Showing papers in "Water Air and Soil Pollution in 1997"

Food as the Dominant Pathway of Methylmercury Uptake by Fish

Abstract: A field experiment was conducted to determine the degree to which fish accumulated methylmercury (MeHg) via their food or via passive uptake from water through the gills. Finescale dace (Phoxinus neogaeus) were held in 2000 L enclosed pens floating in an undisturbed, oligotrophic lake in northwestern Ontario. Fish were exposed to water containing either low (0.10–0.40 ng L-1), intermediate (0.45–1.30 ng L-1), or high (0.80–2.1 ng L-1) concentrations of MeHg. Zooplankton with either low (0.16–0.18 µg g-1 d.w.) or high (0.28–0.76 µg g-1 d.w.) concentrations of MeHg were added daily to each pen. Fish fed zooplankton with high concentrations of MeHg had significantly higher concentrations of mercury in muscle after 32 days than fish fed zooplankton with low concentrations of MeHg (ANCOVA, P<0.0001). Fish feeding on zooplankton with low concentrations of MeHg had the same amount of Hg in their tissues as fish at the start of the experiment. Uptake from water was at most 15%. This is the first experiment to confirm that food is the dominant pathway of MeHg bioaccumulation in fish at natural levels of MeHg.

Arsenic Chemistry in Soils: An Overview of Thermodynamic Predictions and Field Observations

Abstract: Published information, both theoretical and experimental, on As chemical behavior in soils is reviewed. Because of many emission sources, As is ubiquitous. Thermodynamic calculations revealed that As(V) species (HAsO 4 2- >H2AsO 4 - at pH 7) are more abundant in soil solutions that are oxidized more than pe+pH>9. Arsenic is expected to be in As(III) form (HAsO 2 0 =H3AsO 3 0 >AsO 2 - =H2AsO 3 - at pH 7) in relatively anoxic soil solutions with pe+pH<7. Adsorption on soil colloids is an important As scavenging mechanism. The adsorption capacity and behavior of these colloids (clay, oxides or hydroxides surfaces of Al, Fe and Mn, calcium carbonates, and/or organic matter) are dependent on ever-changing factors, such as hydration, soil pH, specific adsorption, changes in cation coordination, isomorphous replacement, crystallinity, etc. Because of the altering tendencies of soil colloids properties, adsorption of As has become a complex, empirical, ambiguous, and often a self contradicting process in soils. In general, Fe oxides/hydroxides are the most commonly involved in the adsorption of As in both acidic and alkaline soils. The surfaces of Al oxides/hydroxides and clay may play a role in As adsorption, but only in acidic soils. The carbonate minerals are expected to adsorb As in calcareous soils. The role of Mn oxides and biogenic particles in the As adsorption in soils appears to be limited to acidic soils. Kinetically, As adsorption may reach over 90% completion in terms of hours. Precipitation of a solid phase is another mechanism of As removal from soil solutions. Thermodynamic calculations showed that in the acidic oxic and suboxic soils, Fe-arsenate (Fe3(AsO4)4)2) may control As solubility, whereas in the anoxic soils, sulfides of As(III) may control the concentrations of the dissolved As in soil solutions. In alkaline acidic oxic and suboxic soils, precipitation of both Fe- and Ca-arsenate may limit As concentrations in soil solutions. Field observations suggest that direct precipitation of discrete As solid phases may not occur, except in contaminated soils. Chemisorption of As oxyanions on soil colloid surfaces, especially those of Fe oxide/hydroxides and carbonates, is believed to a common mechanisms for As solid phase formation in soils. It is suggested that As oxyanions gradually concentrate on colloid surfaces to a level high enough to precipitate a discrete or mixed As solid phase. Arsenic volatilization is another As scavenging mechanism operating in soils. Many soil organisms are capable of converting arsenate and arsenite to several reduced forms, largely methylated arsines which are volatile. These organisms may generate different or similar biochemical products. Methylation and volatilization of As can be affected by several biotic (such as type of organisms, ability of organism for methylation, etc.) and abiotic factors (soil pH, temperature, redox conditions, methyl donor, presence of other ions, etc.) factors. Information on the rate of As biotransformations in soils is limited. In comparison to the biologically assisted volatilization, the chemical volatilization of As in soils is negligible.

Use of Enrichment, and Contamination Factors Together with Geoaccumulation Indexes to Evaluate the Content of Cd, Cu, and Ni in the Rybnik Water Reservoir in Poland

Abstract: In this paper, the contamination degree of the Rybnik Reservoir with cadmium, copper and nickel was analyzed. Quality of the water from the reservoir was determined by drawing comparisons between the metal content in the water and both the officially permitted levels (contamination factor) and levels of metals occurring in the water of non-contaminated areas (enrichment factor). Contamination of bottom sediment with chosen metals was analyzed with reference to the metal content in mudstone (geoaccumulation index, enrichment factor, contamination factor). Trends towards changing the metal content in the bottom sediment was analyzed by determining the enrichment factor of the surface layer of the bottom sediments in relation to a deeper layer. Enrichment of the bottom sediments with metals coming from the water was also determined.

