Relationships between Cd concentrations in different vegetables and those in arable soils, and food safety evaluation of vegetables in Taiwan

Figures & data

Table 1 Selected soil properties and soil cadmium (Cd) concentrations at experimental sites

			CEC^†	OM	Cd contents (mg kg^−1)
Location	Texture	pH	cmol kg^−1	%	Min.	Max.	Mean	SD
Bade-I^‡	SiCL^§	5.02	11.1	2.33	2.31	11.7	5.02	2.60
Bade-II	SiCL	6.60	11.0	2.30	2.12	19.4	7.26	5.11
Bade-III	SiCL	7.26	10.8	2.25	1.90	15.1	7.24	4.92
Dajia	SL	6.74	8.36	3.80	0.48	3.89	1.63	0.84
Houli	SiCL	6.15	7.69	1.41	2.36	3.89	3.16	0.34
Huwei	L	6.63	7.61	2.17	0.26	1.67	0.66	0.45

^†CEC: cation exchange capacity; OM: organic matter content; Min.: minimum values; Max.: maximum values; SD: standard deviation.

^‡Bade site was divided into three blocks in September 2011, of which two blocks were amended with 7.7 Mt ha⁻¹ and 14.8 Mt ha⁻¹ lime, respectively.

^§SiCL: silty clay loam; SL: sandy loam; L: loam.

Figure 1 Map of Taiwan and locations of municipalities where vegetable fields are located. (BD: Bade District, Taoyuan County; DJ: Dajia District, Taichung City; HL: Houli District, Taichung City; HW: Huwei Township, Yunlin County).

Figure 2 Distribution of cadmium (Cd) concentrations at experimental sites. (a) Bade site; (b) Dajia site; (c) Huwei site; (d) Houli site. Both the Bade and Houli sites were composed of two adjacent fields.

Table 2 Overview of pH, cation exchange capacity (CEC), total cadmium (Cd) and available metal concentrations in soil along with Cd concentrations, bioconcentration factor (BCF), and BCF rank of vegetables^†

