Marina Bergen Jensen

Green structure and sustainability - developing a tool for local planning.

Abstract Local authorities face a great challenge in translating officially announced sustainability commitments into everyday management practices. With the objective of developing a tool for supporting such goal-to-practice translation processes, three primary tool criteria were formulated, and used to develop a guide on how to apply the tool. Subsequently, the tool was applied and evaluated in an interactive study involving the local authority of a Danish municipality. The first tool criterion concerns the organisation of the translation process. It states that in order to obtain a clear understanding of the unique local conditions, the tool shall be able to act as a bridge between different disciplines, and allow for direct collaboration between experts with context-independent knowledge and local administrators with context-dependent knowledge. The second criterion concerns the identification of sustainable management strategies. It states that the tool shall secure a thorough two-sided analysis of society’s claims on one side, and on the other side the ability of available resources to meet these claims in a sustainable way. The third criterion concerns the distribution of the results of the analysing phase. It states that in order to support dialogue and decision making across professional and societal boundaries, the identified claims and resources as well as the associated obstacles shall be presented in simple and preferably visual overviews. In testing the tool we focused on the ability of the municipality’s urban green structure (the resource) to contribute to sustainable management of organic waste, surface runoff and biodiversity (the claims). Based on the outcome of the test, and an interview survey with the participating local administrators, it is concluded that the tool criteria are sound. This is despite the fact that the test of the tool was not applied in full accordance with the tool guidelines. It is anticipated that the application of this tool can increase the speed and extent with which local authorities absorb and employ the concepts of sustainable development in their everyday management and planning tasks.

Dissolved and particulate phosphorus in leachate from structured soil amended with fresh cattle faeces

Substantial transfer of phosphorus from land to aquatic environments has been observed in regions supporting intensive animal husbandry. We characterised leaching of P derived from fresh cattle faeces located at the surface of a structured clayey soil. Fresh cattle faeces were placed on top of an undisturbed column of structured soil (diam. and height 0.5 m) subjected to steady, saturated flow (1 mm h-1) with a synthetic rain solution. After 0.01 pore volumes (PV, 1PV = 46.5 1) or 2.5 h of flow the effluent concentrations of both dissolved and particulate P forms increased rapidly, and after 0.15 PV (37 h) a maximum of 12 mg P l-1 was observed for total P. This rapid, strong and permanent leaching of P from applied faeces was ascribed to preferential flow through continuous macropores. Dye tracing showed that especially earthworm burrows were active flow paths. Of the faeces derived P observed in the effluent, dissolved inorganic P (DIP, measured as molybdate reactive P) constituted the largest fraction (37%) followed by particulate organic P (POP, 33%) and particulate inorganic P (PIP, 22%) while dissolved organic P (DOP) accounted for the remaining 8%. Leaching of IP from faeces appeared to be greater than from inorganic sources. This may be ascribed to co-leaching of P complexating compounds, or compounds that compete with faeces derived P for sorption sites. When the flow regime was shifted from saturated to unsaturated conditions (after 5 days), DIP temporarily became undetectable in the effluent, and the concentration of PIP and POP decreased markedly, while DOP remained almost unchanged and became the main P fraction leached. Average effluent concentration of total P for the whole 12 day leaching period was 4.1 mg P l-1. This high concentration suggests well-drained soils with high animal densities to constitute future field research targets.

Phosphate Leaching from Intact Soil Column in Response to Reducing Conditions

Iron(III)(hydr)oxides can dissolve under reducing soil conditions. Simultaneously, oxide-associated inorganic phosphate is released to the soil solution. In this study, the effect of reducing soil conditions on phosphate leaching from transient waterlogging clayey soil is evaluated. We applied glucose solutions (either 100 or 1000 mg glucose-C L-1) at a steady flow rate of 0.63 mm h-1 to a saturated intact column of structured Alfisol (diam. 0.5 m, height 1.0 m). Effluent concentrations of iron(II) and reactive orthophosphate (Pi) increased slightly during 5 d of low glucose application, reaching values of 2.5 mg Fe L-1, and 0.02 mg PO4-P L-1, respectively. During 10 d of high glucose application, the iron(II) concentration increased to 14 mg Fe L-1 and fluctuations in the Pi-concentration between 0.002 and 0.1 mg PO4-P L-1 were observed. The fluctuations in Pi-concentration are ascribed to interactions between progression of the glucose front, and Pi-mobilization/resorption processes at the walls of macropores. The daily P-losses during low and high glucose applications averaged 0.3 mg PO4-P m-2 d-1, and 0.5 mg PO4-P m-2 d-1, respectively. Comparisons with a parallel topsoil study suggest that subsoil exerts a strong control on leaching – probably via resorption – of Pi mobilized in the topsoil.

