Kauko Kujala

Sorption of Pb(II), Cr(III), Cu(II), As(III) to peat, and utilization of the sorption properties in industrial waste landfill hydraulic barrier layers.

The low conductivity landfill barrier layers protect the groundwater and soil by limiting the water flow through the bottom layers of the landfill material. Many materials used in hydraulic barrier layers also have sorption properties which could be used to reduce environmental risks. The adsorption of lead, chromium, copper, and arsenic to peat was studied with a batch-type test and a column test for compacted peat, both without pH adjustment in acidic conditions. Peat adsorbed all the metals well, 40000mg/kg of lead, 13000mg/kg of chromium, and 8400mg/kg of copper in the column test. Arsenic was only tested in a batch-type test, and in that peat adsorbed 60mg/kg of arsenic. The column test showed heavy metals to be adsorbed on the surface layers of the compacted peat sample, on the first centimeter of the sample. The adsorption was much greater in the column test than in the batch-type test, partly due to the different pH conditions and the buffer capacity of the peat in the column test. The liquid/solid ratio of the column experiment represented a time period of approximately 40 years in a landfill, under Finnish climate conditions. The hydraulic conductivity of the peat decreased as it was compressed, but it already met the hydraulic conductivity limits set by European Union legislation for the hydraulic barrier layer (1x10(-9)m/s at a pressure of 150kPa for a 5-m layer), with a pressure of 50kPa. The results show that peat would be an excellent material to construct compacted, low hydraulic conductivity layers with adsorption properties in, e.g. industrial waste landfills.

Chemical and leaching properties of paper mill sludge

Abstract Paper mills produce large amounts of paper mill sludge in the treatment of process water. According to overburden studies, the hydraulic conductivity of the paper mill sludge originating from a paper mill in Northern Finland at a pressure of 30kPa was 4.4×10∓10 ms∓1, and 1.7×10∓ 10 ms∓1at a pressure of 100kPa. These values well meet the generally required values of between 1.0×10∓7 ms∓1 and 1.0×10∓9 ms-1 for a geological barrier in landfill base and sides at landfills in the European Union. Paper mill sludge can also be used in the artificially constructed geological barrier layer of landfill cover structures. The angle of internal friction of the paper mill sludge was 34.8° and the cohesion of inter-particle adhesion 23 kPa, which are important measures for assessing the shear strength of paper mill sludge and thus the stability of the landfill layer in which it is used. During a 28-day period, the biodegradability of the paper mill sludge in soil was ca 0.4% and in ground water under 1%, whereas according to the OECD 301F standard concentrations (BOD28), it was ca 8%. For the determination of total element concentrations in the paper mill sludge, the dried sample was digested using USEPA method 3052. A five-stage sequential leaching procedure was also used to fractionate trace elements in the paper mill sludge between the water-soluble (H2O), exchangeable (CH3COOH), easily reduced (HONH3CD, oxidizable (H2O2 + CH3COONH4), and (5) the residual (HF + HNO3 + HCl) fractions. This paper covers also examples of case studies how paper mill sludge is utilized in Finland.

Seasonal changes in soil temperature and snow-cover under different simulated winter conditions: Comparison with frost hardiness of Scots pine (Pinus sylvestris) roots

Abstract Seasonal changes in soil temperature and in the frost hardiness of the roots of adult Scots pine (Pinus sylvestris L.) trees were studied between August 1992 and May 1993 in a pine forest growing on dry heathland soil. The study area is located in Finnish Lapland (67°N, 29°E). Air (2 m above ground) and soil (5 cm depth of mineral soil) temperatures were measured continuously every second hour. The frost hardiness of the roots in the soil (down to 10 cm) was measured by means of the electrolyte-leakage method. The air temperature remained consistently below 0°C after the first week of October. The coldest month was February with a daily average temperature of −10.3°C. Snow accumulation started in the first week of October and reached a depth of 129 cm in April. The temperature in the mineral soil varied between +15.4°C and 0.8°C. The frost-hardiness of the pine roots was at its lowest in September (−6°C), and at its highest in December (−21°C). Soil temperature and precipitation as snow in different winter conditions were simulated using the SOIL model. The simulations show that the insulating effect of the snow cover is crucial for the frost survival of Scots pine roots even during a moderate winter.

The Use of a Five-stage Sequential Leaching Procedure for Risk Assessment of Heavy Metals in Waste Rock Utilized in Railway Ballast

A five-stage sequential leaching procedure was used to determine the distribution of 10 metals in three combination samples taken from waste rock material, originating from a Finnish zinc mine, and used as railway ballast in Northern Finland. The leaching procedure consists of the following five sequential fractions: a water-soluble fraction (H2O), an exchangeable fraction (CH3COOH), an easily reduced fraction (NH2OH-HCl), an oxidizable fraction (H2O2 + CH3COONH4), and a residual fraction (HF + HNO3 + HCl). The results show, in accordance with all earlier corresponding studies, that a sequential extraction procedure is very suitable for evaluating the effects of external conditions on the solubility of harmful heavy metals, and that external conditions have a large effect on their leachability/solubility, and therefore on their mobility, bioavailability, and environmental risk. In addition, the total concentration of each element is much larger than its solubility in each of the first four fractions (1)–(4) – the potential bioavailability fractions – because the highest concentrations of all metals occurred in the residual fraction (5). The conditions of this phase – three strong acids and strong, long-lasting shaking – are never possible in nature, and therefore the residual fraction is called the inert phase. Thus, the total concentrations of the heavy metals are poor measures of real environmental risk and give no information about the effect of external conditions on their solubility. In addition, the dependency of different elements on the external conditions differs.

