Highly educated but occupationally differentiated: the members of Finland’s Green League

The socio-demographic profiles and occupations of the members of the Green League and other Finnish political parties are examined using survey data collected from the members of Finland’s six major political parties (n = 12,427). Significant differentiation in occupational structure is revealed among Green party members. The importance of understanding how Green party members differ by background is emphasised while providing new approaches to studying party members’ interests and goals.     

Removal of bis (2-ethylhexyl) phthalate from reject water in a nitrogen-removing sequencing batch reactor

Reject water from sewage sludge processing may contain high concentrations of nutrients and organic pollutants and cause internal pollution load at a sewage treatment plant (STP) if circulated to the headworks of an STP. In the present study removal of nitrogen and bis (2-ethylhexyl) phthalate (DEHP) from reject water was studied in two sequencing batch reactors (SBRs) with different aerobic/anoxic periods during a 6-h total cycle period. Ammonia-nitrogen (NH(4)-N) was almost totally removed in both reactors, apparently by nitrification throughout the run, while denitrification declined with decreasing SCOD in the influent resulting in an increase in the effluent nitrate-nitrogen (NO(3)-N) concentration. DEHP removals from the water phases were above 95% in both reactors, while the average total removals were 36 and 42%, calculated on a mass basis. Much higher removals occurred in the experiment where one of the systems was spiked with a given amount of DEHP. The spiking experiment suggested that SBRs had the potential to remove DEHP biologically from reject water but that the removal was restricted by the poor bioavailability of DEHP as a result of sorption to solids. This study showed that SBR has the potential to cut the internal load of nitrogen and hydrophobic organic pollutants in cases where reject water is circulated to the headworks of an STP.     

Biodegradation of chemicals in a standardized test and in environmental conditions

The estimation of biodegradation rates is an important source of uncertainty in chemical risk assessment. The existing OECD tests for ready biodegradability have been developed to devise screening methods to determine whether a chemical is potentially easily biodegradable, rather than to predict the actual rate, of biodegradation in the environment. However, risk assessment needs degradation rates. In practice these rates are often estimated (default values) from ready biodegradability tests. These tests have many compromising arbitrary features compared to the situation in the real environment. One important difference is the concentration of the chemical. In wastewater treatment or in the environment many chemicals are present at ng l(-1) to microg l(-1) levels whereas in the tests the concentrations exceed 10-400 mg carbon per litre. These different concentrations of the chemical will lead to different growth kinetics and hence different biodegradation rates. At high concentrations the chemical, if it is degradable, can serve as a primary substrate and competent microorganisms will grow exponentially, resulting in a sigmoid biodegradation curve. At low environmental concentrations the chemical does not serve as a primary substrate, and therefore does not support significant growth of the degraders, and the substrate has a linear biodegradation rate. In this study the biodegradation rates of two reference chemicals, aniline and 4-chloroaniline, were compared in a standard method and in more realistic conditions at low concentrations, using 14C-labelled substances and different sources of inocula. Biomass evolution during the tests was monitored by adenosine triphosphate measurement and also on the basis of the residual 14C-activity in the particulate matter. The results partly support the thesis that low concentrations lead to different biodegradation kinetics compared to the concentrations used in the standard tests. Furthermore the biodegradation rates of the chemicals studied, particularly of 4-chloroaniline, in Finnish natural waters appeared to be lower than those reported in some other countries.     

Removal of DEHP in composting and aeration of sewage sludge

The potential of composting and aeration to remove bis(2-ethylhexyl) phthalate (DEHP) from municipal sewage sludge was studied with two dewatered sludges: raw sludge and anaerobically digested sludge. Composting removed 58% of the DEHP content of the raw sludge and 34% of that of the anaerobically digested sludge during 85 days stabilisation in compost bins. A similar removal for the anaerobically digested sludge was achieved in a rotary drum in 28 days. Less than 1% of DEHP was removed with the compost leachate. Although DEHP removal was greater from raw sludge compost than anaerobically digested sludge compost, the total and volatile solids removals were on the same level in the two composts. In the aeration of raw sludge at 20 degrees C the DEHP removals were 33-41% and 50-62% in 7 and 28 days, respectively. Both composting and aeration are concluded to have the potential to reduce the DEHP contents typically found in sewage sludges to levels acceptable for agricultural use.     

Anaerobic digestion of autoclaved and untreated food waste

Anaerobic digestion of autoclaved (160 °C, 6.2 bar) and untreated source segregated food waste (FW) was compared over 473 days in semi-continuously fed mesophilic reactors with trace elements supplementation, at organic loading rates (OLRs) of 2, 3, 4 and 6 kg volatile solids (VS)/m³ d. Methane yields at all OLR were 5–10% higher for untreated FW (maximum 0.483 ± 0.013 m³ CH₄/kg VS at 3 kg VS/m³ d) than autoclaved FW (maximum 0.439 ± 0.020 m³ CH₄/kg VS at 4 kg VS/m³ d). The residual methane potential of both digestates at all OLRs was less than 0.110 m³ CH₄/kg VS, indicating efficient methanation in all cases. Use of acclimated inoculum allowed very rapid increases in OLR. Reactors fed on autoclaved FW showed lower ammonium and hydrogen sulphide concentrations, probably due to reduced protein hydrolysis as a result of formation of Maillard compounds. In the current study this reduced biodegradability appears to outweigh any benefit due to thermal hydrolysis of ligno-cellulosic components.     

