Research & reports

María Roo, Cecilia Herbón, Juan Pedro Martín‐Sanz, María Teresa Barral, Remigio Paradelo Núñez · Journal of Soils and Sediments · Spain (Santiago de Compostela)

This study analyzed the chemical extractability and bioaccessibility of five trace metals (Pb, Cu, Zn, Ni, Cr) in 55 urban soils from Santiago de Compostela, Spain, across various land uses. The availability of trace metals in these soils was found to be very low. Plant-available and bioaccessible Cu and Zn were higher in urban garden soils compared to other uses, supporting hypotheses that Cu, Pb, and Zn originate from anthropogenic pollution.

Diana Krabbendam, Emiel Wolf, Bernie Deekens, Rosalie Bak, Hans Krikke · SpringerBriefs in applied sciences and technology · Netherlands (Amsterdam)

This chapter outlined activities for citizen-led projects in the Wildeman neighborhood in Amsterdam. The main challenges identified were a lack of trust and community feeling among inhabitants, a lack of involvement and ownership in neighborhood developments, and fragmented existing community activities and services.

Géant Basimine Chuma, Jean M. Mondo, Adrien Byamungu Ndeko, Etienne M. Akuzibwe, Espoir Mukengere Bagula, Gustave Nachigera Mushagalusa · Discover Sustainability · Democratic Republic of Congo (Bukavu City)

This study investigated the quantity, composition, and disposal practices of domestic waste in Bukavu City, Eastern D.R. Congo. Findings revealed significant challenges in waste management infrastructure and practices, showing that approximately 5% of waste undergoes composting, while 10% is used as livestock feed, 66% incinerated, and 17% buried. Waste management is primarily handled by children (82%), with very limited involvement from non-governmental organizations.

Holger Braun, Dorothee Apfel, Benedikt Rilling, Carsten Herbes · Cleaner and Responsible Consumption · Germany

A study with 44 hobby gardeners in Germany found that substrates are not a major part of gardeners' social interactions, and price is the dominant purchase criterion for substrates, with sustainability not playing an important role. Although basic knowledge about peat is widespread, purchasing substrates is a utility-driven process with mostly passive information behavior.

Cosimo Dondini, Xavier Úbeda, Giacomo Certini, Marcos Francos · Journal of Soils and Sediments · Spain (Barcelona)

This study analyzed soils from ten urban gardens in Barcelona, Spain, with a special focus on possible contaminants. Irrigation water was also analyzed, and some of the waters contained a high concentration of salts and nitrites, which are listed as a pollutant. While three tests for heavy metals did not attest to significant pollution, other toxic elements not considered in this study could come from road transport gases or the port of Barcelona. Overall, the soil quality was concluded to be suitable for growing vegetables.

Simone Trimmel, Stefan Wagner, Laura Feiner, M. Feiner, Daniela Haluza, Rebecca Hood‐Nowotny, Ulrike Pitha, Thomas Prohaska, Markus Puschenreiter, Philipp Spörl, Andrea Watzinger, Elisabeth Ziss, Johanna Irrgeher · Environmental Science and Pollution Research · Europe

A study of urban gardens in Vienna, Austria, building on a previous study of eleven gardens in the city that found elevated lead (Pb) levels in some soil and plant samples. This work examined the elemental composition of soil and plants from two of the affected gardens one year after compost amendment. ICP-MS analysis of tomato fruit skin, pulp and seeds showed only minor variations in elemental composition unlikely to affect food safety, whereas radishes showed a tendency toward contaminant accumulation in root tips and leaves. Washing lettuce significantly reduced levels of potentially toxic elements including Be, Al, V, Ni, Ga and Tl, underscoring the importance of washing garden produce before consumption; compost amendment was associated with reduced Zn, Cd and Pb levels in radish bulbs. Lead isotope ratios in soil and spinach leaf samples from the earlier study, assessed by MC-ICP-MS, showed a direct linkage between the Pb isotopic signatures in soil and spinach leaves, supporting their use as tracers of Pb sources in the environment.

Anne-Kristin Løes, Sebastian Eiter, Tatiana Rittl · Environmental Sciences Europe · Europe

Using soil data from ten peri-urban case farms near Oslo and Bergen, Norway, this study estimated how quickly potentially toxic element (PTE) concentrations would rise in soil under intensive application of compost or digestate from food waste, composted garden waste, or horse and poultry manure applied annually to meet a theoretical carrot crop's nitrogen, phosphorus and potassium demand. Under this intensive fertilization scenario, Norwegian soil quality limits for PTEs would be reached within 20-85 years, faster in soils with more organic matter, with limits reached first for copper and zinc, both essential micronutrients. The urban waste-based fertilizers were also found to be poorly balanced in macronutrients, with rates covering potassium demand leading to high phosphorus and nitrogen surpluses. The study concludes Norway's PTE regulations are stricter than the EU's and do not support recycling organic matter and nutrients from urban waste.

Michele D’Ostuni, C. Stanghellini, A. Boedijn, Leonardo Zaffi, Giuseppina Pennisi, Francesco Orsini · Sustainable Cities and Society · Netherlands (Amsterdam)

The feasibility of using urine and greywater streams as nutrient solutions in a theoretical model of Building-Integrated Agriculture in Amsterdam was evaluated. Results showed it is feasible to use urine and greywater as nutrient solutions; however, treated urine had higher macronutrient concentrations than literature fertilizer recipes, requiring dilution with increasing amounts of greywater to match N or P concentrations. Consequently, P deficiencies in plants or excessive N concentration were found in the final wastewater-based nutrient solution.

