Research & reports

Anna‐Katarina Schilling, Helmut Hotzel, Ulrich Methner, Lisa D. Sprague, Gernot Schmoock, Hosny El‐Adawy, Ralf Ehricht, Anna-Caroline Wöhr, Michael Erhard, Lutz Geue · Applied and Environmental Microbiology · Germany

This study investigated the presence of zoonotic agents in small ruminants kept on city farms in southern Germany, sampling feces and nasal liquid from 48 animals (28 goats, 20 sheep) across 7 city farms and one activity playground. Findings revealed that 100% of sampled sheep and 89.3% of goats carried Shiga toxin-producing Escherichia coli (STEC). Staphylococcus spp. were detected in 75% of both sheep and goats, and Campylobacter spp. in 25% of sheep and 14.3% of goats. Neither Salmonella spp. nor Coxiella burnetii was found.

John Jacob, Samuel E. Kakulu · American Journal of Chemistry · Nigeria

Soil and vegetable samples (spinach, jute mallow, and tomato) were collected from farms and gardens across 20 zones within Kaduna, Nigeria, plus two rural control villages about 30 km from the city, and analyzed for heavy metals by Flame Atomic Absorption Spectrophotometer. Pollution Load Index results showed soils in the city farms were moderately enriched with cadmium and chromium and strongly enriched with lead and nickel from anthropogenic sources. Mean soil concentrations of lead and cadmium exceeded WHO/FAO permissive limits for agricultural soil (nickel and chromium did not), while vegetable metal concentrations exceeded the permissive limits for every metal except nickel — a finding flagged as concerning given the toxicity of lead and cadmium in particular, which have no known biological use.

Sally Brown, Ingrid Clausen, Mark A. Chappell, Kirk G. Scheckel, M. Newville, Ganga M. Hettiarachchi · Journal of Environmental Quality · Global

Against a background in which the safety of urban farming has been questioned because of possible contamination in urban soils, this study tested whether high-iron biosolids-based composts could reduce the bioaccessibility of soil lead (Pb) and arsenic (As), using two laboratory incubations and a field trial. Pb and As bioaccessibility were assessed with an in vitro assay, and changes in Pb, As, and Fe speciation were analyzed on select samples using micro-X-ray fluorescence mapping and micro-XANES. A compost with iron added to wastewater-treatment residuals (Fe WTR compost), applied to soil at 100 g/kg, decreased Pb bioaccessibility in both laboratory incubations, though results for As were mixed. In contrast, the composts tested in the field trial (with iron added as Fe powder or FeCl) did not reduce bioaccessible Pb and showed only limited reductions in bioaccessible As; these same composts also had no effect on Pb bioaccessibility in the second laboratory incubation. The study concludes that high-iron biosolids compost is effective at reducing Pb accessibility only for certain types of iron-rich materials.

Qing Tian · · China (Beijing)

Based on Agricultural Location Theory, 23 matched soil-wheat sample sets were collected from Beijing's central city, suburban plain and exurban plain zones to analyze the accumulation, chemical forms and bioavailability of lead under differing intensities of human activity. Urban soil showed lead contamination with an average concentration of 35.59 mg/kg above the limit, likely from traffic and industrial emissions, and suburban agricultural soil also showed localized lead contamination from long-term sewage irrigation, with lead more mobile in urban agricultural soil than in suburban soil and least mobile in exurban agricultural soil. The average bioconcentration factor of lead in wheat seeds was a low 0.0044, but some lead concentrations in wheat seeds grown in urban and suburban agricultural soil exceeded the standard limit, indicating a potential health risk to residents in those areas.

R. Plant, Jeremy Walker, Scott Rayburg, J Gothe, Teresa Leung · Australian Geographer · Australia

A study of the Hawkesbury-Nepean River in Sydney, Australia, examines the effects of pesticide use by the small-scale horticulturalists supplying the city's fresh vegetable markets on aquatic biodiversity. Through interviews with actors across the institutions responsible for agriculture, water quality, and environmental protection, it assesses the effectiveness of pesticide governance in the Greater Sydney Basin. It finds that pesticide pollution is rarely measured or monitored and is not a priority for any particular agency, meaning the pollution remains effectively uncontrolled. The study concludes that although public health, the long-term viability of local farming, and the ecological health of the river are compatible goals, they currently exist under a system of "organised irresponsibility."