Species	n^‡	pH	CEC cmol kg^−1	Total Cd mg kg^−1 DW	0.1 M HCl extractable metals mg kg^−1 DW					Veg-Cd mg kg^−1 FW	BCF	BCF rank
					Cd	Fe	Mn	Cu	Zn
Leafy vegetables
Sweet potato leaf (Ipomoea  batatas (L.) Lam.)	230	3.82–8.08	5.23–20.9	0.07–17.5	0.02–14.2	141–1241	4.38–243	0.91–70.8	3.46–59.8	0.001–0.707	0.040 ± 0.022	23
Water spinach (Ipomoea  aquatica Forsk.)	541	4.04–8.65	3.75–25.0	0.02–17.2	0.01–12.8	11.8–1477	5.07–280	0.29–108	3.79–157	0.004–2.32	0.146 ± 0.149	11
Amaranth (Amaranthus  tricolor L.)	291	4.04–8.01	5.69–24.1	0.06–16.2	0.03–12.9	37.4–1482	5.39–189	0.99–237	7.07–266	0.005–12.4	0.389 ± 0.348	2
Ceylon spinach (Basella rubra L.)	83	4.14–7.76	6.12–15.6	0.06–12.4	0.03–10.1	35.2–1307	5.11–165	0.79–85.2	4.07–74.3	0.004–2.86	0.226 ± 0.198	6
Chinese leek (Allium tuberosum  Rottl. ex K. Spreng.)	84	4.17–8.07	5.35–20.2	0.15–15.7	0.04–10.2	0.01–1012	6.12–270	0.13–75.0	0.02–99.5	0.003–2.06	0.094 ± 0.084	16
Gynura (Gynura bicolor DC.)	65	3.78–7.59	4.73–17.9	0.09–18.4	0.02–12.1	85.7–1253	5.67–177	1.35–56.3	4.09–87.3	0.014–3.53	0.313 ± 0.246	4
Celery (Apium graveolens L.)	147	4.62–8.89	3.96–26.7	0.06–16.8	0.02–10.2	0.01–1225	2.5–238	0.03–56.1	0.01–141	0.008–0.901	0.131 ± 0.076	14
Spinach (Spinacia oleraceae L.)	184	3.82–8.09	3.46–13.9	0.07–19.4	0.02–13.8	43.0–1300	4.39–280	2.66–71.2	7.73–104	0.016–4.14	0.340 ± 0.187	3
Garland chrysanthemum  (Chrysanthemum  coronarium L.)	158	4.15–7.58	3.54–12.8	0.07–17.3	0.04–14.8	0.01–980	1.83–241	0.08–69.8	0.90–93.0	0.001–6.02	0.210 ± 0.131	7
Green onion (Allium  fistulosum L.)	367	3.79–8.10	2.35–27.0	0.01–9.84	0.02–7.96	0.01–1461	3.16–314	0.04–86.3	0.34–121	0.001–1.77	0.111 ± 0.104	15
Lettuce (Lactuca sativa L. var.  crispa)	238	3.84–7.93	1.99–20.5	0.03–17.3	0.01–13.9	0.01–1072	1.56–462	0.01–84.3	0.01–192	0.001–3.12	0.149 ± 0.167	10
Pak choi (Brassica campestris  L. ssp. chinensis)	310	3.49–7.92	2.71–27.3	0.02–4.21	0.01–3.92	0.01–1305	6.66–318	0.16–82.9	2.10–171	0.004–0.467	0.094 ± 0.079	16
Brassica vegetables
Chinese cabbage (Brassica  pekinensis Skeels.)	295	3.65–8.34	3.65–24.9	0.02–15.4	0.01–12.0	0.01–2031	0.18–307	0.01–54.9	1.84–129	0.002–1.74	0.090 ± 0.072	19
Cauliflower (Brassica oleracea  L. convar. Botrytis)	91	4.44–7.94	2.64–13.3	0.09–15.7	0.01–13.2	41.7–1510	5.98–262	4.02–107	2.21–80.9	0.002–0.252	0.025 ± 0.023	27
Cabbage (Brassica oleracea  L. Capitata Group)	382	3.27–8.28	1.69–28.8	0.04–16.7	0.01–13.8	12.5–1592	5.34–362	1.27–96.8	1.62–73.5	0.001–0.399	0.032 ± 0.036	25
Broccoli (Brassica oleracea  L. Italica Group)	83	4.48–8.06	3.40–13.6	0.06–15.2	0.03–13.7	373–1271	4.40–284	2.11–96.6	2.52–66.9	0.001–0.357	0.035 ± 0.022	24
