Lagoon Sediments Research Articles

Floral remains from the highest Valdeón formation, a marine stephanian unit south of the Picos de Europa, and comparisons with eastern Asturias, NW Spain

A critical analysis is presented of the available data on the Valdeón Formation, a Stephanian unit southwest of the Picos de Europa, in northern Leon. It lies unconformably on Devonian and lower Carboniferous (Mississippian) strata of the Gildar-Montó nappe structure, and is overthrust from the northwest by a variety of older strata of the Ponga unit. The Valdeón Formation, consisting of mudstones, sandstones and lensing conglomerate bands, is largely unfossiliferous and probably marine up to the highest levels where possibly lagoonal deposits contain a drifted megafloral assemblage, which is of Barruelian or later age. This flora is documented here with illustrations and the various taxa are discussed. Comparison is made with a succession of upper Cantabrian and lower Barruelian strata in northern Palencia (Brañosera and Barruelo formations), which show a broadly similar stratigraphic development. Floras from a small terrestrial interval near the base of the predominantly marine strata of Stephanian B age in eastern Asturias (at Fontecha and Arenas de Cabrales) are discussed for the overall comparison, but these floras are later in age and the relevant strata, belonging to the post-Asturian basin, show a different development. These later Stephanian floras are listed but only two species are illustrated.

Heavy metal mobility, bioavailability, and potential toxicity in sediments of the Korle lagoon in Ghana

ABSTRACT This study aimed to identify the mobility, bioavailability, and potential toxicity of heavy metals (HM) in sediments of the Korle lagoon using metal partition. Sediments were analysed using the BCR (Bureau of reference) method. As (60%), Pb (50%), Zn (57%) and Fe (40%) were found in high concentration in the ion exchangeable fraction. The oxidisable fraction was dominated by Cu (51%), Cd (95%), Cr (61%), Ni (63%), As (35%), Fe (21%), Hg (30%), Pb (19%) and Zn (11%). The reducible fraction was dominated by Zn (29%), Pb (24%) and Hg (19%). The residual fraction was dominated by Hg (49%) and Fe (34%). PCA was used to identify pH and organic matter as the most important factors controlling the mobility and bioavailability of HM in the sediments. Arsenic, Pb, Zn and Fe were found to have the highest mobility. Chromium, Cu and Ni have medium mobility. Hg has low mobility. Most of the HM show potential bioavailability and toxicity.

Bioavailability of metals in coastal lagoon sediments and their influence on benthic foraminifera

Coastal lagoons experience removal and leaching of metals due to seasonal fluctuation of salinity coupled with pH and dissolved oxygen variability. Benthic foraminifers are susceptible to seasonal variation in physicochemical conditions. Assessment of bioavailable fraction of selected metals in sediments along the salinity gradient of the largest brackish lagoon in Asia- Chilika was carried out. Further, population density and abnormality index of foraminifera in the sediments were calculated to understand the influence of bioavailable metal on benthic foraminifera. Metal concentrations were higher in the low salinity regions and decreased towards the high salinity regions. This suggests river discharge controls the metal input and distribution in the lagoon. Overall, metal concentrations are high in the residual fraction (F4) followed by interplay within the reducible (F2) or oxidizable (F3) fractions, except for Mn. The seasonal fluctuations of pH and cyclic oxygen deficiency intensified the leaching of Fe, Cr, Cu, Pb, and Zn in the bioavailable fraction in the low salinity region of the lagoon. The presence of metals in bioavailable fractions impacted the normal growth of the abundant Ammonia species. Despite low bioavailable metal concentrations, higher morphological abnormalities were observed in the high salinity regions due to higher energy conditions near the sea. Therefore, abnormalities in the benthic foraminifera are attributed to bioavailability of metals from sediments and natural stress conditions in the coastal lagoon environment.

