Proposta de um índice de qualidade de águas para microbacias hidrográficas sob manejo silvicultural

Gardiman Junior, Benvindo Sirtoli; Garcia, Giovanni de Oliveira; Cecílio, Roberto Avelino; Loos, Rodolfo Araújo

doi:10.5902/1980509817548

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Artigos • Ciênc. Florest. 29 (3) • Jul-Sep 2019 • https://doi.org/10.5902/1980509817548 copiar

Proposta de um índice de qualidade de águas para microbacias hidrográficas sob manejo silvicultural

Autoria SCIMAGO INSTITUTIONS RANKINGS

Resumo

Neste trabalho objetivou-se elaborar um Índice de Qualidade das Águas (IQA) para o setor florestal. Para isso, monitoraram-se as características físicas e químicas da água: Ca, Cu, Fe, K, Mg, Na, P, S, Zn, CI, CO, Clor, Nitr, Sulf, Fosf, Amô, Glif, Alca, CE, Cor, DQO, DC, DC, OD, SS, SD, Sulfl, Temp, Turb e pH, em quatro microbacias hidrográficas (MBs) sob atividades do manejo florestal no município de Aracruz - ES, de janeiro a junho de 2012. As técnicas de estatística multivariadas, Análise de Componentes Principais (ACP) e Análise Fatorial (AF), indicaram que as variáveis mais representativas da variação da qualidade das águas para compor um IQA são: CE, Cor, Clor, Nitr, Mg, Alca, Na, Na, CI, CO, Fe, pH e SS, responsáveis por uma variância total de 61,77% dos dados após a rotação dos fatores pelo método Varimax normatizado. As variáveis relacionadas aos sais dissolvidos na água assumiram maiores pesos, em consequência da proximidade do mar. O IQA proposto demonstrou ser eficiente para avaliar a qualidade das águas das MBs monitoradas, ao invés de examinar as variáveis independentemente.

Palavras-chave:
Estatística multivariada; Análise de componentes principais; Variáveis de qualidade da água

Table 1 Chemical characterization¹ of the soils* of the monitored micro-watersheds (MW).

MW	P	K	Ca	Mg	H+Al	Sum of Bases	T	V	OM	pH
	--mg dm^-3--		----------------cmol_c dm^-3------------------					(%)	dag kg^-1	pH
1	3.0±1.4	13.7±2.7	0.40±0.16	0.13±0.05	4.72±0.07	2.76±0.07	7.48±0.5	36.6±1.5	1.70±0.3	4.0±0.07
2	15.0±10	16.6±4.1	0.61±0.05	0.18±0.03	3.17±0.24	4.11±0.3	7.28±0.6	56.4±2.4	1.65±0.2	4.1±0.18
3	7.1±4.4	22.86.4	1.03±0.24	0.21±0.03	2.94±0.7	6.50±0.09	9.44±0.8	68.8±3.5	2.37±0.4	4.1±0.28
4	7.7±2.4	12.7±4.1	1.03±0.6	0.14±0.03	3.92±0.02	5.89±0.2	9.81±0.5	60.0±2.5	2.20±0.6	4.1±0.25

Table 2 Silvicultural activities monitored in the four micro-watersheds (MW’s) in Aracruz, Espírito Santo state, Brazil.

MW	Activ²	Description of activities³
1	1	Witness (without any silvicultural intervention)
1	2	Opening of roads, harvesting and transportation
1	3	Cleaning of control strains and first control of leafcutter ants with the distribution of sulfluramide-based granular bait (0.03% of active principle)
1	4	First control of leafcutter ants
2	1	Witness (without any silvicultural intervention)
2	5	Mowing
2	4	First control of leafcutter ants
2	6	First control of leafcutter ants and opening of roads
2	7	Harvest
3	1	Witness (without any silvicultural intervention)
3	8	First control of leafcutter ants, chemical weed control before planting, chemical elimination of strain
3	9	Chemical elimination of strain, chemical weed control before planting, subsoiling with fertilization, cleaning of the planting line
3	10	Subsoiling with fertilization and planting
3	11	Planting
3	12	Second control of leafcutter ants
3	13	Chemical weed control after planting
3	15	Third month fertilization
4	1	Witness (without any silvicultural intervention)
4	7	Harvest
4	14	First control of leafcutter ants, chemical weed control before planting, chemical elimination of strain, cleaning of the planting line, subsoiling with fertilization and planting
4	5	Mowing

Table 3 Classification of water quality based on the numeric value of the proposed Water Quality Index (WQI).

Numeric value of the WQI	Classification of the water quality
-3.0 a -1.9	Great
-1.8 a -0.13	Good
-0.12 a 0.79	Acceptable
0.78 a 1.9	Bad
1.8 a 3.0	Terrible

Table 4 Standard water quality variables (qi) used in the calculation of the Water Quality Index (WQI) of each micro-watershed (MW) followed by the dates of collection and monitored activities (Activ) in the city of Aracruz, Espírito Santo state, Brazil.

