Trace element and ΣDDT concentrations in horticultural soils from the Tasman, Waikato and Auckland regions of New Zealand

Abstract

The long-term routine use of agrichemicals can result in elevated levels of trace elements and persistent organic pollutants in soils. Trace element concentrations and ΣDDT levels were measured in soil (0–7.5 cm) samples collected from horticultural and grazing properties in 3 regions of New Zealand (Auckland, Tasman and Waikato). Elevated levels of arsenic (<2 to 58 mg kg − 1 ), cadmium (<0.1 to 1.5 mg kg − 1 ), copper (5 to 523 mg kg − 1 ), lead (5 to 243 mg kg − 1 ) and ΣDDT (<0.03 to 34.5 mg kg − 1 ) were detected in soils from all 3 regions. With the exception of cadmium and zinc, significantly higher levels of contaminants were generally detected in horticultural soils than in grazing soils. Our results have implications for the on-going use of agrichemicals as concentrations of cadmium, copper, tin and zinc in some samples exceeded ecotoxicity based soil criteria. The p, p′-DDE : DDT ratios indicate that the degradation of DDT in NZ horticultural soils may be inhibited by the co-contamination with trace elements.