A pilot scale experimental hybrid constructed wetland (CW) was established in 2005 for the treatm... more A pilot scale experimental hybrid constructed wetland (CW) was established in 2005 for the treatment of mixed effluents from municipal sources and food processing plants in a small village in southern Estonia. The aim was to find optimal operating regimes (varying hydraulic loading rates, loading intervals, recirculation regimes and regimes of hydraulic retention time) for the use of analogous CWs in cold climates. The hybrid wetland system consists of two parallel systems designed on the same principle: a vertical subsurface flow (VSSF) filter followed by a horizontal subsurface flow (HSSF) filter. The VSSF filter of one system (the left filter) is filled with crushed limestone, while the other (right) is filled with light weight aggregates (LWA). Both HSSF filters are filled with LWA. From December 2005 until December 2006, water samples from the outlet of the septic tank and the outlet of both VSSF and HSSF filters were taken once a week. In both systems, a combination of decreasing hydraulic load (from 52 to 14 mm d-1) and increasing recirculation rate (from 34 to 300%) caused a significant increase in the purification efficiency of BOD7 (from 58 to 99%), N tot (from 11 to 82%), and NH4-N (from-16 to 83%). In both systems, the removal efficiency of P tot did not show any significant correlation with hydraulic load, whereas in the right (LWA) system, the increasing recirculation rate significantly increased P tot removal. The dynamics of the COD value was analogous to that of the BOD7 value, but no significant differences were found between the removal efficiency of total suspended solids (TSS) of different flow regimes. Likewise, water temperature did not show a significant correlation between the purification efficiency of all of the studied water quality indicators. For the successful functioning of hybrid CWs in a cold climate, optimal hydraulic load should be ≤20 mm d-1 with a recirculation rate of 150-300%.
WIT Transactions on Ecology and the Environment, Vol 99, 2006
Coastal zones, which have a very high biodiversity value and a long history of being impacted by ... more Coastal zones, which have a very high biodiversity value and a long history of being impacted by human activities, are among the most vulnerable ecosystems on our planet. Moreover, some scenarios predict that within 50 years more than 75% of the global human population will live in coastal zones. Although Europe's coasts are among the most altered, there are significant regional differences within Europe in terms of naturalness and human pressure. During the integrated SENSOR project of the European Union's (EU) 6 th Framework Programme, we have analyzed the sensitivity of the EU's coastal zones using data on 191 coastal cells at The Nomenclature of Territorial Units for Statistics (NUTS) level, based on information from the Statistical Office of the European Community (EUROSTAT) and other Europe-level sources. To determine sensitive coastal areas, multidimensional clustering was provided. The NUTSx level (a combination of NUTS2 and NUTS3 level cells in order to achieve better spatial coverage) clustering resulted in seven clusters which were not, however, well distinguished in terms of the SENSOR sensitivity areas concept. Therefore clustering on the NUTS2 level was provided using 15 parameters characterizing economic, social and environmental aspects, yielding six clusters that were logically distinguishable from each other. The cluster characterized by a rapidly growing economy combined with relatively high but decreasing unemployment, low but increasing income, a low rate of investment in research and development (R&D), a low share of arable land but a high rural population, moderate length of coastline with the highest share of coast exposed to coastal erosion and a highly variable level of environmental protection, including 23 coastal NUTS2 areas plus five islands, has to be considered sensitive and needs further attention from the European Commission.
Two riparian buffers including wet meadows (Filipendula ulmaria-Aegopodium podagraria-Cirsium ole... more Two riparian buffers including wet meadows (Filipendula ulmaria-Aegopodium podagraria-Cirsium oleraceum-Urtica dioica) and grey alder (Ainus incana) stands were investigated. The main inputs and outputs (atmospheric deposition, input and output in surface and subsurface flow, nitrogen fixation and denitrification), and accumulation of N and P in plant biomass, litter and soil were estimated. A 31 m wide complex buffer zone of wet meadow and grey alder forest removed 67% nitrogen and 81% phosphorus, while in a 51 m buffer zone, also containing a grassland strip in addition to wet meadow and alder forest, 96% N and 97% P was retained. In the riparian buffers studied, an effective retention of nutrients (34-186 kg N ha^ yr~* and 1.6-6.0 kg P ha~* yr~') was observed even with very high input loads (276.3 and 12.8 kg ha~* yr^ of N and P, respectively). A twodimensional simulation model RipFor was developed in the STELLA environment to analyse nutrient flows in the complex riparian bu...
This work presents N and P budgets of a horizontal subsurface flow (HSSF) constructed wetland (CW... more This work presents N and P budgets of a horizontal subsurface flow (HSSF) constructed wetland (CW; 2 chambers, 25x6.25x0.8 m each, sealed with polyethylene liner, filled with coarse sand, one planted with Typha latifolia but dominated now by Scirpus sylvestris, and the other planted with Iris pseudacorus and Phragmites australis but covered at present by P. australis, receiving a septic tank effluent of 40-60 population equivalents (pe)) constructed in 1996 for treatment of wastewater from a hospital in Kodijwe, Tartu County, Estonia. Monitoring of water quantity (inflow to the system and outflow from different parts) and quality (BOD7, total-N, NH4-N, NO2-N, NO3-N, total-P, PO,-P, SO4, total-Fe, Ca, pH and suspended solids) took place once every two weeks, there was yearly investigation of bacterial biomass and the plant above-ground and below-ground biomass and N, P and C content in both plants and filter material at 3 depths, as well as quarterly measurement of gaseous N20 and NZ fluxes (using both the closed chamber and the He-0 method) were used as methods in this study. The most important flux in the N budget in 2001 was in the area of NZ emissions (12.4 kg a-' or 41.7%), followed by microbial immobilization (8.7 kg a-'), accumulation in the soil (4.2 kg a-'), plant assimilation (4.1 kg a-'), and N20 emission (0.35 kg a-'). The phosphorus budget was charted for the period 1997-2001. Major pools of P are: accumulation in soil as lactate-soluble P via adsorption (46.5 kg; 88.1%), plant accumulation (3.2 kg), microbial
In this study we quantified carbon balance by analyzing eddy-covariance CO2 flux data (carbon exc... more In this study we quantified carbon balance by analyzing eddy-covariance CO2 flux data (carbon exchange) vs chamber-based measurements (ecosystem respiration) and CO2assimilation (soil and biomass). The annual NEE in this mature coniferous forest was -2.3 t C ha yr−1, showing a clear diurnal and seasonal trend. During the daytime in summer the forest sequestered CO2, while during the night and late night CO2 emitted from the ecosystem to the atmosphere. Within the growing period, the sequestration of CO2 by plants was greater than soil respiration. Thus, the ecosystem sequestered carbon. Most of the carbon is bound in tree biomass (above and below ground biomass) but as well into soil, while the sequestration in soil increases with stand age. In addition, the biomass of understory, especially belowground litter, is playing essential part in carbon input.
