Changes of Estuarine Sedimentation Patterns by Urban Expansion: The Case of Middle Capibaribe Estuary, Northeastern Brazil

The aim of this study is to describe the sedimentary evolution occurred during the last 200-years in the middle Capibaribe Estuary by mean of the sedimentary analysis (magnetic susceptibility, grain size, calcium carbonate, total organic matter—TOM) and geochemical parameters (sedimentation rates, heavy metal concentrations, enrichment and contamination factor) along a core. The core recorded four units and the measured sedimentation rate was 0.52 cm cm∙y. The first unit, dating before 1812, showed environmental characteristics of mangrove with predominance of fine sediments, high total organic matter percentages and heavy metal concentrations probably from natural sources. The second unit, from 1812 to 1937, showed a slight increase in sand percentages and decrease in fine fraction, TOM contents and heavy metals concentrations. These characteristics may be associated with the urban expansion processes and the presence of monoculture of sugar cane occurred in the middle Capibaribe Estuary. The third unit, from 1937 to 2004, showed the highest sand percentages of the core, characterizing a unit exclusively of sand with low fine fractions percentages, total organic matter contents and heavy metals concentrations. This unit represented the intensification of the urban processes expansion of Recife City. The fourth unit showed increases in fine fraction sedimentation, TOM contents and heavy metals concentrations. This new change in sedimentation probably is consequence of rebirth of marginal estuarine banks by mangrove vegetation, due to environmental projects carried out by Recife Prefecture in the early 2000’s. It was not possible to register the anthropic contamination to middle estuary area probably due to the Barreiras Formation influences in the metal concentration records, masking the anthropic contamination inputs in estuarine region. Although, lead and arsenic showing an enrichment level indicating anthropic contamination. How to cite this paper: Barcellos, R.L., Figueira, R.C.L., França. E.J., Schettini, C.A. and de Arruda Xavier, D. (2017) Changes of Estuarine Sedimentation Patterns by Urban Expansion: The Case of Middle Capibaribe Estuary, Northeastern Brazil. International Journal of Geosciences, 8, 514-535. https://doi.org/10.4236/ijg.2017.84027 Received: November 21, 2016 Accepted: April 18, 2017 Published: April 21, 2017 Copyright © 2017 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access DOI: 10.4236/ijg.2017.84027 April 21, 2017 R. Lima Barcellos et al.


Introduction
The estuaries are transition areas between continental and ocean interface and they are important environments in comprehension of the coastal areas development and prevision of future evolving tendencies [1]. The sediments deposits are important because it could preserve the history of sedimentation in coastal environments [2]. Estuarine sedimentation is a consequence of many conditions, such as the sediment source that may be from the river or marine origin [3] [4] [5]. The estuarine regions show a rich fauna and flora and these are important sources of natural resources, and around these estuarine areas located are, in general, in larger cities and industrial complexes [1].
Historically, the coastal areas are attractive to human settlements, and these form huge metropolises, that grew in disorderly way [6]. The urban and industrial development adjacent to estuarine areas may cause environmental imbalance, changing the water column chemical proprieties, sedimentation patterns, mangrove deforestation and typical forest areas, landfill of flood areas to urban expansion, building of dams, contamination of heavy metals and others [7]. The studies with sedimentary columns are used to comprehension the environmental evolution in coastal areas. These sedimentary cores may provide historical records of sedimentation patterns in coastal systems, indicating the natural baselines and changes caused by anthropic modifications during the time [8] [9].
Some parameters are employed to understand the environmental evolution such as sedimentological parameters as grain size, organic matter and calcium carbonate contents in coastal environments, that provide important information for paleoenvironmental reconstructions and may register the historical of the local and regional climatic changes [10]. Variations in magnetic susceptibility have been used for detecting anthropogenic pollution caused by power plants, metallurgical dusts, fly-ashes and urban airborne particulates [11] [12] [13] and heavy metal concentration is employing to identify natural or anthropic sources and contamination levels [14]- [19]. Finally, the use of radionuclides in coastal environments as sediment tracers offers considerable potential for determining sediment sources and sedimentation rates in drainage basins [20].
The sedimentary characteristics in cores may be associated with the development of the urban processes. Anthropic changes around the river, estuary or beach are responsible for a natural imbalance of the coastal systems as well as the interference in transport of sediments and organism cycles [1]. The anthropic induced changes occur in Capibaribe Estuary (8˚S/35˚W) since the start of colonization processes as such as coastline modification, dredging and landfill activities [21]. Currently, this estuary is being polluted by different sources as well as fish and shrimp farming areas, discharge of industrial and domestic wastes and R. Lima Barcellos et al. sewage [22] [23]. In this way, the aim of this study is to describe the sedimentary evolution occurred in the middle Capibaribe Estuary by mean of the sedimentary analysis and geochemical parameters along a sedimentary core, associating with the anthropic change occurred in the estuarine system and infer the background metal values.

