Geochemical characteristics and provenance implication of rare earth elements in surface sediments from bays along Guangdong Coast, Southeast China

A systematic study of the granulometric properties and the occurrence and distribution of rare earth elements (REE) within surface sediments from ten bays situated along the coast of Southeast China has facilitated a more rigorous understanding of constraints on sediment provenance in the area. The results show that REE concentrations are similar within a single bay, but vary considerably (133.58–251.77 mg/kg) among the bays. The chondrite-normalized distribution patterns show the typical enrichment of light REEs (LREEs: La–Eu) relative to heavy REEs (HREEs: Gd–Lu), and an apparent depletion of Eu, which is diagnostic of a terrigenous sediment source. Obvious enrichments of the middle REEs (MREEs: Sm–Ho) in the PAAS-normalized (Post-Archean Australian Shale) distribution patterns of these bay sediments are similar to results reported from large rivers in China. Comparing the REE composition of the bay sediments with those of adjoining fluvial sediments and with the bedrock of the surrounding drainage basins, the latter are indicated as the dominant sediment source. The uniform REE distribution patterns, and MREE enrichments, prove that the sediments are derived from the material transported by the streams and rivers that discharge into the bays.     

Behavior of heavy metals in sulfide mine tailings and bottom sediment (Salair,Kemerovo region,Russia)

The given work focused on solving the problem of environmental geochemistry related to investigation of element speciation, their mobility, and migration in polluted areas. The purpose was to describe quantitatively migration, distribution, and redistribution of heavy metals by the example of the old tailings (Talmovaya sands) of the Lead Zinc Concentration Plant (Salair, Kemerovo region, Russia) and technogenic bottom sediments of the Malaya Talmovaya river. Contents of elements in the sulfide tailings range in the following limits: Zn: 1,100–27,000 ppm, Cd: 1.3–240 ppm, Pb: 0.01–0.81 ppm, Cu: 220–960 ppm, As: 15–970 ppm, Fe: 19,000–76,000 ppm, and Ba: 80,000–1,00,000 ppm. Element concentrations in the river sediment are proportional to the element contents in the sulfide tailings. Element speciations in the sulfide tailings and technogenic bottom sediments were investigated by the modified sequential extraction procedure. Chemical forms of heavy metals in pore water and surface water were calculated by WATEQ4F software. Principles of heavy metal migration in the sulfide tailings and technogenic bottom deposits were established. The obtained results about element species in the sulfide tailings and sediment explain the main principles of element migration and redeposition. In the mine waste and technogenic bottom deposits, there is vertical substance transformation with formation of geochemical barriers.     

Fractionation of heavy metals in bottom sediments using Tessier procedure

The study presents the results of Cu, Pb, Zn, Mn and Fe determination in the samples of bottom sediments collected from the Oder and Warta rivers. The sequential extraction of metals in the samples of bottom sediments was performed after introducing the modification of the extraction scheme suggested by Tessier et al. (Anal Chem 51(7):844–851, 1979). The extraction times of particular stages were optimised. The fifth stage was altered by introducing the new methods of performing extraction. The samples of bottom sediments submitted the following granulometric analyses: dry, wet and wet with (HMP) dispersing reagent. Seven granulometric fractions with the following grain sizes were isolated: >2.0, 2.0–1.0, 1.0–0.5, 0.5–0.25, 0.25–0.1, 0.1–0.063 and <0.063 mm. The sequential extraction of particular granulometric fractions was performed. The concentration of metals variability was analysed depending on the method of sample preparation for the chemical analysis, granulometric fraction of sediments subjected to the analysis, extraction conditions and the site of samples collection. The lack of linearity between the metal concentration and the size of granulometric fraction was observed. The highest concentrations of metals were observed in fractions >2.0, 2.0–1.0 and 0.1–0.063 and <0.063 mm while the lowest concentrations occurred in fractions 1.0–0.5, 0.5–0.25, and 0.25–0.1 mm. The atomic absorption spectrometry with flame atomisation (F-AAS) was used for the determination of the investigated elements.     

