Seasonal variation and chemical composition of total precipitation and throughfall in an urban forest fragment in the Central Brazilian Amazon

Arcos, Adriano Nobre; Trigo, Ana Rosa Tundis Vital; Oliveira, Camila Carvalho Rodrigues de; Rebelo, Mateus Aguiar; Silva, Lueyne Emanuelle dos Santos; Monteiro, Maria Terezinha Ferreira; Cunha, Hillândia Brandão da; Ferreira, Sávio José Filgueiras; Silva, Márcio Luiz da

doi:10.1590/2318-0331.302520250014

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Scientific/Technical Article • RBRH 30 • 2025 • https://doi.org/10.1590/2318-0331.302520250014 linkcopy

Seasonal variation and chemical composition of total precipitation and throughfall in an urban forest fragment in the Central Brazilian Amazon

Variação sazonal e composição química da precipitação total e interna em fragmento florestal urbano na Amazônia Central Brasileira

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

The objective of the research was to determine the total precipitation and throughfall of an urban forest fragment in Manaus and to quantify the concentration of nutrients present in rainwater. The study was developed in two seasonal periods (dry and rainy) between 2020 and 2022. The pluviometers were installed in an urban forest fragment, in an open area (total precipitation), and inside the forest (throughfall). The water samples were sent to the laboratory for analysis of physical and chemical parameters. Precipitation showed a significant difference between periods, where the highest volumes of rain were observed in the second half of each year. The concentrations of nutrients in the water samples were higher in the dry period, and the throughfall showed high concentrations of nutrients in both seasonal periods due to washing the canopy, trunks, and leaves. In addition, the seasonality and volume of rainfall play important roles in the chemistry of rainwater in preserved and urban areas. Therefore, it is a key part of several biological processes in the ecosystem, including in streams and Amazonian rivers. Therefore, studies of this nature are scarce in the region, and the data provided are important for establishing long-term experiments.

Keywords:
Rain; Water quality; Urbanization; Pollution; Manaus

Variable	Unid	Ab. *	Measurement methods, device
Potential of hydrogen	pH	pH	Direct measurement, S230 Seven Compact™
Electrical conductivity	μS/cm^-1	EC	Direct measurement, Mettler Toledo™
Chloride concentration	mg/L^-1	Cl^-	Spectrophotometry, Shimadzu UV-1800
Ammonium concentration	mg/L^-1	NH₄⁺	Spectrophotometry, Shimadzu UV-1800
Nitrite concentration	mg/L^-1	NO₂^-	Spectrophotometry, Shimadzu UV-1800
Nitrate concentration	mg/L^-1	NO₃^-	Spectrophotometry, Shimadzu UV-1800
Phosphate concentration	mg/L^-1	PO₄^-3	Spectrophotometry, Shimadzu UV-1800

Variables			2021		2022
Variables			Rainy	Dry	Rainy	Dry
Nitrate mg/L^-1	Total	Min/Max	<DL - 0.06	<DL - 0.28	<DL - 0.04	<DL - 0.01
	Total	Mean/S.D.	0.03 ± 0.03	0.06 ± 0.06	0.02 ± 0.01	0.01 ± 0.005
	throughfall	Min/Max	<DL - 0.52	0.26 - 1.79	<DL - 1.74	0.01 - 10.32
	throughfall	Mean/S.D.	0.24 ± 0.26	0.88 ± 0.47	0.63 ± 0.54	4.18 ± 3.80
Nitrite mg/L^-1	Total	Min/Max	0.005 - 0.007	<DL - 0.020	<DL - 0.005	<DL - 0.008
	Total	Mean/S.D.	0.006 ± 0.001	0.007 ± 0.004	0.001 ± 0.002	0.004 ± 0.005
	throughfall	Min/Max	<DL - 0.008	0.009 - 0.836	<DL - 0.298	0.005 - 0.082
	throughfall	Mean/S.D.	0.004 ± 0.004	0.198 ± 0.241	0.044 ± 0.096	0.031 ± 0.031
Ammonium mg/L^-1	Total	Min/Max	0.06 - 0.14	0.03 - 0.2	<DL - 0.1	0.1 - 0.2
	Total	Mean/S.D.	0.09 ± 0.03	0.11 ± 0.03	0.08 ± 0.04	0.16 ± 0.05
	throughfall	Min/Max	0.2 - 0.4	0.08 - 1.4	0.1 - 0.9	0.6 - 5.8
	throughfall	Mean/S.D.	0.30 ± 0.10	0.59 ± 0.42	0.32 ± 0.25	2.8 ± 2.22
Phosphate mg/L^-1	Total	Min/Max	0.006 - 0.023	<DL - 0.112	0.001 - 0.017	<DL - 0.01
	Total	Mean/S.D.	0.014 ± 0.008	0.017 ± 0.022	0.008 ± 0.005	0.006 ± 0.005
	throughfall	Min/Max	0.012 - 0.093	<DL - 0.805	0.004 - 0.373	<DL - 1.99
	throughfall	Mean/S.D.	0.044 ± 0.043	0.221 ± 0.231	0.179 ± 0.149	0.832 ± 0.813
Chloride mg/L^-1	Total	Min/Max	1.1 - 1.55	<DL - 9.05	0.5 - 2.75	1.65 - 6.67
	Total	Mean/S.D.	1.33 ± 0.23	1.78 ± 1.65	1.31 ± 0.57	3.62 ± 2.21
	throughfall	Min/Max	1.1 - 2.99	0.02 - 6.63	0.9 - 4.88	3.01 - 7.98
	throughfall	Mean/S.D.	1.91 ± 0.97	2.12 ± 1.53	2.25 ± 1.21	5.05 ± 2.14

	Variables	PC 1	PC 2
Total precipitation	Nitrate (NO₃^-)	0.004	-0.007
	Nitrite (NO₂^-)	-0.006	0.024
	Ammonium (NH₄⁺)	-0.029	0.174
	Phosphate (PO₄^-3)	0.024	-0.133
	Chloride (Cl^-)	0.074	-0.559
	Potential of hydrogen (pH)	-0.165	0.777
	Electrical conductivity (EC)	0.982	0.182
	% variance	83.1	12.8
Throughfall	Nitrate (NO₃^-)	0.014	0.130
	Nitrite (NO₂^-)	-0.000	-0.020
	Ammonium (NH₄⁺)	0.049	0.454
	Phosphate (PO₄^-3)	0.011	0.113
	Chloride (Cl^-)	0.051	0.870
	Potential of hydrogen (pH)	0.002	-0.013
	Electrical conductivity (EC)	0.997	-0.070
	% variance	98.4	0.99

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