N and C Isotope Variations Along an Extreme Eutrophication and Salinity Gradient in the Coorong Lagoon, South Australia

The Coorong Lagoon is a unique hydrological and depositional system at the terminus of the Murray–Darling Basin, the largest river system in Australia. It exhibits large salinity, nutrient, and organic matter gradients, providing a modern analogue to study and validate the use of δ15N and δ13C as tracers of past and contemporary geochemical cycles in estuarine environments. To this end, water and surface sediment samples were analyzed for particulate organic nitrogen (PON) and carbon (POC) concentrations, and the respective δ15N and δ13C signatures of particulate nitrogen and carbon. PON and POC exhibited positive relationships to chlorophyll-a, indicating the dominance of phytoplankton production upon suspended organic matter. There was also a general trend of increasing δ15N of PON (δ15NPON) values and decreasing δ13C of particulate carbon (δ13CPC) values with increasing salinity and eutrophication in the restricted South Lagoon. In a multiple linear regression for δ15NPON, the best two predictors in combination are PON and C:N molar ratio, highlighting the importance of productivity and the type or source of organic matter. For δ13CPC, the best two predictors are total dissolved phosphorus and latitude, suggesting influences from productivity and proximity to the ocean. Sediment δ15N values across the Coorong Lagoon overlap with the δ15NPON in the water column, suggesting that PON derived from algal material represents the main source of nitrogen to lagoon sediments. We hypothesize that limited N loss via denitrification leads to PON being recycled almost exclusively to ammonium, due to low rates of nitrification and dominance of dissimilatory nitrate reduction to ammonium (DNRA). We propose that preferential volatilization of 14N in ammonia increases the δ15N of ammonium assimilated by phytoplankton, thereby increasing the δ15N within suspended organic matter and surface sediment in the South Lagoon. By contrast, the gradient exhibited in δ13CPC data was countered by a relatively constant sedimentary organic carbon δ13C. Data from the Coorong, therefore, suggest that δ15N values in sediments can be used to infer palaeoproductivity in this hypereutrophic and hypersaline depositional environment, however, the measured δ13CPC may be influenced by δ13CDIC or preferential loss of 13C during sedimentation that alter the sedimentary δ13C record of organic carbon.

Compositional, micromorphological and geotechnical characterization of Holocene Tiber floodplain deposits (Rome, Italy) and sequence stratigraphic implications

AbstractThis study reports a high‐resolution micromorphological characterization of floodplain deposits to investigate the relationships among compositional, textural and geotechnical data, and integrate soil micromorphology with sequence stratigraphy. Compositional and textural characterization of facies associations and soil features are calibrated against geotechnical parameters. The latter, obtained from cone penetration and pocket penetrometer tests from a borehole advanced 60 m into the Tiber channel belt and floodplain, show that depositional features and post‐depositional modifications are intrinsically associated with cone penetration test parameters: cone resistance; sleeve friction; and friction ratio. Petrographic and micromorphological features document pedogenetic modifications across stratigraphic markers evidenced by faunal and plant activity, accumulation of peat, and typified by precipitation of heavy metals, iron oxides and secondary carbonates. All of these features developed in correspondence with alluvial flooding surfaces that are correlated with non‐marine and marine flooding surfaces recognized in the transgressive and highstand coastal and lagoonal deposits of the Tiber Depositional Sequence. These observations may serve as a model to reconstruct the sequence‐stratigraphic evolution of ancient relict soils. Nevertheless, additional criteria (for example, their stratigraphic position and correlative surfaces) are necessary to adequately interpret the genesis of such low‐rank stratigraphic surfaces. This work demonstrates that a combination between sedimentological and stratigraphic observations and soil micromorphology can be critical to supplement field observations and determine the relative effect of pedogenic and depositional processes on the organization, composition and texture, and geotechnical properties of floodplain in urban areas.