Lithofacial complexes of quaternary deposits in the central and southeastern baltic sea

Geological and seismic profiling data (more than 25000 km of seismic profiles and about 1000 sediment sampling stations) collected during the last 30 yr by research vessels of the Shirshov Institute of Oceanology, Russian Academy of Sciences are summarized. Seismic records are directly correlated with sediment cores. The distribution map (scale 1 : 500000) of Quaternary lithofacial complexes corresponding to certain stages of the Baltic Sea evolution is compiled. The following four complexes are distinguished (from the base to the top): (I) moraine, with maximum thicknesses 60 and 170 m in valleys and ridges respectively: (II) varved clay of periglacial basins and from the Baltic Ice Lake (BIL), up to 25 m thick in depressions; (III) lacustrinemarine homogeneous clay with a thickness up to 4–8 m in depressions; (IV) marine sediments (mud, aleurite, coarse-grained deposits) accumulated in environments with intense bottom currents activity (thickness 2–4 m in the Gotland Basin, 4–6 m in the Gdansk Basin, and 10–20 m in fans and prodeltas). The Quaternary sequence is cut through by inherited valleys, where the thickest Holocene sediments are noted. Today, these valleys serve as routes of sediment transport to slope bases and central parts of basins. Outblows of deep gas (through faults and fractures) and diagenetic gas (from sediments) to the bottom surface also occur in the valleys. Sedimentation rates are higher in the Gdansk Basin (up to 100–120 cm/ka). Thick sand, aleurite, and mud bodies are accumulated here (about 15–20 m in the Visla River prodelta). The sedimentation rate is slower in the Gotland Basin (up to 50–60 cm/ka), where thin (2–4 m) sections of more fine-grained mud occur     

Cause of elevated as concentrations in the Baltic Sea and Vistula Lagoon

As is less toxic than Hg, Cd, Pb, Se, Zn, and Cu. The As clarke for clays and shales is 10 ppm. Our samples of bottom sediments from Kurshskii Bay were determined to contain from 15 to 26 ppm As and up to 34 ppm As in the vicinity of the Neman River mouth. Elevated As concentrations (50–114 ppm) were detected in four columns of subsurface bottom sediments (at depths of 10–65 cm) from the Vistula Lagoon. Elevated As concentrations (50–180 ppm) were also found in a few surface samples of sand from the Gdansk Deep near oil platform D-6. These sediments are either partly contaminated with anthropogenic As or contain Fe sulfides and glauconite, which can concentrate As and contain its elevated concentrations. The As concentration in columns of bottom sediments from the Gulf of Finland were at the natural background level (throughout the columns) typical of the area (9–34 ppm). We repeatedly detected very high As concentrations (up to 227 ppm As) in pelitic ooze from Bornholm Deep, in the vicinity of the sunken vessel with chemical weapons. The sources of elevated As concentrations in the Baltic Sea are the following: (1) chemical weapon (CW) material buried in the floor of the Baltic Sea; (2) As-bearing pesticides, agricultural mineral fertilizers, and burned coal and other fuels; (3) kerogen-bearing Ordovician rocks exposed on the bottom; and (4) As-rich Fe sulfides brought to the area together with construction sand and gravel. This mixture was used in paper production and for the construction of hydraulic engineering facilities in the Vistula Lagoon in the early 20th century and later caused the so-called lagoon disease.     

Implications for focused fluid transport at the northern Cascadia accretionary prism from a correlation between BSR occurrence a d near-sea-floor reflectivity anomalies imaged in a multi-frequency seismic data set