The aim of this study is to estimate wintertime emissions of greenhouse gases CO2, N2O and CH4 in... more The aim of this study is to estimate wintertime emissions of greenhouse gases CO2, N2O and CH4 in two abandoned peat extraction areas (APEA), Ess-soo and Laiuse, and in two Oxalis site-type drained peatland forests (DPF) on nitrogen-rich sapric histosol, a Norway spruce and a Downy birch forest, located in eastern Estonia. According to the long-term study using a closed chamber method, the APEAs emitted less CO2 and N2O, and more CH4 than the DPFs. Across the study sites, CO2 flux correlated positively with soil, ground and air temperatures. Continuous snow depth > 5 cm did not influence CO2, but at no snow or a thin snow layer the fluxes varied on a large scale (from −1.1 to 106 mg C m−2 h−1). In all sites, the highest N2O fluxes were observed at a water table depth of −30 to −40 cm. CH4 was consumed in the DPFs and was always emitted from the APEAs, whereas the highest flux appeared at a water table >20 cm above the surface. Considering the global warming potential (GWP) of ...
The green infrastructure (GI) is a network of natural and semi-natural areas with environmental f... more The green infrastructure (GI) is a network of natural and semi-natural areas with environmental features that is designed and managed to deliver a wide range of ecosystem services. The concept has roots in the former hierarchical system of ecological networks. There are several examples of GIs, but details of their implementation at a landscape level are often missing or they have been used non-systematically. Here, we demonstrate opportunities for landscape-level implementation of GIs based on spatial analysis through the application of ecological engineering or other measures. Using maps and expert evaluations of different land-use types, we created a methodology for national-scale determination of Estonia's GI. Based on spatially explicit datasets (e.g., land cover, soils, topography, roads), we determined the proportions of greenness and brownness (primarily anthropogenic) landscape indices. Areas with the highest greenness values served as the GI's core areas, whereas areas with the greatest anthropogenic composition represented the brown infrastructure. Identification and classification of hotspots where the two infrastructures are in conflict (e.g., construction, mining areas, roads, settlements, airports, power lines, wind turbines) revealed locations where ecological engineering and other measures are needed to mitigate or eliminate the conflict. Developing spatially explicit models of the conflicts between the infrastructures represents a new approach in landscape planning and environmental management that links coarse-scale landscape planning and regional landscape plans with more detailed local landscape plans that support the design of site-specific ecological engineering and other measures. We demonstrate that the implementation of GIs is inseparably connected with ecological engineering and landscape-scale planning.
The study of purification efficiency and nutrient assimilation in plants was made in two riparian... more The study of purification efficiency and nutrient assimilation in plants was made in two riparian buffer zones with a complex of wet meadow and grey alder (Alnus incana) stand. In the less polluted Porijõgi test site, the 31 m wide buffer zone removed 40% of total nitrogen (total-N) and 78% of total phosphorus (total-P), while a heavily polluted 51 m wide buffer zone in Viiratsi retained 85% of total-N and 84% of total-P. The input of nutrients and purification efficiency displayed a significant relationship. The total-N removal in buffer zone was negative when the input value was less than 0.3 mg l-1 and the purification efficiency was always positive when the input value exceeded 5 mg l-1. The purification efficiency of total-P was positive when the input value exceeded 0.15 mg l-1. Grass vegetation plays an important role in nutrient retention in riparian buffer strips. The maximum phytomass production was measured in Porijõgi site where production of the Filipendula ulmaria comm...
N2O, N2 and CH4 fluxes were measured from a horizontal subsurface flow (HSSF) constructed wetland... more N2O, N2 and CH4 fluxes were measured from a horizontal subsurface flow (HSSF) constructed wetland (CW) for wastewater treatment in Estonia. The closed chamber method was used in the field and the He-O method (intact soil core analyses) in the lab throughout the period from October 2001 to June 2002. The average flux of N2O-N, N2-N and CH4-C from various microsites ranged from 0.1 to 59, 4.1 to 1,458 and -0.04 to 2,094 mg m-2 d-1, respectively. A significantly higher flux of N2O was found in chambers installed above the inlet pipes, while the methane flux was higher in the inlet part of the bed with wetter conditions. The groundwater table significantly correlates with gas emission rates of all the gases studied; N2 emission was enhanced by higher temperature of wastewater. PO43- and NH4+ content significantly enhanced, and NO2- and NO3- content inhibited, both N2O and CH4 fluxes. NH4+ showed a negative correlation with N2 flux. Nitrification and denitrification are the main processe...
Nitrous oxide (NO) is a powerful greenhouse gas and the main driver of stratospheric ozone deplet... more Nitrous oxide (NO) is a powerful greenhouse gas and the main driver of stratospheric ozone depletion. Since soils are the largest source of NO, predicting soil response to changes in climate or land use is central to understanding and managing NO. Here we find that NO flux can be predicted by models incorporating soil nitrate concentration (NO), water content and temperature using a global field survey of NO emissions and potential driving factors across a wide range of organic soils. NO emissions increase with NO and follow a bell-shaped distribution with water content. Combining the two functions explains 72% of NO emission from all organic soils. Above 5 mg NO-N kg, either draining wet soils or irrigating well-drained soils increases NO emission by orders of magnitude. As soil temperature together with NO explains 69% of NO emission, tropical wetlands should be a priority for NO management.
