Trace metals geochemical background in soil in the Suape Port and Industrial Complex, Pernambuco Brazil

Transcription

1 The Sustainable City IX, Vol Trace metals geochemical background in soil in the Suape Port and Industrial Complex, Pernambuco Brazil E. Santos de Lima & A. de Souza Moraes Centro de Tecnologia e Geociências, Universidade Federal de Pernambuco-UFPE, Brazil Abstract The implantation of new industries and infrastructure (roads and piers) in the Suape Industrial Portuary Complex together with the weathering action are responsible for the transportation of particulate matter to the surrounding water bodies. A geochemical behavior study of trace metals was done in the watershed of Tatuoca River aiming to show the geochemical affinity among the chemical elements in order to identify its origin. Thirty six soil samples were collected using helical auger samples and four 50 cm long core samples were collected at the bottom of the river using a percussion sampler. The stream sediment core samples were divided into 5 cm intervals. The samples were analyzed by ICP/AES for: Al, Ba, Be, Cd, Co, Cr, Cu, Fe, La, Li, Mo, Ni, Pb, Sc, Sr, Ti, V, Y, Zn and Zr. Principal component analysis and concentration maps were used to interpret the data. Comparing the soil results to that of stream sediment profiles one can conclude that the stream sediments collected closer to the infrastructure and industrial implementation works are richer in sand fraction, Mo, Zr and Zn. On the other hand, the stream sediment profile further away from the construction works are richer in Fe, Cr, V, Ni, Cd and Pb. The understanding of the geochemical behavior of chemical elements present in the watershed (geogenic or anthropogenic) is important in land use occupation and also in establishing a local background value to evaluate future environmental impacts due to trace metals present in stream sediments. Keywords: soil and stream sediments, trace and heavy metals, background metal level. doi: /sc141462

2 1722 The Sustainable City IX, Vol. 2 1 Introduction The Suape Complex is an industrial and harbor business area in Brazil. Many industries are operating (e.g. petrochemical plants, shipyards, food processing, etc.) in this complex and several other are being in process of concluding their plants to begin operation (refinery, shipyards, etc). The Tatuoca River is part of the Suape estuarine system whose catchment area is totally included in the Suape area. The sanity of estuarine ecosystems can be evaluated through the monitoring of their bottom sediments. Some chemical elements that have a known toxic potential are often used as quality indicator of bottom sediments [1, 2, 6 8]. It is not uncommon that bottom sediments are influenced by the soils present in the basin catchment area. So it is important to consider the geogenic contribution to the present chemical composition of bottom sediments. Even though it is very difficult to separate anthropogenic from the geogenic source in this work we will try to establish if the trace element is from natural or anthropogenic origin. In the Tatuoca River basin sugar-cane plantation was the main land use for centuries, so the soil may contain residuals of fertilizers and pesticides and that also could contribute to the present chemical composition of the bottom sediments. Using geochemistry as a monitoring tool one can interpret the processes that occurred in the river basin catchment area and project the future scenario taking into consideration the ongoing pressure and the resilience of the environment. In order to achieve the main objective of this work, it is necessary to use multivariate statistical methods. 2 Materials and methods Soils samples were collected to determine the natural metal contribution to the bottom sediments and the core samples were collected in order to see the time evolution of the bottom sediments in the Tatuoca River and if any anthropogenic source could be detected. The sampling sites are shown in Fig. 1. The 36 soil samples were collected in the area shown as set soil and the 4 bottom sediments core were collected in the points numbered P1 to P4. Core samples P1 and P2 were collected closer to the area where new industries (refinery and petrochemical plant) is being constructed, core sample P3 was collected in a more restricted area, so could represent an environment not impacted by the port activities and the P4 sample collected in an area that may have influence of intense dredging in the port basin. The 36 soil samples were collected using a helical auger samples and were distributed in grid 100m x 100m and were collected at a 50cm depth. The 4 four 50 cm long core samples were collected at the bottom of the river using a percussion sampler with 4cm diameter. The cores were store at 4 C and then divided into 5cm intervals. After the division the subsamples were oven dried at 50 C. The same drying procedure was applied to the soil samples. Afterwards the samples were homogenized in a porcelain mortar and an aliquot of each sample (1g) was solubilized in acqua regia solution in a hot plate at 100 C for 12 hours. After reaching room temperature then the solution was filtered and place in a 50 ml

3 The Sustainable City IX, Vol volumetric flask and volume completed with HNO 3 solution at 5%. The chemical analysis were done by ICP/AES technique were the following elements were determined: Al, Fe, Ca, K, Mg, P, Ti, Ba, Cr, Cu, La, Li, Mo, Ni, Pb, Sc, Sr, V, Y, Zn, Zr. The grain size distribution was achieved by the use of a sieve shaker and separated into sand fraction (>0.063mm) and silt + clay (<0.063mm). Figure 1: Sample location sites at Suape Industrial Port, Pernambuco, Brazil. 3 Results and discussions The mean and standard deviation values of the analysis performed in the soil and sediment samples are shown in table 1. Values below detection limit of the analytical method (MDL) were used in the statistical analyses as 50% of the MDL so all the raw data could be used. 3.1 Soil To better visualize the results of soil analysis, distribution concentration maps were done (Fig. 2). In these maps chromium, nickel and vanadium show a similar surface distribution which is expected due to their natural chemical affinity.

