Leaching of heavy metals and barium from forest roads reinforced with fly ash

The aim of this study was to determine the effect of leaching of heavy metals (Cr, As, Cd, Cu, Ni, Pb, Zn, Co, Mo) and earth-alkaline metal, barium (Ba), on the percolation and ditch water quality from the forest roads that contained ash in the road structures. Water quality was studied in the immediate vicinity below the ash layers as well as deeper in the road structure. Water quality was also determined in the drainage water in ditches that crossed the forest roads. A mixture of wood and peat based fly ash was used in the road structures. The treatments were: 1) no ash, 2) a 15 cm layer of ash/gravel mixture, 3) a 20 cm layer of ash/ gravel mixture, 4) a 25 cm layer of ash, and 5) a 50 cm layer of ash. Large variation in the concentrations of Cr, As, Cu, Ni, Pb, Mo and Ba in the percolation water, even within the same treatment, caused difficulties to generalize the results. The concentrations of Cr, As, Ni, Pb, Mo and Ba in water samples were high in some treatment plot lysimeters containing ash compared to the control (no ash). On the other hand, many lysimeters had low and similar concentrations in water samples in the treatment plots containing ash compared to concentrations in the control plots. The ash in the roads did not affect the concentrations in the ditches. The leaching is uneven and seems to take place only from some parts of the ash layer. Risk for leaching is minimal if such parts are not widely spread.Peer reviewe

Sprinkling infiltration as an artificial groundwater recharge method - Long-term effects on boreal forest soil, tree growth and understory vegetation

The artificial recharge of groundwater by infiltrating surface water through forest soil has been introduced as a groundwater producing practice in Finland. As a result, the forest soil, as well as the whole ecosystem, is subjected to extremely high inputs of carbon and nutrient rich lake water. The effects of sprinkling infiltration on forest soil, tree growth and understory vegetation and their respective recovery were studied on a forested esker in central Finland. The Scots pine-dominated experimental plots were sprinkled with lake water in 1998-2001 and sampled after a 12-15-year recovery period. Soil pH and base cation concentration, as well as the rate of net N mineralization were significantly higher at the plots that had been infiltrated. The concentrations of base cations calcium and magnesium were thousands of times higher in the infiltrated soil than in the untreated soil. In addition, sprinkling infiltration had favored early-successional herbs, grasses and forbs and negatively affected late successional, slow-growing mosses and lichens. Sprinkling infiltration had significantly increased tree radial growth. Sprinkling infiltration is an environment altering soil treatment method which, based on the findings of this study, can have long-term effects on tree growth, soil processes and understory vegetation.Peer reviewe

Fine root classification matters : nutrient levels in different functional categories, orders and diameters of roots in boreal Pinus sylvestris across a latitudinal gradient

Background: Fine roots and their symbionts are the key drivers of processes such as nutrient cycling and belowground productivity. Their function depends on position in a branching hierarchy, with absorptive roots (responsible for resource acquisition), and transport roots. Aim: We examined how the different diameter cutoffs for root classification mirror concentrations of 11 different nutrients, plus Al in functionally different fine roots of Pinus sylvestris based on anatomical/ functional categorization and in relation to their biomass along a latitudinal gradient. Results: The C:N:P ratios for pooled roots ≤2 mm in diameter reflected the nutrient concentrations of transport roots. In contrast, the C:N:P ratios for all absorptive roots was best reflected by nutrient ratios in the 1st root order, and not by those in root <2 mm. These patterns were more clear along decreasing mean annual temperature, despite increasing contribution of absorptive roots in the fine root biomass. Higher biomass fraction of transport roots did not always mirror higher concentration of element accumulated. Narrowing the root diameter cutoffs to 0.5 mm provided more informative data about nutrient concentrations in the absorptive root pool than <2 mm cut-off. Conclusions: By analyzing nutrient concentration using ≤2 mm cut-off it is impossible to properly understand nutritional properties of roots with different functional attributes. Given that the diameter of fine root orders vary considerably even within a single species between stands, the diameter cutoffs for absorptive roots should be based on the characteristics of the studied species, and not on a fixed, universal diameter cutoff