Background Levels of Heavy Metals in Ohio Farm Soils

Research Circular 275-83

Results

The range, mean, and standard deviations of the analytical parameters arc given by county in Table 1 and the overall values arc given in Table 2. A statistical analysis of the data showed that there were significant differences between counties for sonic parameters, and these are shown in Table 3. There were no consistent trends toward higher metals in one county vs. another. Sonic metals were significantly higher in one or more counties while other metals were highest in other counties. While there were significant differences in metal levels between the counties studied, these differences are small compared to the amounts of heavy metals that are commonly added to the soil in sewage sludges. The overall means in Table 2 are probably adequate as estimates of background heavy metal levels for the state.

Partial correlations between the analytical parameters are presented in Table 4. Only those correlations that were significant at the 0.01 level arc included. DTPA extractable Cd, Cu, and Zn were correlated with the total amounts of those metals but similar correlations for Ph and Ni were not significant. An examination of the data in Table 2 shows that all of the cadmium was DTPA extractable while 11.6, 13.7, 5.0, and 2.4% of the total Cu, Ph, Ni, and Zn, respectively, were extracted by DTPA. Soil pH was negatively correlated with DTPA Ni and Zn, and total P was positively correlated with lead.

Table 5 compares the total metal levels found for Ohio soils with other literature values. The values are quite consistent except those for chromium which were much lower in the Ohio and Minnesota studies than those reported by Allaway (1) or Baker and Chesnin (2).

Background hcavy metal concentrations can be useful in determining if a soil has been contaminated by metals. Values greater than two or three times the mean background levels should be indicative of metal contamination. This study did not idcntify any major regional differences in soil heavy metal concentrations which would indicate areas where metal levels were naturally higher than others; however, the present study did not attempt to cover all soil parent material regions in the state.

TABLE 1. Background Analyses by County of pH, Nutrients (µg/g), and Heavy Metals (µg/g).
	Number of Samples	Mean	Standard Deviation	Minimum	Maximum
CLARK
pH	0
Bray PI	0
Total P	0
TKN*	0
Total K	0
DTPA Cu	0
Cd	0
Pb	0
Ni	0
Zn	0
Total Cu	15	14	2	11	19
Cd	15	< 0.1	0.1	BDL***	0.1
Pb	15	14	1	11	16
Ni	15	15	2	11	18
Zn	15	61	9	47	87
Cr	15	12	6	6	23
Total Kjefdahl nitrogen. **Below detection limit.
TABLE 1 cont. Background Analyses by County of pH, Nutrients (µg/g), and Heavy Metals (µg/g).
	Number of Samples	Mean	Standard Deviation	Minimum	Maximum
DEFIANCE
pH	0
Bray Pl	0
Total P	0
TKN	0
Total K	1	10500		10500	10500
DTPA Cu	8	3.2	1.2	1.9	4.9
Cd	8	0.88	1.22	0.14	3.61
Pb	8	2.5	0.7	1.9	4.2
Ni	8	1.5	0.6	0.7	2.6
Zn	8	2.3	1.4	0.7	4.8
Total Cu	17	23	5	14	30
Cd	15	0.4	0.7	BDL	2.9
Pb	17	15	3	9	21
Ni	17	22	5	10	32
Zn	17	79	17	47	103
Cr	15	18	4	11	23
Total Kjefdahl nitrogen. **Below detection limit.
TABLE 1 cont. Background Analyses by County of pH, Nutrients (µg/g), and Heavy Metals (µg/g).
	Number of Samples	Mean	Standard Deviation	Minimum	Maximum
FRANKLIN
pH	0
Bray PI	0
Total P	0
TKN	0
Total K	2	7000	54	7000	7000
DTPA Cu	2	2.8	0.8	2.3	3.4
Cd	2	0.10	0.01	0.09	0.11
Pb	2	2.0	0.2	1.9	2.1
Ni	2	1.3	0.5	0.9	1.7
Zn	2	1.5	0.3	1.3	1.7
Total Cu	61	19	0.3	13	30
Cd	61	0.1	0.1	BDL	0.8
Pb	61	17	3	10	26
Ni	61	18	4	12	29
Zn	61	77	16	48	138
Cr	59	12	3	5	22
TABLE 1 cont. Background Analyses by County of pH, Nutrients (µg/g), and Heavy Metals (µg/g).
	Number of Samples	Mean	Standard Deviation	Minimum	Maximum
MADISON
pH	0
Bray Pl	0
Total P	0
TKN	0
Total K	0
DTPA Cu	0
Cd	0
Pb	0
Ni	0
Zn	0
Total Cu	4	19	2	17	21
Cd	4	0.1	0.1	BDL	0.3
Pb	4	17	1	15	18
Ni	4	20	4	14	23
Zn	4	73	5	67	79
Cr	4	12	2	10	15
TABLE 1 cont. Background Analyses by County of pH, Nutrients (µg/g), and Heavy Metals (µg/g).
	Number of Samples	Mean	Standard Deviation	Minimum	Maximum
MEDINA
pH	17	6	0	5	7
Bray Pl	17	22	13	8	54
Total P	20	590	120	400	1010
TKN	19	2200	2100	1100	7900
Total K	25	6300	1300	4200	8700
DTPA Cu	25	1.9	1.4	0.9	7.7
Cd	25	0.10	0.04	0.03	0.20
Pb	25	2.7	0.3	1.9	3.2
Ni	25	0.6	0.3	0.3	1.7
Zn	25	1.2	0.3	0.7	2.0
Total Cu	40	17	5	11	37
Cd	40	0.2	0.2	BDL	0.6
Pb	40	23	8	11	39
Ni	40	20	4	13	29
Zn	40	75	10	54	95
Cr	15	7	1	4	9
TABLE 1 cont. Background Analyses by County of pH, Nutrients (µg/g), and Heavy Metals (µg/g).
	Number of Samples	Mean	Standard Deviation	Minimum	Maximum
MUSKINGUM
pH	6	6	1	5	7
Bray Pl	6	26	13	9	39
Total P	6	560	110	390	710
TKN	6	1500	400	1100	2100
Total K	6	4900	500	4200	5400
DTPA Cu	6	1.3	0.6	0.7	2.5
Cd	6	0.09	0.05	0.06	0.19
Pb	6	3.3	2.4	1.7	7.9
Ni	6	0.6	0.5	0.2	1.5
Zn	6	2.1	2.3	0.5	6.6
Total Cu	6	16	2	13	19
Cd	6	0.3	< 0.1	0.2	0.4
Pb	6	33	3	28	36
Ni	6	25	4	20	29
Zn	6	74	10	65	92
Cr	0
TABLE 1 cont. Background Analyses by County of pH, Nutrients (µg/g), and Heavy Metals (µg/g).
	Number of Samples	Mean	Standard Deviation	Minimum	Maximum
PICKAWAY
pH	0
Bray Pl	0
Total P	0
TKN	0
Total K	18	6300	1300	3900	9800
DTPA Cu	18	2.3	0.6	1.3	3.7
Cd	18	0-12	0.03	0.09	0.20
Pb	18	2.5	0.7	1.5	3.9
Ni	18	1.1	0.4	0.6	2.4
Zn	18	2.3	2.4	1.0	11.2
Total Cu	96	20	5	12	36
Cd	96	0.2	0.2	BDL	1.0
Pb	96	17	3	11	27
Ni	96	17	5	9	38
Zn	96	74	14	47	130
Cr	78	11	3	5	20

