different sediment layers of Aha Lake; (2) to evaluate the impact of urbanization on the composition of microplastic communities; and (3) to identify differences in microplastic community composition at varying levels of urbanization and analyze their potential sources. The findings of this study have the potential to provide valuable information for better management and control strategies to reduce microplastic pollution in China (Gao, S. et al, 2023)
The Impact of Microplastics on Soil Health
Soil is a thin layer of material covering the Earth’s surface, formed through the process of rock weathering. It acts as a natural filter for groundwater pollutants and is crucial for human health. Recent studies from around the world have confirmed an increase in the presence of microplastics in soil. However, most of these studies have examined the effects of soil microplastic contamination on only one or two soil health indicators, rather than analyzing them concurrently.
In this review, we selected international studies published over the past decade to investigate the trends in the effects of soil microplastic contamination on three key soil health indicators. The analysis revealed that soil microplastic contamination has led to either an increase or decrease in the trends affecting physicochemical and biological soil properties. In some cases, microplastic pollutants do not significantly impact soil properties. Changes in soil health due to microplastics were attributed to factors such as microplastic concentrations and types, alterations in soil mechanics, and impacts on microorganisms.
Given the expected long-term persistence of these effects, especially with the rising global plastic production, there is a need for ongoing research to assess the impact of microplastic contamination on other, previously unexamined soil health indicators (Chia, R. W. et al, 2022).
Quality Control and Assurance in Microplastic Detection
Microplastics (MPs) in the air and indoor environments have become an increasing concern, leading to a need for more comprehensive testing of these pollutants. This study highlights the importance of laboratory experiments—often neglected or rarely adopted in MP research—that involve solutions, filters, and blank samples to improve the quality and quantification of MP measurements. Experiments were conducted to identify potential contamination sources arising from experimental procedures when detecting MPs in air samples. MPs were counted and categorized based on their shapes in different matrices. Chemical characterization was performed using Raman Spectroscopy. Results indicated that a laminar flow hood is the best option for detecting airborne MPs, compared to standard laboratory environments, due to its effectiveness in reducing blank levels. Predominant colors observed were blue-green and black-gray, with fibers being the most common type of MP. Most MPs were found to fall within the size range of 1-1000 micrometers in various indoor environments and blank samples. Commonly observed MPs included polypropylene, polyvinyl alcohol, polytetrafluoroethylene, polyvinyl chloride, and high-density polyethylene. Thermal processing of fresh, unused filters at 450 °C for four hours effectively reduced MP counts by 50%. The solutions used were mostly contaminated, making pre-filtration essential. On average, blank samples accumulated about 55 MPs over seven days. There is an urgent need for quality control and assurance improvements in MP studies. Therefore, the adoption of a standard protocol is necessary; aligning procedures can yield comparable results and establish accurate levels of MP pollution required for risk assessments (Bhat, M. A. et al, 2024).
Conclusion
The increasing presence of microplastics in both air and indoor environments highlights a growing environmental concern, emphasizing the need for rigorous testing and quality control measures. This study reveals that standardizing laboratory practices, such as using laminar flow hoods and thermal processing of filters, significantly improve the accuracy of microplastic detection and quantification. Our results demonstrate that fibers and specific polymers are prevalent in various indoor settings, reflecting the pervasive nature of microplastic pollution.
Urbanization, a key driver of microplastic contamination, exacerbates the problem by contributing to higher levels of pollution through increased plastic usage and waste. As urban areas expand and industrial activities intensify, the introduction of microplastics into different environments, including air and indoor spaces, becomes more pronounced. This underscores the necessity for integrating urbanization impacts into microplastic research and developing strategies to mitigate pollution effectively.
To enhance the reliability of microplastic studies, it is crucial to adopt standardized protocols that ensure consistency and comparability across research efforts. Improved quality control and assurance practices will facilitate more accurate risk assessments and inform the development of targeted strategies for reducing microplastic pollution. Future research should continue to refine these methods and consider the broader implications of urbanization on microplastic distribution and impacts, providing a more comprehensive understanding of the issue and informing effective environmental policies.
References:
United States Environmental Protection Agency. (2024, February 29). Urbanization - Overview. https://www.epa.gov/caddis/urbanization-overview
Kalhor, K. and Mahdisoltani, M. (2015, June). Urbanization and sustainable development and its impacts on environment and society. Third International Symposium on Environmental and Water Resources Engineering, Tahran, Iran (Vol. 2, No. 3, pp. 1-12).
National Ocean Service (NOAA). (2024, June 16). Microplastics. https://oceanservice.noaa.gov/facts/microplastics.html
Shahul Hamid, F., Bhatti, MS, Anuar, N., Anuar, N., Mohan, P., & Periathamby, A. (2018). Microplastic distribution and abundance worldwide: how dire is the situation? Waste Management and Research , 36 (10), 873-897.
Gao, S., Wu, Q., Peng, M., Zeng, J., Jiang, T., Ruan, Y., ... & Guo, K. (2023). Rapid urbanization affects microplastic assemblages in lake sediments: A case study of Aha Lake in Southwest China. Journal of Environmental Management , 338 , 117824.
Chia, R. W., Lee, J. Y., Jang, J., Kim, H., & Kwon, K. D. (2022). Soil health and microplastics: a review of the impacts of microplastic contamination on soil properties. Journal of Soils and Sediments, 22(10), 2690-2705.
Bhat, M. A., Gaga, E. O., & Gedik, K. (2024). How can contamination be prevented during laboratory analysis of atmospheric samples for microplastics?. Environmental Monitoring and Assessment, 196(2), 159.
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