4 1724 The Sustainable City IX, Vol. 2 Table 1: Analytical results for soil and sediment samples (mean and standard deviation values).

5 The Sustainable City IX, Vol Figure 2: Distribution of chromium (a), lead (b), nickel (c), zinc (d), sand (e), molybdenum (f), vanadium (g) and zirconium (h). Comparing the trace metal concentration in the soil to the standard values established by the World Health Organization (WHO) and by the Brazilian Companhia de Tecnologia de Saneamento Ambiental (CETESB) one can observe that chromium concentration is much higher than the Brazilian standard value of 40 mg.kg -1 and lead slightly above the standard value of 17 mg.kg -1. The worldwide average value for molybdenum in soils is 1.2 mg.kg -1 [4], whereas in the studied soil it was found an average of 0.9 mg.kg -1, but concentration up to 2 mg.kg -1 is found. The higher concentration could be related to fertilizer used at the times the main land use was agricultural use. It can also be observed in Fig. 2 that the sand and silt + clay surface grain size distribution does not show correlation with the trace element concentration in the soil suggesting that the trace metal distribution in the soil is not related to the particle grain size distribution in the soil. Zirconium presents relatively low contents (23.6 mg.kg -1 ) comparing to its worldwide average (230 mg.kg -1 ) [4]. Due to its resistance to weathering it was expected a good correlation with the sand grain size fraction, a fact that was not observed (Fig. 2). This suggests that the processes that determined the coarser grain size fraction in the soil are different from the geochemical processes that kept the zirconium in the same area. The frequent rainfall is responsible for transporting the weathered material into the Tatuoca River. Land use is also an important factor in the transport of

6 1726 The Sustainable City IX, Vol. 2 weathered material to the river. Many chemical elements are lost, while others are fixed in the soil or sediment depending on physical-chemical conditions of the environment. In the studied area there are two predominant types of soil, Argisol (Ultisol) and Gleysol [3]. Thus, it is possible to suggest that the presence of two types of soil has provided distinct pedological materials that were later responsible for the formation of bottom sediments. 3.2 Bottom sediments Trace element distributions along the sediment core (P1, P2, P3 and P4) were made for the same elements previously shown in the soil. Thus, chromium, lead, nickel, zinc, grain size fraction, molybdenum, vanadium and zirconium distribution in each core are shown in Fig. 3. Chromium, lead, nickel and zinc contents (Table 1) showed no concern about the toxicity thresholds established by the USEPA, which uses the approximation of Long et al. [5] to characterize the contamination of sediments. A more detailed interpretation about the geochemical behavior of chromium, lead, nickel and zinc, is limited because the depositional system that prevails in the environment is influenced by strong human intervention, the adsorption capacity of the deposited material, as well the hydrodynamics in each of the sampled sites. Nevertheless, it can be seen that the concentrations of chromium in P1, P2, P3 and P4 cores are depleted in respect to levels found in the soil. Lead, nickel and zinc showed content values about the same as the ones found in the soil, with the exception of P3, which contains values slightly above soil average. This may be due to its higher clay content when compared to P1, P2 and P4. The other elements shown in Fig. 3 do not have a toxic threshold limit established, but helps establish their behavior along with the other elements of this work. As an example, molybdenum, which showed significant increase in concentration in sediment profiles, but in the soil samples in the drainage area, has low content in this element. So, it is likely that the increase in molybdenum in the bottom sediments could be a result of anthropogenic activities in the area or could be related to the higher adsorption capacity of the fine material in the bottom sediments. Zirconium, differently from the soil samples, does not follow the tendency to accumulate with the coarser grain size fraction. For sediment samples, zirconium, as well as most of the elements analyzed in this work shows an association with the finer fraction in profile P3, which is a typical adsorption behavior in the clay size fraction in sediments. Core samples P1 and P2 behave virtually as a single core sample, with some minor differences, but they constitute a material with strong influences of port infrastructure works. The P3 core profile has a different geochemical signature, which could be a result of being isolated from the infrastructure port works, whereas core profile P4 proved to be the one featuring the strongest anthropogenic interference.

