URI: https://soilwise-he.github.io/soil-health#MonitoredHeavyMetals
https://soilwise-he.github.io/soil-health#MonitoredHeavyMetals
arsenic
cadmium
chromium
copper
lead
mercury
nickel
zinc
http://aims.fao.org/aos/agrovoc/c_2223
sampling intervals
VanCamp2004b