What’s the Big Deal About Microplastics?
Microplastics are tiny fragments of plastic, smaller than a grain of rice, that result from the breakdown of larger plastic items. These minuscule bits are practically everywhere—floating in our oceans, lurking in soils, and even sneaking into the food we eat and the air we breathe. But why should you care? Microplastics can carry harmful chemicals and, because of their small size, can easily be ingested by wildlife, potentially entering the food chain and impacting ecosystems and human health.

A particularly vulnerable place to study these microplastic pollutants is California’s Salton Sea, an ecological hotspot with a complex history of agricultural runoff and pollution. Our team sought to find out: how much microplastic is present in the Salton Sea, and where is it coming from?

Why Study the Salton Sea?
The Salton Sea is an unusual ecosystem. Once a vibrant resort area, it’s now better known for its high salinity, pollution, and shrinking size. Despite these challenges, it still supports some hardy species like tilapia and certain insects. The sea is fed by runoff from nearby agricultural fields, which raises questions about whether these fields could be a major source of microplastic pollution. Could the very water used to irrigate these fields also be introducing microplastics into the soil, water, and eventually the Salton Sea?

Our study aimed to investigate:

1. Is the Salton Sea contaminated with microplastics?
2. Are these microplastics coming from nearby agricultural fields?
3. What types of plastics are most common in the area?

How Did We Test for Microplastics?
We collected water samples from five sites, including clean irrigation canals, post-field drainage canals, the Alamo River (a main source of runoff into the Salton Sea), a stagnant ditch near the river, and the Salton Sea itself. At each site, we filtered the water, analyzed the particles using special microscopes, and identified the types of plastics present.

Using tools like fluorescence microscopes and spectroscopy, we identified thousands of microplastics in the samples and categorized their types, such as polypropylene (PP) and high-density polyethylene (HDPE)—common materials used in everyday items like containers and synthetic fertilizers.

Here are our sampling sites:

What Did We Discover?
Our findings were surprising!

• The Alamo River, which collects water from multiple farms, had the highest microplastic count. However, the Salton Sea itself had the lowest count among our sampling sites.
• Unexpectedly, “clean” irrigation water carried more microplastics than water draining from the fields. This suggests that the irrigation water might be bringing microplastics into the fields, where they may settle in the soil instead of flowing into the Salton Sea.

We also found that polypropylene (PP), a type of plastic often used in agriculture, was the most common material identified in our samples.

Below is our full data!

Table 1. Number of microplastics filtered out of the samples at each site. 

Table 2. Percentages of types of plastics present in each sample.

Figure 2. Number of microplastics filtered out of the water samples from each site across the Salton Sea area.

Why Does This Mean for The Sea?
Our research suggests that the soil in agricultural fields around the Salton Sea may act like a filter, trapping microplastics before they can reach the sea. However, this raises another concern: what happens to these plastics in the soil? Over time, they could build up and potentially affect soil health or leach into groundwater.

While the Salton Sea currently appears to have relatively low levels of microplastic pollution, the findings highlight the need for better management of water and plastic use in agriculture. Future studies could look at the long-term impact of these microplastics on soil and explore how to minimize plastic contamination in irrigation systems.

Microplastics may be tiny, but their impact is anything but small. By understanding their movement through ecosystems like the Salton Sea, we can take the first steps toward addressing a growing environmental challenge. Stay tuned as we continue to dig deeper into this hidden pollution problem!

Would you like to learn more about microplastic pollution in agriculture? Check out this study on microplastics in agricultural soils for an in-depth look at the issue.