Table 1.

Environmental quality standard for soils in China (GB 15618-1995) [22], heavy metal standards for food safety (GB2715–2005) [23] (mg·kg⁻¹).

Heavy Metals	Grade 1	Grade 2			Grade 3	Food Safety Standards (In Rice)
	National Backgrounds	pH < 6.5	pH 6.5–pH 7.5	pH > 7.5	pH > 6.5
Cd ≤	0.20	0.30	0.30	0.6	1.0	0.20
Hg ≤	0.15	0.30	0.50	1.0	1.5	0.02
Pb ≤	35	250	300	350	500	0.20
Cr ≤	90	250	300	350	400	1.0