The role of buoyancy in palsa formation

Abstract The formation of a palsa is based on the thermal properties of peat. Frozen wet peat has a high thermal conductivity, and therefore cold can penetrate deep into peat layers if the snow cover is thin; while the dry peat in summer insulates the frozen core of a palsa, so that the permafrost core is preserved. The volumetric growth of the palsa is based on the buoyancy effect of the frozen core, which lifts it, causing some water to accumulate under the core, where it freezes during the next winter and forms thin ice layers. Only when the frozen peat core touches the frost-susceptible silt or silty till layer at the bottom of the mire does ice segregation start to play an important role in the formation of the palsa.

The use of a four-stage sequential leaching procedure and the corresponding one-phase extractions for risk assessment of potential harmful substances in waste rock utilized in railway ballast

The purpose of environmental legislation in the EU is prevention, minimization, and utilization of waste, respectively. When utilization is not possible, the purpose becomes the safe landfill disposal of waste, or disposal by other ecologically beneficial methods. In addition, material efficiency is an essential topic nowadays to promote the sustainable use of natural resources, waste materials, and industrial by-products, in agreement with the principle of sustainable development and LCA. To promote these goals, a four-stage sequential leaching procedure and determination of total concentrations was used in this research to determine the distribution of Cu, Pb, Zn, and V samples taken from waste rock material, originating from a Finnish zinc mine, and used as railway ballast in Northern Finland. The leaching procedure consists of the following five sequential fractions: (i) an acidic water-soluble fraction (H2O, pH = 4), (ii) an exchangeable fraction (CH3COOH), (iii) an easily reduced fraction (NH2OH-HCl), and (iv) oxidizable fraction (H2O2 + CH3COONH4). The results show that conditions and the size of ballast have a significant effect on the solubility of all heavy metals, and therefore on their mobility, bioavailability, and environmental risk. In addition, the total concentration of every element is much larger than its solubility in each four fractions (i)–(iv) or the sum of these concentrations – this sum can be called by the potential bioavailability – because the highest concentration is in the residual fraction. The leachability results determined here for waste rocks utilized as railway ballast show in good agreement with all earlier investigations determined for other waste or industrial by-products. Sequential leaching studies provide valuable information about the effect of conditions on the leachability/solubility, mobility, and bioavailability for risk assessment of harmful heavy metals. This information is necessary if we want to know the real environmental risk of metals in different conditions, possible in natural conditions now and in the future, i.e. not only in terms of the conditions pertaining to permission applications.

Effect of biomass fly ashes as road stabilisation binder

The purpose of the research was to study the usability of two biomass fly ashes as road stabilisation binders. Partial least square structural equation modelling was used as an analytical method. The analysis was based on chemical composition data on SiO2, Fe2O3, Al2O3 and CaO in binder component, compressive strength results (7d and 28d), water to binder ratio, biomass fly ash content in binder, density of the stabilised material and binder to soil ratio as reflective indicators. According to the study, the higher relative biomass fly ash content had a positive relationship with total binder characteristics but indicated reduced strength properties in the stabilised materials. Also SiO2, Fe2O3, Al2O3 and CaO in binder component and binder to soil ratio had a positive effect on strength properties. However, the effect of biomass fly ash content on water demand, and the relationship between water content and strength were not statistically significant in the model.

Adsorption of Ni(II) and Cd(II) in Compacted Peat and the Utilization of the Adsorption Properties in Hydraulic-Barrier Layers in Tailing Impoundments

AbstractLandfills and tailing impoundments contain barrier layers that prevent the migration of contaminants into groundwater by slowing down the water flow through the structures. Many materials used in hydraulic barrier layers also have sorption properties, which could be utilized to reduce environmental risks. The adsorption of Ni(II) and Cd(II) on peat was studied using a single metal column test. Two samples with different dry unit weights, low-density (LD) and high-density (HD) peat, were tested. A batch test was made for comparison. Both samples in the column test adsorbed the metals well; peat adsorbed 9,500  mg/kg of nickel and 11,200  mg/kg of cadmium. The adsorption was twice as high in the column test as in the batch test. Cadmium adsorbed strongly on the top layers of the sample, whereas the adsorption profile of nickel was more even through the sample. The density of the peat did not affect the maximum adsorption capacity. In HD peat, the heavy metals adsorbed more on the top layers of the s...