Leigh Whittinghill, D. Bradley Rowe · Renewable Agriculture and Food Systems · Global

Urban agriculture faces limitations including competition for space, lack of formalized land use rights, and health hazards from food contamination. Green roof technology is proposed as a method to alleviate these issues, potentially reducing the use of contaminated land and water at ground level. However, for large-scale implementation, installation costs must be reduced, roof weight limitations assessed, and appropriate management practices developed.

L Ndiaye M, Y Dieng, S. Niang, Rak H, Mauro Tonolla, Raffaele Peduzzi · African Journal of Microbiology Research · Senegal (Dakar)

A survey in Dakar, Senegal, assessed the effect of irrigation water quality on Salmonella spp. incidence in lettuce. Microbiological analysis revealed that 35% of irrigation water was contaminated by Salmonella spp., with no significant difference between groundwater and wastewater. Lettuce from Dalifort and Grand-Yoff markets showed significantly higher contamination rates than those from Sham and Zinc markets. The study concluded that irrigation water and manure are potential sources of contamination, and lettuce may serve as a vector for pathogen transmission to consumers.

김혁수, 김영남, 김진원, 김계훈 · 한국토양비료학회지 · South Korea (Seoul)

This study investigated the physicochemical properties and heavy metal (Cd, Pb, Cu, Zn) contents in 21 urban agricultural soils in Seoul. The total heavy metal concentrations in these soils were found to be lower than the warning levels specified by the Soil Environmental Conservation Act of Korea for area 1. Phytoavailable concentrations of Cu, Pb, and Zn were also reported.

Hyuck-Soo Kim, Young‐Nam Kim, Jin‐Won Kim, Kye-Hoon Kim · 한국토양비료학회지 · South Korea (Seoul)

This study investigated the properties and total and phytoavailable contents of heavy metals (Cd, Pb, Cu, Zn) in 21 urban agricultural soils in Seoul, South Korea. The total heavy metal concentrations in the examined urban agricultural soils were found to be lower than the warning levels for area 1 according to the Soil Environmental Conservation Act of Korea. Phytoavailable-Cu, -Pb, and -Zn concentrations were also reported as 0.02-0.28, N.D-0.09, and 0.01-0.43 mg/kg, respectively.

Dieudonné E. Musibono, E.M. Biey, M. Kisangala, Camille Ipey Nsimanda, B.A. Munzundu, V. Kekolemba, J.J Palus · VertigO · Democratic Republic of Congo (Kinshasa)

Urban agriculture in Kinshasa, Democratic Republic of Congo, serves as a palliative solution for social survival constraints such as a lack of remunerative salaries and sustainable jobs. However, poorly supervised urban farmers cultivate along busy roads, exposing vegetables to various contaminations, including lead. This practice highlights issues with site selection and supervision.

I Kibona, SL Mkoma, IC Mjemah · International Journal of Biological and Chemical Sciences · Tanzania (Morogoro)

Groundwater samples were collected from 20 wells in six wards of Morogoro municipality, Tanzania, during March-April 2010, and nitrate concentrations were measured. Nitrate levels ranged from 1.4 mg/L to 32.5 mg/L, with an average of 7.76 mg/L. These concentrations were below the upper limits set by the Tanzania Bureau of Standards and the World Health Organization.

I. K. Adewumi, Adebanji Samuel Ogbiye, E. O. Longe, David O. Omole · Covenant University Repository (Covenant University) · Nigeria (Ota)

This study assessed the impact of industrial wastewaters discharged into River Atuwara in Ota, Nigeria, on water quality using standard physical and chemical analyses and QUAL2K software. The majority of water quality parameters exceeded maximum permissible concentrations, with BOD at ≥ 31 mg/L, COD at ≥ 181 mg/L, and alkalinity at ≥ 138.4 mg/L. High concentrations of heavy metals, including Cadmium, Pb, Zn, Fe, and Mn, were detected, indicating an environmental hazard for riparian users.

Haruna Haruna · · Africa

A study of soils irrigated with sewage water on Fadama floodplain land in northern Nigeria used sequential extraction to determine the mobility and availability of cadmium, copper, nickel, lead and zinc. The residual fraction held the largest pool of all five metals, but 2.7-70.2% was present in the potentially available, non-residual fraction. Contamination by cadmium and nickel was less severe than by lead, copper and zinc, and mobility/bioavailability ranked Pb > Zn > Cu > Ni > Cd.

