Several rivers in the Capitale-Nationale and Saguenay-Lac-Saint-Jean contain pesticides, but the situation is less serious there than in Montérégie.
In the Etchemin River in Saint-Romuald, in 2015, 20 pesticides were detected, and 17 were detected in the Chaudière River that same year. In 2016, the Rivière du Sud, in Montmagny, had 12.
It’s not ideal, but it’s still half of what you find in some rivers in the Montérégie.
“These are sectors where crops can be less intensive, less use of pesticides, […] and sometimes there are larger tributaries (watercourses), so more dilution”, explains Anoucka Bolduc, responsible for environmental monitoring of pesticides at the Ministry of the Environment, to explain the discrepancies between the results of Montérégie and sectors further north of Trois-Rivières.
For example, no pesticides were detected in the Batiscan River in 2018. In its watershed, crops cover only 4.6% of the territory, including 1.6% of corn and soybeans, specifies the report of the ministry. .
This explains why rivers in the Capitale-Nationale or Saguenay-Lac-Saint-Jean regions are only sampled on an ad hoc basis.
Potatoes
In the Blanche River, near Sainte-Catherine-de-la-Jacques-Cartier, 10 pesticides were detected in 2018. This river is part of the monitoring network for watercourses located in potato growing areas.
The main potato producing regions in Quebec are the Capitale-Nationale and the Chaudière-Appalaches. Potatoes make up 40.7% of the arable land in the watershed where the Blanche River is located.
Two neonicotinoids, a family of insecticides known as bee-killing pesticides, were detected in 100% of the samples, indicates the most recent report dating from 2019 for the years 2017 and 2018. Their concentration was also particularly high and threatened aquatic life.
However, the regulations tightening the use were introduced in 2018. We will have to wait for the next monitoring planned for 2024-2025 to see if the trend is down and if, as in corn and soybean crops, they have been replaced. by chlorantraniliprole, an insecticide toxic to invertebrate organisms.
However, this insecticide is already present in 100% of the samples from the Rivière Blanche.
Pesticides, not just in water
Pesticides are found in the sediments of these rivers, confirm exploratory sampling by the ministry, the results of which have just been published. Of the 18 rivers that were sampled, pesticides were found in the sediments of each of them.
Glyphosate, this herbicide better known as Round Up which could be carcinogenic (studies are not unanimous) has been detected in the sediments of all waterways. It is also the best-selling herbicide in Quebec.
The highest concentrations of Round Up in the sediments were recorded in the Gibeault-Delisle stream and the Saint-Régis river. It is also in these two watercourses that the greatest number of different pesticides was detected in the sediments, namely 15 and 10 respectively.
Strangely, we do not really know the risks of glyphosate in sediments, because there is little study on its effects on aquatic species, according to the study of the ministry. “There are almost no criteria for pesticides in sediments to assess the effects on aquatic organisms, especially for herbicides such as glyphosate,” says Ms. Bolduc. So we have little information on the effect of the herbicide on aquatic plants rooted in the sediments.
Glyphosate-based herbicides have had a bad reputation for a few years and are beginning to be banned in some municipalities. This has recently been the case in Montreal, Granby and will be in Quebec in 2024.
Fewer bee-killing pesticides, but…
Among the pesticide soup in our rivers are neonicotinoids, the famous bee-killing insecticides. If their presence tends to decrease, however, another substance, just as threatening has come to replace them.
In 2018, a regulation came to tighten the use of five pesticides, including three neonicotinoids.
“That does not mean that they are banned, it takes an agronomist who justifies and prescribes the use, specifies Anoucka Bolduc, of the Ministry of the Environment. But we can see that it had an effect”.
Their presence in waterways has decreased in rivers located in corn and soybean growing areas, according to the department’s report published last fall for the 2018-2020 period.
But despite this decrease, they are still responsible for the vast majority of exceedances of aquatic life protection criteria. “They are still quite persistent, they can remain in the organic matter of the soil,” adds Ms. Bolduc.
THE neonics and their numerous overruns, in addition to all other pesticides, therefore continue to represent “a risk for the aquatic species of these waterways”, specifies the most recent report of the ministry.
Other bad news: the decrease in bee killers seems to have been made in favor of chlorantraniliprole. The insecticide is now detected in almost all of the samples from the four streams located in the corn and soybean zone and the concentrations are on the rise.
This product is extremely toxic to freshwater invertebrates and slightly toxic to freshwater fish, according to the SAgE pesticides database. For example, in the Chibouet River, this pesticide was detected for the first time in 2015. Three years later, it was detected in all samples from the river and it is still the case today.
Water quality criteria exceedances for the protection of aquatic species for chlorantraniliprole also occurred in the Saint-Régis River between 2018 and 2020.
However, the ministry intends to include this insecticide on the list of pesticides covered by the new regulations which limit their use.