Study Area
The

Methods
A 178-cm deep core was collected in 27 th November 2012, with the aid of a push-core operated by a scuba diving at the coordinates of 8˚02'22.56"S and 34˚55'27.12"W, 0.5 m of water column in a marginal bank. After the core recovery, it was analyzed for magnetic susceptibility in a Bartington MS2C meter. The measurements were made with a 0.1 × 10 −5 S.I. resolution and readings were taken at 2 cm intervals [13]. After that, he core was opened, described and continuously sub-sampled at intervals of 2 cm. Samples were dried at 50˚C in order to be analyzed for grain size, organic matter and calcium carbonate contents, metal concentrations and determination of sedimentation rates by 210 Pb xs activity.
Total calcium carbonate and organic matter were determined according the methods proposed by [29]. The calcium carbonate was determined by weight difference of the sediment prior and after addition of hydrochloric acid (10%).
The total organic matter was determined also by weight difference prior and after addition of hydrogen peroxide (10%), until total reaction. Both results are presented as percentages of the bulk sample.

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Grain size was determined in a Malvern Mastersizer 2000 laser sedimentometer, after calcium carbonate and organic matter removal of samples. Results allowed the determination of the grain size statistical parameters proposed by [30] and sediment classification by [31], by mean of the Sysgran 3.0 software [32].
The sedimentation rate result followed radionuclide 210 Pb determination method described by Saito et al. (2001), that is based in 210 Pb half-live decay (t 1/2 = 22.3 years) [34]. The sedimentation rate value was calculated by CIC model (Constant Initial Concentration) [35]. A maximum time span of 200 years was considered for the age determinations [36].
The metal concentrations were obtained by energy dispersive X-ray fluores- To identify the anomalies and evolution of the heavy concentrations, geochemistry standardizations by conservative element were used as tool, to evaluate the level of the anthropogenic contamination [38] [39]. There are two approaches to normalization of metals in sediment, the granulometric and geochemical methods [40]. The geochemical normalization is necessary standardized with alithogenic conservative element [41] [42]. Usually, Aluminum is used as lithogenic conservative element because it is a major constituent of fine-grained alumiosilicates [40] and its concentration is generally not influenced by anthropogenic sources [41] [43].
There are some types of geochemical normalization such as Al-normalized, enrichment factor, geochemical index and contamination factor. In this study will be performed enrichment factor (EF) and contamination factor (CF), and the indexes are based in the trace element concentration in base core, the Earth's background or the metal analysis reference value.
According to [44], the enrichment factor (EF) is defined as follows Equation (1): where C sample is the trace element concentration in the sample, C backgroung is the trace element concentration in base core, Al sampe is the aluminum content in the sample, and Al background is the aluminum content in base core. The EF values were interpreted as the levels of metal pollution as suggested by [45] where EF < 1 indicates no enrichment, <3 is minor, 3 -5 is moderate, 5 -10 is moderately severe, 10 -25 is severe, 25 -50 is very severe and >50 is extremely severe.
The contamination level in sediments by metal is expressed in terms of a contamination factor (CF). According [46] theses values are calculated as follows Equation (2): where, C metal is metal concentration in sample and C background is the Earth's background or reference value of the metal analysis. The CF value is divided into four classes: CF < 1 refers to low contamination; 1 ≤ CF < 3 means moderate contamination; 3 ≤ CF ≤ 6 indicates considerable contamination and CF > 6 indicates very high contamination [47].

Results
The sedimentation rate for the core was 0.52 cm•y −1 , and according to the sedi-

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The Unit 2 showed the same patterns in heavy metal concentration of the Unit 1, when compared with background values of [49] (see Table 2).  Table 2).
The vertical variation records MS, TOM, calcium carbonate, sand, silt and clay percentage and heavy metal concentration peaks along of core are represented by the Figure 2 and Figure 3.
The enrichment factor (EF) [44] shows no enrichment values to Mn, Fe, Co, Ni, Cu, Ga, Ti, Mg with EF < 1. Zn, Pb and V show values of lower enrichment with EF < 3, and As shows a moderate to moderately severe enrichment factor values, with higher enrichment (5 < EF < 25) (Figure 4).

