Dredging in an estuary causes contamination by fluid mud on a tourist ocean beach. Evidence via REE ratios.

Deposits of fluid mud on wave-dominated beaches are rare. Where they happen frequently and periodically, they can be associated with anthropic processes that bring fluid mud to the shoreface and surf zone. To determine the reason for the frequent deposition of fluid mud at Cassino Beach (Southern Brazil) in the 2014-2020 period, the La/Eu and Gd/Yb ratios in marine, beach, and adjacent Patos estuary sediments were investigated. Mud from the beach showed similar ratios of REE to dredged sediments from the harbor basin and navigation channel within the estuary. Industrial and port activity changes REE ratio in sediments of the navigation channel, and they are distinct from naturally deposited marine and estuarine sediments. We conclude that the mud deposition events at the beach are most likely associated with dredging processes in the estuary especially where overflow is the source of fluid mud on the beach shoreface.

Groundwater Contamination by Mercury from the Aforetime Carroting Practice.

In the southernmost Brazilian city of Rio Grande, the chemical treatment of animal fur named carroting was performed between the eighteenth and twentieth century. This type of industry has led to contamination of urban soil with mercury down to the groundwater level. The present study has revealed that the dissolved mercury concentrations in groundwater in the mercury contaminated areas was up to 13 times higher than that found in the reference site. The association between SO42-, Ca2+ and dissolved mercury indicate that urban man-made grounds composed by soil, construction and demolition waste, urban rubbish and mud contaminated by "carroting mercury" serve as a source of this metal to groundwater. Despite the high level of contamination, mercury concentrations found in groundwater were below the permissible level established for potable water. Most of the dissolved mercury was chemically combined, probably with organic matter.

Selenium deficiency in subtropical littoral pampas: environmental and dietary aspects.

Se deficiency has a critical effect on human health. The littoral near Patos Lagoon in the south of Brazil is composed of Quaternary sandy deposits and nutrient-deficient soils, which contribute to Se deficiency in the surrounding environment. The average concentration of Se in littoral soils is six times lower than the metalloid deficiency threshold of 0.5 mg kg-1 and is close to that in countries where Keshan disease is registered. The sediments in the Patos Estuary are also notably lower in Se than near-shore marine sediments. Foodstuffs produced in the littoral pampas are characterised by extremely low Se concentrations compared with the same alimentary products reported worldwide. The total daily dietary intake of Se in the region is 24 µg day-1, which is half the Estimated Average Requirement for adults. Black beans in the local diet provide over 40% of daily Se intake. Prescriptive addition of Se to prevalent products seems the most effective solution to the problem of metalloid dietary deficiency in the region. Similar environmental conditions and significant concentration of the population in the littoral zone suggest that the problem of Se deficiency probably affects a large proportion of the population along the Atlantic coast of Brazil.

Arsenic Environmental Threshold Surpass in Estuarine Sediments: Effects of Bioturbation.

We investigate the distributions of the metalloid arsenic (As) and metals iron (Fe) and manganese (Mn) in the sediments of two pristine areas of a biological reserve in the Patos Lagoon Estuary. This area is occupied by Spartina alterniflora and by Neohelice granulata crab colonies and low concentrations of As are expected. The bioturbation/bioirrigation of sediments by crabs and the roots of plants lead to the penetration of oxygen below the oxic/suboxix division and the subsequent precipitation of Fe-Mn hydroxides. Ferruginous incrustations and nodules along roots and crab channels propagate to depths of over 35 cm and sediment contains up to 33 mg kg- 1 of As. The metalloid distribution in sediments is strongly correlated with that of Fe but not with Mn. This study revealed that areas with biologically disturbed sediments could demonstrate contamination in As, which is not anthropogenic in origin.

Arsenic in groundwater of the Paraiba do Sul delta, Brazil: An atmospheric source?

High concentrations of arsenic (>50µg L(-1)) have been detected for the first time in groundwater of the wave-dominated Paraiba do Sul delta, Brazil. The deltaic shallow groundwater aquifer is enriched in arsenic fixed by authigenic sulfides. A study of palynomorphs confirmed that aquifer sediments were formed in inter-dune lakes/swamps lately covered by eolian sands. The organic sediments of contemporaneous inter-dune lake/swamp contain very high concentration of As: up to 180mg kg(-1) and 163µg L(-1) in dry gyttja material and interstitial water, respectively. The As in recent lake/swamp sediments is retained by iron hydroxides in upper and probably by sulfides in lower layers. In the absence of connection of inter-dune lakes/swamps with fluvial currents, the atmospheric input of As could be considered as the principal source in sediments. The calculation demonstrates the possibility of high concentrations of As accumulation in sediments of inter-dune lakes/swamps from atmospheric precipitations within several centuries before they will be covered by eolian sands and turned into shallow aquifer. Considering the commonalities of wave-dominated delta formations, we can predict more prevalent As accumulation in delta plain groundwater.