Root and tuber vegetables, stalk and stem vegetables
Radish (Raphanus sativus L.)	361	4.32–8.32	1.33–16.9	0.04–16.0	0.01–13.7	25.9–1085	6.06–201	0.92–75.4	1.89–104	0.001–0.373	0.061 ± 0.069	20
Carrot (Daucus carota L.)	409	4.50–8.33	0.60–12.8	0.01–14.6	0.01–12.7	0.01–1468	6.20–237	0.01–82.0	0.29–73.8	0.001–1.15	0.208 ± 0.314	8
Potato (Solanum tuberosum L.)	100	4.15–6.24	5.18–11.0	0.01–0.33	0.09–0.35	984–1754	14.1–164	2.59–7.90	3.16–16.5	0.002–0.088	0.180 ± 0.168	9
Taro (Colocasia esculenta (L.)  Schott)	239	4.16–7.88	0.22–13.6	0.04–0.49	0.06–0.33	0.01–1413	0.93–313	0.01–17.5	0.01–166	0.003–0.079	0.146 ± 0.117	11
Bulb vegetables
Garlic (Allium sativum L.)	53	5.38–8.10	7.01–9.62	0.09–3.20	0.04–2.27	291–1166	10.6–201	4.05–27.4	5.20–49.9	0.002–0.486	0.093 ± 0.050	18
Onion (Allium cepa L.)	50	6.26–7.98	4.41–15.5	0.16–0.26	0.07–0.11	339–669	156–286	5.82–9.31	5.45–8.00	0.003–0.012	0.025 ± 0.009	27
Fruiting vegetables
Corn (Zea mays L.)	158	3.41–8.20	2.14–13.4	0.05–11.7	0.02–10.3	15.8–1345	1.70–338	1.95–82.3	2.34–65.3	0.001–0.226	0.026 ± 0.025	26
Tomato (Lycopersicon esculeutum Mill.)	211	4.38–8.28	2.79–25.1	0.04–18.2	0.01–14.5	113–1305	5.18–202	0.01–102	1.85–91.3	0.001–0.242	0.051 ± 0.061	21
Sweet pepper (Capsicum  annuum L.)	84	4.13–7.85	3.64–15.6	0.04–18.7	0.03–15.0	241–1663	7.45–296	2.32–74.1	3.01–95.3	0.002–0.105	0.048 ± 0.042	22
Eggplant (Solanum melongena L.)	112	4.47–7.78	4.20–17.5	0.04–5.65	0.02–5.67	0.01–1213	6.07–333	0.01–94.3	0.13–111	0.004–1.13	0.135 ± 0.073	13
Cucumber (Cucumis sativus L.)	104	3.28–8.05	4.00–18.5	0.05–12.2	0.01–9.82	126–1276	6.18–302	2.85–95.3	2.69–94.8	0.001–0.083	0.007 ± 0.003	32
Okra (Hibiscus esculentus L.)	84	4.92–8.03	5.12–13.2	0.04–15.0	0.04–12.3	226–1529	5.63–133	2.37–79.7	4.16–105	0.011–2.54	0.239 ± 0.163	5
Sponge gourd (Luffa cylindrica  Roem.)	187	3.60–7.39	3.21–13.1	0.07–14.3	0.02–9.77	109–1178	4.37–191	1.65–40.3	2.42–65.2	0.001–0.108	0.022 ± 0.022	29
Bitter gourd (Momordica  charantia L.)	54	4.33–8.07	4.03–13.4	0.06–0.34	0.04–0.21	0.01–1155	19.7–208	0.08–13.1	1.33–52.1	0.001–0.002	0.006 ± 0.003	33
Pulse and legume vegetables
Snap bean (Phaseolus vulgaris L.)	81	4.65–7.50	5.53–13.8	0.13–15.2	0.08–12.2	274–789	4.82–51.7	4.92–74.1	13.5–55.7	0.001–0.237	0.018 ± 0.010	30
Asparagus bean (Vigna unguiculata (L.) Walp. ssp. sesquipedalis (L.) Verdc.)	92	5.01–7.60	4.03–20.9	0.07–15.0	0.05–12.7	299–1047	5.07–255	4.86–61.3	11.1–84.9	0.013–1.08	0.012 ± 0.007	31
Peanut (Arachis hypogaea L.)	123	4.82–7.84	2.42–13.3	0.01–17.5	0.01–12.3	330–1352	4.20–201	1.07–67.3	3.72–53.1	0.014–2.96	0.613 ± 0.582	1