TABLE 2. Background Analyses for All Farms for pH, Nutrients (µg/g), and Heavy Metals (µg/g).
	Number of Samples	Mean	Standard Deviation	Minimum	Maximum
pH	23	6.4	0.48	4.7	7
Bray PI	23	23	13	8	54
Total P	26	580	120	390	1010
TKN	25	2100	1800	1100	7900
Total K	52	6300	1400	3900	10500
DTPA Cu	59	2.2	1.2	0.7	7.7
Cd	59	0.21	0.50	0.03	3.61
Pb	59	2.6	0.9	1.5	7.9
Ni	59	0.9	0.5	0.2	2.6
Zn	59	1 8	1.6	0.5	11.2
Total Cu	239	19	5	11	37
Cd	237	0.2	0.3	BDL	2.9
Pb	239	19	5	9	39
Ni	239	18	5	9	38
Zn	239	75	15	47	138
Cr	186	12	4	4	23

TABLE 3. Differences in the Total and DTPA Extractable Heavy Metal Contents of Farm Soils by County.
	Total					DTPA
	CU	Cd	Pb	Ni	Zn	CU	Cd	Pb***	Ni	Zn***
	µg/g
Clark	14c*	< 0.1c	14d	15b	79a	**
Defiance	23a	0.4a	15dc	22a	61b	3.2a	0.88a		1.50
Franklin	19b	0.1bc	17c	18b	77a	2.8ab	0.10b		1.3a
Madison	19bc	0.Ibc	17dc	20ab	73ab	**
Medina	17c	0.2b	23b	20ab	75a	1.9b	0.10b		0.6b
Muskingum	16c	0.3ab	33a	25ab	74ab	1.3b	0.09b		0.6b
Pickaway	20b	0.2b	18c	l7b	74a	2.3ab	0.12b		1.1a
Means in each vertical column with the same letter are not significantly different at the 0.05 level. DTPA extractable heavy metals were not measured in Clark and Madison counties. **There were no significant differences between counties for DTPA Pb and Zn.

TABLE 4. Partial Correlation Coefficients for All Parameters at the 0.01 Level of Significance.
			Total						DTPA
	pH	Total P	Cu	Cd	Pb	Ni	Zn	Cr	Cu	Cd	Pb	Ni	Zn
pH												-0.57	-0.77
Total P					0.69
Total Cu				0.29		0.66	0.67	0.57	0.83			0.65
Cd			0.29		0.30	0.32	0.31	0.19		0.94
Pb		0.69		0.30		0.40	0.28	0.29				-0.35
Ni			0.66	0.32	0.40		0.69	0.52
Zn			0.69	0.31	0.28	0.69		0.37	0.51			0.52	0.56
Cr			0.57	0.19	0.29	0.52	0.37
DTPA Cu			0.83	0.94			0.51					0.73	0.40
Cd				0.94
Pb
Ni	-0.57		0.65		-0.35		0.52		0.73				0.53
Zn	-0.77						0.56		0.40			0.53

TABLE 5. Comparison of Ohio Background Heavy Metal Soil Concentrations with Published Values from Other Areas.
	Ohio		Allaway		Baker and Chesnin (2)*		Dowdy et al. (4)**
	Mean	Range	Mean	Range	Mean	Range	Mean	Standard Deviation
	Total Metal Concentration (ug/g)
Cd	0.2	0-2.9	0.06	0.01-7	0.5	0.01-0.70	0.39	0.17
Cu	19	11-37	20	2-100	20	2-100	23	4
Cr	12	4-23	100	5-3000	200	5-1000	39	29
Ni	18	9-38	40	10-1000	40	5-500	18	10
Pb	19	9-39	10	2-200	10	2-200
Zn	75	47-138	50	10-300	50	10-300	60	14
Numerous sources worldwide. *Background levels from uncontaminated soils in Minnesota. Ranges were not given.

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