Saad El‐Din Hassan, Eva Boon, Marc St‐Arnaud, Mohamed Hijri · Molecular Ecology · Canada

A study assessing indigenous arbuscular mycorrhizal fungi (AMF) community structure in roots and soil of Plantago major (plantain) growing on trace-metal (TM)-contaminated versus uncontaminated sites, selected based on a survey of TM concentrations (As, Cd, Cu, Pb, Sn, Zn) in community garden soils in Montreal, Canada. AMF community structure was analyzed using PCR-DGGE, cloning and sequencing, and direct sequencing. Native AMF diversity, measured by the number of AMF ribotypes, was decreased in TM-polluted soils and plant roots compared with unpolluted sites, and community structure was altered by TM contamination. Various Glomus species along with Scutellospora aurigloba and S. calospora were the most abundant ribotypes in unpolluted soil, while G. etunicatum, G. irregulare/G. intraradices and G. viscosum occurred in both polluted and unpolluted soils, and G. mosseae together with unidentified Glomus ribotypes (B9, B13) dominated in TM-polluted sites. The predominance of G. mosseae at metal-polluted sites is interpreted as suggesting tolerance to TM stress and potential use for phytoremediation.

Zhou Pei · · China (Shanghai)

A study conducted in Orchard Village, Nanhui District, Shanghai, from July to September 2009, investigated the effects of phosphorus non-point source pollution on groundwater in an urban agricultural region. Total phosphorus concentrations averaged 1.31 mg/L and phosphate concentrations averaged 0.42 mg/L, with phosphate significantly exceeding the V class surface water standard (0.4 mg/L), rendering the water unsuitable for drinking. Phosphorus non-point source transport was linked to land-use types, with phosphorus content near orchards changing with increased rainfall, and farmland phosphorus loss accelerating with runoff, fertilization, and water leach.

Mamadou Ndiaye, H.‐R. Pfeifer, S. Niang, Y Dieng, Mauro Tonolla, Raffaele Peduzzi · VertigO · Senegal (Dakar)

In Dakar's urban agriculture, untreated wastewater is used for irrigation due to shallow groundwater salinization. A study conducted at Pikine and Patte d'Oie sites evaluated the chemical and microbiological quality of irrigation water. Findings showed that total nitrogen in irrigation water exceeded WHO guideline values, Salmonella spp. was isolated from 35% of irrigation water, and a wastewater sample tested positive for Vibrio cholerae. This research indicates that irrigation with polluted water and the use of organic fertilizers can degrade groundwater quality and pose health risks.

Zhou Pei · · China (Shanghai)

A study from July to September 2009 in an orchard village, Nanhui District, Shanghai, investigated the characteristics of non-point source nitrogen pollution in groundwater. Total nitrogen and its three forms (NO3-N, NH4-N, NO2-N) were monitored, revealing NO3-N as the main form (average 1.43-13.71 mg/L). Nitrogen pollution in groundwater depended on land use, with NH4-N pollution most serious under residential areas (average 0.074-0.457 mg/L). Total nitrogen pollution near the river and orchard (average 33.67-62.57 mg/L and 33.05-65.04 mg/L) was more severe than under residential areas.

Kohei Makita, Eric M. Fèvre, Charles Waiswa, Mark Bronsvoort, Mark C. Eisler, Susan C. Welburn · Land Use Policy · Uganda

This paper describes a spatial representation of the peri-urban interface (PUI) of Kampala, Uganda, and identifies socio-economic factors related to peri-urbanicity using rapid rural mapping. It notes that urban and peri-urban agriculture (UPA) in rapidly expanding cities carries public health risks, such as zoonotic disease transmission. The study provides a methodology for describing the PUI in developing countries.

Laura Whitzling, Michelle M. Wander, Ellen Phillips · Journal of Agriculture Food Systems and Community Development · United States (Chicago)

This study profiled soil quality, including lead levels, in 10 Chicago community gardens, comparing raised beds to non-raised beds and adjacent bare soil. The overall mean soil lead level was 135 ppm (n=86) by EPA method, with a range of 10-889 ppm. While most gardens' lead levels were not a concern, higher lead in adjacent bare soil suggested contamination risk. Use of raised beds reduced lead levels, but further study is needed.

Xiaona Li · Nongye huanjing kexue xuebao · China

A study measuring dioxin-like compound (PCDD/Fs) concentrations in 23 surface soil samples collected from different areas of Baiyin City, China, using HRGC/HRMS (high-resolution gas chromatography/high-resolution mass spectrometry). The concentration range of 2,3,7,8-PCDD/Fs was 0.42-8.56 pg I-TEQ/g, averaging 2.28 pg I-TEQ/g. By land-use type, concentrations averaged 3.37 pg I-TEQ/g in industrial areas, 1.31 in urban areas, 1.01 in agricultural areas, and 0.85 in background areas, following the order industrial > urban > agricultural > background. Higher-chlorinated isomers were the dominant contributors to total toxic equivalency (TEQ) in most samples.

