
The Nižná Slaná landfill is located on the northeastern side of the Nižná Slaná municipality in the hills directly above the Etelka smelter, one of the most unique technical monuments in the Gemer region or perhaps in the entire country, representing the long and rich history of mining in this region. The landfill contains waste from the ore processing in the region and, according to estimates, has reached a volume of almost 5.5 million m3 . The retention wall itself is about 95 meters high. Several experiments have been carried out in the past to see if it is possible to cover the area with vegetation, but without much success. Our colleagues asked the mayor if they could test our humic acid-based product directly on site and see if there would be any reaction. A month later, some very noticeable changes were observed.
Area: around 21 ha (12.5 ha – tailings pond)
Environmental burden: open unsecured landfill with high concentration of heavy metals (As, Cd, Pb, Hg, etc.)
Objective: to prevent mobility of harmful dust by covering the entire site with vegetation
Experiment: application of HUMAC ® Agro with grass seeds on an area of approximately 16 m2 ( August 7, 2020)
After one month (September 7), the area where HUMAC ® Agro was applied was covered with grass .
Unfortunately, much of the test area was damaged by motorcycle riders, but the following images show the extent of the grass's root system.


Abundant roots as long as the above-ground part of the grass, one month after application.
During this one month (August 7 - September 7), there were only 9 days when daily temperatures dropped below 25 degrees and 13 days with precipitation.
Two soil samples were also taken on September 7:
- from a site without HUMAC® Agro treatment = control
- from a place treated with HUMAC® Agro
The samples were sent for analysis to the accredited VEHYDIS laboratory of the State Veterinary and Food Institute, where the contents of free heavy metals were determined.
Results
PARAMETER | CONTROL | TRREATED WITH HUMAC | DIFFERENCE |
---|---|---|---|
Mercury (Hg) | 2.35 mg/kg | 0.55 mg/kg | -76.6 % |
Cadmium (Cd) | 0.27 mg/kg | 0.096 mg/kg | -64.0 % |
Lead (Pb) | 44.98 mg/kg | 46.47 mg/kg | +3.3 % |
Arsenic (As) | 1907 mg/kg | 542.5 mg/kg | -71.6 % |
As for lead, it is one of the least reactive metals and the binding time is much longer. Humic acids are also known for their ion exchange capacity, forming ionic bonds with various metal ions. The binding rate is also greatly influenced by pH, which was not determined in this case.

Unfortunately, over the course of a month, motorcycles destroyed most of the grass that had grown, so the extent of the growth is not fully captured.

During the second visit, a second test was carried out, using a protective net made of coconut fibers to prevent the wind from blowing away the applied seed and humic acid mixture.
In early October 2020, grass was growing in the second test areas:

