Qualidade da água em áreas de barragens subterrâneas do semiárido potiguar

Chianca, Cibele G. C.; Batista, Rafael O.; Melo, Stefeson B. de; Dias, Nildo da S.; Silva, Cássio K. da

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Agricultural Engineering • Rev. Caatinga 36 (3) • Jul-Sep 2023 • https://doi.org/10.1590/1983-21252023v36n319rc copiar

Qualidade da água em áreas de barragens subterrâneas do semiárido potiguar

Autoria SCIMAGO INSTITUTIONS RANKINGS

RESUMO

Os órgãos públicos federais têm priorizado o financiamento de barragens subterrâneas como forma de amenizar a escassez hídrica das regiões rurais semiáridas do Brasil. Este trabalho avaliou a qualidade da água, para fins de irrigação, de barragens subterrâneas do Estado do Rio Grande do Norte, no fim do período seco do ano de 2018 e fim do período chuvoso do ano de 2019. Além disso, elencou quais as variáveis apresentaram maior influência nessa qualidade, por meio de análise multivariada, utilizando o software Statistica 7.0. Os resultados indicaram que os problemas relacionados a salinidade e a toxicidade de íons das águas das barragens subterrâneas reduzem após o período chuvoso, enquanto que os problemas relacionados a obstrução dos sistemas de irrigação localizada aumentam. A salinidade, sodicidade e/ou toxicidade da água das barragens subterrâneas estão relacionadas a mineralização natural dos componentes geológicos do solo, porém também são influenciadas pelas precipitações com núcleos higroscópicos marinhos, presença de aglomerados rurais, existência de currais e decomposição de matéria orgânica na área do barramento. As variáveis relacionadas a salinidade apresentam maior influência na variação hidroquímica da água das barragens, nos dois períodos estudados, sendo a condutividade elétrica e o íon de cloreto os mais representativos.

Palavras-chave
Aquífero aluvial; Análise multivariada; Salinidade

Variable	Methods
Electrical conductivity (EC)	Laboratory method: conductivity meter (HACH-CDC401 probe)
Hydrogen potential (pH)	Electrometric method (Teckna T-1000 pHmeter)
Total solids (TS)	Gravimetric method
Total suspended solids (TSS)	Gravimetric method, using glass fiber filter with 1μm aperture.
Total dissolved solids (TDS)	Difference between TS and TSS
Sodium (Na⁺) and potassium (K⁺)	Flame photometer
Calcium (Ca²⁺) and magnesium (Mg²⁺)	Complexometric method with EDTA
Chloride (Cl^-)	Mohr method
Carbonate (CO₃^2-) and bicarbonate (HCO₃^-)	Volumetric method
Nutrients: boron (B), copper (Cu), sulfur (S), iron (Fe), manganese (Mn), and zinc (Zn)	Atomic absorption spectrophotometry
Heavy metals: chromium (Cr), nickel (Ni), cadmium (Cd), and lead (Pb)	Atomic absorption spectrophotometry

