MICROPLASTICS AND GEOTECHNICAL CHARACTERISTICS OF THE SAND AT PRAIA DO FUTURO, CEARÁ, BRAZIL

Camelo, Paulo Rubens M.; Aguiar, Marcos Fabio P.; Bastos, Juceline B. S.

doi:10.1590/0101-7438.2026.046.00296019

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ARTICLES • Pesqui. Oper. 46 • 2026 • https://doi.org/10.1590/0101-7438.2026.046.00296019 linkcopy

MICROPLASTICS AND GEOTECHNICAL CHARACTERISTICS OF THE SAND AT PRAIA DO FUTURO, CEARÁ, BRAZIL

Authorship SCIMAGO INSTITUTIONS RANKINGS

Microplastic pollution and its environmental impacts are under investigation in marine and coastal environments. However, in Ceará state, Brazil, the impacts of microplastic pollution in coastal areas have not been evaluated. This study assesses the quantity, composition, and physical forms of microplastics in sediment at Praia do Futuro and determines the sand’s geotechnical characteristics. Three study zones were defined, with 21 samples collected. Normality tests were conducted for statistical analyses, comparing results using ANOVA and Kruskal-Wallis tests. No significant differences were found between locations with and without tourist activity. The concentration of microplastics exceeded levels observed in other Brazilian studies, but it was lower than that typically registered in international studies. Additionally, geotechnical characteristics of Praia do Futuro’s sand indicated grain size with diameters under 600 µm and void ratios aligned with literature expectations. The porosity varied along the coast, as is typical of natural sandy soils.

Keywords:
soil characterization; beach sand; microplastic pollution

Polymer	Abbrev.	Density (g/cm³)	Application
Expanded Polystyrene	EPS	0.01 - 0.04	Cups, plates, foam trays.
Polypropylene	PP	0.85 - 0.92	Auto parts, food containers, bottle caps, straws.
Low-Density Polyethylene	LDPE	0.89 - 0.93	Container caps, packaging supports, bottles, pipes, diapers.
High-Density Polyethylene	HDPE	0.94 - 0.98	Cleaning product bottles, dairy containers, supermarket bags, trash bins, playground equipment, buoys.
Acrylonitrile Butadiene Styrene	ABS	1.04 - 1.08	Electronic equipment housings, pipes.
Polystyrene	PS	1.04 - 1.08	Plates, cutlery, optical disc cases, toys.
Polyamide (Nylon)	PA	1.13 - 1.16	Toothbrush bristles, fishing lines and nets.
Polymethyl Methacrylate (Acrylic)	PMMA	1.16 - 1.20	Optical lenses, paints, residential finishing materials.
Polycarbonate	PC	1.20 - 1.22	Optical discs.

Location	Country	Extraction Method	Mesh/Size	Microscopy	Analytical Technique	Concentration	Unit	Reference
Ports of Zeebrugge, Oostende, and Nieuwpoort	Belgium	NaCl flotation	38 µm	Binocular microscope	FTIR	167	Items/kg	Claessens et al. (2011)
Beijiang River	China	NaCl flotation	1 µm	Portable digital microscope	SEM	544	Items/kg	Wang et al. (2017)
Norderney Island	Germany	NaCl flotation	0.45 µm	Leica Wild M3Z stereomicroscope	Pyrolysis-GC	213	Items/kg	Dekiff et al. (2014)
Mallorca and Cabrera Islands	Mediterranean Sea	NaCl flotation	-	Stereomicroscope	-	897	Items/kg	Alomar, Estarellas; Deudero (2016)
Rügen Island	Germany	CaCl₂ flotation	55 µm	Dissecting stereo microscope	-	11	Items/kg	Stolte et al. (2015)
Deukryang Gwangyang, and, Busan	South Korea	NaCl flotation	63 µm	Fluorescence microscope	Nile Red / FTIR	4	Items/m³	Shim et al. (2016)
Lido di Dante	Italy	NaCl flotation	0.45 µm	Stereomicroscope	Raman spectroscopy	1512	Items/kg	Lots et al. (2017)
Bohai Sea	China	NaCl flotation	1 µm	Digital microscope	FTIR	164	Items/kg	Yu et al. (2016)
North Yellow Sea	China	NaCl flotation	30 µm	Optical microscope	FTIR	545	Items/m³	Zhu et al. (2018)
Shenzhen and Hong Kong	China	NaCl flotation	0.7 µm	Stereomicroscope	FTIR	458	Items/kg	Tsang et al. (2017)
South Yellow Sea	China	NaI flotation	50 µm	Stereomicroscope	FTIR	4205	Items/kg	Wang et al. (2019)
Nakdong River	South Korea	Lithium metatungstate flotation	5 µm	FTIR microscope	FTIR	4760	Items/m³	EO et al. (2019)
Mobile Bay, Alabama	USA	-	50 µm	-	FTIR	50.6	Items/m²	Wessel et al. (2016)
Tamil Nadu	India	NaCl flotation	0.45 µm	Stereomicroscope	FTIR	178	Items/m²	Karthik et al. (2018)
Gdansk Bay	Poland	ZnCl₂ flotation	174 µm	Stereomicroscope	-	48.4	Items/kg	Zobkov; Esiukova (2017)

