Meso- and microplastic distribution and spatial connections to metal contaminations in highly cultivated and urbanised floodplain soilscapes – a case study from the Nidda River (Germany)

Microplastics and Nanoplastics

Table 2 Summary of trace metal contents compared to geogenic background levels and legislation values with calculated pollution indices and their thresholds

		Elemental concentrations								Indices
		Cr	Ni	Cu	Zn	Cd	Hg	Pb		PLI^a	EF^b
		mg kg^− 1								(−)	(−)
Mean		29.8	31.2	16.6	55.4	0.28	0.11	23.8		1.1	2.2
Median		26.3	27.6	13.5	40.0	0.16	0.07	17.7		0.9	1.8
Min.		9.8	8.7	3.5	17.0	0.05	0.01	8.3		0.4	1.1
Max.		75.4	100.7	55.8	194.5	1.39	0.46	77.1		3.2	5.9
Mean upper soil	0–50 cm	28.6	29.9	15.1	50.1	0.25	0.09	22.9		1.0	2.1
Mean lower soil	50–200 cm	31.1	32.5	18.1	60.8	0.31	0.13	24.6		1.2	2.4
Wilcox p-value	upper vs lower	0.52	0.55	0.21	0.34	0.54	0.22	0.73		0.45	0.37
SHW^c	Average content surface horizons worldwide	60.0	29.0	38.9		0.41		27.0	perfection \| low ^f	< 1	< 2
GBHF^d	Geochemical background in Hessian floodplain soils (0–2 m)	25.0	24.0	13.3	58.5	0.14	0.04	27.0	baseline \| moderate^f	1	2–5
PV^e	Precautionary values	60.0	50.0	40.0	150.0	1.00	0.50	70.0	deterioration \| significant^f	> 1	> 5

^a Pollution Load Index; ^b Enrichment factor; ^c Kabata-Pendias [62]; ^d Friedrich & Lügger [57]; ^e German Federal Soil Protection Ordinance - BBodSchV [63]; ^f Pollution assessment according to Kowalska et al. [56] with “denote perfection” (PLI) or “deficiency to minimal enrichment” (EF), “baseline level of pollution” (PLI) or “moderate enrichment” (EF) and “deterioration of soil quality” (PLI) or “significant enrichment” (EF)