Processes affecting CO 2 and CH 4 emissions and their budgets have been relatively well studied i... more Processes affecting CO 2 and CH 4 emissions and their budgets have been relatively well studied in northern temperate peatlands, whereas similar studies are almost absent in southern Patagonia and the high-altitude Andean peatlands, both of which are currently under heavy anthropogenic pressure. The objectives of this study were to compare greenhouse gas (GHG) emissions in natural and managed peatlands to examine the effect of management on GHG emissions and identify the environmental parameters affecting them. We analysed CO 2 , CH 4 and N 2 O emissions related to the physical and chemical conditions of the peat: in a natural and managed transitional bog in Quebec, Canada, a natural páramo and grazed peatland in the Colombian Andes, and a bog and a fen in Tierra del Fuego, Argentina. GHG fluxes were measured using the dark static chamber method. Groundwater table, temperature, O 2 content, pH and redox potential were measured from observation wells, soil temperature was measured at four depths, peat samples were analysed for pH, soil organic matter and dry matter content, P, K, Ca, Mg, NH 4-N, NO 3-N, total N and C. In all regions, human-impacted peatlands showed significantly higher CO 2-C, N 2 ON and CH 4-C emissions than their natural counterparts. The Canadian managed transitional bog showed the highest average CO 2-C (575 mg C m −2 h −1) and N 2 ON (0.08 mg N m −2 h −1) emissions, whereas the Colombian pasture was the largest emitter of CH 4-C (2.35 mg C m −2 h −1). CO 2-C emissions were controlled by soil temperature and C content, whereas CH 4-C flux was negatively correlated to dissolved oxygen content in peat water, and positively to water table level and soil log (C/NO 3-N) ratio. Total Inorganic Nitrogen (TIN), C/N ratio, and soil temperature were the main factors controlling N 2 O emissions. Intensive peatland management alters the soil C/N balance, and increases and leads to higher variability of GHG emissions. Agricultural activities, especially crop production in peatlands, as well as intensive grazing in mountain peatland pastures, are the main factors increasing GHG emissions in the peatlands studied. Mitigation is possible via regulation of grazing intensity and replacing arable fields with grasslands.
Riparian buffer zones are considered to be important elements of agricultural watersheds, in that... more Riparian buffer zones are considered to be important elements of agricultural watersheds, in that they control nutrient and carbon fluxes. Although the water purification effect of riparian ecosystems has been well studied, there is little knowledge of their internal cycling, especially in the area of gaseous emissions. We measured fluxes of nitrous oxide (N 2 O), dinitrogen (N 2), methane (CH 4), and carbon dioxide (CO 2) in riparian grey alder stands in southern Estonia and black alder stands in Brandenburg, Germany. Dinitrogen emission was the most important component in N retention in the studied riparian grey alder forests. In 2001-2003, the median values of N 2 emission in the grey alder sites significantly exceeded the N 2 emission rates in the black alder sites, varying from 700 to 1200 and from 360 to 400 kg N 2-N ha-1 year-1 , respectively. In contrast, the median values of N 2 O flux were higher in the black alder sites than in the grey alder sites, i.e., 0.9-2.6 and 0.2-0.7 kg N 2 ON ha-1 year-1 , respectively. The black alder sites acted as a sink for CH 4 , whereas the grey alder sites emitted a small amount of CH 4. The CO 2-C flux was higher in the black alder stands. The estimated N 2-N emission in the grey alder stands for 1994-1995 was 51.2, whereas N 2 ON emission was 0.5 kg N ha-1 year-1. The significant increase in N 2 emission from 1994-1995 to 2001-2003 can be related to changes in microbial activity during the succession of the pioneer grey alder stand into a more stable mixed forest community. Due to CO 2 fluxes and N 2 O fluxes from sites with altered water regime, the estimated GWP of the studied riparian alder stands was relatively high. Further investigations should concentrate on the factors that regulate rates of N 2 O and N 2 emission from riparian buffer zones.
The removal of organic matter and nitrogen in constructed wetlands (CW) is highly dependent on th... more The removal of organic matter and nitrogen in constructed wetlands (CW) is highly dependent on the availability of dissolved oxygen in the treatment system. Therefore it is of great importance to develop innovative methods to enhance oxygen supply in the CW matrix. This paper focuses on and describes the methods used to enhance oxygen supply in CWs. Also, a pilot scale experimental batch-operated lightweight aggregate (LWA) filter system (FS) consisting of eight identical LWA filter cells (with a depth of 1.15 m and an area of 1 m 2 each) was established during the summer of 2005 for the treatment of municipal wastewater. The main objective of this study was to evaluate the performance of the experimental batch-operated FS on the basis of performance indicators. During the experiments, the effect of different operational regimes on the purification efficiency of the filter system was also investigated. The highest purification efficiencies of 96% and 51% for BOD 7 and N tot , respectively, were achieved when the recirculation rate of 200% was applied at the hydraulic retention time of ~2 days. The highest organic matter removal rate of the experimental FS as K BHT =0.19 m d-1 is approximately two times higher than the removal rate of typical horizontal-flow CWs. However, the highest aeration capacity of 21.1 gO 2 m-2 d-1 is somewhat lower than the average aeration capacity of vertical-flow CWs, and substantially lower than the aeration capacity of a VF filter with re-circulation or tidal-flow systems. As the aeration capacity of the system partly depends on the oxygen demand of inflow wastewater, it is necessary to carry out studies of shorter hydraulic loading rates in order to optimize the performance of experimental batch-operated FSs.