Author	Miftah et al. (2022 )	Liu et al. (2020 )	Almajed et al. (2020 )	Visconti et al. (2022 )	Simões (2015 )	Costa (2020 )	Soares (2021 )	Lanzano et al. (2016 )	Suzuki; Yamada (2006 )	Azeiteiro et al. (2017 )
Location	Famagusta Bay, Cyprus	Hawaii, USA	Nafud Desert, Saudi Arabia	Linosa Island, Italy	Ipanema Beach, Brazil	Ipanema Beach, Brazil	Ipanema Beach, Brazil	Leighton Buzzard, UK	Toyoura, Japan	Hostun, France
Moisture(%)	-	6-9	-	8.5	-	-	-	-	-	-
D10 (mm)	0.14	0.15	0.15	-	0.22	0.27	0.28	-	-	-
D50 (mm)	0.75	0.70	0.24	-	0.38	0.38	0.41	0.14	0.17	0.33
Coefficient of Curvature (CC)	1.60	0.60	0.90	-	0.97	0.90	0.92	-	-	-
Uniformity Coefficient (CU)	6.42	6.66	1.73	-	1.90	1.56	1.61	1.58	1.70	1.40
Classification	SP	SW	SP	SP	SP	SP	SP	Uniform	Uniform	Uniform
Grain Shape	-	-	-	Sub-rounded	Sub-angular to rounded	Sub-angular, sub-rounded to rounded	Sub-rounded to rounded	-	Sub-angular	Sub-angular to angular
e_min	0.562	0.85	0.45	-	0.462	0.435	0.433	0.613	0.618	0.66
e_max	0.88	1.74	0.66	-	0.732	0.76	0.698	1.014	0.963	1
Relative	2.700	-	2.650	-	2.659	2.656	2.656	2.650	2.650	2.640
Density (DR)

Mineralogy	Quartz and Calcite	Calcium Carbonate	Quartz	Plagioclase, Clinopyroxene, and Olivine	Quartz and Mica	Quartz, Biotite, and Feldspar	Quartz	-	Quartz and Feldspar	-
Cohesion (kPa)	0	-	-	-	-	-	-	0	0	0
Friction	41	-	-	-	-	-	-	32	31	31.5
Angle (°) Permeability (cm/s)	1.3 × 10^-2 to 9.4 × 10^-4	-	-	-	-	1.1 × 10^-2 to 2.1 × 10^-2	4.2 × 10^-2	-	-	-

Analysis	Reference
In situ Bulk Density	ABNT (2016c)
Natural Moisture Content	ABNT (2016b)
Particle Density	DNER (1994a)
Grain Size Distribution	ABNT (2016a)
Maximum Void Ratio	ABNT (2020a)
Minimum Void Ratio	ABNT (2020b)
Minimum Void Ratio	Miura and Toki (1982)
Permeability	ABNT (2021)
Direct Shear	ASTM (2004)
Shape and Angularity	DNIT (2020)
Elemental and Crystallographic Analysis	Artioli (2010)
Microplastic Occurrence	Masura (2015)

Authors	Miura; Toki (1982 )	Simões (2015 )	Costa (2020 )	Soares (2021 )	This study
Sample	Toyoura Sand, Japan	Ipanema Beach Sand, RJ			Praia do Futuro Sand, CE
Sampling Point	1	1	1	1	1	2	3
D50 (mm)	0.18	0.38	0.39	0.41	0.21	0.26	0.25
Upper sieve opening (mm)	1.41	4.75	4.75	4.75	2.00	2.00	2.00
(#ps)
#ps/D50	7.83	12.5	12.2	11.6	9.52	7.69	8.00
Lower sieve opening (mm)	3.66	12.5	9.25	8.00	4.75	4.75	4.75
(#pi)
#pi/D50	20.3	32.9	23.7	19.51	22.62	18.27	19.00
Number of sieves	7	6	6	7	7	7	7
Sequence of openings (mm)	1.41	4.75	4.75	4.75	2.00	2.00	2.00
	3.66	9.50	8.00	4.75	4.75	4.75	4.75
	3.66	9.50	8.00	4.75	4.75	4.75	4.75
	3.66	12.50	9.50	4.75	4.75	4.75	4.75
	3.66	12.50	9.50	8.00	4.75	4.75	4.75
	3.66	12.50	9.50	8.00	4.75	4.75	4.75
	3.66			8.00	4.75	4.75	4.75

Property	Limit values
2D Shape	<4.0 Circular	4.0 - 11.0 Semi-circular	11.0 - 15.5 Semi-elongated	> 15.5 Elongated	-
Angularity	< 1.260 Rounded	1.260 - 4.080 Sub-rounded	4.080 - 7.180 Sub-angular	> 7.180 Angular	-
Sphericity	< 0.5 Flat/Elongated	0.5 - 0.7 Low sphericity	0.7 - 0.9 Moderate sphericity	> 0.9 High sphericity	-
Surface texture	< 260 Polished	260 - 440 Smooth	440 - 600 Low roughness	600 - 825 Moderate roughness	> 825 High roughness