MW	Activ	Date	Variables⁴
MW	Activ	Date	EC	Color	Chlor	Nitr	Mg	Alka	Na	IC	OC	Fe	pH	SS
1	1	25/01	-0.58	-0.53	-0.59	1.3	-0.3	-0.57	-0.26	0.16	-0.8	-0.67	-1.16	-0.61
	2	17/02	-0.27	-0.7	-0.32	1.53	0.09	-0.47	-0.51	-0.84	0.6	-0.66	-0.41	-0.72
	3	07/03	-0.69	-0.62	0.03	1.4	-0.2	-0.55	-0.21	-0.49	1.26	-0.34	-0.41	-0.34
	4	19/03	-0.65	-0.61	-0.44	1.63	-0.24	-0.33	-0.27	0.19	-0.84	-0.69	-0.28	-0.5
2	1	04/01	1.12	0.5	0.09	1.03	1.59	-0.42	0.68	-0.27	-0.01	-0.48	-1.63	0.33
	5	17/02	1.96	2.21	2.15	-1.24	1.67	-0.2	1.5	-0.85	1.84	-0.36	-0.72	-0.12
	4	07/03	1	2.07	1.75	-1.24	1.13	-0.45	1.37	-0.78	2.08	0.03	-0.77	0.03
	6	20/03	1.12	1.81	0.41	-0.99	1.52	0.18	0.81	-0.02	0.27	-0.11	0.06	0.33
	7	09/04	2.31	1.3	1.81	-1.15	1.93	3.58	0.79	3.35	0.05	0.49	0.38	0.56
3	8	04/01	-0.42	-0.66	-0.49	0.94	-0.78	-0.28	-0.73	-0.42	-0.68	-0.22	0.71	-0.42
	9	06/01	-0.38	-0.36	-0.49	0.2	-0.62	0.08	-0.46	-0.42	-0.74	-0.09	1.05	-0.65
	10	13/01	-0.46	-0.55	-0.63	0.1	-0.8	-0.26	-0.71	0.04	-0.65	-0.16	1.57	-0.5
	11	17/02	0	-0.77	-0.01	-0.09	-0.42	-0.08	-0.14	-0.86	0.46	-0.65	0.19	-0.57
	12	07/03	-0.34	-0.47	0.22	-0.28	-0.59	-0.08	0.33	-0.95	1.67	-0.58	0.56	-0.57
	13	19/03	-0.34	-0.63	-0.23	0.03	-0.72	-0.16	0.04	-0.31	-0.75	-0.71	0.56	-0.57
	15	15/05	0.12	-0.6	0.86	-0.12	-0.23	-0.01	0.98	0.64	-0.86	0.12	-0.59	-0.5
4	1	05/06	-0.19	-0.42	-0.25	-0.33	-0.54	-0.43	1.07	-0.02	-0.83	-0.38	0.95	-0.19
	7	04/01	-1.69	-0.44	-1.81	-0.51	-1.68	-1.21	-2.82	-0.44	-0.54	0.1	-2.21	0.18
	14	09/05	-0.69	-0.02	-0.93	-1.24	-0.38	1.72	-1.04	1.33	-0.73	1.97	0.77	1.09
	1	05/06	-0.92	-0.53	-1.13	-0.99	-0.41	-0.05	-0.42	0.95	-0.8	3.39	1.37	3.73
	5	13/06	-1.23	-0.33	-1.44	-0.91	-0.81	0.02	-1.65	0.8	-0.86	0.45	-0.28	1.09

Table 5 Factor loading matrix of the variables rotated by the varimax algorithm in the four main components selected and the wi weights of the variables.

	Extracted components⁶
Variables⁵	C1	C2	C3	C4	Weights (wi)
Chlor	0.935	-0.126	0.118	0.174	0.1533
Color	0.861	0.270	-0.152	0.089	0.1547
EC	0.845	-0.039	-0.031	0.351	0.1548
Mg	0.767	0.002	-0.144	0.306	0.1367
OC	0.740	-0.080	-0.073	-0.351	0.0722
Na	0.733	-0.121	0.341	0.060	0.1241
Fe	-0.254	0.858	0.039	0.243	0.0568
Nitr	-0.385	-0.798	-0.164	-0.152	-0.1480
SS	-0.225	0.873	-0.079	0.199	0.0529
pH	-0.186	0.252	0.735	0.304	0.0562
IC	-0.088	0.287	0.031	0.910	0.0913
Alka	0.217	0.181	0.121	0.897	0.1323
Sum of the components - P_i	3.96	1.56	0.74	3.03	1.00
Eigenvalues - F	6.30	3.50	2.07	3.57
Unitary variance (%)	25.22	13.98	8.28	14.28
Accumulated variance (%)	25.22	39.20	47.48	61.77

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[TFN1] ¹Average and standard deviation of the values of tests performed at depths. *Legend: P = Phosphorus, K = Potassium, Ca = Calcium, Ma = Magnesium, H + Al = Potential Acidity, T = Cation exchange capacity at pH 7, OM = Organic Matter, V = Saturation of bases and pH = Hydrogenation potential