Discussion
The sedimentary characteristics in cores may be associated with the development of the urban processes. Anthropic changes around the river, estuary or beach are responsible for a natural imbalance of the coastal systems as well as the interference in transport of sediments and organism cycles [1]. The units regis-    unit may be associated with high productivity of organisms with carbonate shells present in mangroves [52] [53]. Probably, the metal concentration values are from natural sources, associated with the local/regional inputs from the Barreiras Formation [54] [55] [56] [57].
According to [58], the Poço da Panela, the neighborhood area located in the

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In this unit (Unit 2) shows a decrease in averages of metal concentrations when compared with Unit 1 (see Table 2). Probably this is associated with greater the sand percentages in sedimentation and decrease in the clay percentages [54] [63]. [64] affirms that clays adsorbs four times more organic matter and metals from sands, and two times more from silts. [56] also affirmed that This project of Recife's prefecture showed great results well as observed by [67] [68], being observed in sedimentary core of middle estuary represented by Unit 4. This unit showed increases in silt and clay percentages (averages of 45.4% and 6.5%, respectively) when compared with unit 3, and a layer highly sandy (averages of 11.4% and 2.1%, respectively). In Unit 4, the increases in fine sedimentation are associated possibly with progradation of the mangrove areas located in margins of Capibaribe Estuary as well as the TOM contents increasing and metal concentrations (see Figure 2).
According to the graphic of enrichment factor (EF) and contamination factor (CF), the majority of metals do not show high levels of enrichment and contamination ( Figure 5 and Figure 6). Only Pb and As showed enrichment and contamination levels. According [38] [45] [69], rich rocks in heavy metals in its composition may mask the enrichment and contamination level. In the case of Capibaribe Estuary, the Barreiras Formation is a greater contributor of metal source [57].  R. Lima Barcellos et al. cur in any layer during sedimentation processes, depending of the available organic matter. This relation may be observed in correlation values between Iron and calcium carbonate and total organic matter (r = 0.6) (see Table 3).
Arsenic and Lead enrichment in Brazilian coastal environments were reported in several works as [79]- [84]. High levels of As (i.e. above the nationally thereshold of 70 mg. kg-1 ) were found in shelf, beach and nearshore sands, lagoonal/swamp and mangrove sediments of Espírito Santo, Bahia [80] [81], Rio de Janeiro [82] and Rio Grande do Sul states [84]. A significant positive correlation between As and calcium carbonate (r=0.6) could indicate that the calcareous bioclasts participate in metalloid retention and its accumulation in coastal sediments as observed by [81]. This affinity with carbonates added to the As inputs from: (a) the eroded material from continental rocks and sediments [80] local sources (Borborema Crystalline Complex and the Barreiras Group ferrous sandstones); (b) the groundwater aquifer [82]; (c) the atmospheric fallout [82], could implies in the high values observed in the studied core (> 120.0 mg.kg -1 ). Similarly as observed for the Paraíba do Sul delta region [82] and Patos Lagoon estuarine sediments [84] the Arsenicis retained mainly by iron hidroxides in upper and probably by sulfides in lower layers due to diagenetic processes. In fact the high significant correlation of As with iron (r = 0.9) and Pb (1.0) reinforce the local enrichment from post depositional processes and atmospheric fallout, also indicated by the Pb enrichment, especially in the upper units of the core (1 and 2).
[85] observed finer sedimentation and TOM peaks associated with occurrence of floods registered in Recife to the lower Capibaribe Estuary. In case of middle estuary is not possible to identify finer sedimentation associated with flood registers. It is believed that the suspended sediments by rains transport is deposited mainly in the middle estuarine area, registering a prevalence of fine sedimentation.

Conclusions
The modification of urban space changed the sedimentation patterns in the Although all modifications that occurred since the 18 th century, the Capibaribe River was not possible to register clearly the anthropic contamination to middle estuary area. The metal concentration records may have been also influenced by natural sources, which are rich in heavy metal concentrations and surround the estuarine area. And this way, the anthropic influences could have been masked by this geological character. Although as observed by the presented results, and in similar studies, that the enrichment of As and Pb could be directly related to these elements retention and accumulation by diagenetic processes, associated to several local sources as: the carbonate sediments, the local rocks and continental sediments, the groundwater aquifer and the atmospheric fallout.
Lastly, this research may be useful in the comparison with similar sedimentary studies in densely urban estuarine areas. As well as to subsidize the determination of local metals reference/background levels in future studies employing the data collection presented in this paper.