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The popularity and use of green infrastructure measures such as green roofs, green walls, and curb extensions is growing, especially in dense urban areas. At the same time, from an ecosystem services perspective, interest in urban nature and reconciliation ecology is underlined. Attempts to introduce more biodiverse vegetation in cities can conflict with the responses of some urbanites to the appearance of "wild" vegetation. Through semi-structured interviews with 47 randomly picked bypassers in Copenhagen, Denmark, this study explored urbanites' aesthetical perceptions of wild vegetation, especially of three green infrastructure types employed in landscape-based stormwater management: green roofs, green walls and curb extensions. The results confirm the importance of the physical plant properties, especially the color of plants and the presence of flowers; they point also to the strong influence of cultural factors, especially familiarity with a site or a similar project, and knowledge of the project's environmental value. Interestingly, the results indicate that cultural factors might be capable of garnering support for a project among people whose initial impression of its appearance was negative. Additionally, affective and emotive responses were found to be of significance. Compared to other studies, perceptions of wild vegetation in green infrastructure elements prove to be perceived more positively than reported previously. [ABSTRACT FROM AUTHOR]

Implementation of sustainable urban drainage systems (SUDS) as part of cities’ transition towards climate resilience encompasses unique opportunities to enhance urban nature qualities. SUDS include individual elements integrated in the urban landscape, e.g. rain gardens or wet basins, which are usually constructed with low structural heterogeneity. Structural heterogeneity of habitats is, however, associated with a high degree of biodiversity. This study explored potentials of habitat heterogeneity enhancement in SUDS using structural heterogeneity as a proxy for biodiversity potential. In an interdisciplinary workshop, landscape architects and urban ecologists designed individual SUDS elements with enhanced structural habitat heterogeneity, hereafter bio-SUDS. The redesigned SUDS elements were infiltration trench, curb extension, rain garden, swale, wet basin, and dry basin. To evaluate the bio-SUDS designs, we developed an index of habitat heterogeneity in SUDS based on registration of 45 structurally important components. The conversion from standard SUDS to bio-SUDS entailed substantial increases in structural heterogeneity ranging from 4 to 18 additional components within elements. Larger bio-SUDS elements returned higher index scores, but the relative score increases were substantial for all bio-SUDS and in the range of a factor of 2-5.5. Increased terrain differences, meandering edges, stones, gravel, boulders, deadwood, and brown roof-like vegetation were the components most often employed in the bio-SUDS designs. In conclusion, implementation of bio-SUDS has potential to increase structural habitat heterogeneity thereby providing habitat for biodiversity in urban green areas. The developed bio-SUDS index can assist in future assessments of ecological qualities in designs and real-world SUDS elements. [ABSTRACT FROM AUTHOR]

Highway runoff contains pollutants in concentrations that can harm ecosystems of receiving freshwaters. To suggest control measures the hydrological conditions for pollutant transport from road edge to receiving water, and the associated retention mechanisms must be identified. Often, the transfer of highway runoff to receiving water bodies is accomplished by means of roadside swales equipped with gullies and underdrains. It is well documented that infiltration into the swale constitutes the primary runoff removal mechanism, while surface flow across and along the swale is mainly restricted to heavy storm episodes. Dye tracing at four Danish highways was used to describe the hydrological conditions for leaching of highway runoff pollutants through highway swales. At all sites the surface layer of the exposed swale profiles consists of a homogeneous sandy material deposited after construction of the highway, reaching a thickness correlated with, among other things, the road age. The dye solution infiltrated these deposition layers uniformly, replacing all antecedent soil water. The below-swale soil profiles were percolated through more preferential pathways, but contrary to the expectation no earthworm burrows or other biopores played a part. At two sites the preferential flow patterns resembled macroporous flow through physical voids in heterogeneous construction materials (stony loam) and at borders between construction materials with different texture (gravel, clayey till, fine and coarse sand). At the other two sites, which were built almost exclusively from homogeneous sand, the flow patterns resembled fingered flow initiated around thin, deep-running roots from the surface vegetation. The contaminant transport consequences of these flow patterns are discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]