Past environmental changes: using sedimentary photosynthetic pigments to enhance subtropical reservoir management.

The historical impacts of eutrophication processes were investigated in six subtropical reservoirs (São Paulo, Brazil) using a paleolimnological approach. We questioned whether the levels of pigment indicators of algal biomass could provide information about trophic increase and whether carotenoid pigments could offer additional insights. The following proxies were employed: organic matter, total phosphorus, total nitrogen, photosynthetic pigments (by high-performance liquid chromatography), sedimentation rates, and geochronology (by 210 Pb technique). Principal component analysis indicated a gradient of eutrophication. In eutrophic reservoirs (e.g., Rio Grande and Salto Grande), levels of lutein and zeaxanthin increased over time, suggesting growth of Chlorophyta and Cyanobacteria. These pigments were significantly associated with algal biomass, reflecting their participation in phytoplankton composition. In mesotrophic reservoirs, Broa and Itupararanga, increases and significative linear correlations (r > 0.70) between pigments and nutrients are mainly linked to agricultural and urban activities. In the oligotrophic reservoir Igaratá, lower pigment and nutrient levels reflected lesser human impact and good water quality. This study underscores eutrophication's complexity across subtropical reservoirs. Photosynthetic pigments associated with specific algal groups were informative, especially when correlated with nutrient data. The trophic increase, notably in the 1990s, may have been influenced by neoliberal policies. Integrated pigment and geochemical analysis offers a more precise understanding of eutrophication changes and their ties to human factors. Such research can aid environmental monitoring and sustainable policy development.

Historical mercury contamination in a major Latin American industrial and port complex: The case of the Santos estuary, Southeastern Brazil.

The present study determined total mercury (Hg) in four 210Pb dated sediment cores to assess the historical anthropogenic Hg accumulation in the Santos estuary, Southeastern Brazil. Background levels were identified using the deepest sections of the cores, corresponding to pre-industrial ages. Mercury distribution in the sediment cores (0.02-2.64 mg kg-1) presented a large spatial and temporal variation. Contamination is highest in the upper estuary and indicates that the industrial hub, especially a chlor-alkali plant is the primary source of Hg. A contaminant trap effect is observed in this area associated with high fine sediment accumulation and Hg fluxes. The contamination pattern indicates that the regions not affected by direct inputs are influenced by reworking, resuspension, and transport of contaminated sediments by tidal flows. The Hg enrichment in the upper layers of the sediment cores demonstrates that the environmental actions fulfilled in the 1980s were insufficient to control Hg pollution in the Santos estuary.

A 140-year record of environmental changes in São Sebastião, Brazil.

Over the past two centuries, coastal and estuarine areas have experienced environmental stress due to rapid population growth, leading to higher demand, overexploitation, habitat transformation, and pollution, which have severe consequences on the overall ecosystem and human health. This work aims to understand historical perspectives of such environmental stress in a coastal area of São Sebastião city in the São Paulo State of Brazil, which has witnessed rapid changes in land use over the past 60-70 years. We collected eleven surface sediments and one 64 cm long core from the shallow water depth sector of the São Sebastião Channel (SSC), adjacent to the Araçá Bay region. Sediments were dominantly composed of terrestrial siliciclastic material carrying signatures of both local inputs (i.e., weathered granitic and gneissic rocks of Serra do Mar Mountain ranges) and Plata Plume sediments brought by Brazilian coastal currents. Low sediment accumulation (avg. = 0.10 cm yr-1) between 1880 and 1947 showed a stable environment followed by an abrupt increase in sedimentation (avg. = 0.84 cm yr-1) from 1947 to 2017. This approximate eight-fold increase in sedimentation after 1947 marked significant anthropogenic changes in the region, which is coincidental with major changes in land use through the construction of the port of São Sebastião (1930s) and BR-101 Highway (1980s). While recent surface sediments showed no pollution of heavy metals, anthropogenic Zn enrichment was found between 1880 and 2000. Zn enrichment was from the combined sources, e.g., agriculture activities, domestic sewage, and possibly Zn coated ship paints. Our study also indicates that planned future expansion of São Sebastião port may further increase the sedimentation rate in SSC and impact the ecosystem of Araçá Bay and SSC.