Mercury in freshwater, estuarine, and marine fishes from Southern Brazil and its ecological implication.

In this study, we measured the mercury concentration in 27 different fish species with high commercial value. Samples were taken from a region characterized by the diversity of aquatic environments. Mercury concentration in marine fish species varied from 30.4 to 216 ng g(-1), while in estuarine species, it varied from 12.4 to 60.3 ng g(-1). Compared to mercury concentration in marine species, none of the specimens from estuarine environment has reached a mercury concentration of 100 ng g(-1). However, mercury concentrations in species from the freshwater Patos lagoon are remarkably higher (15.3 to 462 ng g(-1)) than those from the estuarine or marine region. Even though mercury concentrations in these fish species did not exceed the maximum level (500 ng g(-1)) allowed by WHO for human consumption, they represent the main food source for sea birds and mammals coming from South Pole during their migration period.

An assessment of the chemical composition of precipitation and throughfall in rural-industrial gradient in wet subtropics (southern Brazil).

The chemical composition of bulk precipitation and throughfall were analyzed, during a 1-year period (2002), in rural-urban-industry gradients with similar forest cover (Eucalyptus spp.) in southern Brazil (Rio Grande and Porto Alegre cities). Values of pH varied from 5.0-5.1 in rural to 5.4-6.1 in industrial sites, and were intermediate in urban sites. The major ions in bulk precipitation were Na+, Cl-, NH+(4), NO-(3), and PO(3-)(4), and concentrations increased in urban and industrial sites. Principal component analysis identified the local main anthropogenic sources. Estimated annual amounts of dry deposition were generally greater in both industrial and urban sites than in rural sites. Areas close to industrial activity showed greater S and N total deposition (10.4-10.9 and 20.2-30.6 kg/ha, respectively) than in urban (3.4-7.3 and 14.6-24.1 kg/ha) and in rural (1.7-2.6 and 8.9-12.1 kg/ha) sites. Annual deposition of Ca and P varied from 0.6 and 3.0 kg/ha in rural to 45.4 and 32.4 kg/ha in industrial sites, maximum values being observed closed to the phosphate fertilizer plant of Rio Grande. Deposition in urban and industrial sites may be balanced by the alkaline cations, as bulk precipitation pH varied from 5.4 to 6.1, and was greater than in rural sites (5.0-5.1).

Mercury in lakes and lake fishes on a conservation-industry gradient in Brazil.

Mercury contamination in freshwater food webs can be severe and persistent, and freshwater fish are a major source of mercury contamination in humans. Northern hemisphere studies suggest that the primary pathway by which freshwater fish accumulate mercury is the food web, and that atmospheric deposition is the primary route by which mercury enters freshwater systems. Levels of atmospheric deposition are closely linked to proximity to sources of mercury emissions. These propositions have not been tested in the southern hemisphere. In this study, we measured mercury levels at three lakes in southern Brazil and assessed relationships between mercury in precipitation, lake water, sediment and fish tissues at sites close to (industrial and suburban areas) and distant from (protected conservation area) sources of mercury emissions. We also assessed relationships between mercury in fish species and their trophic habits. Mercury concentrations in sediment and lake water did not vary among lakes. In contrast, mercury in precipitation at the study lakes increased with proximity to industrial sources. Mercury in fish tissue generally increased along the same gradient, but also varied with trophic level and preferred depth zone. Atmospheric mercury deposition to these closed lakes may be directly linked to concentrations in fish, with surface-feeding piscivorous species attaining the highest concentrations.

The effect of accidental sulphuric acid leaking on metal distributions in estuarine sediment of Patos Lagoon.

In August of 1998 the tanker BAHAMAS belonging to the Chem Oil Company containing 12,000 t of concentrated sulphuric acid, had an accident on board, after which estuarine water entered one of the compartments of the tanker, resulting in a vigorous exothermic reaction. The reaction of acid with the metallic interior hull of the ship and the accompanying heat and H2 production resulted in an imminent risk of explosion. To avoid an explosion, given the fact that neutralization was not possible, some of the cargo was discharged into the surrounding water. Neutralization was done in January 1999, after the acid concentration in the tanker had decreased and the concentrations of Fe, Cr and Ni remained elevated. Metal concentrations in bottom sediments showed significant modifications. Leached mercury migrated and redeposited downstream, reaching approximately 76 times the background values. Such an anomaly has a well expressed barrier character. The mechanism for redeposition of Hg and other metals probably followed the pattern: Downstream as a result of dilution and mixing with seawater the pH of acid-water increases, favouring adsorption and/or precipitation of metals. The leading edge of a geochemical barrier, at positions 7-9 of sampling sites (Fig. 1), is confirmed by pH variations in the water. The reestablishment of normal pH occurred after a short time due to the high buffering capacity of seawater and large natural dilution process. The concentration of metals in estuarine water during and after the accident showed insignificant anomalies.