^† Potato, taro, onion, and bitter gourd were only collected from general survey and by Lin et al. (2012).

^‡ n: sample size; Fe: iron; Mn: manganese; Cu: copper; Zn: zinc; Veg-Cd: Cd concentration in vegetables.

Table 3 Derived soil–plant transfer models of cadmium (Cd) concentrations in vegetables used in field experiments^†

			R^2§
	n	Soil to plant transfer model^‡	S1	S2	S3
Leafy vegetables
Sweet potato leaf (Ipomoea batatas (L.) Lam.)	230	log(Cd)veg = −0.1363 + 0.9633 log(Cd) – 0.2964 log(Mn) – 0.5599 log(Zn)	0.88	0.91	0.92
Water spinach (Ipomoea aquatica Forsk.)	541	log(Cd)veg = 0.6312 + 0.9289 log(Cd) – 0.4372 log(Mn) – 0.4983 log(Zn)	0.82	0.89	0.92
Amaranth (Amaranthus tricolor L.)	291	log(Cd)veg = 1.4977 + 0.8502 log(Cd) – 0.5822 log(Mn) – 0.1818 pH	0.83	0.89	0.93
Ceylon spinach (Basella rubra L.)	83	log(Cd)veg = 0.2072 + 0.7927 log(Cd) – 0.5531 log(Mn)	0.85	0.93
Chinese leek (Allium tuberosum Rottl. ex K. Spreng.)	84	log(Cd)veg = 0.7497 + 0.7521 log(Cd) – 0.2439 pH – 0.2272 log(Mn)	0.90	0.95	0.96
Gynura (Gynura bicolor DC.)	65	log(Cd)veg = 1.1947 + 0.7025 log(Cd) – 0.5462 log(Mn) – 0.156 pH	0.83	0.91	0.95
Celery (Apium graveolens L.)	147	log(Cd)veg = −0.332 + 0.594 log(Cd) – 0.3047 log(Mn) – 0.0876 log(Zn)	0.79	0.84	0.85
Spinach (Spinacia oleraceae L.)	184	log(Cd)veg = 0.692 + 0.6819 log(Cd) – 0.3975 log(Mn) – 0.085 pH	0.88	0.92	0.93
Garland chrysanthemum (Chrysanthemum coronarium L.)	158	log(Cd)veg = 1.2146 + 0.8481 log(Cd) – 0.2443 pH – 0.3117 log(Mn)	0.82	0.90	0.91
Green onion (Allium fistulosum L.)	367	log(Cd)veg = 1.6048 + 1.1543 log(Cd) – 0.3113 pH – 0.5006 log(Zn)	0.59	0.79	0.81
Lettuce (Lactuca sativa L. var. crispa)	238	log(Cd)veg = 0.7537 + 0.8902 log(Cd) – 0.1712 pH – 0.3611 log(Mn)	0.78	0.83	0.85
Pak choi (Brassica campestris L. ssp. chinensis)	310	log(Cd)veg = 0.0242 + 0.8036 log(Cd) – 0.3687 log(Zn) – 0.2869 log(Mn)	0.61	0.75	0.80
Brassica vegetables
Chinese cabbage (Brassica pekinensis Skeels.)	295	log(Cd)veg = −0.7406 + 0.6815 log(Cd) – 0.2458 log(Mn)	0.80	0.83
