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Final Report
Energy Conservation, Urban Gardens, and Heavy Metal Exposure Mitigation
Submitted by
Salvatore Engel-Di Mauro
Geography Department
SFB 104, 1 Hawk Drive
State University of New York at New Paltz
New Paltz, NY 12561 USA
Tel:(845)257-2991, Fax:(845)257-2992
Email: engeldis@newpaltz.edu
The project was a pilot study to assess the feasibility of non-experts using basic field
techniques and generally affordable equipment to identify urban garden areas with a potential for
soil heavy metal (HM) crop contamination. The importance of this study relative to energy
conservation is that urban agriculture contributes to reducing energy use in food systems, among
other ecological benefits. However, its long-term feasibility, particularly in industrialised cities,
may be affected by the degree to which contamination problems can be addressed. The
development of detection capacity from the bottom up is one way to achieve this, but there has
been too little research done to assess this possibility. Exposure to HMs, for example, could be
mitigated through the active involvement of better informed gardeners, who will not then be
dissuaded from urban farming when finding out the total HM content in the soils they use.
Analytical results showed that using non-expert field pH tests and organic matter
estimation based on Munsell colour identification are sufficiently accurate to use in identifying
potential problem areas in urban gardens, but more research, using additional variables, needs to
be undertaken to verify the relationship with actual HM crop uptake. A non-expert guide (which
could be counted as an innovation) was developed as a result of this project and an abstract and
paper presentation delivered by Salvatore Engel-Di Mauro at the SUITMA7 congress, in Toruń,
Poland, on 20th September 2013 (see http://www.suitma7.umk.pl/program/). A manuscript has
been prepared and will be reworked to publishable form within the next three months. It will be
submitted to Soil Use and Management or a similar outlet.
The study was carried out through the collaboration of faculty and students at the SUNY
Colleges of New Paltz, Cobleskill, and Environmental Science and Forestry (Syracuse), as well
as urban gardeners in Albany, Brooklyn, Manhattan, Syracuse, and Troy. As a result of a delayed
growing season and logistical difficulties in coordinating all participants, lab results were not
available until the end of the first week of September 2013. They also remain incomplete relative
to soil texture data, but enough samples have been processed to reach a statistically acceptable
sample number. The overall effect has been a delay in conducting multivariate analyses and
manuscript preparation for eventual publication.
A total of 23 sites were included, 22 of which are urban gardens and one a farm in
Delmar (in the Albany-Troy area), serving as control site. Thirty-nine soil samples were taken at
0-15 cm depth adjacent to the crop to be sampled, prior to and after any placement of soil
amendments (e.g., fertilizer, lime, compost, imported soil). Sample numbers varied according to
urban garden heterogeneity, with more than one sample taken from sites exhibiting greater
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variability, namely in terms of duration of use for various areas, differences in land use history
prior to urban garden conversion, physiographical variability (e.g., topography), and vegetation
predominance (e.g., trees or herbaceous crops). Farmland away from the city centres was used as
control sites, except for New York City, for which it was logistically unfeasible to do so. Soil
sampling equipment was washed with deionized water and wiped clean with paper towels after
each use. At least 2 kg of soil was placed in a sterile plastic bag for each sample. During the
harvesting period, edible parts of crops were sampled at each site, dusting each specimen prior to
putting them in sterile paper bags to exclude airborne-derived contaminants and prevent fungal
infestation. Soil and plant tissue samples were sent to the Cornell Nutrient Analysis Lab. Soil
samples were analysed for variables affecting HM-mobility in soils, namely % clay, % organic
matter (%OM, LOI method), pH (water based). Total HM content was analysed for samples
derived from both soils (ICAP Elements Hot plate HNO3/HCIO4 digestion) and plant tissues
(hot plate digestion and ICP/AES HM analyses).
Field analyses for colour, pH, and texture served as proxies for variables known to be
associated with HM movement and bioavailability. A non-specialist guide was developed for this
purpose that contains an explanatory note and a field-analysis protocol. The explanatory section
aims to enable urban gardeners to understand soil processes with particular attention to heavy
metal mobility and contamination. The protocol contains information on how to carry out soil
field analyses with relatively inexpensive equipment and interpret the results of such analyses.
The guide, available upon request, represents a distillation of research-oriented pedagogical
fieldwork protocols from the Global Learning and Observation to Benefit the Environment
(GLOBE, http://www.globe.gov/web/soil/protocols) programme and on selected materials from
the NRCS/USDA (e.g., texture determination flowchart). The equipment used included the
cheaper GLOBE version of the Munsell soil colour chart and a Soil pH Kit (wide pH range)
available through the Cornell Nutrient Analysis Lab. The latter involves interpreting colour
changes by comparisons to a colour chart after applying Bromocresol green (soil pH 4.0 to 5.6)
and Phenol red (soil pH 7.0 to 8.6). These resources can be used for multiple age groups and
education levels at once and so are more appropriate in a context such as urban gardens in New
York State, where people have wide-ranging backgrounds and life experiences.
Urban gardeners conducted field tests following training through workshops. The
workshops’ objective was to inform about soil HM contamination processes and have gardeners
conduct the soil descriptions. Workshop-based training for participation in the project was held
at the selected urban garden sites and the control site, involving gardeners from the same and
other urban gardens or rural farm. The content of the workshops included a brief introduction to
soils and soil processes and conducting investigator-led practice-oriented exercises to determine
carbonate content (using white vinegar with an acid wash bottle), colour (for the A horizon,
using a Munsell-based colour chart), pH (using a field pH tester), and texture (using a USDA
flowchart-based field assessment technique). Supervision by the investigator was minimal and
concentrated solely on ensuring that participants followed instructions correctly. The final
interpretations were entered by the participants as a group, following discussion and agreement
within the group on the data to enter.
Results from the field tests done by urban gardeners, students, and professional lab
analysts were compared through multiple bivariate statistical analyses and found not to diverge
significantly for pH and organic matter (based on Munsell colour estimation). This in itself is a
very promising finding. Texture (percentage clay), however, was poorly correlated among the
different tiers. There is thus much work to be done relative to how gardeners receive training on
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soil texture interpretation. In this phase of the project, it appears possible, through the techniques
used to train participants, to enable non-expert pH and organic matter determination with
sufficient accuracy. There was no statistically significant relationship between the three variables
and actual crop HM uptake, but discerning the effects will necessitate multivariate analyses and
additional data for other HM-affecting variables.
Future work will involve analysing such additional variables, by way of free carbonate
field tests, iron oxide estimation by way of Munsell colour identification, and a combination of
colour identification, bulk density estimation, and soil structure determination as proxies for
reduction-oxidation potentials. Although the research team has reached its dissolution as a result
of changed life circumstances for two of the project members, additional funding will be sought
to extend the project with other potential collaborators within and outside the SUNY, including
at the international level. The relative success of the pilot study suggests that the research merits
attempted at seeking further funding, perhaps from Federal agencies to conduct a survey in the
US Northeast with the aim of developing an urban soil-screening protocol that sufficiently
reduces requirements of resources and scientific background so as to reach the widest possible
applicability. To this end, efforts have been made to seek collaboration with projects already
under way at Cornell University Waste Management Institute to understand the multiple
pathways whereby pollutants may accumulate in urban grown crops. A future survey would not
only involve many more sites in multiple cities within the US Northeast, but also more precise
lab tests (e.g., sequential analysis) and multiple years of field testing, sampling, and lab analyses
to improve the accuracy of a potential, publicly usable protocol.