My translation The sampling strategy was in accordance with DZ/T 0258-2014 Specification of Multi-Purpose Regional Geochemical Survey (1: 250000). Surface and deep layer soil samples were collected in double-layer grid cell respectively, according to normalized protocols of sample density, sample depth and sampling procedure. Deep layer soil represents the First Environment, natural soil environment in which no human influence occurs, while surface layer soil represents the Second Environment, natural soil environment in which human influence occurs. Surface layer soil samples are collected at a density of 1 site per 1 km2 in plains, basins, hills, mountain, Loess Plateau, etc. and at a higher density of 2 sites per 1 km2 in cities and towns, mines and surrounding area. Sample density is lower to 1 or 2 sites per 4 km2 in wetlands like lakes, rivers and swamps/marshes and in the special area like forests, grasslands and deserts. Deep layer soil samples are collected at a density of 1 site per 4 km2 in plains, basins, hills, mountain, Loess Plateau, etc. Sample density is lower to 1 or 2 sites per 16 km2 in wetlands like lakes, rivers and swamps/marshes and in the special area like forests, grasslands and deserts. Sampling should be at ten meters below the low tide line of depth in coastline marine. Surface layer samples of submarine sediments are collected at a density of 1 or 2 sites per 4 km2, at a higher density of 1 site per 1 km2 in estuaries and gulfs and at a lower density of 1 or 2 sites per 16 km2 in flat terrain. Deep layer samples of submarine sediments are collected at a density of 1 site per 16 km2 and at a lower density of 1 or 2 sites per 16 km2 in flat terrain. Surface layer soil were sampled at a depth of 0-20 cm. Deep layer soil were sampled at a depth of 150-180 cm in thick-soil-covering and flat areas of the eastern and central China, lakes and sea areas, at a depth of 120-150 cm in hills and mountains, and at a depth of 100-120 cm in thin soil areas of the west. Sampling depth depended on average soil thickness and was consistent with each other in a certain geographic area when thin soil can’t meet requested sample depth.