The purpose of this study was to (i) analyse trends in the runoff of organic matter (by BODs) and... more The purpose of this study was to (i) analyse trends in the runoff of organic matter (by BODs) and nutrients from the medium-size (256 km 2) rural watershed of O hne River in southern Estonia, and (ii) model variations in nitrogen and phosphorous runoff. Chemical and hydrological monitoring data between 1980 and 2000 were used in this study. Due to a large and unprecedented decrease in agricultural production and land-use in the O hne River catchment losses of nutrients and organic matter have decreased significantly. For example arable land decreased from 27 % to 16 % during the period 1980-2000. The results from this study showed that the runoff of NH4-N, NOrN, P04-P and organic matter (after BODs), calculated by linear trend, decreased from 1.50 to 1.05, 2.89 to 2.08, 0. 111 to 0.053, and 7.73 to 5.29 kg ha-' yr-I , respectively. To analyse temporal changes of the studied trends, the whole research period was divided into two equal parts:
Due largely to unprecedented land-use changes in the Porijõgi River catchment (southern Estonia) ... more Due largely to unprecedented land-use changes in the Porijõgi River catchment (southern Estonia) losses of nutrients and organic matter have decreased significantly. During the period 1987–1997 abandoned lands increased from 1.7 to 10.5% and arable lands decreased from 41.8 to 23.9%. At the same time, the runoff of total-N, total-P, SO4 and organic matter (after BOD5) decreased from 25.9 to
The main objective of this paper is to present a national level attempt at designing the Pan-Euro... more The main objective of this paper is to present a national level attempt at designing the Pan-European Ecological Network (PEEN) that is based on Estonian data from a one square kilometre grid. We propose an ecological network design comprising of three principal layers: (1) general topographical features like coastlines, the water network, major roads, and place names for locating the depicted network, (2) habitatbased field of suitability for the ecological network, calculated from network values of landscape features using a predefined algorithm, (3) ecological network as an administrative decision. The second layer serves as a tool supporting decision making while the third layer consists of traditional components of an ecological network, like core areas, corridors, buffer zones, and nature development/restoration areas. The CORINE land cover map, which was adjusted and supplemented using the soil and landscape data, served as the base for PEEN habitat classification. All habitats, linear structures and designated areas were ranked according to their expert-assessed values (from 0 to 10) based on their naturalness, rarity, and potential influence on biodiversity and landscapes. These values served as a basis for calculating the suitability (ranging from-3.65 to +3.75 in our study area) of each square kilometre for the ecological network. Ranking the suitability allows one to distinguish between the core areas, buffer zones and nature development areas. Suitability values were calculated including the influence of designated areas and without it. The natural suitability was calculated without the designated areas. The most common suitability for the ecological network in Estonia was found to be between 1.0 and 1.5. As a rule, the ecological network suitability of protected areas is higher than that of non-protected areas. The mean natural suitability value of square kilometres which contain more than 80% protected territory is 1.34, and the mean natural suitability of those square kilometres which do not include protected areas, is 0.819. The relative amount of protected areas per square kilometre decreases if the natural suitability for the ecological network decreases. Nearly a half (47.4%) of ecologically highly valuable areas in Estonia are under nature protection. On the other hand, it means that more than a half are not protected. We found a great similarity between the suitability map for the ecological network (both with and without including the designated areas) and the expert-made map of the ecological (green) network presented in the work on "Vision for Estonia 2010".
Sustainability Impact Assessment of Land Use Changes
Cross-cutting environmental, social and economic changes may have harsh impacts on sensitive regi... more Cross-cutting environmental, social and economic changes may have harsh impacts on sensitive regions. To address sustainability issues by governmental policy measures properly, the geographical delineation of sensitive 472 Oliver Dilly et al. regions is essential. With reference to the European impact assessment guidelines from 2005, sensitive regions were identified by using environmental, social and economic data and by applying cluster analysis, United Nation Environmental Policy priorities and expert knowledge. On a regionalised 'Nomenclature of Territorial Units for Statistics' (NUTS) level and for pre-defined sensitive region types (post-industrial zones, mountains, coasts and islands) 31 % of the European area was identified as sensitive. However, the delineation mainly referred to social and economic issues since the regional data bases on environmental indicators are limited and do not allow the separation of medium-term vital classes of sensitive regions. Overall, the sensitive regions showed indicator values differing from the EU-25 average.
Transects were established on two hillslopes and two study nitrogen budgets in two complex ripari... more Transects were established on two hillslopes and two study nitrogen budgets in two complex riparian buffer zones receiving different nitrogen loading. In the heavily loaded site the average total-N content decreased from 23 mg 1� 1 to 3.1 mg 1� 1 in a 40-years-old riparian grey alder forest (80 % removal). At the site with low loading the average removal of total-N was 48 %. In both transects the budget of N fluxes was established. In the older forest it was estimated as high as 321.1 kg ha� 1 yr� l , being 285.3 kg ha� 1 yr� 1 in the younger one. Considering all inputs and outputs, the N removal efficiency in grey alder stands slows down with increase of age. In the same time, immobilization in soil is increasing. This suggests that grey alder buffer communities should be managed by regeneration cutting and tending to keep their nitrogen removal rate high.
In 2001 and 2002, fluxes of N(2)O, CH(4), CO(2) and N(2) were measured in two constructed wetland... more In 2001 and 2002, fluxes of N(2)O, CH(4), CO(2) and N(2) were measured in two constructed wetlands (CW) for domestic wastewater treatment in Estonia. The difference between the median values of N(2)O, CH(4), and N(2) fluxes in the horizontal subsurface flow (HSSF) CWs was non-significant, being 1.3-1.4 and 1.4-4.1 mg m(-2) d(-1) for N(2)O-N and CH(4)-C, and 0.16-0.17 g N m(-2) d(-1) for N(2)-N respectively. The CO(2)-C flux was significantly lower (0.6 g C m(-2) d(-1)) in one of the HSSF filters of a hybrid CW, whereas the single HSSF and VSSF filters emitted 1.7 and 2.0 g C m(-2) d(-1). The median value of CH(4)-C emission in CWs varied from 1.4 to 42.6 g C m(-2) d(-1), being significantly higher in the VSSF filter beds. We also estimated C and N budgets in one of the HSSF CWs (312.5 m(2)) for 2001 and 2002. The total C input into this system was similar in 2001 and 2002, 772 and 719 kg C year(-1), but was differently distributed between constituent fluxes. In 2001, the main input flux was soil and microbial accumulation (663 kg C year(-1) or 85.8% of total C input), followed by plant net primary production (NPP) (10.2%) and wastewater inflow (3.9%). In 2002, 55.7% of annual C input was bound in plant NPP, whereas the increase in soil C formed 28.5% and wastewater inflow 15.7%. The main C output flux was soil respiration, including microbial respiration from soil and litter, and the respiration of roots and rhizomes. It formed 120 (97.5%) and 230 kg C year(-1) (98.2%) in 2001 and 2002 respectively. The measured CH(4)-C flux remained below 0.1% of total C output. The HSSF CW was generally found to be a strong C sink, and its annual C sequestration was 649 and 484 kg C year(-1) per wetland in 2001 and 2002 respectively. However, negative soil and microbial accumulation values in recent years indicate decreasing C sequestration. The average annual N removal from the system was 38-59 kg N year(-1) (46-48% of the initial total N loading). The most important flux of the N budget was N(2)-N emission (22.7 kg in 2001 and 15.2 kg in 2002), followed by plant belowground assimilation (2.3 and 11.9 kg N year(-1) in 2001 and 2002), and above-ground assimilation (1.9 and 9.2 kg N year(-1), respectively). N(2)O emission was low: 0.37-0.60 kg N year(-1)(.).