Potential ecological risk assessment of rare earth elements in sediments cores from the Oualidia lagoon, Morocco

ABSTRACT This study’s objective was to evaluate the depth profiles of rare earth elements (REEs) in two Pb-210 dated sediments cores retrieved from the Oualidia lagoon, reconstruct their anthropogenic history, and assess their potential ecological risk. The sediment cores analysis was carried out using instrumental neutron activation analysis. Other physical-chemical parameters (bulk, organic matter, grain size) were also measured. The results indicated that the highest values were recorded in the topmost layers of the sediment cores and depleted with depth. The historical records of REEs revealed an exponential increase in their concentrations from the 50s. The enrichment factor, geo-accumulation index, and contamination factor calculated for each sediment core layer have exhibited important concentrations of Gd, Sm, and Eu, suggesting an anthropogenic origin of detected elements. Based on ecological risk >40 and the risk index >220, Gd, Eu, and Sm pose a high risk on the study area, while the other elements present moderate and mild risk. The obtained results revealed an increasing tendency of REEs accumulation into the Oualidia lagoon and suggested that a new source is feeding the lagoon sediments by these elements. These findings provided a clear picture of REEs evolution between 1903 and 2014 and baseline information on the historical deposition of these elements in the Oualidia lagoon.

Microbial diversity in intensively farmed lake sediment contaminated by heavy metals and identification of microbial taxa bioindicators of environmental quality

The cumulative effects of anthropogenic stress on freshwater ecosystems are becoming increasingly evident and worrisome. In lake sediments contaminated by heavy metals, the composition and structure of microbial communities can change and affect nutrient transformation and biogeochemical cycling of sediments. In this study, bacterial and archaeal communities of lake sediments under fish pressure contaminated with heavy metals were investigated by the Illumina MiSeq platform. Despite the similar content of most of the heavy metals in the lagoon sediments, we found that their microbial communities were different in diversity and composition. This difference would be determined by the resilience or tolerance of the microbial communities to the heavy metal enrichment gradient. Thirty-two different phyla and 66 different microbial classes were identified in sediment from the three lagoons studied. The highest percentages of contribution in the differentiation of microbial communities were presented by the classes Alphaproteobacteria (19.08%), Cyanophyceae (14.96%), Betaproteobacteria (9.01%) y Actinobacteria (7.55%). The bacteria that predominated in sediments with high levels of Cd and As were Deltaproteobacteria, Actinobacteria, Coriobacteriia, Nitrososphaeria and Acidobacteria (Pomacocha), Alphaproteobacteria, Chitinophagia, Nitrospira and Clostridia (Tipicocha) and Betaproteobacteria (Tranca Grande). Finally, the results allow us to expand the current knowledge of microbial diversity in lake sediments contaminated with heavy metals and to identify bioindicators taxa of environmental quality that can be used in the monitoring and control of heavy metal contamination.

Exposure of Mercury from Gold Ming Area: A Case Study in Tendo and Aby Lagoon in Côte d’Ivoire

Lagoons of West African countries are seriously threatened by rapid artisanal and small-scale gold mining (ASGM) that exposes lagoons to mercury pollution. In this study, the mercury level in the sediments of the Tendo and Aby lagoons in Côte d’Ivoire had been evaluated. A total of 87 samples from 25 stations located on Tendo and Aby lagoons were analyzed by atomic fluorescence spectrometry. The mean Hg concentrations obtained in the sediments of Tendo and Aby lagoons were 0.89 ± 0.26 mg⋅kg-1 and 0.70 ± 0.18 mg⋅kg-1, respectively. Hg concentrations evaluated in the bays of Tendo and Aby during the dry season were 1.38 ± 0.45 mg⋅kg-1 and 1.07 ± 0.31 mg⋅kg-1, respectively. The minimum and maximum total Hg concentrations in the sediments from 25 stations were 0.04 and 3.56 mg⋅kg-1, respectively. Mercury contamination in lagoons during ASGM poses risks of pollution for the lagoon ecosystem and also poses health risks for the population living near these lagoons.

