Management of human health risk in the context of kitchen gardens polluted by lead and cadmium near a lead recycling company

Purpose

At the global scale, gardening activities are often performed in urban areas with a historical background of pollution. In this study, a participatory program was developed with citizens concerned by gardening activities near a 50-year-old regulated lead recycling company, with the aim of co-constructing the tools for the assessment and management of potential sanitary risks induced by historic pollution with persistent (eco) toxic metals: lead and cadmium.

Materials and methods

Soils and vegetables (lettuce, leek, celery, carrot, chard, pumpkin, and celeriac) samples were collected from four kitchen gardens neighboring a 50-year-old secondary lead smelter. Both total and in vitro human bioaccessible metal concentrations in the cultivated plants were measured in relation to soil characteristics.

Results and discussion

The results showed that the soils of these gardens were slightly contaminated by metals (Pb, 77 to 236 mg kg^?1; and Cd, 0.5 to 1 mg kg^?1) in comparison with the natural geologic background. However, significant pollution of vegetables can occur especially with lead (Pb up to 9.8 mg kg^?1 in lettuce) and certainly as a result of direct foliar transfer. The washing of plants before consumption is therefore recommended in the context of atmospheric fallout of ultrafine particles enriched with metals.

Conclusions

Metal bioaccessibility measure integrates the influence of metal type, plant type, and soil physico-chemical properties. Based on the results, it is proposed that human bioaccessible fraction of metals may also be currently taken into account as well as total metal quantities and bioaccumulation factors in risk assessment studies performed in gardens. Overall, this study has led to reflections and functional recommendations aimed at reducing human exposure and to finally developing sustainable gardening practices.

     

Metal soil pollution differentially affects both the behaviour and exposure of <Emphasis Type="Italic">A. caliginosa</Emphasis> and <Emphasis Type="Italic">L. terrestris</Emphasis>: a mesocosm study

The effects on two earthworm species of a gradient of metal contamination in soil collected close to a 50-year-old lead recycling factory were investigated in mesocosms filled with soil sampled at three distances from the factory (10, 30 and 60 m). After 5 weeks of exposure, earthworm litter consumption and weight change were measured. Burrow systems were analysed using X-ray tomography, and water infiltration was measured. No significant differences in earthworm weight or activity were observed between mesocosms filled with soil from 30 and 60 m. In contrast, both earthworm species significantly lost weight and burrowed less in the soil sampled at 10 m. In the cores filled with the soil collected at 10-m distance, Aporrectodea caliginosa avoided the highly contaminated first layer (0–5 cm) and burrowed deeper whereas Lumbricus terrestris burrowed relatively more in this layer. We assume that these different reactions are associated with their ecological types. Epi-anecic earthworms forage litter at the soil surface, whereas endogeic earthworms are geophagous and thus are able to forage deeper. This was further corroborated by the bioaccumulation factors measured for each species: for L. terrestris, BAF values for Pb and Cd only decreased slightly in the 10-m soil correlating with their overall reduced activity. However, BAF values for A. caliginosa were 20-fold lower compared to those observed in soil from 30 and 60 m. These modifications in burrowing behaviour in the 10-m mesocosms resulted in a significant and marked decrease in water infiltration rates but only for L. terrestris.     

Enhancing Household Food Security Under Changing Climatic Conditions: A Case Study of Gokwe North and Hurungwe Districts in Zimbabwe

The effects of climate change are largely felt by smallholder farmers in southern Africa who rely on rain-fed agricultural production. This study used data from a cross-sectional household to investigate the factors that influence a household's adaptive capacity. Results show that there is a positive and statistically significant correlation between receiving information on crop production (p <.01), access to early warning information (p <.01 and adaptive capacity. Without adaptation, it is impossible for smallholder farmers to enhance food security. The study recommends that there is need to improve farmers' knowledge of climate change adaptation technologies and access to early warning information.     

Expression of the limited‐transpiration trait under high vapour pressure deficit in peanut populations: Runner and virginia types

Drought can be a critical limitation on peanut yield. A physiological trait that may help to ameliorate drought is limited transpiration (TR_lim), defined as a limitation on further increases in transpiration rate (TR) under high vapour pressure deficit (VPD) conditions. The advantage of the TR_lim trait is that it allows plant water conservation to increase soil water availability for use during late‐season drought. While this trait has been identified in peanut, there is no information of how readily the trait may be transfer to progeny lines. The objective of this study was to obtain preliminary information on the expression of the TR_lim trait in two peanut progeny populations. One population was runner type of 88 RILs derived from the mating of Tifrunner × NC 3033. The second set was selected for the virginia‐type phenotype of large pods obtained from mating of PI 585005 (ICGV 86015) and N0808olJCT, both of which expressed the TR_lim trait. A two‐tier screen was applied to both populations. The initial screen was based on exposure of de‐rooted shoots to silver ions. Fifteen runner type and 12 virginia type were selected for direct measures of transpiration response to varying VPD. The results from each of the two populations showed that an effective expression of the TR_lim trait occurred in about 30% of the progeny in each population. While these results do not offer a definitive index of inheritance, they do indicate that there appears to be a strong possibility of transferring the TR_lim trait to progeny genotypes.