 A high-resolution seismic survey was carried out at the accretionary prism on the continental slope off Vancouver Island, Canada. Two GI-Gun data sets with different source frequency ranges of 50–150 and 100–500 Hz were combined with 4 kHz narrow-beam echosounding data (Parasound). The data allow spatial correlation between a gas hydrate bottom simulating reflector (BSR) and distinct areas of high near-sea-floor reflectivity. An integrated interpretation of the multi-frequency data set provides insight into the regional distribution of tectonically induced fluid migration and gas hydrate formation in the vicinity of ODP Leg 146 Sites 889 and 890. The BSR at the base of the gas hydrate stability field is observed within accreted and deformed sediments, but appears to be absent within bedded slope basin deposits. It is suggested that these basin deposits inhibit vertical fluid flow and prevent the formation of a BSR, whereas the hydraulic conductivity of the accreted sediments is sufficiently high to allow for pervasive gas migration. An elevation of the BSR beneath the flanks of a topographic high is interpreted as an indicator for local upflow of warm fluids along permeable pathways within outcropping accreted sediments. Parasound data reveal discontinuous zones of high reflectivity at or directly beneath the sea floor, which may indicate local cementation of surface sediments. In combination with GI-Gun data, the occurrence of these reflective areas can be related to the location of slope sedimentary basins acting as hydraulic seals. It is proposed that the seals sometimes fail along faults extending beneath the BSR, leading to focused upflow of methane-bearing fluid and the formation of carbonate pavements at the sea floor. Received: 9 November 1998 / Accepted: 6 April 1999     

Interstitial water – sediment geochemistry of N, P and Fe and its response to overlying waters of tropical estuaries: a case from the southwest coast of India

 The concentrations of N, P and Fe in surface sediments and interstitial and overlying (bottom and surface) waters of the Ashtamudi estuary located in the southwest coast of India are reported along with the various chemical species of N (NO₂–N, NO₃–N, NH₃–N and total N) and P (organic P, inorganic P and total P) in interstitial and overlying waters and discussed in terms of the physico-chemical environment of the system. The interstitial water exhibits higher salinity values compared to bottom and surface waters, indicating the coupled effects of salt-wedge phenomena and gravitational convection of more saline-denser marine water downward through surface sediments. N, P and Fe as well as their chemical forms are enriched in the interstitial water compared to bottom and surface waters. However, the dissolved oxygen (DO) shows an opposite trend. The marked enrichment of NH₃–N in the interstitial water and its marginal presence in bottom and surface waters, together with the substantial decrease in the DO concentrations of bottom water and consequent increase in the concentrations of NO₂–N and NO₃–N in interstitial and bottom waters, points to the nitrification process operating in the sediment-water interface of the Ashtamudi estuary. The enrichment of total N, P and Fe in the interstitial water compared to the overlying counterparts and the positive correlation of sediment N, P and Fe with mud contents as well as organic carbon indicate that these elements are liberated during the early diagenetic decomposition of organic matter trapped in estuarine muds. Received: 5 Oktober 1998 · Accepted: 9 February 1999     

First data on U-Pb SHRIMP-II isotopic dating based on zircons of ash sediments from Cenozoic depressions in Southwest of Primorie

U-Pb (SHRIMP-II) isotopic dating has been conducted for zircons of the ash sediments of the Ust’-Suifun Suite, which was the final stage of Late Cenozoic explosive volcanism in Southwest Primorskii krai. These pyroclastic units are widespread within sediments that fill in Cenozoic depressions including large coalfields. The concordant dates (23.7–24.6 Ma) are in line with the results of the K-Ar determinations for volcanic tephra (23.6–27.1 Ma) and correspond to the beginning of the active phase of spreading and taphrogenesis in the neighboring Trench of the Sea of Japan. These processes started as early as the Eocene and are reflected in the continental vicinity with the formation of riftogenic depressions and the occurrence of a peculiar gas volcanism.     

Migrations of adult horseshoe crabs,Limulus polyphemus, in the Middle Atlantic Bight: A 17-year tagging study

