Urban gardening has become increasingly popular, creating green oases in cities; however, many of these activities are undertaken in areas of high traffic density or on ex-brown field sites. As a consequence, there are still some barriers to the adoption of these urban gardening practices for food production. One of the public concerns is the transfer of urban pollutants such as heavy metals into the consumer’s food chain, however, city-wide data is often difficult and expensive to collect. In the citizen science project described herein, we conducted simple citizen-led common collaborative experiments in urban community gardens. These data provided information on the potential risk of heavy metal contaminants and ways in which to mitigate those risks in an urban gardening context. Generally, values were below guideline thresholds, however, at a few garden sites, soil trace metal concentrations (Pb, Cd, Zn) exceeded Austrian recommended limits. Moreover, only at two sites were plant trace metal concentrations shown to be above European food standards limits. Given the citizen’s positive response to the project, we suggest expanding this study to the whole of Vienna, giving newly established gardens a chance to predetermine the risks posed by their local soils.
A b s t r a c t. Concerning the contribution of fungi to soil carbon sequestration, various methods have been used to extract ergosterol from soil samples. This study aims to explore the extraction ability and applicability of commonly used methods to extract ergosterol from two contrasting soils. An agricultural soil (chernozem) and a forest soil (podzol) were extracted with different types of cell lysis such as alkaline, glass bead, and ultrasonication methods in association with simple shaking. The ergosterol concentration was measured by high pressure liquid chromatography. Regardless of the method applied, ergosterol yield was higher in podzol than in chernozem. Alkaline extraction resulted in the highest ergosterol concentrations for both soils and miniaturized glass bead extraction produced comparable results in the case of chernozem. In terms of applicability, the non-alkaline methods were simpler to conduct and less demanding of labour, chemical use and glassware and more flexible in terms of the equipment used for mechanical disruption. Despite the limit of the two soil types in the present study, only the simple shaking method was revealed to be dependent on soil type. Based on our results, we recommend the miniaturized glass bead method for agricultural soils, low in organic matter for high throughput. However, not all of the methods described allow for the proper separation of coextracted organic substances from organic-rich soil.
<p>Urban Gardening has become increasingly popular globally in the past two decades as urbanites begin to recognise the benefits of growing their own food and the sense of community these gardening activities engender. These activities grow as citizens reclaim derelict land and are increasingly using roof top gardens and novel containers, providing much needed green oases in the city, concepts which are particularly popular with the &#8220;share&#8221; generation. However, many such sites are in areas of high traffic density, on brown field sites or on sites overlying landfill, as a result of their urban location. The proximity to such sites may lead to worries about the food safety and reduction of the adoption of such healthy urban gardening practices. One of the main concerns is the transfer of urban pollutants into the consumer&#8217;s food chain. Trace metals are one of the contaminants frequently found in urban crops and soils. Perceived concerns about the effects of these heavy metal contaminants on human health often outweigh the true risk; part of the problem is the lack of data in the urban production context. Moreover, collection of city-wide data on the health of the soil is often difficult and expensive to collect. In this project we intend to attempt to overcome these issues by recruiting citizens to conduct simple common collaborative experiments in their urban gardens, from these data we will create a city map of soil health status and providing information on potential risk of heavy metal contaminants and ways in which to mitigate those risks in an Urban Gardening context. We chose a citizen science approach in this project, not only as it will allow us to gather a wealth of data but also it will empower us to jointly generate useful information for the greater public good which can contribute towards creating green sustainable cities.</p><p>This project will place the citizen at the heart of the experimental process in contrast to more traditional observational data collection. Using an experimental approach really exposes the citizens to the scientific process and enables them to gain tacit knowledge of how scientists overcome variance, bias and arrives at scientifically sound evidence based conclusions. As a result, citizen science can provide reassurance to the public about the rigour and process of scientific enquiry. In doing so it can inspire confidence and understanding of the nuances of political bias; putting contextual knowledge together, in learning by doing.</p>
The remediation of Pb, Cd, and Zn contaminated soil by ex situ EDTA washing was investigated in two pot experiments. We tested the influence of (i) 0, 0.5, 1.0, and 1.5%wt zero-valent iron (ZVI) and (ii) a combination of 5%wt vermicompost, 2%wt biochar, and 1%wt ZVI on the metal availability in EDTA-washed soil using different soil extracts (Aqua regia, NH4NO3) and plant concentrations. We found that EDTA soil washing significantly reduced the total concentration of Pb, Cd, and Zn and significantly reduced the Cd and Zn plant uptake. Residual EDTA was detected in water extracts causing the formation of highly available Pb-EDTA complexes. While organic amendments had no significant effect on Pb behavior in washed soils, an amendment of ≥ 1%wt ZVI successfully reduced EDTA concentrations, Pb bioavailability, and plant uptake. Our results suggest that Pb-EDTA complexes adsorb to a Fe oxyhydroxide layer, quickly developing on the ZVI surface. The increase in ZVI application strongly decreases Zn concentrations in plant tissue, whereas the uptake of Cd was not reduced, but even slightly increased. Soil washing did not affect plant productivity and organic amendments improved biomass production.
Soil remediation is an important practice in the restoration of heavy metal-contaminated soils and reduce the heavy metal exposure of the local population. Here, we investigated the effect of an ex-situ soil washing technique, based on ethylenediaminetetraacetic acid (EDTA) as a chelating agent, on a contaminated Cambisol. Lead, Cd and Zn were investigated in different soil fractions, drainage water and four vegetables from August 2019 to March 2021. Three treatments consisting of (C) contaminated soil, (W) washed soil and (WA) washed soil amended with vermicompost and biochar were investigated in an outdoor raised bed set up. Our results showed that the total and bioavailable metal fractions were significantly reduced but failed to meet Austrian national guideline values. Initial concentrations in the soil leachate increased significantly, especially for Cd. Vegetables grown on the remediated soil took up significantly lower amounts of all heavy metals and were further reduced by the organic amendment, attaining acceptable values within EU guideline values for food safety. Only spinach exceeded the thresholds in all soil treatments. The increase in soil pH and nutrient availability led to significantly higher vegetable yields.
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