Establishing grassland mixtures on mine wastes – a two-year mesocosm study

Figures & data

Table 1. Mixing ratios, pH and element composition (nutrients and metals) of the five substrates (CON, and two dilutions of each from the Mansfeld (M) and the Davidschacht (D) mine wastes) that were used in the experiments. In the final columns, heavy metal concentrations in the substrates can be compared to the limits for sandy and clayey agricultural soils that have been set by the German Soil Protection Ordnance (BBSchV 2021).

			Davidschacht		Mansfeld		BBSchV (2021)
		CON	D125	D06	M125	M06	sandy	clayey
Mixing ratios
LD80	vol.%	50	50	50	50	50
Sand	vol.%	50	37.5	43.75	37.5	43.75
Mine waste	vol.%	0	12.5	6.25	12.5	6.25
pH (CaCl2)		6.22	6.33	6.32	6.78	6.46
NO3^+-N	mg L^−1	49.2	42.9	40.5	31.2	46.05
NH4--N	mg L^−1	1.94	0.76	1.08	1.11	1.1
N [%]	wt. %	0.067	0.068	0.087	0.119	0.094
C [%]	wt. %	2.21	2.47	3.14	4.95	3.59
S [%]	wt. %	0.024	0.952	0.614	0.98	0.359
K2O	mg 100 g^−1	34	34.5	34.3	38.2	34.5
P2O5	mg 100 g^−1	14.6	14.4	13.9	13.8	10.1
Mg	mg 100 g^−1	13.3	20.5	18	20.6	17.7
Metals and metalloids
Cu	mg kg^−1	5	62	71.8	3772	1904	20	60
Ni	mg kg^−1	116	91	127	103	110	15	70
Pb	mg kg^−1	6	231	158	3036	1428	40	100
Zn	mg kg^−1	12.9	611	292	1586	803	60	200
Cd	mg kg^−1	0.1	6.18	3.02	5.82	2.67	0.4	1.5
Li	mg kg^−1	2.99	9.88	6.8	15.7	9.02
Sn	mg kg^−1	0.114	6.1	2.81	0.37	0.236
Fe	mg kg^−1	3990	21956	12110	9527	7606
As	mg kg^−1	1.43	2709	1108	35.5	17.3

Figure 1. Photographs showing the established vegetation on the mesocosm in the seasons 2021 (left) and 2022 (right). The 42 trays were arranged after blocks for the two grassland mixtures (RIES and GRIES) and after seven rows for the treatments. While the treatments CON, CON 1 and CON2 were based on unpolluted substrates, the other four made use of two mine wastes from either the Davidschacht (D) or the Mansfeld (M).

Figure 2. Dry shoot biomass produced in the wet (above, blue) and dry (below, orange) grassland mixtures during the first 92 days of the experiment (left) and loss of solids due to the draining of water in the first season (right). In each of the panels, boxplots are arranged after the control (CON, left) greywater (CON1, CON2) and mine waste treatments (see x-axes). The intensity of color shading is sorted after the median values. Same letters above the boxes indicate non-significant differences between the treatments in post-hoc multiple comparisons (Tukey tests).

Table 2. Correlation matrix for 25 variables addressed in the mesocosm study. Positive product moment coefficients are indicated in lighter and darker blue (r > 0.5, r > 0.8) and negative relationships are indicated in lighter and darker orange (r< −0.5, r < −0.8). The upper triangle refers to the calculation of data from the GRIES grassland, while the lower represents the data from the RIED mesocosms. For the abbreviations of the parameters refer to the materials and methods section.

