Plutonium occurrence and phase distribution in sediments of the Wyre estuary,northwest England

The occurrence of plutonium isotopes derived from the Windscale reprocessing facility discharges and weapons test fallout in intertidal sediments of the Wyre estuary, northwest England, is reported. Windscale plutonium appears to be slowly transported to the estuary in association with sedimentary material, and its distribution in surface and buried sediments is controlled by the variations in organic matter content of the sediments and/or their grain size characteristics. Results from chemical leaching experiments suggest that very little plutonium is ion exchangeable or in humic substances, but it is in other organic and Fe/Mn hydrous oxide fractions of the sediments. Plutonium shows a similar depositional behaviour to mercury which enters the Wyre directly in local industrial discharges.     

Cadmium and manganese distributions in the Hudson River estuary: interannual and seasonal variability

Surface waters collected along the salinity gradient of the Hudson River estuary in four cruises between 1995 and 1997 were size-fractionated into particulate (>0.45 μm), ‘dissolved' (<0.45 μm), colloidal (10 kDa, 0.45 μm) and low molecular weight (<10 kDa) phases. Dissolved Cd concentrations (range: 0.11–1.19 nM) in surface waters of the estuary appear to have decreased fourfold (from an average of 2.36 to 0.61 nM) over a 23-year period, since the initial analysis of samples collected in the 1970s by Klinkhammer and Bender [Estuar. Coastal Shelf Sci. 12 (1981) 629–643]. This interannual decline reflects improvement in sewage treatment and the elimination of industrial Cd sources to the Hudson River estuary. In contrast, dissolved Mn levels (range: 0.033–1.46 μM) have remained relatively constant over the same period of time, suggesting that anthropogenic sources have very limited impact on Mn concentrations in the estuary. The concentrations of both Cd and Mn appeared to strongly depend on the season and/or river discharge. The highest concentrations were detected under low freshwater discharge, implying that limited hydraulic flushing allows a build-up of metals in the water column. Although the decline in Cd levels within the estuary reflects a reduction in the magnitude of anthropogenic inputs, mass balance estimates indicated that current sources of Cd to the estuary include sewage discharges (in the lower estuary around Manhattan) and diagenetic remobilization from industrial Cd deposited in sediments nearly 2 decades ago (in the upper estuary near Foundry Cove). Moreover, under low river discharge, the sources considered in our model (sewage, riverine input, atmospheric deposition, and benthic fluxes) could account for no more than 60% of the Cd exported from the lower estuary to the ocean. This suggests that undefined sources such as ground water and inputs from other watersheds (e.g., Long Island Sound and Newark Bay) may potentially influence the water quality of the New York Harbor. The size-fractionated metal concentrations indicated that most of the traditionally defined ‘dissolved' Cd and Mn consisted of <10 kDa molecular weight species. High molecular weight colloidal species of Mn accounted for about 50% of the dissolved fraction at the riverine end-member and <5% at intermediate and high salinities. Colloidal Cd accounted for <6% of the dissolved phase throughout the estuary. Unlike the non-conservative excess (relative to ideal dilution of river water and seawater) of dissolved Mn observed along the estuary, high molecular weight colloidal Mn appeared to be removed at the head of the estuary. The small contribution of colloidal Cd and Mn to the ‘dissolved' phase suggests that remobilization from suspended particulate phases and/or from sediments occurs through the formation of small molecular weight species.     

Desorption of Ba and226Ra from river-borne sediments in the Hudson estuary

The pronounced desorption of Ba and²²⁶Ra from river-borne sediments in the Hudson estuary can be explained quantitatively by the drastic decrease in the distribution coefficients of both elements from a fresh to a salty water medium. The desorption in estuaries can augment, at least, the total global river fluxes of dissolved Ba and²²⁶Ra by one and nine times, respectively. The desorptive flux of²²⁶Ra from estuaries accounts for 17–43% of the total²²⁶Ra flux from coastal sediments. Two mass balance models depicting mixing and adsorption-desorption processes in estuaries are discussed.     