A pilot scale experimental hybrid constructed wetland (CW) was established in 2005 for the treatm... more A pilot scale experimental hybrid constructed wetland (CW) was established in 2005 for the treatment of mixed effluents from municipal sources and food processing plants in a small village in southern Estonia. The aim was to find optimal operating regimes (varying hydraulic loading rates, loading intervals, recirculation regimes and regimes of hydraulic retention time) for the use of analogous CWs in cold climates. The hybrid wetland system consists of two parallel systems designed on the same principle: a vertical subsurface flow (VSSF) filter followed by a horizontal subsurface flow (HSSF) filter. The VSSF filter of one system (the left filter) is filled with crushed limestone, while the other (right) is filled with light weight aggregates (LWA). Both HSSF filters are filled with LWA. From December 2005 until December 2006, water samples from the outlet of the septic tank and the outlet of both VSSF and HSSF filters were taken once a week. In both systems, a combination of decreasing hydraulic load (from 52 to 14 mm d-1) and increasing recirculation rate (from 34 to 300%) caused a significant increase in the purification efficiency of BOD7 (from 58 to 99%), N tot (from 11 to 82%), and NH4-N (from-16 to 83%). In both systems, the removal efficiency of P tot did not show any significant correlation with hydraulic load, whereas in the right (LWA) system, the increasing recirculation rate significantly increased P tot removal. The dynamics of the COD value was analogous to that of the BOD7 value, but no significant differences were found between the removal efficiency of total suspended solids (TSS) of different flow regimes. Likewise, water temperature did not show a significant correlation between the purification efficiency of all of the studied water quality indicators. For the successful functioning of hybrid CWs in a cold climate, optimal hydraulic load should be ≤20 mm d-1 with a recirculation rate of 150-300%.
WIT Transactions on Ecology and the Environment, Vol 99, 2006
Coastal zones, which have a very high biodiversity value and a long history of being impacted by ... more Coastal zones, which have a very high biodiversity value and a long history of being impacted by human activities, are among the most vulnerable ecosystems on our planet. Moreover, some scenarios predict that within 50 years more than 75% of the global human population will live in coastal zones. Although Europe's coasts are among the most altered, there are significant regional differences within Europe in terms of naturalness and human pressure. During the integrated SENSOR project of the European Union's (EU) 6 th Framework Programme, we have analyzed the sensitivity of the EU's coastal zones using data on 191 coastal cells at The Nomenclature of Territorial Units for Statistics (NUTS) level, based on information from the Statistical Office of the European Community (EUROSTAT) and other Europe-level sources. To determine sensitive coastal areas, multidimensional clustering was provided. The NUTSx level (a combination of NUTS2 and NUTS3 level cells in order to achieve better spatial coverage) clustering resulted in seven clusters which were not, however, well distinguished in terms of the SENSOR sensitivity areas concept. Therefore clustering on the NUTS2 level was provided using 15 parameters characterizing economic, social and environmental aspects, yielding six clusters that were logically distinguishable from each other. The cluster characterized by a rapidly growing economy combined with relatively high but decreasing unemployment, low but increasing income, a low rate of investment in research and development (R&D), a low share of arable land but a high rural population, moderate length of coastline with the highest share of coast exposed to coastal erosion and a highly variable level of environmental protection, including 23 coastal NUTS2 areas plus five islands, has to be considered sensitive and needs further attention from the European Commission.
Two riparian buffers including wet meadows (Filipendula ulmaria-Aegopodium podagraria-Cirsium ole... more Two riparian buffers including wet meadows (Filipendula ulmaria-Aegopodium podagraria-Cirsium oleraceum-Urtica dioica) and grey alder (Ainus incana) stands were investigated. The main inputs and outputs (atmospheric deposition, input and output in surface and subsurface flow, nitrogen fixation and denitrification), and accumulation of N and P in plant biomass, litter and soil were estimated. A 31 m wide complex buffer zone of wet meadow and grey alder forest removed 67% nitrogen and 81% phosphorus, while in a 51 m buffer zone, also containing a grassland strip in addition to wet meadow and alder forest, 96% N and 97% P was retained. In the riparian buffers studied, an effective retention of nutrients (34-186 kg N ha^ yr~* and 1.6-6.0 kg P ha~* yr~') was observed even with very high input loads (276.3 and 12.8 kg ha~* yr^ of N and P, respectively). A twodimensional simulation model RipFor was developed in the STELLA environment to analyse nutrient flows in the complex riparian bu...
This work presents N and P budgets of a horizontal subsurface flow (HSSF) constructed wetland (CW... more This work presents N and P budgets of a horizontal subsurface flow (HSSF) constructed wetland (CW; 2 chambers, 25x6.25x0.8 m each, sealed with polyethylene liner, filled with coarse sand, one planted with Typha latifolia but dominated now by Scirpus sylvestris, and the other planted with Iris pseudacorus and Phragmites australis but covered at present by P. australis, receiving a septic tank effluent of 40-60 population equivalents (pe)) constructed in 1996 for treatment of wastewater from a hospital in Kodijwe, Tartu County, Estonia. Monitoring of water quantity (inflow to the system and outflow from different parts) and quality (BOD7, total-N, NH4-N, NO2-N, NO3-N, total-P, PO,-P, SO4, total-Fe, Ca, pH and suspended solids) took place once every two weeks, there was yearly investigation of bacterial biomass and the plant above-ground and below-ground biomass and N, P and C content in both plants and filter material at 3 depths, as well as quarterly measurement of gaseous N20 and NZ fluxes (using both the closed chamber and the He-0 method) were used as methods in this study. The most important flux in the N budget in 2001 was in the area of NZ emissions (12.4 kg a-' or 41.7%), followed by microbial immobilization (8.7 kg a-'), accumulation in the soil (4.2 kg a-'), plant assimilation (4.1 kg a-'), and N20 emission (0.35 kg a-'). The phosphorus budget was charted for the period 1997-2001. Major pools of P are: accumulation in soil as lactate-soluble P via adsorption (46.5 kg; 88.1%), plant accumulation (3.2 kg), microbial
In this study we quantified carbon balance by analyzing eddy-covariance CO2 flux data (carbon exc... more In this study we quantified carbon balance by analyzing eddy-covariance CO2 flux data (carbon exchange) vs chamber-based measurements (ecosystem respiration) and CO2assimilation (soil and biomass). The annual NEE in this mature coniferous forest was -2.3 t C ha yr−1, showing a clear diurnal and seasonal trend. During the daytime in summer the forest sequestered CO2, while during the night and late night CO2 emitted from the ecosystem to the atmosphere. Within the growing period, the sequestration of CO2 by plants was greater than soil respiration. Thus, the ecosystem sequestered carbon. Most of the carbon is bound in tree biomass (above and below ground biomass) but as well into soil, while the sequestration in soil increases with stand age. In addition, the biomass of understory, especially belowground litter, is playing essential part in carbon input.
