Leaching of Heavy Metals in Soils Conditioned with Biosolids from Sewage Sludge

Campos, Thaís; Chaer, Guilherme; Leles, Paulo dos Santos; Silva, Marcelo; Santos, Felipe

doi:10.1590/2179-8087.039918

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Original Article, Silviculture • Floresta Ambient. 26 (spe1) • 2019 • https://doi.org/10.1590/2179-8087.039918 copy

Leaching of Heavy Metals in Soils Conditioned with Biosolids from Sewage Sludge

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

A promising use of biosolids is as organic fertilizer in agricultural and forestry activities. However, its composition might contain several pollutants, especially heavy metals, which may result in an increase in the concentrations of these elements in the soil and the risk of groundwater contamination. This study aimed to determine the leaching levels of ions in a Ferralsol (clayey texture) and in a Planosol (sandy texture). The experiment was conducted in a greenhouse at Embrapa Agrobiologia, Seropédica, Rio de Janeiro state. Soils were packed in PVC columns and received 2 L/column of biosolids. The concentrations of heavy metals present in the biosolids composition were below the limits established by the legislation (CONAMA 375). In addition, the performed simulations showed the absence of contamination risk of soil or groundwater and surface water, according to the limits allowed by CONAMA 375. However, it should be emphasized the potential of nitrate leaching.

Keywords:
contamination risk; chemical elements percolation; test with columns; risk analysis

Metal	Metal content in biosolids (mg/kg)		Theoretical accumulated load of metal by application of sewage sludge (kg/ha)		The theoretical maximum load of biosolids to reach critical level (Mg/ha)
Metal	CONAMA 375/06	Biosolids ETE-IG	CONAMA 375/06	Biosolids ETE-IG ^{^} Load accumulated by the theoretical application of 10 m3/ha (7 Mg/ha) of biosolids.	CONAMA 375/06 ^{^} Estimate based on the theoretical cumulative load of metals by the application of sludge as defined in CONAMA Resolution nº 375/06.	Biosolids ETE-IG
As	41	<1	30	0.007	732	30,000
Ba	1,300	137	265	0.959	204	1,934
Cd	39	1.4	4	0.01	103	2,857
Pb	300	58.4	41	0.409	137	702
Cu	1,500	162	137	1.134	91	846
Cr	1,000	21.9	154	0.153	154	7,032
Hg	17	<1	1.2	0.007	71	1,200
Mo	50	1.6	13	0.011	260	8,125
Ni	420	12.7	74	0.089	176	5,827
Se	100	<1	13	0.007	130	13,000
Zn	2,800	531	445	3.717	159	838

Metal	^{^} Prevention value according to CONAMA Resolution nº 420/2009. VP for metals in the soil (mg/kg)	^{^} Research value according to CONAMA Resolution nº 420/2009. VI for metals in agricultural soils (mg/kg)	Concentration of metal accumulated in the planting hole (mg/kg)		Accumulated metal concentration in the soil to 10 m³/ha of biosolids (mg/kg)		Percentage of the total leaching of metal contained in the biosolids
Metal			Planosol	Ferralsol	Planosol	Ferralsol	Planosol	Ferralsol
Al	-	-	9,622	9,619	33	33	0%	0%
Sb	2	5	-	-	-	-	-	-
As	15	35	1	1	0.004	0.004	0%	0%
Ba	150	300	134	135	0.47	0.47	1.30%	0.60%
B	-	-	0.59	0.54	0.005	0.005	58.10%	59.30%
Cd	1.3	3	1.39	1.39	0.005	0.005	0%	0.30%
Pb	72	180	58	58	0.2	0.2	0%	0%
Co	25	35	-	-	-	-	-	-
Cu	60	200	161	161	0.57	0.56	0.10%	0%
Cr	75	150	21	21	0.08	0.08	0%	0%
Fe	-	-	19,252	19,249	67	67	0%	0%
Mn	-	-	254	301	0.96	1.08	15.80%	5.60%
Hg	0.5	12	-	-	-	-	0%	0%
Mo	30	50	-	-	-	-	0%	0%
Ni	30	70	12.6	12.5	0.04	0.04	0.10%	1%
NO₃^-	-	-	-	-	-	-	-	-
Ag	2	25	-	-	-	-	-	-
Se	5	-	0.84	0.84	0.003	0.003	11.20%	11.30%
V	-	-	-	-	-	-	-	-
Zn	300	450	527	510	1.85	1.81	0.50%	2.70%

Metal	^{^} According to CONAMA Resolution nº 420/2009. Intervention value in underground water (µg/L)	Metal concentration in groundwater after percolation of 140 mm (µg/L)
Metal		Planosol	Ferralsol
Al	3,500	0.33	13
Sb	5	0.03	0.01
As	10	0	0
Ba	700	9.1	4
B	500	9.3	9
Cd	5	0.001	0.02
Pb	10	0	0
Co	70	1.4	0.2
Cu	2,000	0.4	0.3
Cr	50	0.04	0.001
Fe	2,450	9	20
Mn	400	259	91
Hg	1	-	-
Mo	70	-	-
Ni	20	0.06	0.7
NO₃^-	10,000	7,672	8,195
Ag	50	0.1	0.05
Se	10	0.6	0.6
V	-	0	0
Zn	1,050	13	72
^ Trophic State Classification according to Carlson’s Index (Cetesb, 2007). PO₄^3-	-	176	19

Instituto de Florestas da Universidade Federal Rural do Rio de Janeiro Rodovia BR 465 Km 7, CEP 23897-000, Tel.: (21) 2682 0558 | (21) 3787-4033 - Seropédica - RJ - Brazil
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[1] Thaís CamposUniversidade Federal Rural do Rio de Janeiro – UFRRJ, BR-465, Km 7, CEP 23897000, Seropédica, RJ, Brasil e-mail: thaiscampospbi@gmail.com; thaiscampos@ufrrj.br