Adult horseshoe crabs,Limulus polyphemus, were tagged in the Middle Atlantic Bight area, from New York to Virginia on the continental shelf and within bays, to determine their migratory patterns and longevity. Of 30,432 horreshoe crabs that were tagged during the years 1986–2002, 1,122 were recovered alive, and 1,027 were dead. Many of the live recoveries were observed within 30 d (54.4%) and after years (37.53%) with one tagged animal surviving up to 10 yr. In 9 locations from Great Kills Harbor, New York, to Chesapeake Bay, Maryland, the horseshoe crabs return to their release beach within days during the spawning season. Of the 762 (100%) recoveries from crabs released along the Delaware Bay shoreline, 75.07% traveled 0–20 km, 21.0% traveled 20–50 km, 2.36% traveled 50–100 km, and 1.57% traveled over 100 km. Within Delaware Bay, 327 tagged animals (43.6%) had moved away from the release points to other locations, and 59 of these had moved out of the bay onto the continental shelf along the Mid-Atlantic Bight coastline. Horseshoe crabs migrate into Delaware Bay from waters off Ocean City, Maryland, and adjacent coastal bays. In addition to defining the range of the Delaware Bay spawning populations, 2 neighboring populations were identified by the tagging program. In one, animals tagged in southern New York mingled with those in the Sandy, Hook, New Jersey area, comprising a population that ranged from Raritan Bay across New York Harbor to Jamaica Bay. The second confirmed that a discrete population existed in northern Chesapeake Bay in the general vicinity of the Annapolis Bay Bridge.     

Bottom sediments of Kandalaksha Bay in the White Sea: The phenomenon of Mn

The redox stratification of bottom sediments in Kandalaksha Bay, White Sea, is characterized by elevated concentrations of Mn (3–5%) and Fe (7.5%) in the uppermost layer, which is two orders of magnitude and one and a half times, respectively, higher than the average concentrations of these elements in the Earth’s crust. The high concentrations of organic matter (C_org = 1–2%) in these sediments cannot maintain (because of its low reaction activity) the sulfate-reducing process (the concentration of sulfide Fe is no higher than 0.6%). The clearest manifestation of diagenesis is the extremely high Mn²⁺ concentration in the silt water (>500 μM), which causes its flux into the bottom water, oxidation in contact with oxygen, and the synthesis of MnO₂ oxyhydroxide enriching the surface layer of the sediments. Such migrations are much less typical of Fe. Upon oxygen exhaustion in the uppermost layer of the sediments, the synthesized oxyhydroxides (MnO₂ and FeOOH) serve as oxidizers of organic matter during anaerobic diagenesis. The calculated diffusion-driven Mn flux from the sediments (280 μmM/m² day) and corresponding amount of forming Mn oxyhydrate as compared to opposite oxygen flux to sediments (1–10 mM/m² day) indicates that >10% organic matter in the surface layer of the sediments can be oxidized with the participation of MnO₂. The roles of other oxidizers of organic matter (FeOOH and SO₄²⁻) becomes discernible at deeper levels of the sediments. The detailed calculation of the balance of reducing processes testifies to the higher consumption of organic matter during the diagenesis of surface sediments than it follows from the direct determination of C_org. The most active diagenetic redox processes terminate at depths of 25–50 cm. Layers enriched in Mn at deeper levels are metastable relicts of its surface accumulation and are prone to gradual dissemination     

Heavy metal concentrations in shallow marine sediments affected by submarine tailings disposal and artisanal gold mining,Buyat-Ratototok district,North Sulawesi,Indonesia

Trace element concentrations in shallow marine sediments of the Buyat-Ratototok district of North Sulawesi, Indonesia, are affected by submarine disposal of industrial gold mine tailings and unregulated dumping of tailings and wastewater from small-scale gold mining using mercury amalgamation. Industrial mine tailings contained 590–690 ppm arsenic, 490–580 ppm antimony, and 0.8–5.8 ppm mercury. Tailings-affected sediment As and Sb concentrations were 20–30 times higher than in muddy sediments not contaminated with tailings, and 50–60 times higher than pre-mining average. Highest mercury concentrations were observed in sediments affected by small-scale mining using mercury amalgamation (5–29 ppm). Concentrations of most other trace elements were comparable in sediments affected by both types of mining and were slightly higher than regional averages for sediments collected before the onset of industrial mining. Elevated concentrations of both As and Sb in approximately equal proportions suggest tailings dispersal of at least 3.5 km. Mercury released from artisanal gold mining dispersed up to 4 km from river mouths. Slight increases in concentrations of non-mercury trace elements in areas affected by artisanal mining over pre-industrial mining concentrations were probably caused by increased rates of erosion. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