		1	2	3
1	Mean difference	-	30.00	8.57
1	p-value	-	0.385	0.921
2	Mean difference		-	-21.43
2	p-value		-	0.606
3	Mean difference			-
3	p-value			-

Relation		W	p
1	2	3.98	0.014
1	3	4.43	0.005
2	3	3.35	0.047

		1	2	3
1	Mean difference	-	0.0256	0.02896
1	p-value	-	0.430	0.344
2	Mean difference		-	0.00336
2	p-value		-	0.985
3	Mean difference			-
3	p-value			-

		1	2	3
1	Mean difference	-	0.0341	0.0671
1	p-value	-	0.084	< 0.001
2	Mean difference		-	0.0330
2	p-value		-	0.097
3	Mean difference			-
3	p-value			-

Relation		W	p
1	2	-3.166	0.065
1	3	-4.251	0.007
2	3	0.632	0.896

Relation		W	p
1	2	-31.693	0.065
1	3	-33.578	0.046
2	3	-0.0913	0.998

Relation		W	p
1	2	-3.18	0.064
1	3	-3.35	0.047
2	3	2.46	0.190

Relation		W	p
1	2	3.39	0.044
1	3	3.90	0.016
2	3	-1.03	0.747

Relation		W	P
1	2	3.78	0.020
1	3	4.60	0.003
2	3	-2.56	0.165

Relation		W	p
1	2	0.00	1.000
1	3	-1.90	0.370
2	3	-2.46	0.192

Relation		W	P
1	2	0.00	1.000
1	3	-2.08	0.305
2	3	-2.08	0.305

Designation	Diameters (mm)
Boulder	1000 a 200
Coarse gravel	200 a 60
Coarse gravel	60 a 20
Medium gravel	20 a 6
Fine gravel	6 a 2
Coarse sand	2 a 0.6
Medium sand	0.6 a 0.2
Fine sand	0.2 a 0.06
Silt	0.06 a 0.002
Clay	Menor que 0.002

Relation		W	P
1	2	3.16	0.065
1	3	4.43	0.005
2	3	-2.89	0.101

Relation		W	p
1	2	-3.34	0.048
1	3	-4.43	0.005
2	3	2.80	0.117

		1	2	3
1	Mean difference	-	-0.0203	-0.0634
1	p-value	-	0.535	0.009
2	Mean difference		-	-0.0431
2	p-value		-	0.080
3	Mean difference			-
3	p-value			-

Relation		W	p
1	2	26.202	0.153
1	3	37.044	0.024
2	3	0.0904	0.998

Relation		W	p
1	2	0.0905	0.998
1	3	0.8132	0.834
2	3	1.4488	0.562

Relative Density	Soil Deposit Description
0.00 - 0.15	Very loose
0.15 - 0.50	Loose
0.50 - 0.70	Medium
0.70 - 0.85	Dense
0.85 - 1.00	Very dense

		1	2	3
1	Mean difference	-	0.0249	0.134
1	p-value	-	0.935	0.174
2	Mean difference		-	0.109
2	p-value		-	0.302
3	Mean difference			-
3	p-value			-

Relation		W	p
1	2	2.62	0.153
1	3	2.98	0.088
2	3	2.62	0.153

		1	2	3
1	Mean difference	-	-0.650	-1.99
1	p-value	-	0.526	0.009
2	Mean difference		-	-1.33
2	p-value		-	0.088
3	Mean difference			-
3	p-value			-

Point	k₂₀ (cm/s)	e_mol	CR_mol	Relative Density	e_nat
1	1.1 × 10^-2	0.73	0.43	Fofo	0.76
2	1.3 × 10^-2	0.73	0.46	Fofo	0.78
3	1.3 × 10^-2	0.78	0.32	Fofo	0.82

Relation		W	p
1	2	3.162	0.065
1	3	3.162	0.065
2	3	0.994	0.762

	2D Shape	Angularity	Classification 2D Shape	Angularity
1.1	7.0	2647.5	Semicircular	Subrounded
1.2	7.3	2697.0	Semicircular	Subrounded
1.3	7.1	2732.2	Semicircular	Subrounded
1.4	7.5	2795.4	Semicircular	Subrounded
1.5	6.9	2764.4	Semicircular	Subrounded
1.7	7.4	3010.1	Semicircular	Subrounded
2.1	7.1	3035.4	Semicircular	Subrounded
2.3	7.2	3176.2	Semicircular	Subrounded
2.5	7.1	3038.8	Semicircular	Subrounded
3.1	7.2	2894.4	Semicircular	Subrounded
3.3	7.1	2948.7	Semicircular	Subrounded
3.5	7.4	3144.5	Semicircular	Subrounded

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