Pesticides banned in Estonia for decades detected in surface, groundwater

Agricultural field.
Agricultural field. Source: Olev Kenk/ERR

The prosperous years of Estonian agriculture have damaged the quality of groundwater and associated surface waters. However, there are no easy ways to make food production more sustainable, experts say.

"So far, trends indicate that Estonian agriculture is rapidly catching up to Western European agricultural practices. We are primarily intensifying. Pesticides and mineral fertilizers have been used more in the last decade," Aveliina Helm, the professor of restoration ecology at the University of Tartu, told ERR's Vikerraadio on Monday.

In a recent study, researchers from the LIFE IP CleanEST project examined the northern portion of the Pandivere uplands (Pandivere kõrgustik) and nearby areas to determine the effect of agriculture on groundwater and surface water in the region.

Agriculture is a major contributor to human-caused water pollution, accounting for 78 percent of the eutrophication of the world's seas and freshwaters, which occurs when the environment becomes adversely enriched with nutrients.

Estonia is no different from the rest of the world in that our agriculture has a significant impact on the environment.

During the study, the chemical composition of rivers and groundwater, as well as the concentration of pesticides and pharmaceutical residues in groundwater and their uptake in rivers, were measured in the northern Pandivere Upland.

Focus was placed on three rivers with a large base flow component for surface water, and on springs and existing and new wells for groundwater.

As the Pandivere region is one of the most groundwater-sensitive regions in Estonia — a limestone plateau with a thin, less than five-meter-deep sedimentary rock cover and an undeveloped surface water network — the majority of rainfall quickly enters the groundwater through the soil (i.e. diffuse groundwater recharge) and nourishes the springs on the slopes of the plateau.

Nonetheless, it is an important agricultural region where water has been a worry for decades.

Pandivere Upland has been designated as a Nitrate Vulnerable Zone (NVZ), which is essentially a conservation status for areas that are vulnerable to agricultural nitrate pollution.

"Perhaps we should consider the possibility that, as long as agricultural production in the region remains at its current level, water quality will not improve much. We have extensive time data from the Pandivere basin dating back to 1980. If we dig deeper, we can clearly see productivity cycles, such as how nitrate levels dropped in the early 1990s and then surged again at the end of the first decade of the 21st century," Joonas Pärn, a hydrogeologist at the Estonian Geological Survey, explained.

The study reviewed the chemical composition of the water in the rivers and the levels of pesticides and pharmaceutical residues. The findings suggest that agriculture has a significant impact on the groundwater quality in Pandivere.

Due to the lack of proper surface water drainage on the Pandivere plateau, the bulk of polluted snow-melt continues to slowly seep into the groundwater.

Joonas Pärn taking water samples in March 2022. Source: Merle Truu

Arvo Iital, the professor of environmental engineering at the Tallinn University of Technology (TalTech), said that one of the most intriguing findings of the study was the discovery of pesticides that have been outlawed in Estonia for a considerable amount of time, indicating that pesticides can be highly persistent, particularly in groundwater.

The concentrations of agro-chemicals and fertilizers are known to fluctuate roughly in line with economic cycles. Nitrate concentrations, for example, fell in the early 1990s before rising again near the end of the first decade of the 21st century. Iital said that the current difficult conditions are likely to motivate farmers to use fertilizers more sparingly, as overuse would become extremely costly.

Another source of concern is waste, as Estonia's livestock industry is highly concentrated, with one of the highest manure production rates in Europe. If waste water treatment systems are not functioning as required, the polluted water may end up in the surface and groundwater.

However, not all of the water absorbed into the earth reaches the springs, and the next critical step in deciphering the underground water network, Pärn said, would be to undertake more complex investigations to better understand where the springs get their water.

"If we could do something about the sources of nutrients and target agricultural measures there, we might be able to reduce their concentrations," the hydrologist said.

Precise fertilization is one way to reduce pollution. Farmers' economic interests and environmental concerns coincide here.

By applying fertilizer close to the roots of plants, less nitrogen and phosphorus will reach rivers, lakes and seas and hence minimizing eutrophication.

Over-fertilization is also not in the farmer's best interest, especially when fertilizer prices rise. Monitoring systems for soil activity have been sought after in many parts of the world.

Paul-Tech, an Estonian company, has developed soil stations that measure soil water and nutrient levels in real time. This allows fertilization to take place at the optimal time and location, avoiding the costs and environmental damage associated with excessive fertilizer use.

Kristo Elias, host of the program, with Margus Lepp, manager of Vandra AS, and Teet Liiv, agronomist of Paul-Tech OÜ, a firm that manufactures soil monitoring stations. Source: ERR's TV program "Osoon"

"Agriculture has the advantage that if all activities are performed at the right time, the results are immediately visible in the harvest. A successful farm is distinguished by the fact that its objectives are reevaluated on a regular basis in light of current reality. /.../ If environmental factors prevent me from spraying, I double-check the spray formulations and do the bare minimum to avoid undue stress," Teet Liiv, an agronomist at Paul-Tech, explained.

Another advantage of soil monitoring, Liiv said, is that the measurement data can guide farmers toward more sustainable methods. For example, there is a big problem of large amounts of nutrients being released from arable land freed by crop rotation.

"Today, I can notice that our customers are beginning to understand how important it is to reduce the period of time without vegetation. A balance sheet or Excel spreadsheet containing the quantity of free nutrients is less persuasive than a soil station," Liiv said.

One such farmer is Margus Lepp, who has been using the Estonian company's soil stations for some time. "I was concerned about what the cold would do to the nutrients, and whether they would be locked in the soil or washed away by the water. It was really encouraging to see that they have been bound to the soil," Lepp said.

Aveliina Helm, an ecologist, said that precision farming is unquestionably part of the required reforms in agriculture, but that the solutions must be far more comprehensive overall.

Aveliina Helm. Source: ERR's TV program "Osoon"

"Top-dressing is certainly part of the systemic change," Helm said, "but more diverse landscapes are also required: that we respect buffer strips and minimize nutrient leaching."

Natural solutions should reduce the need for agro-chemicals as well. A prime example is the 2018 drought, which reduced Estonian grain output by 40 percent. The following year conditions improved, but if climate change continues there might be more consecutive summers of severe drought.

"In these circumstances, it is important to think about how to make our fields more climate-resistant, drought-resistant and resilient," Helm said. "How can we ensure that current and future pests have natural adversaries in the environment?
Insecticides can help, but they cannot keep up with the pace of environmental unpredictability. So it comes down to securing our future by doing everything we can to make fields as climatically resilient and landscape diverse as possible."


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Editor: Kristina Kersa

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