A minimum data set of water quality parameters to assess and compare treatment efficiency of stormwater facilities.

Urban stormwater runoff is often of poor quality, impacting aquatic ecosystems and limiting the use of stormwater runoff for recreational purposes. Several stormwater treatment facilities (STFs) are in operation or at the pilot testing stage, but their efficiencies are neither well documented nor easily compared due to the complex contaminant profile of stormwater and the highly variable runoff hydrograph. On the basis of a review of available data sets on urban stormwater quality and environmental contaminant behavior, we suggest a few carefully selected contaminant parameters (the minimum data set) to be obligatory when assessing and comparing the efficiency of STFs. Consistent use of the minimum data set in all future monitoring schemes for STFs will ensure broad-spectrum testing at low costs and strengthen comparability among facilities. The proposed minimum data set includes: (i) fine fraction of suspended solids (<63 μm), (ii) total concentrations of zinc and copper, (iii) total concentrations of phenanthrene, fluoranthene, and benzo(b,k)fluoranthene, and (iv) total concentrations of phosphorus and nitrogen. Indicator pathogens and other specific contaminants (i.e., chromium, pesticides, phenols) may be added if recreational or certain catchment-scale objectives are to be met. Issues that need further investigation have been identified during the iterative process of developing the minimum data set.

Phosphate mobilization and immobilization in two soils incubated under simulated reducing conditions

Inorganic phosphate (P) associated with Fe(III) (hydr)oxides can be mobilized by reductive dissolution of the oxides. Bulk Ap samples from two loamy soils differing by nearly 50% in total P were amended with 6 or 60 mg glucose‐C per 100 g soil at a water tension of 0.2 m. During 29 days of anoxic incubation at room temperature, the soil solution pH, concentrations of Fe(II) and molybdate reactive P were measured. The concentrations of P were correlated to neither total soil‐P nor Fe(II) concentrations. Lack of proportionality between Fe(II) and P in solution was attributed to microbial uptake, resorption of P and also, at high Fe(II)‐concentrations, to precipitation of Fe(II)‐P compounds (e.g. vivianite). The highest P concentrations were observed in samples amended with the low‐C dose, where the concentrations increased six‐fold to approximately 0.3 mg PO4‐P 1−1. This indicated that P leaching might increase from clayey soils subjected to moderately reducing conditions.

Doing the first loop of planning for sustainable urban drainage system retrofits: A case study from Odense, Denmark

The planning and implementation of sustainable urban drainage systems (SUDS) requires intensive collaboration between professions and institutions. To improve the conditions for such practice in Denmark, the first loop of a SUDS-based retrofitting project was completed in Odense over a 6-month period. The project involved officials from the City of Odense and Odense Water Ltd., as well as university researchers. Studies of hydrological, environmental and socio-cultural aspects were developed by disciplinary teams and used to draft integrated solutions for two selected city districts. Albeit sewer surcharge was the initial catalyst, the main driver for the drafted solutions was urban planning. An assessment of the impact 1.5 years after completion indicated that the employed approach is valuable. In Odense, a planning procedure reflecting the loop process has become new practice. The project represents a key reference for the introduction of SUDS in Denmark.

Assessment of Existing Roadside Swales with Engineered Filter Soil: I. Characterization and Lifetime Expectancy

Roadside infiltration swales with well-defined soil mixtures (filter soil) for the enhancement of both infiltration and treatment of stormwater runoff from roads and parking areas have been common practice in Germany for approximately two decades. Although the systems have proven hydraulically effective, their treatment efficiency and thus lifetime expectancies are not sufficiently documented. The lack of documentation restricts the implementation of new such systems in Germany as well as other countries. This study provides an assessment of eight roadside infiltration swales with filter soil from different locations in Germany that have been operational for 6 to16 yr. The swales were assessed with respect to visual appearance, infiltration rate, soil pH, and soil texture, as well as soil concentration of organic matter, heavy metals (Cd, Cr, Cu, Pb, Zn), and phosphorus. Visually, the swales appeared highly variable with respect to soil color and textural layering as well as composition of plants and soil-dwelling organisms. Three swales still comply with the German design criteria for infiltration rate (10 m/s), while the remaining swales have lower, yet acceptable, infiltration rates around 10 m/s. Six of the eight studied soils have heavy metal concentrations exceeding the limit value for unpolluted soil. Provided that the systems are able to continuously retain existing and incoming pollutants, our analysis indicates that the soils can remain operational for another 13 to 136 yr if the German limit values for unrestricted usage in open construction works are applied. However, no official guidelines exist for acceptable soil quality in existing infiltration facilities.

