Progress 07/20/05 to 07/19/08

Outputs
OUTPUTS: In the time period of this report, 50 soil samples were submitted for analysis. These samples were all from community garden sites or potential community garden sites. In all cases, the sample was analyzed for over twenty elements of concern such as arsenic, lead, and chromium. The overarching goal of this work is to assess sites throughout Connecticut in urban, surburban, and rural locations in order to ascertain their suitability for community garden locations. If it is determined that the presence of one or more elements is in excess of state residential guidelines, our scientists will discuss with the garden operator attentuation alternatives. PARTICIPANTS: For the period of this report: David Stilwell, Craig Musante, John Ranciato TARGET AUDIENCES: Communities throughout the state with an interest in establishing community gardens. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Many community gardens or intended sites are located in urban areas. Such sites are commonly suspected of heavy metal contamination. Nevertheless, should this be found to be the case at a given location, we have often been able to suggest approaches to attentuate the contamination burden. At such sites our advice may be critical to the establishment of gardens to address issues such as food security and even obesity. At the very least, such community resources as gardens have been shown to increase a sense of community pride and responsibility. It should not be assumed that community garden sites are limited to urban locations and thus the typical pollutation sources associated with such locations. Gardens intended for former agricultural locations also need to be surveyed for potential contamination.

Publications

• B1018 (2008) Use of Phosphates to Immobilize Lead in Community Garden Soils. David E. Stilwell and John F. Ranciato.
• B1019 (2008) Lead and Other Heavy Metals in Community Garden Soils in Connecticut. David E. Stilwell, Thomas M. Rathier, Craig L. Musante, and John F. Ranciato.
• B1020 (2008) Comparison of Heavy Metals in Community Garden Produce versus Store-Bought Produce. David E. Stilwell, Thomas M. Rathier, and Craig L. Musante.

Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: Community gardens are public spaces, typically managed by members of the local community. Industrial and agricultural practices resulted in increased amounts of lead (Pb) and other heavy metals in soils. Consequently, many people working in community gardens are concerned about the possibility of excess Pb and other heavy metals in the soil. We are conducting a multi-year study to determine the amounts of heavy metals in garden soils. Over this period we acquired 31 composite samples from 8 community gardens in 6 cities. The results for Pb ranged from <10 to 2020 mg/kg, and for arsenic they ranged from 3 to 58 mg/kg. Of the eight gardens, 5 of them (62%) had at least one sample exceeding the 400 mg/kg limit for Pb, or the 10 mg/kg limit for As. The copper and zinc levels tended to be higher than farm soil, but were all well below limits. The cadmium, chromium, and nickel content in the gardens soils were the same as those in the farm soil. One remediation strategy in soils containing high Pb level involves adding phosphate (P) based compounds to the soil, which form insoluble Pb compounds. Care should be taken, though, because excess P can be a major pollutant in watersheds. We added 3 types of P soil amendments at a concentration of 1000 and 5000 mg/kg P to 8 garden soils with Pb contents ranging from 30 to 8000 mg/kg. The three amendments were, in increasing order of solubility, rock phosphate (RP), triple super phosphate (TSP), and monobasic sodium phosphate (NAP). After ageing for two months the heavy metal and phosphorus content in a total of 224 extracts was determined using the simulated precipitation extraction procedure (SPLP), EPA method 1312, which is used to predict the potential for pollutants, including phosphates and heavy metals to leach into surface and ground water after rain events. The most noticeable decrease was at the 0.5% P level for both TSP and RP, where the SPLP Pb was reduced by 39%(RP)and 58%(TSP). The average % Pb extracted from unamended soils was 0.7, 0.3 in the RP amended soils at the 0.5% P level and 0.4 in the TSP amended soils at the 0.5% level. Thus, at the 0.5% amendment level for RP or TSP the Pb extracted was reduced by roughly 50%. The SPLP P in TSP and NAP extracts tended to increase with soil P following a second power relationship. The average SPLP P (mg/l) in the 0.1% and 0.5% TSP amended soils were 7 and 47, respectively, while the average P in SPLP extracts from NAP soils were much higher 13(0.1% NAP) and 101(0.5% NAP). In soils amended with RP, the SPLP P remained flat over the entire concentration range. The average SPLP P (mg/l) in the RP amended soils were 1.1 and 1.0 in the 0.1% and 0.5% amended soils, compared to 0.9 in the unamended soils. Using RP as an amendment was vastly superior to TSP and NAP in minimizing soluble P. Though soil ingestion is the major source of exposure in contaminated gardens, consumption of plants grown in these soils is also important to consider. We have developed a method for analyzing heavy metals in plants using ICP-MS and are analyzing a number of vegetable samples. PARTICIPANTS: Dr. David Stilwell is the principal investigator on the project. TARGET AUDIENCES: Community gardeners, home gardeners, community garden groups (CT Community Gardeners Association, American Community Garden Association), State soil testing laboratories, State Cooperative Extension Services, lead treatment and educational agencies, State Environmental and Health Agencies, city based urban land use and development agencies and non-profit urban land use advocacy groups.