Trace element fluxes during the "Anthropocene" in a large South American industrial and port area (Santos and São Vicente estuarine system, SE, Brazil).

The worldwide evidence of human activities on the environment led the scientific community to recognize a new geologic time unit known as the "Anthropocene." Since the twentieth century, urbanization and industrialization needs driven by population and economic growth have impacted several ecosystems including the estuaries. To assess the contamination, provenance, and fluxes of trace elements (As, Cr, Cu, Ni, Pb, Sc, V, and Zn) over the last century, a geochemical and chemometric technique was employed in sediment cores of an industrial and port region of international importance, the Santos and São Vicente Estuarine System (SSVES). The results indicated low contamination, with the highest enrichment factors (EFs) for Cu (EF = 3.1), Pb (EF = 2.7), Zn (EF = 2.4), and As (EF = 2.3) found next to the harbor area. The Pre-industrial records confirm the relatively high concentrations of As and its naturally enriched occurrence on the Brazilian shelf. Sediment accumulation rates and trace element fluxes showed a general increase over the years, since the early 1960s, associated with the "Great Acceleration" of the mid-twentieth century. These alterations are human-induced and include urbanization and industrialization. Nonetheless, as the contents and enrichment of trace elements indicate that the region is not severely polluted, we hypothesize that the contamination in the SSVES is likely related to the drainage and erosion of the urbanized adjacent area, rather than direct disposal of inorganic contaminants from the industrial activity.

Historical deposition of PAHs in mud depocenters from the Southwestern Atlantic continental shelf: The influence of socio-economic development and coal consumption in the last century.

Polycyclic aromatic hydrocarbon (PAH) concentrations were determined in four dated sediment cores collected in mud depocenters of the southern Brazilian continental shelf. Core dating results covered the interval between 1925 and 2017. The total PAH concentrations (ΣPAHs) ranged from 44.69 ng g-1 to 305.43 ng g-1 and were similar between the analysed cores. Fine-grained sediments and total organic carbon (TOC) results did not correlate with the ΣPAHs, indicating that the variations in PAH concentrations are mostly related to variations in sources and emissions. PAH source appointment indicated a high input of a natural compound (perylene) and the predominance of anthropogenic PAHs from coal, biomass, and fuel combustion. Alkylated PAHs presented high contributions throughout all cores. The historical deposition of PAHs was associated with different periods of the socio-economic and industrial development of near coastal cities and reflected very well the history of coal production and consumption in the southern region of Brazil. The low levels of ΣPAHs before 1945 in all analysed cores may be related to the beginning of the industrialization process and the lower urbanization degree in the region. Between 1945 and 1965, the gradual ΣPAHs increase reflects the establishment and enlargement of the southern Brazilian industrial sector. The interval between 1965 and 1990 corresponded to the highest ΣPAHs in three of the four analysed cores. After 1990, a relative decrease in the ΣPAHs was observed in most cores and may be related the multiple cuts of incentives to the industrial usage of coal, as well as to Brazil's efforts in environmental regulation for coal extraction and consumption.

Long-term eutrophication and contamination of the central area of Sepetiba Bay (SW Brazil).

