Assessing pesticide, trace metal, and arsenic contamination in soils and dam sediments in a rapidly expanding horticultural area in Australia.

Industrial horticulture can release pesticides and trace metals/metalloids to terrestrial and aquatic environments. To assess long-term and more recent land contamination from an expanding horticultural region, we sampled soils from chemical mixing, crop production, and drainage areas, as well as retention reservoirs (dam) sediments, from 3 blueberry farms with varying land-use history in subtropical Australia. Soils were analysed for 97 different pesticides and trace metal/metalloid contents. The most recent farm had fungicides propiconazole and cyprodinil contents that may compromise soil invertebrate survival and/or nutrient recycling (5-125 mg kg). A site previously used to cultivate bananas had 6 dam sediment subsamples with arsenic contents over sediment quality guidelines (SQG); however, the soil content values were just below Australian health investigation levels (100 mg kg). Arsenic is suspected to originate from pesticide application during previous banana cultivation in the region. Dam sediment cores at all sites had mercury contents over the SQG likely due to fungicides or fertiliser impurities. Mean contents of mercury from dam sediments (141 ± 15.5 µg kg) were greater than terrestrial soils (78 ± 6.5 µg kg), and sediment profiles suggest mercury retention in anoxic sediments. Soils in chemical mixing areas at two sites were contaminated with copper and zinc which were above the national soil ecological investigation levels. Based on toxicity data, distribution, persistence, and mobility, we identified the fungicide cyprodinil, mercury, and phosphorus as contaminants of the greatest concern in this intensive horticulture area of Australia. Additional sampling (spatial, chemical speciation, biotic) is required to support mitigation efforts of the emerging contamination in the rapidly expanding blueberry farms of this region of Australia.