Impacts
In urban areas, activities such as transportation, construction and manufacturing have resulted in increased heavy metals, notably lead in the surrounding soils. Community gardeners in these urban areas need to be aware of the potential for elevated levels of these metals in the soil and of the potential health risks that is posed by gardening in these soils. The EPA lists lead and arsenic among contaminants of widespread concern on its priority list. These contaminants may be ingested by breathing contaminated dust, participating in hand to mouth activities (primarily by children) or by consuming contaminated produce. The CDC (Center for Disease Control) recognizes that Pb exposure can cause health problems and has a national goal to eliminate childhood lead exposure by 2010. There are hundreds of community gardens located in urban, suburban and rural communities throughout New England, and over 6000 community gardens were identified in a recent survey of the USA. These gardens are typically managed by members of the local community and/or school systems. To help community gardeners assess risk, we are determining the extent of contamination in urban garden environments compared to suburban gardens in a geographically similar region. In order to assure the safety of foods grown in community gardens we are developing methods using a very sensitive technique (ICP-MS) for elemental analysis to compare heavy metals in produce grown in community gardens to those from market. We are also conducting soil remediation experiments using phosphate based soil amendments.

Publications

• No publications reported this period

Progress 01/01/06 to 12/31/06

Outputs
Community gardens are community spaces that are open to the public. Over 6000 community gardens were identified in a recent survey of 38 US cities. However, industrial activities increased the heavy metal content, notably lead, in urban soils. As a result, community garden soils in urban areas can be severely contaminated with lead (Pb) and other heavy metals. Because Pb exposure can result in health problems, we are conducting a study to determine the amounts of Pb and other heavy metals in soils and plants in urban areas. Over this reporting period, we acquired 54 composite samples from 9 community gardens in 5 cities. The results for Pb ranged from <20 to 558 mg/kg, and for arsenic (As) they ranged from 2 to 25 mg/kg. Of the seven gardens in native soil, 5 of them (71%) had at least one sample exceeding the 400 mg/kg limit for Pb, or the 10 mg/kg limit for As. The copper and zinc levels tended to be higher than farm soil, but the levels were all well below the limit. The cadmium, chromium, and nickel content in the gardens' soils were the same as those in the farm soil. We also sampled two other gardens that had been remediated by filling raised beds with clean soil and these were confirmed to be uncontaminated. Continued testing is planned. Another remediation strategy in soils containing high Pb level involves adding phosphate based compounds to the soil, which form insoluble Pb compounds. We added 3 types of phosphorus (P) soil amendments at a concentration of 1000 and 5000 mg/kg P to 8 garden soils with Pb contents ranging from 30 to 8000 mg/kg. The three P amendments were, in increasing order of solubility, rock phosphate (tri-calcium di-phosphate), triple super phosphate (calcium dihydrogenphosphate), and monobasic sodium phosphate. After ageing for two months the heavy metal and phosphorus content was determined in extracts. In general, when the soil P was in excess of 1000 ppm, no further lowering in Pb in the extracts were noted, and as the P levels increased the As levels in the extracts increased. The P in the extracts were much lower in rock phosphate amended soils, suggesting that this amendment worked best since P in rainwater runoff can be harmful to streams and lakes. Further work to optimize this remediation strategy is in process. Though soil ingestion is expected to be the major source of exposure in contaminated gardens, consumption of plants grown in these soils is also important to consider. We now have a sensitive instrument (ICP-MS) which allows use to determine heavy metals at levels at least an order of magnitude lower than our previous detection limits. In one trial, we compared the heavy metal content in lettuce and collard greens grown in a modestly contaminated garden to those bought at market. Many of the heavy metals were elevated in the garden grown plant samples. For example, the Pb was 120 ppb in lettuce and 34 ppb in the collard greens compared to 2-4 ppb in market produce. These levels did not, however, exceed international limits for Pb in produce (300-1000 ppb). We are in process of analyzing a number of other vegetable samples acquired during the growing season.

