Relationship of Arsenic and Lead in Soil with Fruit and Leaves of Apple Trees at Selected Orchards in Michigan

Abstract

Historically, lead arsenate pesticides were commonly used in fruit orchards. Residues of metals from this historical use can persist in soil for decades, which can result in potential risk for humans if they consume fruits grown on contaminated soil. This research was conducted to assess lead and arsenic levels in apples, leaves, and orchard soil where the apples were grown to determine the relationship between metal levels in fruits and fruit products with those in orchard soil. Soil and tree tissue samples were collected from several Michigan farms, and metal concentrations were quantified by using microwave extraction and inductively coupled plasma mass spectrometry. Soil samples were collected at depths of 0 to 20 cm and 20 to 40 cm at a distance of 1 m from the tree trunk. Fruit samples also were processed into juice and pomace fractions to assess the partitioning of arsenic and lead during juice processing. The lead concentration was significantly higher in topsoil (9.4 μg/kg) compared with subsoil (6.9 μg/kg), but the arsenic content did not differ between the two soil layers (P > 0.05). Lead concentrations in apple leaves were correlated with lead in topsoil (0 to 20 cm; P = 0.03). Concentrations of total arsenic in all juice samples were less than 1 μg/kg and showed less potential than lead for uptake and translocation to fruits. There was no significant relationship between soil arsenic content and total arsenic concentrations in juice, pomace, and leaf samples (P > 0.05). Results of this research indicate that lead and total arsenic concentrations in apples and apple products from these selected orchards in Michigan are unlikely to be impacted by the contamination of these metals in orchard soil. HIGHLIGHTS

Trace Elements in Garden Soils, Vegetables and Apples Near a Large Cu Tailings Pond in SW Poland

“…Arsenic concentrations were similar to typical levels reported for potato and beetroot commercially offered in Poland but higher in carrot, parsley, and apple. The legal threshold for As has not been specified in Poland/EU, but all samples under study had As concentrations lower than 0.5 mg kg -1 of a fresh mass (the highest observed was 0.18 mg kg -1 ) established as a limit in China [45]. The legal limits for Zn and Cu in vegetable and apple have not been established either in Europe, America, or China, as these metals are important microelements, often supplied to crops intentionally in fertilizers.…”

“…Although adversely oriented, these two relationships may have similar explanations. Cao and Bourquin [45] reported little impact of soil contamination with Pb and As on the quality of apple fruit, due to element blocking in roots and vegetative parts. The significant correlation between Pb in soil and apple in this study may be, therefore, an apparent effect of parallel relationships of the correlations between the distance from the tailings pond and Pb content in the garden/orchard soils (Table 3) and apple fruit (Table 5).…”