Ediacaran-Cambrian microbialites of the Southern Amazon Craton: relation with the metazoan rise, sea-level changes, and global tectonics

Microbialites are the most abundant life evidence in Precambrian sedimentary rocks. They are produced by microbial interaction activity and sedimentary processes reflecting paleoenvironmental conditions. The Ediacaran-Cambrian carbonate and siliciclastic successions in the Southern Amazon Craton in Central Brazil, provide a key opportunity to understand how the metazoan life coexisted with the microbial communities. The spatial and temporal distribution of microbialites as well as morphological and paleoenvironmental changes have been assessed, reinterpreting previous works and including new data from the Araras-Alto Paraguai and Corumbá basins. The deposition was controlled by subsidence and sea-level changes that affected these basins, considered extensions of epicontinental seas during the Gondwana assembly. The stromatolites are restricted to coastal deposits and experienced thriving flourishment intervals after the Marinoan Glaciation (635 Ma). Post-glacial transgression was marked by microbial colonization in shallow platforms represented by stratiform and giant domical stromatolites in the Araras-Alto Paraguai Basin. The continuity of the transgression generated a moderately deep aragonite sea at about 622 Ma. A progressive sea-level fall caused the implantation of coastal environments under greenhouse conditions with tidal flat and sabkha settings colonized by centimetric-scale stromatolites. The sea retreat was accompanied by progressive uplift, causing a moderate inversion of the basin and erosion of the succession until ~560 Ma with the deposition of the last preserved tidal flat deposits with the occurrence of thrombolites. The subsiding Corumbá Basin was the site of microbially-induced deposition of carbonates in a shallow platform connected to an offshore setting with the proliferation of metazoan straddling the Ediacaran-Cambrian boundary. Microbial communities were restricted to lagoon deposits during the Lower Cambrian transgression in the Araras-Alto Paraguai Basin and the last phase refers to the sea retreat towards southeast, developing a fluvial system connected with the arid and evaporitic tidal flats colonized by microbialites that lasted until the upper Cambrian. Except for the post-glacial stromatolites, the columnar and domal microbialite indicate that the coastal settings dominated the Ediacaran-Cambrian transition. The preservation of microbialites in the post-glacial intervals can be associated with the Mg-Ca-CO3 oversaturation in dolomitic platforms. The rapid calcification and ability to resist the dissolution and replacement have increased the stromatolites’ preservation potential reported here, where its well-preserved occurrence in tidal flats and sabkha occurs due to intense early diagenetic silicification. The change from carbonate accumulation to siliciclastic-rich environments contributed to the demise of microbially-induced strata. In general, the scarce coexistence between coastal stromatolite and metazoan-bearing marine deposits makes it challenging to establish a competitive relationship between these organisms, as previously postulated.

Mid- to Late Holocene (5200–980 cal YR BP) paleoenvironmental dynamics in the Ilha Grande, Brazil, assessed by terrestrial and marine microfossils

Ilha Grande is a Brazilian island that has a high vegetal biodiversity with a well-documented prehistoric human occupation but has few paleoenvironmental studies developed in this area. In view of this, multiproxy analysis of lagoonal sediments including radiocarbon dating were carried out on a 139 cm-long continental sediment core. The aim of our study was to recognise and explain environmental dynamics in this region during the Holocene (∼5200 cal yr BP). The palynomorphs indicate the continuous presence of Atlantic Forest under humid conditions during the last Holocene sea-level highstand, after 5200 cal yr BP. A phase of low palynomorph concentrations was followed by a marked increase in palynomorph accumulation and diversity which may be linked to the subsequent drop of the sea-level. Dinoflagellate cysts showed a higher accumulation at the base of the sediment core. The high accumulation of charcoal particles identified between approximately 3700 and 3000 cal years BP might indicate human activity related to the long-lasting bonfires kept burning by the inhabitants of the archaeological site of Ilhote do Leste.