Cauliflower (Brassica oleracea L. convar. Botrytis)	91	log(Cd)veg = −0.2687 + 0.2918 log(Cd) – 0.5325 log(Mn) – 0.0908 pH	0.72	0.84	0.85
Cabbage (Brassica oleracea L. Capitata Group)	382	log(Cd)veg = −0.2028 + 0.9462 log(Cd) – 0.5953 log(Zn) – 0.0935 pH	0.76	0.82	0.85
Broccoli (Brassica oleracea L. Italica Group)	83	log(Cd)veg = −0.427 + 0.9973 log(Cd) – 0.7186 log(Zn)	0.86	0.94
Root and tuber vegetables, stalk and stem vegetables
Radish (Raphanus sativus L.)	361	log(Cd)veg = −1.1169 + 0.5133 log(Cd) – 0.2731 log(Mn) – 0.097 pH	0.42	0.45	0.46
Carrot (Daucus carota L.)	409	log(Cd)veg = 0.5360 + 0.6985 log(Cd) – 0.7402 log(CEC) – 0.6569 log(Mn)	0.55	0.58	0.61
Bulb vegetables
Garlic (Allium sativum L.)	53	log(Cd)veg = 1.6924 + 1.6671 log(Cd) – 1.337 log(Zn) – 0.3089 log(Mn)	0.92	0.95	0.96
Fruiting vegetables
Corn (Zea mays L.)	158	log(Cd)veg = 0.4826 + 0.8236 log(Cd) – 0.5999 log(Fe) – 0.2979 log(Mn)	0.75	0.79	0.92
Tomato (Lycopersicon esculeutum Mill.)	211	log(Cd)veg = −0.1841 + 0.9173 log(Cd) – 0.822 log(Zn)	0.83	0.88
Sweet pepper (Capsicum annuum L.)	84	log(Cd)veg = −1.0287 + 0.6045 log(Cd) – 0.3611 log(Zn)	0.88	0.89
Eggplant (Solanum melongena L.)	112	log(Cd)veg = −0.1647 + 0.9125 log(Cd) – 0.2465 log(Mn) – 0.1928 log(Zn)	0.84	0.86	0.87
Cucumber (Cucumis sativus L.)	104	log(Cd)veg = −1.457 + 0.8186 log(Cd) – 0.109 pH	0.85	0.88
Okra (Hibiscus esculentus L.)	84	log(Cd)veg = 0.3565 + 0.9992 log(Cd) – 0.5309 log(Zn) – 0.1423 log(Mn)	0.90	0.94	0.95
Sponge gourd (Luffa cylindrica Roem.)	187	log(Cd)veg = −1.0044 + 0.8292 log(Cd) – 0.2878 log(Zn) – 0.0784 pH	0.40	0.42	0.44
Pulse and legume vegetables
Snap bean (Phaseolus vulgaris L.)	81	log(Cd)veg = 0.0368 + 1.0855 log(Cd) – 0.1446 pH	0.65	0.76	0.78
Asparagus bean (Vigna unguiculata (L.) Walp. ssp. sesquipedalis (L.) Verdc.)	92	log(Cd)veg = −1.2676 + 0.6044 log(Cd) – 0.4597 log(Mn)	0.86	0.89
Peanut (Arachis hypogaea L.)	123	log(Cd)veg = 0.9439 + 0.9146 log(Cd) – 0.5698 log(Cu) – 0.0699 pH	0.78	0.88	0.89