The aim of this study is to estimate wintertime emissions of greenhouse gases CO2, N2O and CH4 in... more The aim of this study is to estimate wintertime emissions of greenhouse gases CO2, N2O and CH4 in two abandoned peat extraction areas (APEA), Ess-soo and Laiuse, and in two Oxalis site-type drained peatland forests (DPF) on nitrogen-rich sapric histosol, a Norway spruce and a Downy birch forest, located in eastern Estonia. According to the long-term study using a closed chamber method, the APEAs emitted less CO2 and N2O, and more CH4 than the DPFs. Across the study sites, CO2 flux correlated positively with soil, ground and air temperatures. Continuous snow depth > 5 cm did not influence CO2, but at no snow or a thin snow layer the fluxes varied on a large scale (from −1.1 to 106 mg C m−2 h−1). In all sites, the highest N2O fluxes were observed at a water table depth of −30 to −40 cm. CH4 was consumed in the DPFs and was always emitted from the APEAs, whereas the highest flux appeared at a water table >20 cm above the surface. Considering the global warming potential (GWP) of ...
The green infrastructure (GI) is a network of natural and semi-natural areas with environmental f... more The green infrastructure (GI) is a network of natural and semi-natural areas with environmental features that is designed and managed to deliver a wide range of ecosystem services. The concept has roots in the former hierarchical system of ecological networks. There are several examples of GIs, but details of their implementation at a landscape level are often missing or they have been used non-systematically. Here, we demonstrate opportunities for landscape-level implementation of GIs based on spatial analysis through the application of ecological engineering or other measures. Using maps and expert evaluations of different land-use types, we created a methodology for national-scale determination of Estonia's GI. Based on spatially explicit datasets (e.g., land cover, soils, topography, roads), we determined the proportions of greenness and brownness (primarily anthropogenic) landscape indices. Areas with the highest greenness values served as the GI's core areas, whereas areas with the greatest anthropogenic composition represented the brown infrastructure. Identification and classification of hotspots where the two infrastructures are in conflict (e.g., construction, mining areas, roads, settlements, airports, power lines, wind turbines) revealed locations where ecological engineering and other measures are needed to mitigate or eliminate the conflict. Developing spatially explicit models of the conflicts between the infrastructures represents a new approach in landscape planning and environmental management that links coarse-scale landscape planning and regional landscape plans with more detailed local landscape plans that support the design of site-specific ecological engineering and other measures. We demonstrate that the implementation of GIs is inseparably connected with ecological engineering and landscape-scale planning.
The study of purification efficiency and nutrient assimilation in plants was made in two riparian... more The study of purification efficiency and nutrient assimilation in plants was made in two riparian buffer zones with a complex of wet meadow and grey alder (Alnus incana) stand. In the less polluted Porijõgi test site, the 31 m wide buffer zone removed 40% of total nitrogen (total-N) and 78% of total phosphorus (total-P), while a heavily polluted 51 m wide buffer zone in Viiratsi retained 85% of total-N and 84% of total-P. The input of nutrients and purification efficiency displayed a significant relationship. The total-N removal in buffer zone was negative when the input value was less than 0.3 mg l-1 and the purification efficiency was always positive when the input value exceeded 5 mg l-1. The purification efficiency of total-P was positive when the input value exceeded 0.15 mg l-1. Grass vegetation plays an important role in nutrient retention in riparian buffer strips. The maximum phytomass production was measured in Porijõgi site where production of the Filipendula ulmaria comm...
N2O, N2 and CH4 fluxes were measured from a horizontal subsurface flow (HSSF) constructed wetland... more N2O, N2 and CH4 fluxes were measured from a horizontal subsurface flow (HSSF) constructed wetland (CW) for wastewater treatment in Estonia. The closed chamber method was used in the field and the He-O method (intact soil core analyses) in the lab throughout the period from October 2001 to June 2002. The average flux of N2O-N, N2-N and CH4-C from various microsites ranged from 0.1 to 59, 4.1 to 1,458 and -0.04 to 2,094 mg m-2 d-1, respectively. A significantly higher flux of N2O was found in chambers installed above the inlet pipes, while the methane flux was higher in the inlet part of the bed with wetter conditions. The groundwater table significantly correlates with gas emission rates of all the gases studied; N2 emission was enhanced by higher temperature of wastewater. PO43- and NH4+ content significantly enhanced, and NO2- and NO3- content inhibited, both N2O and CH4 fluxes. NH4+ showed a negative correlation with N2 flux. Nitrification and denitrification are the main processe...
Nitrous oxide (NO) is a powerful greenhouse gas and the main driver of stratospheric ozone deplet... more Nitrous oxide (NO) is a powerful greenhouse gas and the main driver of stratospheric ozone depletion. Since soils are the largest source of NO, predicting soil response to changes in climate or land use is central to understanding and managing NO. Here we find that NO flux can be predicted by models incorporating soil nitrate concentration (NO), water content and temperature using a global field survey of NO emissions and potential driving factors across a wide range of organic soils. NO emissions increase with NO and follow a bell-shaped distribution with water content. Combining the two functions explains 72% of NO emission from all organic soils. Above 5 mg NO-N kg, either draining wet soils or irrigating well-drained soils increases NO emission by orders of magnitude. As soil temperature together with NO explains 69% of NO emission, tropical wetlands should be a priority for NO management.