PCBs in the Hudson River

Hydrocarbon distribution in sediments from three lakes are related to the level of human activity in the respective drainage basins. Petroleum hydrocarbon contamination is found in surface sediments of a lake surrounded by a major city, compared to no detectable contamination in a lake located in a National Park.     

Assessment of heavy metal contamination in the surficial sediments from the lower Meghna River estuary,Noakhali coast,Bangladesh

Sediment samples were collected from ten selected sites of the lower Meghna River estuary,and six heavy metals were analyzed with Atomic Absorption Spectrophotometry(AAS)to assess the contamination level and the metals’association with sediment grain size.The current results revealed that the mean concentrations of the studied metals were ranked in descending order of iron(Fe)(1.29×103 mg/kg)>zinc(Zn)(42.41 mg/kg)>lead(Pb)(12.48 mg/kg)>chromium(Cr)(10.59 mg/kg)>copper(Cu)(6.22 mg/kg)>cadmium(Cd)(0.28 mg/kg).The geo-accumulation,contamination,and pollution load indexes suggested that the lower Meghna river estuary was not contaminated by Fe,Zn,Pb,Cr,and Cu.The mean size of the sediment ranged from 28.92 to 126.2 mm,and the Pearson correlation coefficient showed a significant association between Fe and Pb(coefficient of determination,r2=0.836;p<0.05),and no significant correlation was found between individual metals and grain size,indicating no or low influence on the metals distribution.     

Assessment of arsenic and heavy metal pollution and ecological risk in inshore sediments of the Yellow River estuary,China

In order to investigate the pollution levels, sources and ecological risks of arsenic (As) and heavy metals (Cr, Ni, Cu, Zn, Pb and Cd) in inshore sediments of the Yellow River estuary, the surface sediment in areas of inshore coastal waters were sampled in October 2014 as the flow-sediment regulation project (FSRP) was implemented for 13 years. Results showed that the concentrations of As and heavy metals in inshore sediments of the Yellow River estuary were in the order of Zn?>?Cr?>?Cu?>?Ni?>?Pb?>?As?>?Cd. Higher levels of As, Cr, Ni, Cu, Zn and Pb generally occurred in fine-grained sediments of the Yellow River estuary and the southeast region, which was consistent with the spatial distribution of clay. In contrast, higher concentrations of Cd were generally observed in northwest area of the Yellow River estuary and near the Qingshuigou estuary, which showed similarly spatial distribution with that of sand. The sediment quality guidelines (SQG_S) and geoaccumulation indices (I_geo) indicated that the inshore sediments were polluted by Cu, Cd, As, Pb and Zn, and, among them, Cd pollution was more serious. Ecological risk indices (E _r ⁱ ) demonstrated low risks for Cr, Ni, Cu, Zn, Pb and As, and high potential toxicity by Cd. The integrated ecological risk index implied that 6.8% of stations presented moderate risk, 4.5% of stations exhibited disastrous risk, and 88.7% of stations demonstrated considerable risk. Principal component analysis indicated that Ni, Cu, Zn, Pb and As might originate from common pollution sources, while Cr and Cd might share another similar sources. With the continuous implementation of FSRP, As and heavy metal levels in inshore sediments of the Yellow River estuary could be classified as stage I (2002–2010) and stage II (2010–2014). In the stage I, As, Cr, Ni, Cu, Zn and Pb levels fluctuated but decreased significantly, whereas Cd concentrations showed little variation. In the stage II, As and heavy metal levels significantly increased although some little fluctuations occurred. The continuous accumulation of As and heavy metals (especially for Cd) in inshore sediments of the Yellow River estuary would occur again as the FSRP was implemented for 9 years (since 2010). The ecotoxicological risk of Cd, As, Ni and Cu in inshore sediments might be more serious since the accumulation of the four elements would be continuously occurred in future years. Next step, there will be long-term potential consequences for marine organism if effective measures are not taken to control the loadings of metal pollutants into estuary.     

