Many soils have contamination for various historical reasons. For example some cotton (and some tobacco?) fields in southern states formerly used arsenic as a p

Many soils have contamination for various historical reasons. For example some cotton (and some tobacco?) fields in southern states formerly used arsenic as a pesticide, then later switched to rice production, and this rice has significantly more arsenic in it than rice grown in California, which had no such history. I assume some of the arsenic in these juice samples is from a similar pattern of usage.