Processes affecting CO 2 and CH 4 emissions and their budgets have been relatively well studied i... more Processes affecting CO 2 and CH 4 emissions and their budgets have been relatively well studied in northern temperate peatlands, whereas similar studies are almost absent in southern Patagonia and the high-altitude Andean peatlands, both of which are currently under heavy anthropogenic pressure. The objectives of this study were to compare greenhouse gas (GHG) emissions in natural and managed peatlands to examine the effect of management on GHG emissions and identify the environmental parameters affecting them. We analysed CO 2 , CH 4 and N 2 O emissions related to the physical and chemical conditions of the peat: in a natural and managed transitional bog in Quebec, Canada, a natural páramo and grazed peatland in the Colombian Andes, and a bog and a fen in Tierra del Fuego, Argentina. GHG fluxes were measured using the dark static chamber method. Groundwater table, temperature, O 2 content, pH and redox potential were measured from observation wells, soil temperature was measured at four depths, peat samples were analysed for pH, soil organic matter and dry matter content, P, K, Ca, Mg, NH 4-N, NO 3-N, total N and C. In all regions, human-impacted peatlands showed significantly higher CO 2-C, N 2 ON and CH 4-C emissions than their natural counterparts. The Canadian managed transitional bog showed the highest average CO 2-C (575 mg C m −2 h −1) and N 2 ON (0.08 mg N m −2 h −1) emissions, whereas the Colombian pasture was the largest emitter of CH 4-C (2.35 mg C m −2 h −1). CO 2-C emissions were controlled by soil temperature and C content, whereas CH 4-C flux was negatively correlated to dissolved oxygen content in peat water, and positively to water table level and soil log (C/NO 3-N) ratio. Total Inorganic Nitrogen (TIN), C/N ratio, and soil temperature were the main factors controlling N 2 O emissions. Intensive peatland management alters the soil C/N balance, and increases and leads to higher variability of GHG emissions. Agricultural activities, especially crop production in peatlands, as well as intensive grazing in mountain peatland pastures, are the main factors increasing GHG emissions in the peatlands studied. Mitigation is possible via regulation of grazing intensity and replacing arable fields with grasslands.
Riparian buffer zones are considered to be important elements of agricultural watersheds, in that... more Riparian buffer zones are considered to be important elements of agricultural watersheds, in that they control nutrient and carbon fluxes. Although the water purification effect of riparian ecosystems has been well studied, there is little knowledge of their internal cycling, especially in the area of gaseous emissions. We measured fluxes of nitrous oxide (N 2 O), dinitrogen (N 2), methane (CH 4), and carbon dioxide (CO 2) in riparian grey alder stands in southern Estonia and black alder stands in Brandenburg, Germany. Dinitrogen emission was the most important component in N retention in the studied riparian grey alder forests. In 2001-2003, the median values of N 2 emission in the grey alder sites significantly exceeded the N 2 emission rates in the black alder sites, varying from 700 to 1200 and from 360 to 400 kg N 2-N ha-1 year-1 , respectively. In contrast, the median values of N 2 O flux were higher in the black alder sites than in the grey alder sites, i.e., 0.9-2.6 and 0.2-0.7 kg N 2 ON ha-1 year-1 , respectively. The black alder sites acted as a sink for CH 4 , whereas the grey alder sites emitted a small amount of CH 4. The CO 2-C flux was higher in the black alder stands. The estimated N 2-N emission in the grey alder stands for 1994-1995 was 51.2, whereas N 2 ON emission was 0.5 kg N ha-1 year-1. The significant increase in N 2 emission from 1994-1995 to 2001-2003 can be related to changes in microbial activity during the succession of the pioneer grey alder stand into a more stable mixed forest community. Due to CO 2 fluxes and N 2 O fluxes from sites with altered water regime, the estimated GWP of the studied riparian alder stands was relatively high. Further investigations should concentrate on the factors that regulate rates of N 2 O and N 2 emission from riparian buffer zones.
The removal of organic matter and nitrogen in constructed wetlands (CW) is highly dependent on th... more The removal of organic matter and nitrogen in constructed wetlands (CW) is highly dependent on the availability of dissolved oxygen in the treatment system. Therefore it is of great importance to develop innovative methods to enhance oxygen supply in the CW matrix. This paper focuses on and describes the methods used to enhance oxygen supply in CWs. Also, a pilot scale experimental batch-operated lightweight aggregate (LWA) filter system (FS) consisting of eight identical LWA filter cells (with a depth of 1.15 m and an area of 1 m 2 each) was established during the summer of 2005 for the treatment of municipal wastewater. The main objective of this study was to evaluate the performance of the experimental batch-operated FS on the basis of performance indicators. During the experiments, the effect of different operational regimes on the purification efficiency of the filter system was also investigated. The highest purification efficiencies of 96% and 51% for BOD 7 and N tot , respectively, were achieved when the recirculation rate of 200% was applied at the hydraulic retention time of ~2 days. The highest organic matter removal rate of the experimental FS as K BHT =0.19 m d-1 is approximately two times higher than the removal rate of typical horizontal-flow CWs. However, the highest aeration capacity of 21.1 gO 2 m-2 d-1 is somewhat lower than the average aeration capacity of vertical-flow CWs, and substantially lower than the aeration capacity of a VF filter with re-circulation or tidal-flow systems. As the aeration capacity of the system partly depends on the oxygen demand of inflow wastewater, it is necessary to carry out studies of shorter hydraulic loading rates in order to optimize the performance of experimental batch-operated FSs.