7 The Sustainable City IX, Vol Figure 3: Trace element distribution along core profiles. 3.3 Statistical analysis A Principal Components Analysis was performed with data from soil and sediments (a total of 72 samples: 36 soil and 36 sediment samples). As shown in Fig. 4, there is a grouping between the cores samples P1 and P2 on the negative side of the axis of PC1, which contains 33% of the variance information. Such clustering suggests that these two profiles have some similarity. In this same side of the axis are also all soil samples which show a tendency to form two groups, one in the positive sector and another in the negative sector of PC2 axis. On the positive side of the axis of PC1 are located the samples of profiles P3 and P4, but P3 is farthest from the axis. One can conclude that profiles P1 and P2 samples are very similar to each other and also to the surrounding soils, since they are grouped on the same side

8 1728 The Sustainable City IX, Vol. 2 of the PC1 axis. P3 samples plot in the more positive side of PC1 corroborating their distinct geochemical behavior. It can also be noticed that the P4 profile samples show some geochemical similarity with the soil samples and with profiles samples P1 and P2. Observing the second graph obtained by the PCA (Fig. 4(B)), a fraction of the soil samples located above the dashed line, in Fig. 4(A), correlates with molybdenum and the coarser grain size fraction. It is found that below the dashed line are virtually all elements analyzed and the finer grain size fractions, the majority of soil samples and profile samples P3. P4 is the closest to the mouth of the Tatuoca River, therefore have more influence of dredging action in the port of Suape in addition to a higher energy condition. This fact may be responsible for the behavior of molybdenum which sometimes is associated to fine grain size fraction sometimes is associated to the coarser grain size fraction of the soil. As more alkaline environments tend to favor the molybdate ion (MoO 4 2- ), it is possible that it could concentrate closer to the mouth of the river as a result of changes in hydrodynamics and dredging. Figure 4: Soil and bottom sediments graphs obtained through statistical analyses. (A) PCA loadings graph; (B) PCA scores graph; (C) Dendrogram. The P3 profile that was collected in a restricted area in the Tatuoca River, with lesser human activities, showed a uniformity of its chemical content and may be considered a natural geochemical pattern for the studied area. It can also

9 The Sustainable City IX, Vol be suggested that due to its high fine grain size particle content the adsorption of chemical element is more efficient. It is noteworthy that molybdenum does not show the same behavior as the other elements in the profile P3, which corroborates the fact that it is an element added to the system. Fe, Cr, V, Sc, Ti and Cu show an interdependence in the soil and in the bottom sediment cores suggesting that the origin of ferrous metals is geogenic. The elements that appear associated with calcium, such as strontium, lead, phosphorus and barium form a distinct group and may come from the addition of elements to agricultural correctives, which by its historical use may have affected the entire watershed, including profile P3. A dendrogram was prepared for this group of samples using the Ward's method and the Euclidean distance (Fig. 4(C)). The dendrogram shows that there is a hierarchical grouping which relates some soil samples to profile P3, as already observed in the PCA. From the findings in Fig. 4 we can say that the statistical analysis could separate two compartments by their geochemical affinity: one formed by P1, P2 and soil samples and another one formed by P3 and P4 bottom sediment core samples, which have more pronounced sedimentary features. 4 Conclusions The land use in the area primarily sugarcane plantation responsible for addition of fertilizers and pesticides to the soil and the present industrial boom responsible for the land removal are responsible for the geochemical signature of bottom sediments in the Tatuoca River. Through the use of multivariate it was possible to highlight geochemical grouping and interpret the source of chemical elements in the bottom sediments. The sediment cores were differentiated into three different groups according to main sediment load source, being the port infrastructure works responsible for the geochemical signature of the bottom sediment cores. Regarding the quality of the soil in the drainage basin and bottom sediment of the River Tatuoca, it can be stated that the area has suffered an important environmental impact, but according to results of the present study but they are not yet considered polluted. References [1] Chagas-Spinelli, A.C., Kato, M.T., de Lima, E.S. & Gavazza, S.S. Bioremediation of a tropical clay soil contaminated with diesel oil. Journal of Environmental Management, 113, pp , [2] Dorraji, S.S., Golchin & A., Ahmadi, S. The effects of hydrophilic polymer and soil salinity on corn growth in Sandy and loamy soils. Clean Soil, Air Water, 38 (7), pp , [3] Embrapa Solos. Sistema Brasileiro de Classificação de Solos, EMBRAPA, Brasília, 412p, 1999.

10 1730 The Sustainable City IX, Vol. 2 [4] Koljonen, T (Ed). The geological atlas of Finland. Part 2. Till. Geological Survey of Finland, Espoo, 218p, [5] Long, E.R., MacDonal, D.D., Smith, S.L. & Calder, F.D. Incident of adverse biological affects within ranges of chemical concentrations in marine and estuarine sediments. Environmental Management, 19, pp , [6] Morales-Caseles, C., Riba, I., Sarasquete, & C., Ángel DelValss, T. Using a classical weight-of-evidence approach for 4-years monitoring of the impact of an accidental oil spill on sediment quality. Environment International, 34, pp , [7] Santos Bermejo, S.C., Beltran, R. & Gomez Ariza, J.L. Spatial variations of heavy metal contamination in sediments from Odiel River (Southwest Spain). Environment International, 29, pp , [8] Yaman, M., Ince, M. & Cengiz, E. Distribution study of U, V, Mo and Zr in different sites of Lakes Van and Hazar, river and seawater. Clean Soil, Air, Water, 39 (6), pp , 2011.