	HAR1	HAR2	HAR3	COV21	COV22	VOL21	VOL22	GRAS21	GRAS22	CD	PB	CA	CU	FE	K	NI	ZN	NO3	NH4	pH 1	EC 1	pH21	pH22	DRAIN21	DRAIN22
HAR1		0.55	0.83	0.80	0.62	−0.68	−0.24	−0.17	−0.03	−0.67	−0.15	−0.15	−0.19	−0.02	0.22	0.24	−0.35	−0.03	−0.73	0.49	−0.60	0.34	0.61	−0.66	−0.61
HAR2	0.81		0.78	0.81	0.74	−0.42	−0.40	−0.28	−0.13	−0.56	−0.37	0.12	−0.26	−0.33	0.32	−0.26	−0.24	−0.16	−0.58	0.56	−0.55	0.49	0.49	−0.63	−0.67
HAR3	0.71	0.86		0.85	0.82	−0.57	−0.13	−0.10	0.06	−0.73	−0.47	−0.20	−0.44	−0.33	0.19	−0.08	−0.48	−0.18	−0.82	0.65	−0.76	0.53	0.69	−0.77	−0.66
COV21	0.83	0.89	0.73		0.70	−0.40	−0.27	−0.22	−0.08	−0.77	−0.33	−0.02	−0.29	−0.16	0.34	0.00	−0.41	−0.14	−0.73	0.69	−0.71	0.59	0.74	−0.74	−0.74
COV22	0.75	0.73	0.78	0.62		−0.44	−0.29	−0.20	−0.01	−0.64	−0.43	−0.10	−0.40	−0.39	0.11	−0.31	−0.30	−0.16	−0.60	0.50	−0.60	0.35	0.56	−0.59	−0.57
VOL21	−0.78	−0.72	−0.62	−0.75	−0.61		0.35	0.08	0.02	0.52	0.07	0.11	0.15	−0.12	−0.11	−0.31	0.26	−0.04	0.54	−0.40	0.39	−0.30	−0.40	0.61	0.40
VOL22	−0.65	−0.50	−0.61	−0.37	−0.53	0.53		0.58	0.30	−0.11	−0.02	−0.53	−0.11	−0.05	−0.43	0.17	−0.20	0.14	−0.15	−0.15	0.12	−0.16	0.01	0.26	0.58
GRAS21	0.68	0.49	0.45	0.49	0.67	−0.61	−0.27		0.43	0.04	−0.19	−0.73	−0.39	−0.03	−0.63	−0.02	−0.38	0.29	−0.11	0.03	0.10	0.05	0.08	0.05	0.54
GRAS22	0.17	0.10	0.00	0.17	−0.02	−0.21	0.08	0.31		0.10	−0.45	−0.76	−0.66	0.08	−0.52	0.13	−0.64	−0.58	−0.09	0.25	−0.35	0.38	0.29	−0.27	0.15
CD	−0.75	−0.72	−0.74	−0.73	−0.81	0.60	0.39	−0.67	0.13		0.18	0.33	0.26	0.25	0.14	0.10	0.32	−0.14	0.64	−0.44	0.53	−0.18	−0.71	0.49	0.41
PB	−0.47	−0.41	−0.14	−0.54	−0.35	0.51	0.14	−0.58	−0.64	0.13		0.27	0.90	0.36	−0.18	0.31	0.80	0.34	0.23	−0.68	0.71	−0.68	−0.60	0.67	0.32
CA	−0.80	−0.76	−0.69	−0.86	−0.75	0.76	0.29	−0.80	−0.30	0.86	0.48		0.59	0.06	0.78	−0.02	0.53	0.43	0.28	−0.26	0.23	−0.19	−0.43	0.12	−0.37
CU	−0.54	−0.41	−0.31	−0.60	−0.36	0.56	0.07	−0.52	−0.82	0.20	0.79	0.56		0.16	0.15	0.18	0.91	0.47	0.25	−0.57	0.65	−0.64	−0.63	0.63	0.16
FE	0.06	0.15	0.09	−0.03	−0.13	−0.13	−0.21	0.04	−0.10	−0.01	0.45	0.10	0.36		0.05	0.77	−0.11	−0.10	0.05	−0.38	0.15	0.11	−0.17	−0.07	0.14
K	−0.43	−0.34	−0.17	−0.53	−0.17	0.54	0.07	−0.47	−0.80	0.04	0.79	0.50	0.78	0.02		0.13	0.00	0.38	−0.06	0.21	−0.17	0.31	−0.05	−0.36	−0.48