The distribution and transportation of fine-grained sediments on the inner continental shelf off the Keum River estuary,Korea

A study of suspended particulate matter in the Keum estuary and the adjacent continental shelf, southeastern Yellow Sea, showed that most of the suspended matter (average amount of2.7 × 10⁴ tons in October 1980) is derived from the Keum River and the major dispersal directions are westward and southwestward. Associated investigations of the clay mineral and trace element of the bottom sediment in the same study area confirmed that the bulk of fine-grained sediments derived from the Keum River and its estuary probably is dispersed essentially to the southwest, but indicated that less significant amounts are dispersed to the west or northwest.     

Biodiversity loss in benthic macroinfaunal communities and its consequence for organic mercury trophic availability to benthivorous predators in the lower Hudson River estuary, USA

Organic mercury such as methylmercury is not only one of the most toxic substances found in coastal ecosystems but also has high trophic transfer efficiency. In this study, we examined implications of chronically altered benthic macroinfaunal assemblages for organic mercury trophic availability (based on organic mercury intracellular partitioning) to their predators in the Arthur Kill-AK (New York, USA). Despite low species diversity, both density and biomass of benthic macroinvertebrates in AK were significantly higher than those at the reference site. Disproportionately high biomass of benthic macroinvertebrates (mostly polychaetes) in the northern AK resulted in a more than twofold increase (‘ecological enrichment’) in the trophically available organic mercury pool. These results suggest that altered benthic macroinfaunal community structure in AK may play an important role in organic mercury trophic availability at the base of benthic food webs and potentially in mercury biogeochemical cycling in this severely urbanized coastal ecosystem.     

Mercury in sediments of Ulhas estuary

Hg levels in water, suspended particulate matter and sediment of the Ulhas estuary are under considerable environmental stress due to the indiscriminate release of effluents from a variety of industries including chlor-alkali plants. Concentration ranges of dissolved (0.04-0.61 micro gl(-1)) and particulate (1.13-6.43 micro gg(-1)) Hg reveal a definite enhancement of levels in the estuary. The Hg burden in sediment upstream of the weir that limits the tidal influence is low (0.08-0.19 micro gg(-1)) with low C(org) content (1.8-2.9%). The high Hg content of the sediment just below the weir varies seasonally (highest concentration recorded being 38.45 micro gg(-1)) due to incremental accretion of sediment as the fresh water flow over the weir progressively decreases. The 30 km segment of the estuary sustains markedly high levels of Hg in the sediment with an exponential decrease in the seaward direction from the weir. Higher concentrations than the expected background prevail in all the estuarine cores up to the bottom, though the overall concentration decreases from about 20 micro gg(-1) in core 7 (inner estuary) to 1 micro gg(-1) in core 31 (outer estuary). The Hg in sediment is associated with C(org), while its correlation with Al, Fe and Mn is poor. The Hg profiles in cores from the Arabian Sea (stations 34, 35 and 37) have a distinct horizon of enhanced concentration in the 5-60 cm segment. Based on 210Pb dating of core 37, the sediment at the bottom of this core is inferred to have been deposited in the year 1949, roughly two year prior to the establishment of the first chlor-alkali plant and represents the background (0.06-0.10 micro gg(-1)). The Hg profiles in the offshore cores indicate a marked increase in transfer of Hg to sediment subsequent to 1980, with a peak around 1990-1992. Based on the index of geoaccumulation it is considered that the estuarine segment between stations 4 and 23 is extremely polluted, while the sediment from the open coast is moderately polluted in the top 25-30 cm with respect to Hg. The enrichment factor of Hg in the sediment is 350-700 for core 4 and decreases to 0-7 for the open-shore cores.     