The regularities of distribution of radionuclides and reare-earth elements in bottom sediments of Siberian lakes

Geochemical studies of the ecosystems of 184 Siberian lakes in three largest zones of northern Asia (humid, arid, and semiarid) and in mountainous area were carried out. The contents of natural radionuclides, radiocesium, and rare-earth elements in conjugate components of the systems and the types of the main sources of the bottom sediment material have been determined.Dating of the bottom sediments was made by the activity of radioisotopes ¹³⁷Cs and ²¹⁰Pb, which permitted estimation of the sedimentation rates in lakes in different regions of Siberia: 0.35 cm/year in the south and 0.25–0.3 cm/year in the north.Six main ions have been determined in the waters of the studied lakes: Ca²⁺, Mg²⁺, Na⁺, HCO₃^?, SO₄^2?, and Cl^?. The distribution of natural radionuclides in the stratified sections of bottom sediments of Siberian lakes evidences the stable sedimentation and characterizes their contents in the soils of water-catchment areas, which can be considered background contents there. Sediments enriched in organic matter have higher concentrations of U and lower ones of Th and K. The Th/K ratio in the studied bottom sediments is the same as in the soils. The Th/U ratios are somewhat lower than those in the soils because U is accumulated by chemogenic and organic components. The overall ¹³⁷Cs pollution of bottom sediments of Siberian lakes is close to the global background (40 mCi /km² in 2000), but in the Altai Territory and Buryatia and Altai Republics it is twice higher. The uneven areal and temporal distribution of residual radiocesium is observed not only in the lacustrine sediments but also in the lake water areas. The REE patterns of bottom sediments of different mineral types are similar to those of continental crust and clays of the Russian Platform, though organogenic and carbonate sediments have higher absolute REE contents than terrigenous ones. Pelitic fraction is the main REE concentrator in the bottom sediments.     

Phytoplankton Patterns in Massachusetts Bay—1992–2007

The Massachusetts Water Resources Authority (MWRA) conducts a comprehensive multidisciplinary monitoring program in Massachusetts Bay, Cape Cod Bay, and Boston Harbor to assess the environmental effects of a relocated secondary-treated effluent outfall. Through 2007, 8.7 years of baseline data and 7.3 years of postdiversion data (16 total years), including species level estimates of phytoplankton and zooplankton abundance, have been collected. MWRA’s monitoring program and other studies make this region one of the most thoroughly studied and well-described marine systems in the world. The data show that the diversion of MWRA effluent from the harbor to the bay has decreased nutrients concentrations and improved water quality in the harbor (e.g., higher dissolved oxygen, lower chlorophyll). The diversion also resulted in an increase in dissolved inorganic nutrients (especially ammonium) in the vicinity of the bay outfall, but no obvious impacts such as increased biomass or decreased bottom water dissolved oxygen have been observed. Regional changes in phytoplankton and zooplankton unrelated to the diversion have been seen, and it is clear that the bays are closely connected both physically and ecologically with the greater Gulf of Maine. Direct responses to modifications of the nutrient field within a 10 × 10-km area centered near the midpoint of the 2-km long outfall diffuser in Massachusetts Bay (a.k.a. the nearfield) have not been seen in the plankton community. However, plankton variability in the bays has been linked to large regional to hemispheric scale (NAO) processes.     

Trace metals (Cd,Pb, Cu,Zn and Ni) in sediment of the submarine pit Dragon ear (Soline Bay,Rogoznica, Croatia)