Angelica Mendoza Beltrán, Kelzy Jepsen, Martí Rufí-Salís, Sergi Ventura, Cristina Madrid‐López, Gara Villalba · The Science of The Total Environment · Spain (Barcelona)

This study mapped N2O emissions from peri-urban agriculture in the Metropolitan Area of Barcelona (AMB), Spain. Researchers spatially distributed factors like crop type, fertilizer use, and irrigation, creating N2O emission maps using crop-specific and Tier 1 IPCC emission factors (EFs). The study found that Tier 1 IPCC EFs estimated 15% more emissions (7718 kg N2O-N year−1) than crop-specific EFs (6533 kg N2O-N year−1) for the entire AMB, indicating higher emissions for rainfed crops with Tier 1 EFs and for irrigated horticultural crops with crop-specific EFs. The mapping helps evaluate spatial variability of key factors but carries uncertainties due to downscaling regional data.

Elizabeth Regier, Walter McDonald · Journal of Sustainable Water in the Built Environment · United States (Milwaukee)

This study monitored two bioswales treating runoff from an urban farm in Milwaukee, WI, United States, to assess their hydrologic and water quality performance. The bioswales effectively reduced runoff volume, peak flows, total phosphorus, and high concentrations of total suspended solids (TSS >25 mg/L), achieving a median 98% load reduction across all pollutants. However, they showed mixed results in reducing total nitrogen concentrations and TSS at low influent concentrations (≤25 mg/L).

Cecilia Herbón, María Teresa Barral, Remigio Paradelo · Applied Sciences · Spain (Santiago de Compostela)

The concentrations of trace elements Cu, Pb, Zn, Ni, Cr, and As were investigated in 55 urban soils in Santiago de Compostela, northwestern Spain. While most soils showed higher trace element concentrations than regional backgrounds, they were not classified as contaminated according to Spanish regulations. However, geoaccumulation index values indicated low to moderate pollution levels in most soils, with Cu, Pb, and Zn highest in city center green areas, and Cr and Ni linked to parent material lithology.

Martí Rufí-Salís, Felipe Parada, Verónica Arcas‐Pilz, Anna Petit‐Boix, Gara Villalba, Xavier Gabarrell · Frontiers in Plant Science · Spain (Barcelona)

This study investigated a closed-loop crop cascade system in a Barcelona rooftop greenhouse, using tomato leachates to irrigate five successive lettuce cycles. The results showed that low yields (below 130 g per lettuce plant) were obtained when the cascade system was used during the early stage of the donor crop, as the nutrient amount, especially nitrogen, was insufficient for the receiving lettuce crop. Additionally, electrical conductivity values became too high (near 3 dS/m) at the end of the donor crop cycle, indicating limitations in maintaining optimal conditions throughout.

Cécile Le Guern, Liliane Jean‐Soro, Béatrice Bechet, Thierry Lebeau, Dorine Bouquet · Land Degradation and Development · France

Urban allotment gardens in Nantes, France, were found to have soil contamination, with lead (Pb) levels ranging from 100–400 mg kg−1, posing health risks. Local actors collaborated to characterize soil, evaluate sanitary risks, and discuss management options. The most frequent solution was replacing polluted soils with clean soils, while other strategies included on-site management of excavated soil, non-accumulative cropping, or changing land use.

Marta Bożym · Ochrona Środowiska i Zasobów Naturalnych · Poland

A study measuring heavy-metal content (cadmium, lead, copper, zinc, nickel, chromium) in compost and resident earthworms sampled from home composters and allotment gardens in the Opole region of Poland. The compost samples themselves were not contaminated with heavy metals and stayed within Polish legal limits for solid organic fertilizers. However, metal accumulation in earthworms varied by metal: the bioaccumulation factor (BAF) was high for cadmium, lead and zinc, while no accumulation was found for nickel, chromium or copper. The authors conclude that earthworm species native to Poland, such as Eisenia fetida, can serve as potential bioindicators of metals in the environment.

Andrew Hursthouse, T. E. Leitão, Annette Voigt, Avigail Heller, Béatrice Bechet, Paulo Brito da Luz · HAL (Le Centre pour la Communication Scientifique Directe) · Europe

This chapter overviews factors influencing the chemical, physical, and biological status of soils, water, and the biosphere in urban allotment gardens. It highlights that urban garden soils, water, and biosphere are affected by pollution due to their location in city centers or suburbs, with traffic infrastructure and industrial zones widely identified as impacting soil and water quality. Concerns over long-term risks from pollutant transfer (mainly metals) from soil to plants in these uncontrolled environments have been widely publicized.

B. Jankiewicz, B. Ptaszyński · Polish Journal of Environmental Studies · Poland

This study determined the levels of bioavailable and total chromium (III) and chromium (VI) in the soil of an allotment garden located in the center of Łódź, Poland. Chromium was measured using the spectrophotometric method and atomic absorption spectrometry. The research also examined the effects of iron and copper ions on the determination results.