Assessment of the heavy metal sources and concentrations in the Nador Lagoon sediment, Northeast-Morocco

This study investigates the heavy metals (HM) and sulfurs concentration, enrichment level and potential sources in the bottom sediments of Nador lagoon, North-East Morocco. 50 samples of sediments from Nador lagoon heavy metals were analyzed by ICP-MS, while their spatial distribution and source identification were evaluated by Enrichment Factor (EF), QGis Inverse Distances Weighted (IDW) interpolation models, multivariate statistical techniques (Principal Component Analysis - Agglomerative Hierarchical Clustering - Pearson correlation matrix), Positive matrix factorization (PMF model) and grain size/organic matter analysis. The average heavy metal concentrations in the sediments are in the decreasing order: Sr > Ba > V > Zr > Zn > Cr > Rb > La > Cu > Pb > Ni > Ce > Nd > Co > Sc > Nb > Ga > Th > Y > Hf, and the Sulfurs. The results showed that the average concentrations of the S, Sr, Pb, and Nd in bottom sediments were higher than their background contents. The EF values demonstrated that HM contents were enriched by anthropogenic activities, especially for Sr and S, and secondly for Th, V, Ce, Nd, and Pb. The potential HM and sulfurs identified sources showed that: 1) Ga, Y, Hf, Nb, Rb, Sc, Zr, Nb, Co, Zn, Th, Ni, V, Ba, Cr, and Cu were derived industrial activities related to stealing and mining; 2) Wastewater treatment station and lagoon watershed were the main sources of Sr in the lagoon; 3) Zn, Cu, and Pb also linked to sulfurs, mostly origin from agriculture inputs and mining activities; 4) Ce, Cr, and Ni linked to sulfurs, mainly origin form metallurgical activities and solid wastes. The results suggest that heavy metal concentrations were significantly affected anthropogenic activities. Severe enrichment of Sr was found in the lagoon ecosystem with no correlation with carbonates, with four sources of heavy metals apportioned by Geostatistics and Positive matrix factorization. Solid waste, water waste and industrial activities were the main anthropogenic source. Lutite fraction and organic matter show a high accord with heavy metals concentration distribution.

Late Holocene environmental change in Celestun Lagoon, Yucatan, Mexico

Epikarst estuary response to hydroclimate change remains poorly understood, despite the well-studied link between climate and karst groundwater aquifers. The influence of sea-level rise and coastal geomorphic change on these estuaries obscures climate signals, thus requiring careful development of paleoenvironmental histories to interpret the paleoclimate archives. We used foraminifera assemblages, carbon stable isotope ratios (δ13C) and carbon:nitrogen (C:N) mass ratios of organic matter in sediment cores to infer environmental changes over the past 5300 years in Celestun Lagoon, Yucatan, Mexico. Specimens (> 125 µm) from modern core top sediments revealed three assemblages: (1) a brackish mangrove assemblage of agglutinated Miliammina and Ammotium taxa and hyaline Haynesina (2) an inner-shelf marine assemblage of Bolivina, Hanzawaia, and Rosalina, and (3) a brackish assemblage dominated by Ammonia and Elphidium. Assemblages changed along the lagoon channel in response to changes in salinity and vegetation, i.e. seagrass and mangrove. In addition to these three foraminifera assemblages, lagoon sediments deposited since 5300 cal yr BP are comprised of two more assemblages, defined by Archaias and Laevipeneroplis, which indicate marine Thalassia seagrasses, and Trichohyalus, which indicates restricted inland mangrove ponds. Our data suggest that Celestun Lagoon displayed four phases of development: (1) an inland mangrove pond (5300 BP) (2) a shallow unprotected coastline with marine seagrass and barrier island initiation (4900 BP) (3) a protected brackish lagoon (3000 BP), and (4) a protected lagoon surrounded by mangroves (1700 BP). Stratigraphic (temporal) changes in core assemblages resemble spatial differences in communities across the modern lagoon, from the southern marine sector to the northern brackish region. Similar temporal patterns have been reported from other Yucatan Peninsula lagoons and from cenotes (Nichupte, Aktun Ha), suggesting a regional coastal response to sea level rise and climate change, including geomorphic controls (longshore drift) on lagoon salinity, as observed today. Holocene barrier island development progressively protected the northwest Yucatan Peninsula coastline, reducing mixing between seawater and rain-fed submarine groundwater discharge. Superimposed on this geomorphic signal, assemblage changes that are observed reflect the most severe regional wet and dry climate episodes, which coincide with paleoclimate records from lowland lake archives (Chichancanab, Salpeten). Our results emphasize the need to consider coastal geomorphic evolution when using epikarst estuary and lagoon sediment archives for paleoclimate reconstruction and provide evidence of hydroclimate changes on the Yucatan Peninsula.

