Table 1.

Total soil metal concentrations (expressed in mg kg⁻¹ of dry mater) at three different study areas determined by modified Community Bureau of Reference (BCR) sequential extraction, aqua regia procedure and X-Ray Fluorescence (XRF)

		Study sites
Heavy metals	Method	Valcamonica Median (IQR)	Bagnolo Mella Median (IQR)	Garda Lake Median (IQR)	p values §
Al	BCR modified	10514 (4493–19169)	10280 (8030–11803)	6948 (3334–11201)	<0.001
Cd	BCR modified	2.54 (1.29–4.16)	2.38 (2.05–2.70)	2.04 (1.00–2.60)	<0.001
	aqua regia procedure	1 (0.00–3.00)	2 (1.00–3.00)	3 (1.00–4.00)	2*
Cr	BCR modified	15.63 (6.96–34.4)	18.11 (13.3–30.5)	17.85 (7.21–277)	0.28
	aqua regia procedure	93 (47.0–120)	50 (43.00–64.00	77 49.00–690.00	150*
	XRF	69.93 (25.1–416)	29.02 (24.2–65.5)	84.21 (36.1–237)	<0.001
Cu	BCR modified	64.65 (24.8–373)	31.24 (23.8–58.7)	66.69 (23.4–162)	0.005
	aqua regia procedure	74 (28.0–410)	43 (30.0–84.0)	87 (36.0–237)	120*
	XRF	29037 (16414–37502)	21854 (17547–24508)	15813 (7952–23660)	<0.001
Fe	BCR modified	14173 (7648–19629)	11768 (8568–13654)	9268 (3431–12570)	<0.001
	aqua regia procedure	17160 (15920–18040)	17400 (16880–17680)	15680 (13040–17320)	<0.001
	XRF	1337 (690–2570)	806 (552–1440)	577 (442–893)	<0.001
Mn	BCR modified	982 (473–2113)	623 (466–1357)	393 (288–747)	<0.001
	aqua regia procedure	1025 (493–1612)	712 (555–1254)	437 (315–658)	<0.001
	XRF	62.1 (34.0–127)	45.6 (21.4–59.3)	39.9 19.0–212	0.005
Pb	BCR modified	47.1 (24.2–109)	43.08 (27.0–50.0)	37.3 (16.9–128)	0.07
	aqua regia procedure	65 (36.0–125)	90 (47.0–147)	64 (50.0–207)	100*
	XRF	225.1 (90.7–643)	178 (89.7–216)	145 (65.8–458)	0.01
Zn	BCR modified	172 (70.4–426)	128 (70.3–192)	113 (32.4–305)	0.01
	aqua regia procedure	258 (92.0–845)	220 (114–275)	153 (58.0–474)	150*

^§comparison between Valcamonica, Bagnolo Mella and Garda Lake

^*Maximum allowable concentration.