The fate of Chernobyl radiocesium in the River Öre catchment,northern Sweden

A¹³⁷Cs-balance for the catchment of the River Öre in central northern Sweden which received about 30 kBq m^–2 of radiocesium from the Chernobyl accident was calculated for the period 1986–1991. Altogether, slightly less than 10% of the total deposition in the catchment was estimated to be exported from the terrestrial parts during this period of time. More than 90% of this loss is transported with the River Öre to the outer sea of the Gulf of Bothnia. The retention in Lake Örträsket which is the only lake along the river course and the Öre Estuary outside the river mouth was thus slightly less than 10%. Nearly all of the radiocesium deposited in the lake is permanently retained in the sediments and successively covered with less radioactive sediment. A considerable export of radiocesium from the estuary to the outer sea takes place due to resuspension and subsequent transport by wind and wave generated currents.     

Polychlorinated biphenyls in the Brisbane River estuary, Australia

The concentrations of PCBs in water, sediments, fish (6 species), crustacea (3 species), molluscs (1 species), polychaetes (mixed species) and birds (1 species) from the Brisbane River estuary were determined. Levels were comparable to other similar situations elsewhere. No relationship was found between trophic class and PCB concentration although pelicans at the highest trophic level examined exhibited the highest muscle tissue concentration (i.e., 15.7 mg kg⁻¹ on a wet weight basis). The pattern of distribution of PCBs within body tissues of fish was closely related to lipid content.     

Hydrocarbons in the bottom sediments of the Northern Dvina estuary

The results of studying hydrocarbons during the flood in May 2005 are discussed. The concentration of aliphatic and polycyclic aromatic hydrocarbons are shown to match their concentrations in water areas with steady input of pollutants. Weathered oil and pyrogenic compounds dominated in their composition. The geochemical barrier the Northern Dvina River-Dvina Gulf is shown to become a filter during floods and prevents pollutants from penetrating into the White Sea.     

Impact of millennial mining activities on sediments and microfauna of the Tinto River estuary (SW Spain)

In this paper, we analyze two short cores collected in the Tinto estuary (SW Spain), and describe the palaeoenvironmental evolution of this area during the last two millennia, along with the influence of historical mining activities and recent industrial pollution on sediments and microfauna (foraminifera and ostracoda). Although there were no significant changes in the distribution of microorganisms, a first pollution period (0-150 AD) was recorded in high sediment pollution by Cu in the shallow palaeochannels of the middle estuary. During this period and the following 1700 years, tolerant pioneer species of both foraminifera and ostracoda were found predominantly in the inner, protected areas of the estuary, while the bottom sediments were subjected to high hydrodynamic gradients, and consequently showed lower density and diversity of organisms. In the last 150 years, acid mine drainage processes, introduction of a new mining period, and the polluted inputs derived from two industrial processes resulted in increased heavy metal contamination of the bottom sediments, and corresponding extirpation of ostracodes and restriction of foraminifers to the inner zones of the estuary.     

REE in the Great Whale River estuary, northwest Quebec

We report rare earth element (REE) concentrations of a longitudinal profile within the estuary of the Great Whale River in northwest Quebec and in Hudson Bay. All of the measured REE have concentrations less than those predicted by conservative mixing of seawater and river water, demonstrating removal of the REE from solution. REE removal is rapid, occurring primarily at salinities less than 2‰. Removal of the REE is greatest for the light REE, and ranges from about 7% for the light REE to no more than 40% for the heavy REE. Fe removal is essentially complete at low salinity. The shape of the Fe and REE vs. salinity profiles is not consistent with a simple model of destabilization and coagulation of iron and REE-bearing colloidal material. A linear relationship between the activity of free ion REE³⁺ and pH is consistent with a simple ion-exchange model for REE removal.Surface and subsurface samples of Hudson Bay seawater are characterized by high REE concentrations and high La/Yb relative to average seawater. The subsurface sample has a Nd concentration of 100 pmol/kg and an ε_Nd of −29.3 ± 0.3. These characteristics are consistent with the high REE concentration, high La/Yb, and low ε_Nd of river inputs into Hudson Bay. These results indicate that rivers draining the Canadian Shield are a major source of non-radiogenic Nd and REE to the Atlantic Ocean. We estimate that outflow of water from Hudson Bay to the Labrador Sea could supply ≈ 30% of the non-radiogenic Nd in North Atlantic Deep Water.     