New Geological Evidence of the 1755 Lisbon Tsunami from the Rock of Gibraltar (Southern Iberian Peninsula)

This paper presents the easternmost mineralogical and geochemical evidence of the 1755 Lisbon tsunami found in the Western Mediterranean. This multidisciplinary analysis of a sediment core obtained in Gibraltar (southern Iberian Peninsula) has allowed us to differentiate a tsunamiite from an old lagoon (The Inundation). This tsunamigenic layer has increased levels of calcite and aragonite and higher concentrations of Ba and ferromagnesian elements in comparison with the underlying lagoonal sediments of this core. This layer is also differentiated by its paleontological record, with the introduction of marine species within this lagoon. The uppermost part of the core includes a transition from swampy/marsh paleoenvironments to terrestrial scenarios, with a final anthropogenic filling occurring during the last century.

Palaeoshoreline reconstruction and underwater archaeological potential of Liman Tepe: A long-occupied coastal prehistoric settlement in western Anatolia, Turkey

Rising post-glacial sea levels had a major influence on the prehistoric settlement of the Aegean coastal zone. At Liman Tepe, an important Chalcolithic-Bronze Age coastal settlement on the south coast of the Bay of Izmir, archaeological evidence suggests a Neolithic (ca. 9600-5500 BCE) presence, but no settlement has been discovered on land. Sea levels during the Neolithic period were between 6 and >20 m below present and there is high potential for discovery of submerged prehistoric sites. Marine sediment coring and geophysical investigations (bathymetry, sub-bottom seismic profiling; >600 line-km) were conducted over a 4-km2 inshore area to assess the underwater archaeological potential. Multi-proxy sediment analysis (sedimentary facies, micropalaeontology, micro-XRF geochemistry) was conducted on 20 cores to reconstruct the relative sea level (RSL) history and coastal palaeogeography. Palaeoshoreline positions were estimated by back-stripping of the decompacted sediment thickness from a digital bathymetric model (DBM).The DBM reveals a drowned middle Holocene coastal plain with well-preserved relict river channels, palaeoshorelines and coastal headlands. The inshore stratigraphy consists of shoreface, foreshore and lagoonal deposits overlying terrestrial clay and palaeosols, defining a marine transgressive surface (MTS). The MTS records the inundation of the coastal plain prior to ca. 4000 BCE (transgressive systems tract; TST) and is marked in cores by an increasing abundance of foraminifera and a rise in Ca/Ti. During the Early Neolithic (ca. 6700 BCE), the shoreline was >500 m seaward (RSL ∼ −14 to −16 m) and Karantina Island was a broad coastal headland with a sheltered western embayment. By the Middle Chalcolithic (ca. 4800 BCE), the coastline had transgressed ∼800 m inland of the present shoreline and the Liman Tepe headland was separated from the mainland by a shallow coastal wetland. The maximum transgression (∼1 km inland at ca. 4000 BCE) was followed by a shift to a high-stand systems tract (HST) and rapid coastline progradation by barrier accretion and lagoon development. Palaeogeographic maps identify areas with high underwater archaeological potential: 1) palaeoriver channels and lowland riverine habitats formed during the TST, prior to 4000 BCE, 2) submerged palaeoshorelines and coastal promontories (water depths 10–14 mbsl) with high potential for Neolithic sites, and 3) protected coastal embayments and lagoons representing possible prehistoric anchorage sites.