Mamadou Ndiaye, S. Niang, H.‐R. Pfeifer, Raffaele Peduzzi, Mauro Tonolla, Y Dieng · Irrigation and Drainage · Senegal

Lettuces grown at two urban agricultural sites (Pikine and Patte d'Oie) near Dakar, Senegal, and sold in local markets were tested for microbial contamination linked to irrigation water. Salmonella spp. positivity was 6% at Pikine and 7% at Patte d'Oie farm sites, with lettuces irrigated by shallow 'Ceanes' groundwater most contaminated at both sites (8%), compared to wastewater irrigation (4% at Pikine) and well water (5% at Patte d'Oie); at market, Salmonella was isolated at every marketplace surveyed, with higher rates around Patte d'Oie (9% at Grand Yoff, 11% at Dalifort) than around Pikine (4% at Zinc, 2% at Sham) or the control site Rufisque (2%), and lettuces washed with Ceanes water before sale were more contaminated than those rinsed with tap water. Reusing wastewater for irrigation is presented as an alternative to animal manure, with the microbial contamination risk significantly reducible by washing vegetables with tap water before sale.

G. M. Hettiarachchi, Sabine Martin, A. David Rae, Phillip P. Defoe, Dennis Presely, G. M. Pierzysnki · · United States

Using a newly established urban community garden in Kansas City as a case example, this study examines the challenges of converting brownfield sites — abandoned or underutilized properties where environmental concerns impede redevelopment — into community gardens. Soil at the site was found to contain mildly elevated levels of lead (Pb) and detectable levels of DDT/DDE (an organochlorine pesticide). Based on an evaluation of soil properties, safety and corrective measures were proposed and implemented to reduce both direct (soil-to-human) and indirect (soil-to-plant-to-human) exposure for gardeners and their children, and field test plots with three crop types showing different contaminant-uptake patterns were established to evaluate site-specific soil amendments for reducing lead bioavailability.

Mark Matsa, Thomas Marambanyika · Journal of Environmental Extension · Africa

A study assessing concentration levels of lead (Pb), cadmium (Cd) and sulphides (SO2) within and around Gweru's sole official waste dumpsite in Zimbabwe. Harsh economic conditions in the city have driven further expansion of urban agriculture on open spaces, with residents growing staple food crops such as maize and sweet potatoes for subsistence on numerous plots surrounding the dumpsite; the study states that ingesting crops grown near the dumpsite is likely to put residents' lives at risk. Soil sampling points along transects on and around the dumpsite were randomly selected using ArcView GIS, with sulphide concentrations measured by Leco machine and lead and cadmium by atomic absorption spectrometer. Independent t-test results showed the concentration levels of the three pollutants were significantly elevated from one sampling point to the next, within and around the dumpsite.

O. Muñiz, M. Ternero, Álvarez Montero, F. Martínez, T. Limeres, O. Jouber, M. Orphee, Julia Vidan Estevez, B. Calero, F. A. de Alcantara, Adriana María de Aguiar Accioly · Portuguese National Funding Agency for Science, Research and Technology (RCAAP Project by FCT) · Global

This paper situates its topic within the urban agriculture movement, which it describes as having successfully enabled low-input food production in cities, noting that organoponicos — plots focused on producing leafy vegetables and condiment crops in organic substrates — have driven up demand for organic material sources. The title indicates the study addresses the effect of using heavy-metal-contaminated compost on vegetable production, but the available abstract provides only this background context, with no results on contamination or crop impact stated.

Cezary Kabała, T. Chodak, L. Szerszeń, Anna Karczewska, Katarzyna Szopka, Urszula Fratczak · Fresenius environmental bulletin · Poland (Wroclaw)

An analysis of 180 allotment garden soils in Wroclaw, Poland, found that concentrations of Cu, Pb, and Zn (12.5-659 mg Pb kg-1, 38.1-2103 mg Zn kg-1, 12.9-595 mg Cu kg-1) were influenced by industrial pollution sources, organic matter, pH, and macronutrients. Soils in gardens on former housing or industrial areas had significantly higher metal concentrations. Up to 35% of soils in the city zone were excessively contaminated, making them unsuitable for vegetable and fruit production and requiring reclamation.