Variables	End of the dry season (2018)				End of the rainy season (2019)
Variables	Minimum	Maximum	Mean	SD	Minimum	Maximum	Mean	SD
pH	7.06	9.87	8.08	0.53	6.67	8.59	7.87	0.44
EC (μS cm^-1)	134	13010	1708	2643	92	12365	1141	2025
K⁺ (mmolc L^-1)	0.02	1.08	0.24	0.23	0.01	0.81	0.19	0.17
Na⁺ (mmolc L^-1)	0.38	102.18	9.64	18.66	0.31	94.41	7.22	15.73
Ca²⁺ (mmolc L^-1)	0.41	32.95	4.07	5.39	0.29	16.02	2.48	2.45
Mg²⁺ (mmolc L^-1)	0.15	23.93	3.39	5.45	0.13	28.06	2.17	4.36
Cl - = bicarbonate; SAR = sodium adsorption ratio; H = hardness; TSS = total suspended solids; TDS = total dissolved solids; S = sulfur; B = boron; Cu = copper; Mn = manganese; Fe = iron; Zn = zinc; Cr = chromium; Ni = nickel; Cd = cadmium; Pb = lead. - (mmolc L^-1)	0.70	134.40	12.12	25.38	0.60	102.93	7.15	17.09
CO₃^2- (mmolc L^-1)	< Ld	2.00	0.51	0.54	< Ld	1.80	0.34	0.48
HCO₃ - = bicarbonate; SAR = sodium adsorption ratio; H = hardness; TSS = total suspended solids; TDS = total dissolved solids; S = sulfur; B = boron; Cu = copper; Mn = manganese; Fe = iron; Zn = zinc; Cr = chromium; Ni = nickel; Cd = cadmium; Pb = lead. - (mmolc L^-1)	0.58	18.00	5.01	3.59	0.50	12.45	4.00	2.70
SAR (mmolc L^-1)^1/2	0.39	19.97	3.69	4.63	0.38	20.11	3.66	4.80
H (mg L^-1)	40.5	2618.0	373.2	505.9	27.0	2203.8	232.8	332.3
TSS (mg L^-1)	0.3	358.0	29.2	67.6	< Ld	487.0	37.6	81.4
TDS (mg L^-1)	155.5	10695.5	1254.8	2016.1	11.4	9237.5	722.6	1449.1
S (mg L^-1)	Nd	Nd	Nd	Nd	2.640	398.620	58.701	92.251
B (mg L^-1)	Nd	Nd	Nd	Nd	< Ld	0.300	0.048	0.074
Cu (mg L^-1)	< Ld	0.045	0.003	0.008	< Ld	0.070	0.010	0.017
Mn (mg L^-1)	< Ld	2.621	0.495	0.720	< Ld	4.190	0.752	0.954
Fe (mg L^-1)	< Ld	20.780	1.756	3.865	0.030	38.030	4.066	7.979
Zn (mg L^-1)	< Ld	0.137	0.017	0.028	< Ld	0.370	0.058	0.091
Cr (mg L^-1)	< Ld	0.022	0.002	0.004	< Ld	0.020	0.001	0.003
Ni (mg L^-1)	< Ld	0.029	0.003	0.007	< Ld	0.010	0.002	0.004
Cd (mg L^-1)	< Ld	0.040	0.004	0.009	< Ld	< Ld	< Ld	0.000
Pb (mg L^-1)	< Ld	0.480	0.050	0.106	< Ld	0.010	0.002	0.004

	pH	EC	K⁺	Na⁺	Ca⁺	Mg²⁺	Cl - = bicarbonate; TSS = total suspended solids; Cu = copper; Mn = manganese; Fe = iron; Zn = zinc; Cr = chromium; Ni = nickel; Cd = cadmium; Pb = lead. -	CO32-	HCO₃ - = bicarbonate; TSS = total suspended solids; Cu = copper; Mn = manganese; Fe = iron; Zn = zinc; Cr = chromium; Ni = nickel; Cd = cadmium; Pb = lead. -	TSS	Cu	Mn	Fe	Zn	Cr	Ni	Cd	Pb
pH	1.00
EC	0.33	1.00
K⁺	0.61	0.61	1.00
Na⁺	0.40	0.97	0.64	1.00
Ca⁺	0.31	0.87	0.55	0.85	1.00
Mg²⁺	0.19	0.94	0.53	0.87	0.74	1.00
Cl - = bicarbonate; TSS = total suspended solids; Cu = copper; Mn = manganese; Fe = iron; Zn = zinc; Cr = chromium; Ni = nickel; Cd = cadmium; Pb = lead. -	0.33	0.99	0.62	0.98	0.91	0.90	1.00
CO32-	0.62	0.30	0.39	0.34	0.28	0.16	0.27	1.00
HCO₃ - = bicarbonate; TSS = total suspended solids; Cu = copper; Mn = manganese; Fe = iron; Zn = zinc; Cr = chromium; Ni = nickel; Cd = cadmium; Pb = lead. -	-0.05	0.31	0.10	0.22	0.06	0.47	0.18	0.15	1.00
TSS	-0.17	-0.03	-0.02	-0.01	-0.06	0.00	-0.03	-0.11	0.02	1.00
Cu	0.32	0.63	0.55	0.70	0.72	0.48	0.70	0.16	-0.16	0.01	1.00
Mn	-0.35	0.09	-0.11	-0.02	0.14	0.20	0.07	-0.22	0.27	0.44	-0.08	1.00
Fe	-0.26	-0.16	-0.01	-0.15	-0.11	-0.13	-0.14	-0.25	-0.06	0.51	0.06	0.33	1.00
Zn	0.37	0.23	0.35	0.28	0.28	0.19	0.26	0.17	-0.08	-0.01	0.42	0.03	-0.07	1.00
Cr	0.19	0.39	0.36	0.47	0.56	0.22	0.46	0.14	-0.23	0.21	0.76	0.06	0.26	0.24	1.00
Ni	0.18	0.86	0.51	0.81	0.81	0.85	0.87	0.20	0.13	-0.02	0.54	0.12	0.01	0.17	0.27	1.00
Cd	0.04	0.38	0.29	0.27	0.21	0.45	0.30	-0.05	0.49	-0.05	0.01	0.14	-0.14	-0.13	-0.13	0.23	1.00
Pb	0.00	0.72	0.32	0.59	0.47	0.79	0.66	-0.02	0.47	-0.03	0.22	0.18	-0.15	-0.08	0.05	0.57	0.60	1.00