Transfer of elements relevant to radioactive waste from soil to five boreal plant species

In long-term safety assessment models for radioactive waste disposal, uptake of radionuclides by plants is an important process with possible adverse effects in ecosystems. Cobalt-60, ^59,63Ni, ⁹³Mo, and ²¹⁰Pb are examples of long-living radionuclides present in nuclear waste. The soil-to-plant transfer of stable cobalt, nickel, molybdenum and lead and their distribution across plant parts were investigated in blueberry (Vaccinium myrtillus), May lily (Maianthemum bifolium), narrow buckler fern (Dryopteris carthusiana), rowan (Sorbus aucuparia) and Norway spruce (Picea abies) at two boreal forest sites in Eastern Finland. The concentrations of all of the studied elements were higher in roots than in above-ground plant parts showing that different concentration ratios (CR values) are needed for modelling the transfer to roots and stems/leaves. Some significant differences in CR values were found in comparisons of different plant species and of the same species grown at different sites. However, large within-species variation suggests that it is not justified to use different CR values for modelling soil-to-plant transfer of these elements in the different boreal forest plant species.     

Theoretical comparison of how soil processes affect uptake of metals by diffusive gradients in thinfilms and plants

The theoretical basis for using measurements of metal uptake by the technique of diffusive gradients in thinfilms (DGT) to mimic processes in soils that affect uptake of metals by plants is examined. The uptake of metals by plants and DGT were compared conceptually and quantitatively by using the classic Barber model of plant uptake and the DIFS (DGT-induced fluxes in soils) model of uptake by DGT. For most metals and plants considered, uptake fluxes were similar to those induced by DGT using the most common gel layer thicknesses of 0.2 to 2 mm. Consequently DGT perturbs the chemical equilibrium of metals in the soil solution and between soil solution and solid phase, to a similar extent to plants, and therefore induces a similar balance in supply by diffusion and by release from the solid phase. DIFS was used to show that desorption kinetics, which are not considered by the plant uptake model, are likely important for uptake when the capacity of the soil solid phase is large. Model calculations showed that mass flow into a plant root would only contribute appreciably to the total flux of metal under circumstances when the solid phase reservoir of metal was very low. Generally, however, DGT is likely to emulate supply processes from the soil that govern uptake of metal by plants. Exceptions are likely to be found in poorly buffered soils (typically sandy and/or low pH), and at very high concentrations of metals in soil solution, such that the soil solution concentration at the plant root interface is higher than the Michaelis-Menten constant (Km).     

Meiofauna ratios as environmental indicators in the profundal depths of large lakes

Two sets of samples from Lake Päijänne and one from Lake Ladoga were used to examine the relations between the meiofauna and environmental variables. The most obvious indicators of an unpolluted environment were, in order of importance, the true meiofauna/total meiofauna ratio, the proportion of Aeolosomatidae, the proportion of Harpacticoida (excluding C. staphylinus), the meiofauna/macrofauna biomass ratio, the proportion of Naididae and the A. crassa + P. schmeili/true meiofauna ratio. Conversely, the clearest indicators of a polluted environment were the proportion of resting stages of Cyclopinae, the Nematoda/non-resting Copepoda ratio, and the proportions of Tubificidae, Oligochaeta, Cladocera, C. staphylinus and benthic Eucyclopinae. Oxygen saturation exercised a highly significant effect on the meiofauna variables, and the next in order of importance were sedimentation, sediment chlorophenols originating from the chlorobleaching of pulp, total phosphorus, COD and phytoplankton biomass. The dependence of the meiofauna on environmental variables was somewhat more pronounced in the deepest areas of Lake Päijänne than in the epiprofundal zone, and largely similar in the two lakes.     

Detailed internal characterisation of two Finnish landfills by waste sampling

The aim of this study was to characterise the internal structure and composition of landfilled waste at two Finnish landfills to provide information for active and post-landfill operations. The two sites, Ämmässuo and Kujala, have been in operation for 17 and 48 years, respectively. Waste was sampled (total 68 samples) and analysed for total solids (TS), volatile solids (VS), total Kjeldahl nitrogen (TKN), biological methane potential (BMP) and leaching of organic material (determined as chemical oxygen demand, COD) and ammonium nitrogen (NH₄–N). The results showed high vertical and horizontal variability, which indicated that both the waste composition and state of degradation varied greatly in both landfills. Ämmässuo was characterised by 2- to 4-fold higher BMP, NH₄–N and COD leaching than Kujala. Moreover, the ratio of VS to TS was higher at Ämmässuo, while TS content was lower. The highest mean BMPs (68 and 44 m³/t TS), TKN content (4.6 and 5.2 kg/t dry weight) and VS/TS ratio (65% and 59%) were observed in the middle and top layers; and the lowest mean BMP (21 and 8 m³/t TS), TKN content (2.4 kg/t dry weight, in both landfills) and VS/TS ratio (55% and 16% in Ämmässuo and Kujala, respectively) in the bottom layers. In conclusion, waste sampling is a feasible way of characterising the landfill body, despite the high variation observed and the fact that the minimum number and size of samples cannot easily be generalized to other landfills due to different methods of waste management and different landfilling histories.