This work sheds light on the recent evolution (≈1915-2015 AD) of Sepetiba Bay (SB; SE Brazil), a subtropical coastal lagoon on the southwestern Brazilian coast, based on a multiproxy approach. Variations in geochemical proxies as well as textural, mineralogical and geochronological data allow us to reconstruct temporally constrained changes in the depositional environments along the SP3 sediment core collected from the central area of SB. At the beginning of the twentieth century, the substrate of the study site was composed of coarse-grained sediments, largely sourced from felsic rocks of proximal areas and deposited under moderate to strong shallow marine hydrodynamics. Since the 1930s, the study area has undergone silting and received high contributions of materials from mafic rocks sourced by river basins. The SP3 core reveals a shallowing-upward sequence due to human-induced silting with significant eutrophication since the middle of 1970, which was caused by significant enrichment of organic matter that was provided by not only marine productivity but also continental and human waste. In addition, the sediments deposited after 1980 exhibit significant enrichment and are moderately to strongly polluted by Cd and Zn. Metals were dispersed by hydrodynamics from the source areas, but diagenetic processes promoted their retention in the sediments. The potential ecological risk index (PERI) indicates that the level of high (considerable) ecological risk is in sediments deposited in ≈1995 (30-32 cm; subsurface). The applied methodology allowed us to understand the thickness of the bottom sediment affected by eutrophication processes and contaminants. Identical methodologies can be applied in other coastal zones, and can provide useful information to decision makers and stakeholders that manage those areas.

Geochemical behavior, environmental availability, and reconstruction of historical trends of Cu, Pb, and Zn in sediment cores of the Cananéia-Iguape coastal system, Southeastern Brazil.

The Cananéia-Iguape system is located in a coastal region of southeastern Brazil, recognized by UNESCO as an Atlantic Forest Biosphere Reserve. This system has suffered substantial environmental impacts due to the opening of an artificial channel and by past intensive mining activities. In this paper was performed the sequential chemical extraction of Cu, Pb, and Zn, on previously described sediment cores, and the statistical treatment of the data, allowing to estimate the remobilization geochemical behavior, the available content and the trend of accumulation between 1926 and 2008. The maximum available level (sum of all mobile fraction) were, in mgkg-1, 18.74 for Cu, 177.55 for Pb and 123.03 for Zn. Considering its environmental availability, Pb remains a concern in the system. It was possible to recognize the anthropic contribution of Pb, being the mining activities considered the only potential source of this metal in the region.

Environmental availability of potentially toxic elements in estuarine sediments of the Cananéia-Iguape coastal system, Southeastern Brazil.

The Cananéia-Iguape system is located in a Southeastern Brazilian coastal region, acknowledged by UNESCO as Biosphere Reserve of the Atlantic Rainforest. This system underwent important environmental changes due to the opening of the artificial channel of Valo Grande and by past intensive Pb ore mining activities. In view of this scenario, this study evaluated Cu, Pb and Zn availability in sediments from Cananéia-Iguape system, based on the content associated with the main components of the sediments. Moreover, in order to assess local contamination, the metals' contents were compared to Canadian quality guidelines, the past levels of metals preceding the mining activities and background sediment values. Concerning Cu and Zn in a state of chemical remobilization, both elements would possibly present no harm to the local communities. However, Pb available content exceeded the comparison values in various sampling sites, suggesting the need of monitoring regarding its bioavailability.

Sources and temporal patterns of polychlorinated biphenyls around a large South American grain-shipping port (Paranaguá Estuarine System, Brazil).

The Paranaguá Estuarine System (PES) is an important estuarine environment on the Brazilian coast. The economic importance of the PES is mainly related to industries, fuel terminals, and the main South American grain-shipping port. The aim of this work was to determine the vertical distribution of polychlorinated biphenyls (PCBs) in three sediment cores from the PES. The methods included Soxhlet extraction, clean-up, and quantification by gas chromatography with electron capture detection. The concentrations of total PCBs ranged from lower than the detection limit to 6.65 ng g(-1). Low PCB concentrations were detected in P1 and P3, which were collected far away from direct human activities. In P2, the compositional pattern of PCB congeners showed greater concentrations of tetra- and penta-chlorinated congeners associated with urban and port activities near Paranaguá city. The differences in concentrations between the three sediment cores were attributed to the distance of the sampling points in relation to the possible sources of pollution, which are mostly related to Paranaguá city. The vertical distribution of PCBs in the sediment core P2 was related to historical anthropogenic activities. The highest PCB input was from 1970 to the early 1990s, which coincides with a period of greater use of PCBs in Brazil as well as their greater worldwide production.