Impacts
In urban areas, activities such as transportation, construction and manufacturing have resulted in increased heavy metals, notably lead in the surrounding soils. Community gardeners in these urban areas need to be aware of the potential for elevated levels of these metals in the soil and of the potential health risks that is posed by gardening in these soils. To help with this assessment, we are determining the extent of contamination in urban garden environments compared to suburban gardens in a geographically similar region. In order to assure the safety of foods grown in community gardens, we are developing methods using a very sensitive technique (ICP-MS) for elemental analysis to compare heavy metals in produce grown in community gardens to those from market. We are also conducting soil remediation experiments using phosphate-based soil amendments designed to maximize lead immobilization, while minimizing phosphorus mobility. Thus, the bioavailability of lead, simulated by soil extraction techniques, can be compared with other extraction methods that relate to phosphorus and heavy metal mobility. The use of phosphate amendments to immobilize heavy metals can be compared to other remediation schemes, include soil fractionation and washing using non-toxic lead release agents.

Publications

• No publications reported this period

Progress 07/20/05 to 12/31/05

Outputs
Community gardens are community-managed spaces that are open to the public. Over 6000 community gardens were identified in a recent survey of 38 US cities. However, activities such as transportation, construction and manufacturing have increased the heavy metal content, notably lead, in urban soils. As a result, community garden soils in urban areas can be severely contaminated with lead and other heavy metals. Because prolonged lead exposure can result in health problems, we are conducting a study to determine the amounts and bioavailability of this toxic element, as well as other heavy metals, in soils in urban areas. The results should help in adequately assessing the risks associated with gardening in these areas and in developing rational remediation strategies to reduce this risk. One method to reduce the bioavailability of lead is to add phosphate-based compounds. These compounds immobilize lead by forming insoluble compounds. Care should be taken to avoid adding excess phosphorus to the soil because excess phosphorus can damage plants, release arsenic from the soil, and be a major pollutant in watersheds. Accordingly, we have initiated experiments which will help to determine the optimal amount of phosphorus, which maximizes lead containment while minimizing its environmental effects. In this experiment, 3 types of phosphorus soil amendments, of various solubility, were added at a concentration of 1000 and 5000 mg/kg phosphorus, in duplicate, to 8 garden soils with lead contents ranging from 30 to 8000 mg/kg. After mixing, water was added to 100% holding capacity, and the soil mixtures were placed into 50 ml containers, and topped with a watch glass. The mixtures were weighed so that water could be added over the 2 month aging period to maintain the moisture level between 70-100% of capacity. The three phosphorus amendments were, in increasing order of solubility, rock phosphate (tri-calcium di-phosphate, 8% phosphorus), triple super phosphate (calcium dihydrogenphosphate, 21% phosphorus), and monobasic sodium phosphate (22% phosphorus). After ageing, we will compare these soil samples using standard extracts for phosphorus availability to those extracts designed to predict the mobility and bioavailability of heavy metals. Though soil ingestion is expected to be the major source of exposure in contaminated gardens, consumption of plants grown in these soils is also important to consider. In a preliminary trial, we grew lettuce, basil, chives, and arugula in pots containing uncontaminated and soil contaminated with copper, lead and arsenic. The uptake factor (concentration plant/concentration soil) was higher for copper and arsenic (0.1 to 2) than lead <.005 to 0.01, and in some cases, the lead content in the plants were below our limit of detection (0.5 mg/kg dry weight). We have just acquired a much more sensitive instrument (ICP-MS), which will allow use to determine lead at levels of least an order of magnitude lower than our previous detection limits. We are developing methods for lead in plant tissue using the ICP-MS.

Impacts
In urban areas, activities such as transportation, construction and manufacturing have resulted in increased heavy metals, notably lead in the surrounding soils. Community gardeners in these urban areas need to be aware of the potential for elevated levels of these metals in the soil and of the potential health risks that is posed by gardening in these soils. To help with this assessment, we are determining the extent of contamination in urban garden environments compared to suburban gardens in a geographically similar region. We are also conducting soil remediation experiments using phosphate-based soil amendments designed to maximize lead immobilization, while minimizing phosphorus mobility. Thus, the bioavailability of lead, simulated by soil extraction techniques, can be compared with other extraction methods that relate to phosphorus and heavy metal mobility. The results of the bioavailability trials will be compared to plant uptake of lead in field conditions. The use of phosphate amendments to immobilize heavy metals can be compared to other remediation schemes, include soil fractionation and washing using non-toxic lead release agents.

Publications

• No publications reported this period