Pollution, ecological risk, and source identification of potentially toxic elements in sediments of a landscape urban lagoon, China

Given the great importance of Yundang lagoon (China), a detailed evaluation and source identification of multiple potentially toxic elements (PTEs) is required. Low concentrations of the PTEs were found in the Diversion canal, while high in the Main canal, Inner lagoon, and Outer lagoon. Evaluation results indicated that the pollution of PTEs was widespread, and that the extremely high eco-risks and evident toxicity were owing to the great contributions of Hg and Cd. Positive matrix factorization model demonstrated that the PTEs were from both natural and different types of anthropogenic sources. TOC played a critical role in the PTEs. It was also found that the limited environmental carrying capacity and the poor hydrological condition of the lagoon may still accumulate the pollution in a progressive fashion. These findings provide a detailed information on making effective strategies of new directions for long-term prevention of PTEs pollution in the landscape urban lagoon.

Trace Metal Residues in Swimming Warrior Crab Callinectes bellicosus: A Consumption Risk

This study was carried out in the Navachiste coastal lagoon, Mexico, surrounded by intensive agricultural and aquaculture activities that cause environmental pollution by the deposition of trace metal residues in the sediments of this coastal lagoon. The trace metals are bioaccumulated by benthic organisms such as the blue swimming warrior crab, Callinectes bellicosus, which inhabits this lagoon and is consumed by humans. Ninety-five C. bellicosus edible tissue samples were collected (April 2014–January 2015). The extraction procedure of the trace metals in edible tissue samples was carried out by acid digestion with nitric acid. Based on the Environmental Protection Agency (EPA) of the United States, two indices were used to measure health risk: the estimated daily intake (EDI) and the target hazard quotient (THQ). The hazard index (HI) was used to calculate the probability of adverse carcinogenic risk and the target hazard quotient per sample (MHI) to calculate the probability of developing a carcinogenic or non-carcinogenic risk. The analysis of variance (ANOVA) showed significant differences among trace metal concentrations (p < 0.01), but all trace metal concentrations in the edible tissues of C. bellicosus were higher than the maximum residual limits (MRLs). The highest EDI was for Zn, Fe, and Cu, showing that the consumption of these crabs might represent health risks. The THQ >1 was for Ni, Zn, Cd, and Cu, and the HI = 16 revealed the risk of C. bellicosus for high-level consumers. The MHI showed that 98% of samples presented a THQ >1, implying a high rate of bioaccumulation of trace metals by the crabs independent of the sampling site in the NAV. The presence of trace metals in the edible tissue of crabs reflects contamination by trace metals, and the indices results mean that the NAV lagoon is constantly polluted with trace metal residues by neighboring agriculture and aquaculture activities. These trace metal residues are being bioaccumulated in the edible tissues of C. bellicosus due to its feeding habits, resulting in a health risk if its consumption is high, including carcinogenic and non-carcinogenic risks.

Environmental impact on the natural resources of an area affected by mining activity in Bolivia: a geochemical evaluation of soils and sediments

The current methods used in Bolivia to extract gold using the amalgamation process with mercury result in environmental contamination and a risk to human health. The objective of this study was to determine Hg, As, Cu, Cd, Pb and Zn concentrations in soils and sediments from three mining districts. Results showed As and Hg concentrations were higher in the topsoil than in the sub-surface soils in the Sunchullí-Viscachani area, indicating active As/Hg atmospheric deposition, where concentrations exceeded the threshold levels. In addition, concentrations of Cd and Zn largely exceeded the threshold levels in the Katantica and Sural mining districts. In addition, the Sunchullí and Viscachani lagoon sediments were contaminated by Hg, As, Cd, Zn and Cu, whilst Katantica lagoon showed high concentrations of Zn, Cd and Hg, and high levels of As, Zn and Cu were reported in the Sural lagoon. Our results showed that the Cu, Pb, As and Hg concentrations in sediments in the Sunchullí river; As, Hg and Cu in the Pelechuco river, and As and Hg in the Rayo Rojo river all come from direct mine discharges into the rivers. These high concentrations of metals and metalloids must cause an impact on the aquatic ecosystems and human health. Therefore, there is a need to study the availability and speciation of metals and metalloids in soils and sediments to better understand the cycling of these elements and their transfer to the food chain.