The purpose of this study was to (i) analyse trends in the runoff of organic matter (by BODs) and... more The purpose of this study was to (i) analyse trends in the runoff of organic matter (by BODs) and nutrients from the medium-size (256 km 2) rural watershed of O hne River in southern Estonia, and (ii) model variations in nitrogen and phosphorous runoff. Chemical and hydrological monitoring data between 1980 and 2000 were used in this study. Due to a large and unprecedented decrease in agricultural production and land-use in the O hne River catchment losses of nutrients and organic matter have decreased significantly. For example arable land decreased from 27 % to 16 % during the period 1980-2000. The results from this study showed that the runoff of NH4-N, NOrN, P04-P and organic matter (after BODs), calculated by linear trend, decreased from 1.50 to 1.05, 2.89 to 2.08, 0. 111 to 0.053, and 7.73 to 5.29 kg ha-' yr-I , respectively. To analyse temporal changes of the studied trends, the whole research period was divided into two equal parts:
Due largely to unprecedented land-use changes in the Porijõgi River catchment (southern Estonia) ... more Due largely to unprecedented land-use changes in the Porijõgi River catchment (southern Estonia) losses of nutrients and organic matter have decreased significantly. During the period 1987–1997 abandoned lands increased from 1.7 to 10.5% and arable lands decreased from 41.8 to 23.9%. At the same time, the runoff of total-N, total-P, SO4 and organic matter (after BOD5) decreased from 25.9 to
The main objective of this paper is to present a national level attempt at designing the Pan-Euro... more The main objective of this paper is to present a national level attempt at designing the Pan-European Ecological Network (PEEN) that is based on Estonian data from a one square kilometre grid. We propose an ecological network design comprising of three principal layers: (1) general topographical features like coastlines, the water network, major roads, and place names for locating the depicted network, (2) habitatbased field of suitability for the ecological network, calculated from network values of landscape features using a predefined algorithm, (3) ecological network as an administrative decision. The second layer serves as a tool supporting decision making while the third layer consists of traditional components of an ecological network, like core areas, corridors, buffer zones, and nature development/restoration areas. The CORINE land cover map, which was adjusted and supplemented using the soil and landscape data, served as the base for PEEN habitat classification. All habitats, linear structures and designated areas were ranked according to their expert-assessed values (from 0 to 10) based on their naturalness, rarity, and potential influence on biodiversity and landscapes. These values served as a basis for calculating the suitability (ranging from-3.65 to +3.75 in our study area) of each square kilometre for the ecological network. Ranking the suitability allows one to distinguish between the core areas, buffer zones and nature development areas. Suitability values were calculated including the influence of designated areas and without it. The natural suitability was calculated without the designated areas. The most common suitability for the ecological network in Estonia was found to be between 1.0 and 1.5. As a rule, the ecological network suitability of protected areas is higher than that of non-protected areas. The mean natural suitability value of square kilometres which contain more than 80% protected territory is 1.34, and the mean natural suitability of those square kilometres which do not include protected areas, is 0.819. The relative amount of protected areas per square kilometre decreases if the natural suitability for the ecological network decreases. Nearly a half (47.4%) of ecologically highly valuable areas in Estonia are under nature protection. On the other hand, it means that more than a half are not protected. We found a great similarity between the suitability map for the ecological network (both with and without including the designated areas) and the expert-made map of the ecological (green) network presented in the work on "Vision for Estonia 2010".
Sustainability Impact Assessment of Land Use Changes
Cross-cutting environmental, social and economic changes may have harsh impacts on sensitive regi... more Cross-cutting environmental, social and economic changes may have harsh impacts on sensitive regions. To address sustainability issues by governmental policy measures properly, the geographical delineation of sensitive 472 Oliver Dilly et al. regions is essential. With reference to the European impact assessment guidelines from 2005, sensitive regions were identified by using environmental, social and economic data and by applying cluster analysis, United Nation Environmental Policy priorities and expert knowledge. On a regionalised 'Nomenclature of Territorial Units for Statistics' (NUTS) level and for pre-defined sensitive region types (post-industrial zones, mountains, coasts and islands) 31 % of the European area was identified as sensitive. However, the delineation mainly referred to social and economic issues since the regional data bases on environmental indicators are limited and do not allow the separation of medium-term vital classes of sensitive regions. Overall, the sensitive regions showed indicator values differing from the EU-25 average.
Transects were established on two hillslopes and two study nitrogen budgets in two complex ripari... more Transects were established on two hillslopes and two study nitrogen budgets in two complex riparian buffer zones receiving different nitrogen loading. In the heavily loaded site the average total-N content decreased from 23 mg 1� 1 to 3.1 mg 1� 1 in a 40-years-old riparian grey alder forest (80 % removal). At the site with low loading the average removal of total-N was 48 %. In both transects the budget of N fluxes was established. In the older forest it was estimated as high as 321.1 kg ha� 1 yr� l , being 285.3 kg ha� 1 yr� 1 in the younger one. Considering all inputs and outputs, the N removal efficiency in grey alder stands slows down with increase of age. In the same time, immobilization in soil is increasing. This suggests that grey alder buffer communities should be managed by regeneration cutting and tending to keep their nitrogen removal rate high.
In 2001 and 2002, fluxes of N(2)O, CH(4), CO(2) and N(2) were measured in two constructed wetland... more In 2001 and 2002, fluxes of N(2)O, CH(4), CO(2) and N(2) were measured in two constructed wetlands (CW) for domestic wastewater treatment in Estonia. The difference between the median values of N(2)O, CH(4), and N(2) fluxes in the horizontal subsurface flow (HSSF) CWs was non-significant, being 1.3-1.4 and 1.4-4.1 mg m(-2) d(-1) for N(2)O-N and CH(4)-C, and 0.16-0.17 g N m(-2) d(-1) for N(2)-N respectively. The CO(2)-C flux was significantly lower (0.6 g C m(-2) d(-1)) in one of the HSSF filters of a hybrid CW, whereas the single HSSF and VSSF filters emitted 1.7 and 2.0 g C m(-2) d(-1). The median value of CH(4)-C emission in CWs varied from 1.4 to 42.6 g C m(-2) d(-1), being significantly higher in the VSSF filter beds. We also estimated C and N budgets in one of the HSSF CWs (312.5 m(2)) for 2001 and 2002. The total C input into this system was similar in 2001 and 2002, 772 and 719 kg C year(-1), but was differently distributed between constituent fluxes. In 2001, the main input flux was soil and microbial accumulation (663 kg C year(-1) or 85.8% of total C input), followed by plant net primary production (NPP) (10.2%) and wastewater inflow (3.9%). In 2002, 55.7% of annual C input was bound in plant NPP, whereas the increase in soil C formed 28.5% and wastewater inflow 15.7%. The main C output flux was soil respiration, including microbial respiration from soil and litter, and the respiration of roots and rhizomes. It formed 120 (97.5%) and 230 kg C year(-1) (98.2%) in 2001 and 2002 respectively. The measured CH(4)-C flux remained below 0.1% of total C output. The HSSF CW was generally found to be a strong C sink, and its annual C sequestration was 649 and 484 kg C year(-1) per wetland in 2001 and 2002 respectively. However, negative soil and microbial accumulation values in recent years indicate decreasing C sequestration. The average annual N removal from the system was 38-59 kg N year(-1) (46-48% of the initial total N loading). The most important flux of the N budget was N(2)-N emission (22.7 kg in 2001 and 15.2 kg in 2002), followed by plant belowground assimilation (2.3 and 11.9 kg N year(-1) in 2001 and 2002), and above-ground assimilation (1.9 and 9.2 kg N year(-1), respectively). N(2)O emission was low: 0.37-0.60 kg N year(-1)(.).
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