Research & reports

James R. Hollyer · PubMed Central · United States

This article discusses the potential risk of rat lungworm (Angiostrongylus cantonensis) in Hawai‘i's local food supply, which can cause eosinophilic meningitis if ingested by humans. While the statistical risk is extremely low compared to other foodborne agents, two individuals in Hawai‘i developed serious eosinophilic meningitis in late 2008 after consuming insufficiently washed local produce. The article highlights the challenge of informing the public about this rare but potentially serious disease, especially amidst efforts to promote local produce and school gardens.

Laura Knapp, Jodi L. Sangster, Shannon L. Bartelt‐Hunt · International Journal for Service Learning in Engineering Humanitarian Engineering and Social Entrepreneurship · United States (Omaha NE)

This study investigated the influence of lead hyperaccumulating plants on lead uptake by vegetables in an urban community garden in Omaha, NE, a region with significant lead contamination. Tomatoes, carrots, and amaranth were grown alongside sunflowers and mustard greens (hyperaccumulators) in lead-contaminated soil. Data showed higher lead concentrations in the hyperaccumulators and suggested that their presence might have impacted the amount of lead available to surrounding vegetation. Previous work at the garden detected lead in produce, indicating a potential exposure pathway for humans.

Kyle Kessler, Seth Umbenhauer, Alison R. Noble · Journal of the Pennsylvania Academy of Science · United States (Harrisburg)

Eight soil samples were collected from an urban land plot in Harrisburg, PA, to determine concentrations of copper, nickel, zinc, and lead and assess suitability for an urban garden. While copper, nickel, and zinc concentrations were below EPA recommended limits, lead concentrations ranged from 26 ± 1 mg/kg to 402+ mg/kg, with some samples exceeding EPA standards for heavy metals in home and vegetable gardens. This indicates potential lead contamination in the soil.

Chris Zimmerman · Soil Horizons · United States

A narrative article profiling the work of soil scientist Samantha Langley-Turnbaugh of the University of Southern Maine, investigating lead contamination in urban soils in Portland, Maine. It traces the concern to the Great Fire of 1866, whose lead paint ash was spread across the city and used as landfill to extend the Portland peninsula, compounded by the city's historical ties to lead-producing industries. The article states that, across US cities generally, lead paint and leaded gasoline are the primary sources of soil lead contamination, and that this contamination is becoming a concern as urban gardening expands.

Nahed N. Mahrous · The Journal of Pediatrics · Canada (Hamilton)

This project investigated metal, bacteria, and corn root interactions in metal-contaminated soils from Blackfrairs Community Garden and a Hamilton home. It found that bacterial numbers were lower than in uncontaminated soils, and bioavailable metal concentrations increased over time. High concentrations of metals were detected in grains, with copper, iron, and manganese accumulating in rhizospheres, and zinc distributed throughout root tissue in Blackfrairs plants.

Jodi L. Sangster, Andrew Nelson, Shannon L. Bartelt‐Hunt · International Journal for Service Learning in Engineering Humanitarian Engineering and Social Entrepreneurship · United States (Omaha)

Soil and vegetable samples were collected from a community garden in Omaha, Nebraska, which had known soil lead contamination. Total lead content was evaluated using atomic absorption spectroscopy, revealing lead concentrations in soil ranging from 4 to 574 ppm, with an average of 128.4 ppm in growing beds and 31.5 ppm in OmaGro compost. Lead was also present in vegetable samples at or below 16.25 ppm.

Adam J Long · Scholarship @ Claremont (The Claremont Colleges) · United States (Washington, DC)

This study investigated heavy metal soil contaminants in 13 urban community gardens in Washington, DC, analyzing 45 soil samples using X-ray fluorescence (XRF). While most samples fell below US EPA action levels for common contaminants, high concentrations of lead (above the US EPA action level of 400 ppm) were found in the native soil of three garden sites, meriting concern due to potential health problems in children.

Josh Beniston · The Knowledge Bank (The Ohio State University) · United States (Ohio)

An experiment on assessing and managing soil quality for urban agriculture was conducted during the 2011 and 2012 growing seasons on demolished vacant urban lots in Youngstown, Ohio. Soil compaction was identified as a primary constraint, with high bulk density values of 1.79 g cm⁻³ for in-ground plots and 1.55 g cm⁻³ for raised beds. Crop yield data from 2011 showed that both compost-amended and compost + biochar-amended plots had significantly greater crop yields than control plots, with compost + biochar plots achieving the highest harvest index values.

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.

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.

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.

Wendy Heiger‐Bernays, Alexa Fraser, Vaughn R. Burns, Kerry Diskin, David Pierotti, K Merchant-Borna, Michael D. McClean, Daniel J. Brabander, H. Patricia Hynes · PubMed · United States

A study characterized urban community garden soils contaminated by timbers, specifically finding elevated levels of polycyclic aromatic hydrocarbons (PAHs) from railroad ties and arsenic from chromated copper arsenate (CCA) treated lumber. Researchers determined the extent of contamination, designed a remediation plan, and assessed the safety of adding city compost as a soil amendment in Boston community gardens. Recommendations for healthful gardening practices were also provided.

Andréa Andreis, Graziela Maria Schuh, Rejane Giacomelli Tavares · LA Referencia (Red Federada de Repositorios Institucionales de Publicaciones Científicas) · Brazil (Novo Hamburgo)

An evaluation of parasite contamination in playground soils at Horta Comunitária Joanna de Angelis in Novo Hamburgo, RS, Brazil, detected rhabditoid larvae in 33% of soil samples. An enteroparasitological survey (n=22) confirmed parasitism in 59.10% of samples. However, it was not possible to establish a correlation between the presence of parasitosis in children and in the soil.

Evan Green · · United States (California)

A literature meta-analysis on lead contamination in urban farms was applied to Alemany Farm in San Francisco, California, where soil lead concentrations range from 60 to 720 ppm. It found that every food crop except tree fruits may pose a health risk if grown in Alemany Farm's soil. A phytoremediation plan using Indian mustard (Brassica juncea) to remove lead was found to exceed the farm's available budget, and its timescale made it impractical. The study concludes that phytoremediation is generally not feasible for small-scale urban farms and that other measures are needed to reduce lead exposure for urban farmers.

Samantha Langley-Turnbaugh, David E. Wilkinson, D. Rocque · Soil Survey Horizons · United States

This study characterized urban soils in a low-income neighborhood of Portland, Maine, that was heavily industrialized in the late 1800s, examining seven pedons for particle size, cation exchange capacity (CEC), base saturation, exchangeable bases, pH, and trace elements (Pb, Cr, Cu, Co, Cd, Ni, Zn, Hg, Ti, Zr). The soils contained numerous artifacts and showed a high degree of horizontal and vertical spatial variability; several trace elements were present at elevated levels, with lead (Pb) the dominant metal in surface horizons (600 mg/kg), and many metals correlated with each other and with iron and aluminum, and some with clay content and pH, though the study concludes that mapping soil units by specific trace element ranges would be difficult given the extreme variability observed.

T. M. Spittler, William A. Feder · Communications in Soil Science and Plant Analysis · United States

This study demonstrated a serious problem of lead contamination in Boston's urban environment by analyzing about 900 soil samples from backyards, play areas, community gardens, and playgrounds using X-ray fluorescence spectroscopy. An average lead level of 800 ppm was found, traceable to the past widespread use of lead paint. Selected plant species grown in soils with lead levels ranging from 100–2000 ppm showed differing affinities for lead uptake, with fruits taking up less than roots and roots less than tops, indicating positive translocation of lead from soil into plant tissue.