Tracking historical storm records from high-barrier lagoon deposits on the southeastern coast of Hainan Island, China

Tracking historical storm records from high-barrier lagoon deposits on the southeastern coast of Hainan Island, China

A review of last interglacial sea-level proxies in the western Atlantic and southwestern Caribbean, from Brazil to Honduras

Abstract. We use a standardized template for Pleistocene sea-level data to review last interglacial (Marine Isotope Stage 5 – MIS 5) sea-level indicators along the coasts of the western Atlantic and southwestern Caribbean, on a transect spanning from Brazil to Honduras and including the islands of Aruba, Bonaire, and Curaçao. We identified six main types of sea-level indicators (beach deposits, coral reef terraces, lagoonal deposits, marine terraces, Ophiomorpha burrows, and tidal notches) and produced 55 standardized data points, each constrained by one or more geochronological methods. Sea-level indicators are well preserved along the Brazilian coasts, providing an almost continuous north-to-south transect. However, this continuity disappears north of the Rio Grande do Norte Brazilian state. According to the sea-level index points (discrete past position of relative sea level in space and time) the paleo sea-level values range from ∼ 5.6 to 20 m above sea level (a.s.l.) in the continental sector and from ∼ 2 to 10 m a.s.l. in the Caribbean islands. In this paper, we address the uncertainties surrounding these values. From our review, we identify that the coasts of northern Brazil, French Guiana, Suriname, Guyana, and Venezuela would benefit from a renewed study of Pleistocene sea-level indicators, as it was not possible to identify sea-level index points for the last interglacial coastal outcrops of these countries. Future research must also be directed at improving the chronological control at several locations, and several sites would benefit from the re-measurement of sea-level index points using more accurate elevation measurement techniques. The database compiled in this study is available in spreadsheet format at the following link: https://doi.org/10.5281/zenodo.5516444 (Version 1.02; Rubio-Sandoval et al., 2021).

Geochemical baseline establishment, contamination level and ecological risk assessment of metals and As in the Limoncocha lagoon sediments, Ecuadorian Amazon region

PurposeThe Limoncocha lagoon, inside a Ramsar site in the Ecuadorian Amazon, increasingly hosts ecotourism and energy development activities. This work estimates the local sediments’ baseline of As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, V and Zn using four methods. This makes it possible to apply single and integrated pollution indices to estimate the contamination level and the ecological risk of the sediments.MethodsSeven sites were analysed for metal(oid)s by ICP-MS. The local baseline was estimated using the relative cumulative frequency method, the iterative 2σ- and 4σ-outlier-techniques and the normalisation method to a “conservative” element. Combinations of single Cf and Ef and integrated indices (NPI, mNPI, mCd, MEQ, RI, mPELq, mERMq and TRI) were applied.ResultsThe relative cumulative frequency method had the best performance for the geochemical baselines. Cf and Ef indices classify sediments from a “low contamination” remote site to the “moderate contamination” and “minor enrichment” of the remaining sites due to As, Cd and Zn concentrations. The overall analysis of the integrated indices results in Ni, Zn and Cu being identified as priority pollutants because they have occasionally been associated with adverse biological effects in the centre of the lagoon and in the most anthropised areas. These are classified as moderately polluted with a medium–low priority risk level.ConclusionsThis work provides sediment baseline and contamination indicators for pollutants, which could be incorporated into the sediment quality assessment and monitoring programme of the Limoncocha lagoon. Ni, Cd and Cr due to the high baseline values in comparison with SQGs, and Cu and Zn due to their potential risk, should be of special attention.Graphical abstract