Скачать или смотреть How is pollution in the St. Lawrence measured? | Ask a Scientist

Édith Lacroix, a scientific researcher with the St. Lawrence Action Plan, explains how water samples, sediment analysis, and tiny creatures in the river serve as good indicators of the St. Lawrence's pollution levels.
This video was produced alongside the release of the 2024 Overview of the State of the St. Lawrence.

https://planstlaurent.qc.ca/en/

** Transcript **

Kalina: The St. Lawrence River is an integral part of Canada. Not only does it provide drinking water and support diverse ecosystems, but it is also essential to our economy and culture. On that note, we have a question from Jean Philipe of Mont-Joli, Quebec.

Jean-Philippe: Hi my name is Jean Philippe Laliberté and I live near the St. Lawrence river. We hear that the St. Lawrence River’s water quality is sensitive. How do we check for pollution?

Kalina Parisien: Our scientist, Édith Lacroix, answers this question and explains how water samples, sediment analysis, and even the tiny creatures in the river help tell the story of the St. Lawrence’s health! Let's dive right in and discover how scientists are tackling this important issue!

Édith Lacroix: In 1988, the Canadian and Quebec governments set up the St. Lawrence Action Plan, which assesses not only water pollution, but also pollution of the sediments that make up the mud at the bottom of the river and of the benthic fauna; that is, all the little bugs that live on the bottom and on aquatic plants.

Chemists, biologists and field technicians go out into the field to take samples. So we fill several bottles with water. When all the bottles are filled with water, we bring them to a laboratory for analysis, so that we can analyze the results and determine the state of the river.

Then, for the sediments, it’s more or less the same thing. We go to our sampling sites, we use what we call a grab sampler, which is a large instrument with a big jaw that picks up a sample of mud from the bottom of the river. We fill some jars, and then do the same thing, we send the jars to the laboratory for analysis.

The third component, benthic fauna, is collecting benthic macroinvertebrates. They are caught in wetlands and seagrass beds along the St. Lawrence River using a kick net. We call it a multimedia site, because all these samples—sediment, water, and benthic fauna—are collected in a single location. Analyzing all the results at a multimedia site gives us a truly comprehensive picture of pollution at a site.

As you can imagine, sampling stations are strategically located. For example, to assess the quantities of pesticides in the water, we position our sampling sites at the outlets of major tributaries in the river. So this is how we measure pollution in the St. Lawrence River.

Even if water quality has improved somewhat over the years, the state of the river remains fragile, so monitoring must continue. Several factors could have an effect on water quality in the years to come, such as climate change, extreme weather events, more rain, greater drought, the appearance of new pollutants, the emergence of new industries, or even a more extensive period of growth and agricultural production than previously experienced. And this is why a monitoring system that allows us to collect data is crucial, because the more we know, the better decisions we can make to protect our beautiful river.

Kalina: Thanks to ongoing research, we can continue improving water quality in the St. Lawrence. The more we learn, the better we can protect this vital resource. Keep sending us your questions, and you might get an answer in the next episode of “Ask a Scientist.”