Browsing by Subject "lysimetri"

Finnish energy production is producing around 1.5 million tons ashes annually. The aim is to utilize ashes instead of landfilling as well as to replace the use of exhaustible natural materials. Wood and peat ashes can be used, for example, in field and forest fertilization and land construction. In road construction and rehabilitation, ash can be used to replace expensive aggregates and achieve better load capacity features. This study was part of the Natural Resources Institute Finland’s (formerly the Finnish Forest Research Institute) project: "New technologies as assistance for the lower road network construction and maintenance". The purpose of this research was to investigate the leaching of heavy metals, nutrients and salts from ash treatments by collecting infiltrate waters with zero-tension lyzimeters, taking water samples from nearby ditch waters and clarify influencing factors. The plots were established in Jämsä on the old forest roads, which are rehabilitated with mixed wood and peat ash in the autumn 2011. The site consists of two forest roads, which had four types of ash treatments and control treatment. For each plot, six zero-tension lysimeters (0.1 m2) were installed every 20 meters, tree to the roads surface and tree to deeper levels. In addition to lysimeters, water samples were taken from nearby ditches. Water samples were collected during 2012 – 2014 once a month from May onwards for 6-8 months. The relations between the substances were tested for statistical correlations (Pearson) and the effects of treatments to leaching were tested with the Tukey HSD-test. Concentrations of 32 elements, ions and compounds were determined from lyzimeter and ditch water samples. Heavy metal concentrations were during the entire follow-up period mainly low. There were no elevated heavy metal concentrations in ditch waters either. The content of nutrients and salts in the water samples were higher from ash treatments than from control treatments. The content of nutrients and salts were also higher in ditch water samples compared to control ditch. Several soluble substances from the ashes had a statistically significant positive correlation (p <0.01) with each other. The results varied a lot progressively, between plots and between the lysimeters of the same plot. Significantly higher concentrations were measured from two lysimeters for number of elements compared to the other lysimeters in other plots (p <0.05). In most cases, the results were very mixed and there was no clear difference between the control and ash treatments. The study yielded valuable information about the leaching of substances from ash structures. A three-year follow-up period is short, for example, compared to the long-term forest fertilization experiments that can last for decades. The pH of the ash decreases in time and decrease in pH could increase solubility of heavy metals. The average concentrations of many elements in water samples from lysimeters and ditch waters were at the same level than in soil waters in forest. Although during the monitoring period, there were no increases in heavy metal concentrations in ditch waters, the accumulation of elements to nearby aquatic ecosystems is difficult to assess in the long-term if leaching behavior changes with time. Ash seems to be a promising material for road construction, as long as the ash quality is suitable to this particular purpose.