PCB and HCB in the sediments and waters of the Tiber estuary

The contamination by polychlorinated biphenyls (PCB) and hexachlorobenzene (HCB) in sea waters and sediments of Tiber River estuary has been studied in 1976 and 1977.PCBs have been detected in all the samples analysed at mean levels of 0.297 ppb (1976) and 0.135 ppb (1977); these levels are much higher than those proposed as acceptable for surface waters. Contamination increases with increasing distance from the shore.HCB has been identified in only 16% of the water samples analysed and it was found absent in sediment samples.The results are discussed relative to both the levels of PCB in other sea waters and the toxicity of these products to the aquatic animals.     

The hydrology of Piermont Marsh,a reference for tidal marsh restoration in the Hudson river estuary,New York

The topography, hydroperiod, water table, and selected edaphic characteristics are described for Piermont Marsh, an irregularly flooded tidal marsh in the Hudson River Estuary, New York, USA. Despite variations in microtopography, overall the marsh is flat, and although the observations were conducted at a high point in the Estuary's 18.6 year metonic cycle, its surface was only inundated 10–12 times a month. Observations of spatial differences in the saturated hydraulic conductivity and surface infiltration rates are also discussed. ‘Edge’ portions of the marsh are characterized by a slightly higher, more uniform, more structured, less organic, and less hydrologically conductive substrate than found in the marsh interior. Preferential flow is facilitated by macropores in the creekbank wall. The water table is close to the marsh surface for a lesser percentage of the lunar month in the marsh ‘edge’ when compared to the interior, where it is almost always within 10 cm of the surface. The extent to which the spatial variability of these hydrologic characteristics determines the marsh's ability to provide various ecosystem services is also discussed and the implications of these observations on tidal marsh restoration efforts briefly presented.     

An approximate petroleum hydrocarbon budget for the Hudson Raritan estuary—New York

The quantities of petroleum hydrocarbons being discharged to the Hudson Raritan estuary have been estimated, in tonnes day^?1, from data in the literature as: sewage discharges (35), oil refinery discharges (1.3), non-oil refinery industrial discharges (17), oil spills (1.5), atmospheric deposition (0.002), urban and rural run-off (37). Losses have been estimated in a somewhat similar manner as: permanent deposition in sediments (11), dredging (5.8), advection (6.5), bed sedimentary transport (0.007), decomposition in water and sediments (42), evaporation (0.4), movement of surface slicks (0.4). The results are approximate but suggest that petroleum hydrocarbons originate principally from sewage as well as urban and rural run-off and only moderate proportions are discharged through the estuary mouth. However, this discharge combined with that due to dredging spoil disposal operations results in a considerable quantity of petroleum hydrocarbon entering the adjacent New York Bight.     

Modeling Sediment Transport Dynamics in Thompson Island Pool,Upper Hudson River

Two-dimensional, vertically-averaged hydrodynamic and sediment transport models were developed and applied as part of a PCB fate and transport modeling study of Thompson Island Pool (TIP), Upper Hudson River. Mechanistic formulations were used to simulate cohesive and non-cohesive suspended load transport; site-specific data were extensively used to determine model inputs. This modeling approach is compared and contrasted to non-mechanistic solids transport sub-models used in other contaminant fate studies. A minimum number of model parameters were adjusted to calibrate the sediment transport model using data collected during the 1994 spring flood. The model was validated during the 1997 spring flood and for a 22-year (1977–1998) period. Successful calibration and validation of the model showed that: (1) deposition and resuspension processes were realistically and accurately formulated in the model; (2) the model is an effective diagnostic tool for quantitatively evaluating net deposition and erosion from various areas of TIP; and (3) sediment transport results can be coupled with a PCB fate model with a high degree of confidence.