^†Field experimental data, general surveyed data and those collected by Lin et al. (2012) were used to derive the soil to plant transfer models.

^‡The variables of each model equation were put in order according to the sequence they were selected into the model in stepwise regression.

^§Coefficients of determination. S1, S2 and S3 were coefficients of determination of model equation when first, second and third variables were selected into the model, respectively. All R² are significant at the level p < 0.001.

^¶log(Cd)_veg represents log₁₀ values of Cd concentrations in vegetables in mg kg⁻¹ fresh weight; log(Cd), log(Mn), log(Zn), log(Fe) and log(Cu) represent log₁₀ values of 0.1 M hydrochloric acid (HCl)-extractable Cd, manganese (Mn), zinc (Zn), iron (Fe) and copper (Cu) concentrations in soils in mg kg⁻¹ dry weight, respectively.

Figure 3 Measured versus predicted cadmium (Cd) concentrations in vegetables. The solid line is a 1:1 line of measured and predicted concentrations.

Table 4 Cadmium (Cd) concentrations in vegetables (maximum, minimum, mean and standard deviation values) collected from major production areas, and percentages of vegetables exceeding the regulatory concentration of Cd in Taiwan

Vegetable group	Vegetable name	n^†	Min.	Max.	Mean	SD	Above the regulatory standard^‡ (%)
			(mg kg^−1 fresh weight)
Leafy vegetables	Sweet potato leaf (Ipomoea batatas (L.) Lam.)	85	0.001	0.020	0.006	0.004	0
	Water spinach (Ipomoea aquatica Forsk.)	375	0.004	0.181	0.021	0.022	0
	Amaranth (Amaranthus tricolor L.)	133	0.005	0.313	0.071	0.073	9.8
	Ceylon spinach (Basella rubra L.)	23	0.004	0.050	0.023	0.012	0
	Chinese leek (Allium tuberosum Rottl. ex K. Spreng.)	52	0.003	0.072	0.017	0.012	0
	Gynura (Gynura bicolor DC.)	35	0.001	0.122	0.028	0.028	0
	Celery (Apium graveolens L.)	128	0.006	0.093	0.037	0.021	0
	Spinach (Spinacia oleraceae L.)	55	0.016	0.180	0.061	0.034	0
	Garland chrysanthemum (Chrysanthemum coronarium L.)	22	0.001	0.055	0.020	0.014	0
	Green onion (Allium fistulosum L.)	301	0.001	0.151	0.020	0.022	0
	Lettuce (Lactuca sativa L. var. crispa)	121	0.001	0.101	0.019	0.018	0
	Pak choi (Brassica campestris L. ssp. chinensis)	201	0.001	0.049	0.019	0.009	0
Brassica vegetables	Chinese cabbage (Brassica pekinensis Skeels.)	222	0.002	0.052	0.016	0.010	0.9
	Cauliflower (Brassica oleracea L. convar. Botrytis)	42	0.002	0.016	0.006	0.004	0
	Cabbage (Brassica oleracea L. Capitata Group)	309	0.001	0.056	0.007	0.008	1.0
	Broccoli (Brassica oleracea L. Italica Group)	40	0.001	0.016	0.007	0.003	0
Root and tuber vegetables, stalk and stem vegetables	Radish (Raphanus sativus L.)	305	0.001	0.062	0.013	0.008	0
	Carrot (Daucus carota L.)	334	0.001	0.117	0.021	0.018	0.6
	Potato (Solanum tuberosum L.)	100	0.002	0.088	0.026	0.019	0
	Taro (Colocasia esculenta (L.) Schott)	239	0.003	0.079	0.034	0.015	0
Bulb vegetables	Onion (Allium cepa L.)	50	0.003	0.012	0.005	0.002	0
	Garlic (Allium sativum L.)	33	0.002	0.029	0.011	0.006	0
Fruiting	Corn (Zea mays L.)	57	0.001	0.022	0.004	0.004	0
vegetables	Tomato (Lycopersicon esculeutum Mill.)	83	0.001	0.044	0.013	0.011	0
	Sweet pepper (Capsicum annuum L.)	45	0.002	0.017	0.010	0.004	0
	Eggplant (Solanum melongena L.)	48	0.004	0.037	0.018	0.009	0
	Cucumber (Cucumis sativus L.)	53	0.001	0.002	0.001	0.000	0
	Sponge gourd (Luffa cylindrica Roem.)	160	0.001	0.019	0.005	0.004	0
	Bitter gourd (Momordica charantia L.)	54	0.001	0.002	0.001	0.000	0
Pulse and legume vegetables	Asparagus bean (Vigna unguiculata (L.) Walp. ssp. sesquipedalis (L.) Verdc.)	32	0.001	0.004	0.002	0.001	0

^†n:sample size; Min.: minimum values; Max.: maximum values; SD: standard deviation.

^‡The regulatory concentrations for Cd in leafy; Brassica; root, tuber, stalk and stem; bulb; fruiting; and pulse and legume vegetables are 0.2, 0.05, 0.1, 0.05, 0.05 and 0.2, respectively.

Table 5 The percentage distribution of vegetables with cadmium (Cd) concentrations in edible parts exceeding the regulatory concentrations of Cd for plants grown in different soil Cd