NI	0.21	0.43	0.32	0.28	0.03	−0.31	−0.22	0.16	−0.05	−0.26	0.38	−0.17	0.24	0.92	−0.07		−0.16	−0.10	−0.32	−0.07	−0.12	0.10	0.04	−0.26	−0.02
ZN	−0.70	−0.65	−0.49	−0.83	−0.45	0.76	0.20	−0.56	−0.70	0.44	0.82	0.76	0.87	0.11	0.84	−0.10		0.42	0.40	−0.57	0.74	−0.75	−0.68	0.78	0.20
NO3	−0.55	−0.37	−0.22	−0.49	−0.36	0.73	0.25	−0.59	−0.28	0.23	0.74	0.48	0.53	−0.13	0.59	−0.15	0.54		0.05	−0.24	0.52	−0.44	−0.23	0.35	0.37
NH4	−0.41	−0.54	−0.48	−0.58	−0.34	0.76	0.02	−0.39	−0.19	0.49	0.16	0.60	0.38	−0.26	0.33	−0.47	0.58	0.50		−0.65	0.70	−0.47	−0.74	0.72	0.51
pH 1	0.69	0.66	0.60	0.72	0.57	−0.79	−0.35	0.48	0.41	−0.47	−0.68	−0.67	−0.80	−0.08	−0.59	0.09	−0.81	−0.67	−0.66		−0.74	0.80	0.80	−0.79	−0.56
EC 1	−0.88	−0.76	−0.68	−0.86	−0.68	0.84	0.48	−0.69	−0.17	0.76	0.51	0.89	0.60	−0.14	0.57	−0.32	0.78	0.74	0.62	−0.79		−0.72	−0.85	0.90	0.77
pH21	0.65	0.65	0.60	0.73	0.59	−0.70	−0.42	0.36	0.35	−0.42	−0.85	−0.64	−0.75	−0.22	−0.61	−0.05	−0.79	−0.62	−0.45	0.90	−0.74		0.60	−0.80	−0.46
pH22	0.84	0.81	0.83	0.82	0.75	−0.73	−0.44	0.57	0.07	−0.84	−0.20	−0.82	−0.45	0.08	−0.28	0.31	−0.63	−0.44	−0.61	0.72	−0.85	0.67		−0.79	−0.60
DRAIN21	−0.86	−0.80	−0.75	−0.88	−0.66	0.90	0.58	−0.57	−0.23	0.68	0.65	0.86	0.70	−0.05	0.67	−0.27	0.89	0.66	0.62	−0.87	0.92	−0.86	−0.83		0.73
DRAIN22	−0.73	−0.57	−0.70	−0.54	−0.53	0.54	0.89	−0.31	0.12	0.60	−0.04	0.46	0.12	−0.26	0.08	−0.33	0.31	0.22	0.19	−0.44	0.65	−0.47	−0.66	0.69

Figure 3. Copper (Cu, ppm) concentrations in the shoot dry biomass produced in the wet (above, blue) and dry (below, orange) grassland mixtures during the first 92 days of the experiment (left) and the respective cadmium (Cd, ppm) concentrations (right). In each of the panels, boxplots are arranged after the control (CON, left) greywater (CON1, CON2) and mine waste treatments (see x-axes). The intensity of color shading is sorted after the median values. Same letters above the boxes indicate non-significant differences between the treatments in post-hoc multiple comparisons (Tukey tests).

BBschV. 2021. Bundes-Bodenschutz- und Altlastenverordnung vom 9. (BGBl. I S. 2598, 2716). [accessed on 2024 Feb 2]. https://www.gesetze-im-internet.de/bbodschv_2023/BBodSchV.pdf.

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Data availability statement

Data are available in the supplementary information (SI) to this article.