Table 3.

Statistical analysis of eight trace elements in three crops. The different capital letters after the Mean values indicate a significant difference (p < 0.05) in trace element content or soil properties among the three farmlands using One-way ANOVA, whereas same capital letters show no significant differences (p > 0.05). Risk Control Standard (RCS) is regulated by the China Health Ministry (supporting information Table S7).

Farmlands	Trace elements	Min (mg kg−1)	Max (mg kg−1)	Mean (mg kg−1)	RCS	SD (mg kg−1)	Exceedance rate (%)
Grain N = 63	As	< 0.01	0.08	1.78 × 10–2 A	≤ 0.70	1.48 × 10–2	0.00
	Cd	< 0.001	0.02	3.17 × 10–3 A	≤ 0.05	4.42 × 10–3	0.00
	Cr	0.03	1.98	0.37 B	≤ 1.00	0.34	4.76
	Cu	0.52	2.39	1.48 A	≤ 10.00	0.32	0.00
	Hg	< 0.003	0.01	2.13 × 10–3 A	≤ 0.02	2.92 × 10–3	0.00
	Ni	< 0.05	0.05	0.03 × 10–2 B	≤ 0.40	0.01	0.00
	Pb	< 0.02	0.20	4.01 × 10–2 B	≤ 0.40	4.81 × 10–2	0.00
	Zn	0.73	15.80	10.21 A	≤ 50.00	4.10	0.00
Melon and fruits N = 135	As	< 0.01	0.15	1.68 × 10–2 A	≤ 0.50	1.94 × 10–2	0.00
	Cd	< 0.001	0.07	4.03 × 10–3 A	≤ 0.03	8.67 × 10–3	2.22
	Cr	< 0.05	3.44	0.26 B	≤ 0.50	0.34	11.11
	Cu	< 0.20	3.47	1.06 A	≤ 10.00	0.53	0.00
	Hg	< 0.003	0.01	1.50 × 10–3 A	≤ 0.01	2.23 × 10–3	0.00
	Ni	< 0.05	0.33	0.02 A	≤ 0.40	0.06	0.00
	Pb	< 0.02	0.18	0.06 AB	≤ 0.20	0.04	0.00
	Zn	0.23	6.12	1.36 C	≤ 5.00	1.08	1.48
Vegetables n = 337	As	< 0.01	0.31	0.02 A	≤ 0.50	0.03	0.00
	Cd	< 0.001	0.04	8.33 × 10–3 B	≤ 0.05	7.56 × 10–3	0.00
	Cr	< 0.20	0.73	0.09 A	≤ 0.50	0.08	1.18
	Cu	< 0.003	3.22	0.94 A	≤ 10.00	0.56	0.00
	Hg	< 0.05	0.64*10–2	1.76 × 10–4 B	≤ 0.01	0.85 × 10–4	0.00
	Ni	< 0.02	0.15	2.84 × 10–2 B	≤ 0.40	1.71 × 10–2	0.00
	Pb	< 0.02	0.26	0.06 A	≤ 0.20	0.04	0.89
	Zn	0.49	8.37	2.99 B	≤ 20.00	1.31	0.00