Vegetables	n^†	Soil Cd (mg kg^−1)
		< 0.5	0.5–1.0	1.1–2.0	2.1–3.0	3.1–4.0	4.1–5.0
Leafy vegetables
Sweet potato leaf (Ipomoea batatas (L.) Lam.)	186	0.0	0.0	0.0	6.5	10.0	62.5
Water spinach (Ipomoea aquatica Forsk.)	491	0.0	14.3	61.5	100	100	100
Amaranth (Amaranthus tricolor L.)	237	0.9	34.4	62.5	100	100	100
Ceylon spinach (Basella rubra L.)	67	0.0	0.0	50.0	93.8	100	100
Chinese leek (Allium tuberosum Rottl. ex K. Spreng.)	78	0.0	0.0	0.0	69.2	83	-^‡
Gynura (Gynura bicolor DC.)	74	2.3	33.3	83.3	100	100	100
Celery (Apium graveolens L.)	178	0.0	0.0	30.8	60.9	88.9	100
Spinach (Spinacia oleraceae L.)	148	0.0	33.3	100	100	100	100
Garland chrysanthemum (Chrysanthemum coronarium L.)	118	0.0	0.0	58.3	88.6	71.4	100
Green onion (Allium fistulosum L.)	356	0.0	0.0	56.5	88.9	100	100
Lettuce (Lactuca sativa L. var. crispa)	196	0.0	10.0	38.5	93.9	93.3	100
Pak choi (Brassica campestris L. ssp. chinensis)	423	0.0	0.0	27.3	38.5	100	100
Brassica vegetables
Chinese cabbage (Brassica pekinensis Skeels.)	309	0.9	22.2	60.0	88.5	100	100
Cauliflower (Brassica oleracea L. convar. Botrytis)	82	0.0	0.0	10.0	25.0	60.0	83.0
Cabbage (Brassica oleracea L. Capitata Group)	378	1.0	0.0	13.3	25.0	40.0	100
Broccoli (Brassica oleracea L. Italica Group)	75	0.0	0.0	25.0	36.0	40.0	100
Root and tuber vegetables, stalk and stem vegetables
Radish (Raphanus sativus L.)	368	0.0	0.0	0.0	0.0	12.5	0.0
Carrot (Daucus carota L.)	394	0.6	50.0	95.2	95.8	100	100
Bulb vegetables
Garlic (Allium sativum L.)	53	0	100	100	100	100	–
Fruiting vegetables
Corn (Zea mays L.)	139	0.0	0.0	31.3	58.8	66.7	50.0
Tomato (Lycopersicon esculeutum Mill.)	158	0.0	0.0	76.9	77.8	100	100
Sweet pepper (Capsicum annuum L.)	84	0.0	–	–	16.7	75.0	100
Eggplant (Solanum melongena L.)	106	4.0	85.7	100	100	100	100
Cucumber (Cucumis sativus L.)	95	0.0	0.0	0.0	0.0	0.0	–
Okra (Hibiscus esculentus L.)	70	18.8	–	100	100	100	–
Sponge gourd (Luffa cylindrica Roem.)	179	0.0	0.0	0.0	0.0	0.0	0.0
Pulse and legume vegetables
Snap bean (Phaseolus vulgaris L.)	56	0.0	0.0	0.0	0.0	0.0	0.0
Asparagus bean (Vigna unguiculata (L.) Walp. ssp. sesquipedalis (L.) Verdc.)	49	0.0	–	0.0	0.0	0.0	0.0
Peanut (Arachis hypogaea L.)	77	23.5	100	100	100	100	100

^†sample size.

^‡“-” means no data.

^§The regulatory concentrations for Cd in leafy; Brassica; root, tuber, stalk and stem; bulb; fruiting; and pulse and legume vegetables are 0.2, 0.05, 0.1, 0.05, 0.05 and 0.2, respectively.

Figure 4 Relationships between the bioconcentration factor (BCF) of cadmium (Cd) and soil pH for garland chrysanthemum (Chrysanthemum coronarium L.), water spinach (Ipomoea aquatica Forsk.), amaranth (Amaranthus tricolor L.), gynura (Gynura bicolor DC.), and spinach (Spinacia oleraceae L.; only the trend lines derived using linear regression are shown).

Lin YW, Liu TS, Chen CT et al. 2012: Contents of cadmium and lead in vegetable crops produced in Taiwan. J. Agric. Res. Taiwan, 61, 38–51. (in Chinese with English abstract)

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