	Factor axis for the end of the dry season (2018)				Factor axis for the end of the rainy season (2019)
Variables	Factor 1	Factor 2	Factor 3	Factor 4	Factor 1	Factor 2	Factor 3	Factor 4	Factor 5	Factor 6
					Factorial loads
pH	0.17	-0.04	-0.25	0.86	0.09	0.07	0.59	0.03	0.14	0.34
EC	0.93	0.26	-0.03	0.21	0.98	0.04	0.10	0.01	-0.03	0.09
K⁺	0.54	0.08	0.02	0.61	0.13	0.25	0.39	-0.39	0.19	0.46
Na⁺	0.91	0.12	-0.04	0.29	0.98	0.02	0.06	0.02	-0.07	0.04
_Ca2+	0.91	-0.04	0.00	0.19	0.91	0.09	0.13	0.08	0.17	0.13
Mg²⁺	0.86	0.44	0.02	0.09	0.95	0.03	0.08	0.01	0.00	0.15
Cl^-	0.96	0.12	-0.04	0.19	0.98	0.05	-0.02	0.01	-0.04	0.10
_CO32-	0.08	0.10	-0.16	0.79	0.16	0.09	0.92	-0.11	0.04	-0.09
HCO3^-	0.09	0.83	0.13	0.09	0.17	-0.06	0.87	0.09	0.09	-0.17
TSS	-0.04	0.01	0.84	0.03	-0.02	-0.89	-0.01	-0.08	0.26	0.17
Cu	0.77	-0.41	0.07	0.25	-0.06	-0.30	0.11	-0.09	0.89	-0.04
Mn	0.10	0.29	0.70	-0.23	0.00	-0.82	0.06	0.16	0.17	-0.05
Fe	-0.05	-0.20	0.78	-0.12	-0.10	-0.80	-0.19	-0.17	0.00	0.01
Zn	0.23	-0.25	0.10	0.49	-0.05	-0.09	0.12	-0.01	0.95	0.03
S	NU	NU	NU	NU	0.70	0.00	0.32	-0.05	-0.15	-0.26
B	NU	NU	NU	NU	0.60	-0.42	0.30	-0.03	-0.17	-0.21
Cr	0.55	-0.52	0.32	0.19	-0.07	0.09	-0.24	-0.85	-0.03	-0.06
Ni	0.87	0.13	0.01	0.06	0.01	-0.27	0.27	-0.80	0.11	-0.04
Cd	0.27	0.70	-0.04	-0.04	NU	NU	NU	NU	NU	NU
Pb	0.65	0.59	-0.05	-0.17	0.13	-0.14	-0.10	0.11	-0.07	0.84
Eigenvalues	7.51	2.63	2.24	1.24	5.99	3.09	2.35	1.57	1.51	1.07
Total variance (%)	41.72	14.63	12.47	6.89	31.50	16.24	12.36	8.26	7.93	5.64
Accumulated variance (%)	41.72	56.35	68.82	75.71	31.50	47.75	60.11	68.37	76.30	81.94

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[1] Conflict of interest: The authors declare no conflict of interest related to the publication of this manuscript.