Stormwater management challenges as revealed through a design experiment with professional landscape architects

Despite a number of potential benefits, using the urban landscape for managing stormwater runoff is spreading rather slowly. As urban planners and landscape architects are considered key protagonists of this trend, the objective of the study was to identify the challenges they confront when asked to retrofit an urban landscape for the management of stormwater runoff. Monitoring a two-week design experiment involving six teams of professional landscape architects identified 11 challenges, including sizing of elements, estimating costs, understanding water dynamics, aspects of biodiversity promotion, and dealing with land administrations and ownership issues. Measures to address the challenges are discussed. It should be noted that all six teams approached the stormwater management challenge in an energetic and focused way, applying their technical, personal and site-specific knowledge, and delivered innovative, flexible and coherent solutions. This emphasizes that the design process constitutes a strong and unique problem solving tool.

PHOSPHATE SORPTION TO MACROPORE WALL MATERIALS AND BULK SOIL

Preferential flow through macropores may allow reactive solutes to travel long distances in soil. The amount of solute transported is expected to depend on the ability of the macropore wall materials to retain the solute from the bypassing solution. From a loamy sand soil, samples of bulk Ap-horizon, bulk Btg-horizon, earthworm burrow lining, and both iron-depleted and iron-enriched materials from glossic fracture walls were obtained. The different soil materials were shaken for 5 min, 2 hr and 7 d in 0.01 M CaCl2 with initial P concentrations from 0 to 3.3 mg H2PO4--P L-1 at pH 5. The resulting changes in solution P-concentration were interpreted in terms of P-desorption or P-sorption. Burrow lining and bulk-Ap were poor P sorbents, especially at short contact times (5 min and 2 hr). They were unable to sorb P at concentrations below approximately 1 mg PO4-P L-1. In contrast, fracture wall materials and bulk-Btg were much stronger sorbents. They removed P from solutions having P-concentrations of only about 0.03 mg PO4-P L-1. The results of the study suggest that environmentally critical concentrations of dissolved Pi will be leached more easily through earthworm burrows than fractures, and that sorption characteristics of bulk soil may deviate strongly from sorption characteristics of macropore wall materials.

Assessment of existing roadside swales with engineered filter soil: II. Treatment efficiency and in situ mobilization in soil columns.

Use of roadside infiltration systems using engineered filter soil for optimized treatment has been common practice in Germany for decades, but little documentation is available regarding their long-term treatment performance. Here we present the results of laboratory leaching experiments with intact soil columns (15 cm i.d., 25-30 cm length) collected from two German roadside infiltration swales constructed in 1997. The columns were irrigated with synthetic solutions of unpolluted or polluted (dissolved heavy metals and fine suspended solids) road runoff, as well as a soluble nonreactive tracer (bromide) and a dye (brilliant blue). The experiments were performed at two irrigation rates corresponding to catchment rainfall intensities of approximately 5.1 and 34 mm/h. The bromide curves indicated that preferential flow was more pronounced at high irrigation rates, which was supported by the flow patterns revealed in the dye tracing experiment. Nonetheless, the soils seemed to be capable of retaining most of the dissolved heavy metals from the polluted road runoff at both low and high irrigation rates, except for Cr, which appears to pass through the soil as chromate. Fluorescent microspheres (diameter = 5 μm) used as surrogates for fine suspended solids were efficiently retained by the soils (>99%). However, despite promising treatment abilities, internal mobilization of heavy metals and P from the soil was observed, resulting in potentially critical effluent concentrations of Cu, Zn, and Pb. This is mainly ascribed to high concentrations of in situ mobilized dissolved organic carbon (DOC). Suggestions are provided for possible improvements and further research to minimize DOC mobilization in engineered filter soils.