Vertical profiles of trace metal (Cd, Pb, Zn, Cu, Ni) concentrations, organic matter content, carbonate content and granulometric composition were determined in two sediment cores from the submarine pit Dragon Ear (Middle Adriatic). Concentrations of the analyzed metals (Cd: 0.06–0.12 mg kg⁻¹, Pb: 28.5–67.3 mg kg⁻¹, Zn: 17.0-65.4 mg kg⁻¹, Cu: 21.1–51.9 mg kg⁻¹, Ni: 27.8–40.2 mg kg⁻¹) were in usual range for Adriatic carbonate marine sediments. Nevertheless, concentrations of Cu, Zn, and especially Pb in the upper layer of sediments (top 12 cm) were higher than in bottom layer, while Cd and Ni concentration profiles were uniform. Regression analysis and principal component analysis were used to interpret distribution of trace metals, organic matter and carbonate content in sediment cores. Results of both analysis showed that concentrations of all trace metals in the core below the entrance to the pit were significantly positively correlated with organic matter and negatively correlated with carbonate, while in the core more distant from the entrance only Pb showed significant positive correlation with organic matter. Obtained results indicated that, except for lead which was enriched in surface sediment, in the time of sampling (before the building of the nautical marina) investigated area belonged to unpolluted areas.     

U-Pb geochronology of zircons from metasediments of the Ladoga Group (North Ladoga Region,Baltic Shield)

During our study we obtained the first age datings of detrital zircons from metasandstones of the Ladoga Group (North Ladoga Region, Russia) with the U-Pb isotopic method using the SHRIMP-II ion microprobe. The data obtained made it possible to clarify the lower age limit of sedimentation and to obtain additional age data for evaluating the chemical composition and an age of source areas. This work presents the results of isotopic-geochemical (Sm-Nd) and geochemical studies of metasediments. High LREE concentrations, a high La/Sc ratio and a low Cr/h ratio, and the presence of a distinct Eu-minimum (Eu/Eu* = 0.54–0.72) indicate a significant role of acidic terrigenous material in source areas. In addition, the data of the isotope analysis of detrital zircons show that sediments of the Ladoga Group accumulated from the destruction of Proterozoic rocks (1.9–2.0 Ga; a proportion in sediments is 60–70%) and, to a lesser extent, Archean rocks (2.54–2.74 and 2.9–3.01 Ga; the proportion in sediments is 30–40%). One of the Archean source areas could be granite-gneisses of the Pitkyaranta-Koirinoya dome structure with the U-Pb zircon age of 2659 ± 15 Ma. We have established the lower age limit of sedimentation as 1.9 Ga within the measurement error. The Sm-Nd model ages obtained (2.5–2.6 Ga for sediments of the Ladoga Group and over 3.4 Ga for granite-gneisses of the dome structure) suggest a significant contribution of ancient crustal source area into source rocks. Our age data agree well with those for svecofennides of Finland.     

Mapping of accumulated nitrogen in the sediment pore water of a eutrophic lake in Iowa, USA

A large pool of nitrogen in the sediment pore fluid of a eutrophic lake in Iowa, USA, was mapped in this study. Previously, the lake had supported fishing and boating, but today it no longer supports its designated uses as a recreational water body. In the top 5 cm of the lake bottom, the pore water nitrogen ranges between 3.1 and 1,250 μg/cm³ of sediments, with an average of 160.3 μg/cm³. Vertically, nitrate concentrations were measured as 153 μg/cm³ at 0–10 cm, 162 μg/cm³ at 10–20 cm, and 32 μg/cm³ at 20–30 cm. Nitrate mass distribution was quantified as 3.67 × 10³ kg (65%) in the bottom sediments, 172 kg (3%) in suspended particulates, and 1.83 × 10³ kg (32%) in the dissolved phase. Soil runoff nutrients arrive at the lake from the heavily fertilized lands in the watershed. Upon sedimentation, a large mass of nitrogen desorbs from mineral particles to the relatively immobile pore fluid. Under favorable conditions, this nitrogen diffuses back into the water column, thereby dramatically limiting the lake’s capability to process incoming nutrients from farmlands. Consequently, a condition of oxygen deficiency disrupts the post-season biological activities in the lake.     

Concentrations and contamination trends of heavy metals in the sediment cores of Taihu Lake,East China,and their relationship with historical eutrophication

To assess the contamination trends and potential bio-availability of sediment-bound heavy metals, concentrations of heavy metals in acid-leaching fraction and in bulk sediments from the two typical bays (the Meiliang Bay and Xuhu Bay) of the Taihu Lake, East China, were studied. Pb and Zn showed elevated concentrations in the sediments from both areas, although sedimentation history and degree of pollution are different between the two bays. In the Meiliang Bay, both Pb and Zn pollutions started in the late 1970’s, the same time as the beginning of eutrophication of the lake, while the in the Xuhu Bay the metal contamination started since recent 10 years. The concentrations of acid-leachable Pb in the sediments from the Meiliang Bay are correlated with the historical eutrophication process. Before the eutrophication and heavy metal pollution, the chemical properties of the lake sediments were the same as the source compositions of the Xiashu loess. Both Pb and Zn in the sediments mainly occur in leachable forms by nitric or hydrochloric acid, whilst most of Cu is in residual fraction. The results indicate that both Pb and Zn may have higher mobility and bioavailability in water and biology than Cu.     

Assessment of the radiological hazards of sand sediments collected from streams and streamlets of the uranium deposit areas in West Khasi Hills District,Meghalaya, India

Primordial radionuclides in sand sediments that are often used as constructing materials are one of the sources of radiation hazard in dwellings. Activity concentrations of the primordial radionuclides of ⁴⁰K, ²²⁶Ra and ²³²Th have been measured in sand sediments collected from streams and streamlets lying within and around the uranium mineralization deposit blocks of Kylleng-Pyndensohiong, Mawthabah Areas of West Khasi Hills District, Meghalaya, India. The technique of gamma-ray spectroscopy using a NaI(Tl) detector with a PC-based multi channel analyser was applied for determination of the activity concentrations. The activity of the sand sediments obtained in this study ranges from 95.3 to 1,088.8 Bq kg⁻¹ for ⁴⁰K; 38.3 to 784.1 Bq kg⁻¹ for ²²⁶Ra and 78.0 to 316.1 Bq kg⁻¹ for ²³²Th. Sand sediments from two sampling locations lying within the mineralization zone show highest concentrations of these radionuclides. The radiological hazards of the sand sediments were calculated using various models given in the literature. The radium equivalent activity was found to be higher than the accepted standard criterion value of 370 Bq kg⁻¹ and the values of external and internal hazard indices were also found to be higher than unity in these two sampling locations. Besides these two sampling locations, a sampling location lying at a nearby distance from the mineralization zone also exhibits hazard indices values greater than unity.     

Metal accumulation in surface salt marsh sediments of the Bay of Fundy,Canada

We measured the amount of arsenic, chromium, copper, lead, nickel, vanadium, and zinc accumulated over a five-year period from 1997 to 2002 in surface sediments of seven salt marshes along the New Brunswick coast of the Bay of Fundy, Canada. Study sites extended from outer to inner Bay, spanning a gradient in tidal range (6–12 m) and mean sediment deposition rate (0.27–1.76 cm yr⁻¹). In each study site, metal concentrations were measured in low and high marsh areas. Concentrations of chromium, nickel, and zinc appear to be within their natural range, while arsenic, lead, and vanadium are enriched in some sites. Calculated sediment metal loadings rates showed variability among marsh sites that closely followed sediment deposition patterns, suggesting sediment deposition rate is the driving factor of short-term metal accumulation in Fundy marshes. The value of salt marshes as a sink for metals may be enhanced by high sedimentation rates.     

Source of pollution as a factor controlling distribution of heavy metals in bottom sediments of Chechło River (south Poland)

 The influence of sources of effluents on pollution of bottom sediments of the small Chechło River (23 km long, mean discharge 1.5 m³ s^–1) in southern Poland was examined through analysis of heavy metals distribution in transverse and longitudinal cross sections. Underground waters from a Pb–Zn mine cause very high concentrations of Zn, Cd, and Pb in both fractions investigated (<1 mm and <0.063 mm) of sediments in the active channel zone, whereas sedimentation of huge amounts of suspended matter discharged from oil refinery cause concentrations of heavy metals in fine fractions rather uniform in cross sections. In the lowest reach, with relatively reduced contamination, the highest concentration both in fine and coarse fractions occurs close to the river banks and in the deepest points of the channel. The lowest concentrations have been found at the points of strongest reworking and accumulation of sandy material in the riverbed. Received: 25 April 1995 · Accepted: 11 September 1995