Copper solubility and speciation of in situ contaminated soils : Effects of copper level, pH and organic matter

Abstract: This study attempts to identify the soil properties controlling the fractionation of copper into various soil pools and determine the influence of pH and metal loading on soil-solution free copper activity (pCu2+). The pCu2+ was determined in 0.01 M CaCl2 soil extracts using a copper ion selective electrode. We analyzed a wide variety of soils: urban, agricultural and forest soils from the Province of Quebec, New York State and Denmark. The pCu2+ ranged from 12.21 to 6.18. The relationships among pCu2+, total soil copper, total dissolved copper and soil pH are studied for their variability within and between sites as well as for the whole data set. Regression equations are presented for predicting soluble copper as a function of total soil copper and also for predicting pCu2+ as a function of total soil copper and soil pH.

Mercury from combustion sources: A review of the chemical species emitted and their transport in the atmosphere

Abstract: Different species of mercury have different physical/chemical properties and thus behave quite differently in air pollution control equipment and in the atmosphere. In general, emissions of mercury from coal combustion sources are approximately 20–50% elemental mercury (Hg°) and 50–80% divalent mercury (Hg(II)), which may be predominantly HgCl2. Emissions of mercury from waste incinerators are approximately 10–20% Hg° and 75–85% Hg(II). The partitioning of mercury in flue gas between the elemental and divalent forms may be dependent on the concentration of particulate carbon, HCl and other pollutants in the stack emissions. The emission of mercury from combustion facilities depends on the species in the exhaust stream and the type of air pollution control equipment used at the source. Air pollution control equipment for mercury removal at combustion facilities includes activated carbon injection, sodium sulfide infection and wet lime/limestone flue gas desulfurization.

Evaluation of heavy metal remediation using mineral apatite

Abstract: The current study investigated the sorption and desorption of dissolved lead (Pb), cadmium (Cd) and zinc (Zn) from aqueous solutions and a contaminated soil by North Carolina mineral apatite. Aqueous solutions of Pb, Cd, and Zn were reacted with the apatite, followed by desorption experiments under a wide variety of pH conditions ranging from 3 to 12, including the extraction fluids used in the Toxicity Characteristic Leaching Procedure (TCLP) of the United States Environmental Protection Agency (US EPA). The sorption results showed that the apatite was very effective in retaining Pb and was moderately effective in attenuating Cd and Zn at pH 4–5. Approximately 100% of the Pb applied was removed from solutions, representing a capacity of 151 mg of Pb/g of apatite, while 49% of Cd and 29% of Zn added were attenuated, with removal capacities of 73 and 41 mg g-1, respectively. The desorption experiments showed that the sorbed Pb stayed intact where only 14–23% and 7–14% of the sorbed Cd and Zn, respectively, were mobilized by the TCLP solutions. The apatite was also effective in removing dissolved Pb, Cd, and Zn leached from the contaminated soil using pH 3–12 solutions by 62.3–99.9, 20–97.9, and 28.6–98.7%, respectively. In particular, the apatite was able to reduce the metal concentrations in the TCLP-extracted soil leachates to below US EPA maximum allowable levels, suggesting that apatite could be used as a cost-effective option to remediating metal-contaminated soils, wastes, and/or water. The sorption mechanisms are variable in the reactions between the apatite and dissolved Pb, Cd, and Zn. The Pb removals primarily resulted from the dissolution of the apatite followed by the precipitation of hydroxyl fluoropyromorphite. Minor otavite precipitation was observed in the interaction of the apatite with aqueous Cd, but other sorption mechanisms, such as surface complexation, ion exchange, and the formation of amorphous solids, are primarily responsible for the removal of Zn and Cd.

Global mercury emissions from gold and silver mining

Abstract: Mercury has been used m gold and silver mining since Roman times With the invention of the “patio” process in Spanish colonial America, silver and gold were produced in large scale, mostly in the Americas but also in Australia, Southeast Asia and even m England Mercury released to the biosphere due to this activity may have reached over 260,000 t from 1550 to 1930, when silver reserves in Spanish colonial America were nearly exhausted and Hg-amalgamation was replaced by the more efficient cyanidation process Exceptional increases in gold prices and the worsening of social-economic conditions m the third world in the 1970's, resulted in a new gold rush in the southern hemisphere, involving over 10 million people in all continents, Presently, Hg amalgamation is used as a major technique for gold production in the South America especially the Amazon, China, Southeast Asia and in some African countries Mercury inputs to the environment from this activity may reach up to 460 t yr−1 Compared with other anthropogenic Hg sources, gold mining is presently responsible for approximately 10% of the global anthropogenic Hg emissions, but has never been included m global models of Hg cycling in the biosphere Further, most of the Hg released to the biosphere through gold and silver mining during the last 500 ,years, roughly 300,(100 t, may still participate in the global Hg cycle through remobilization from abandoned tailings and other contaminated areas

The Freshwater Floc: A Functional Relationship of Water and Organic and Inorganic Floc Constituents Affecting Suspended Sediment Properties

Abstract: Flocculated fine-grained sediment is a complex matrix of microbial communities and organic (detritus, cellular debris and extracellular polymers) and inorganic material. Suspended flocs within any aquatic system play a significant ecological role as they can regulate the overall water quality through their physical, chemical and/or biological activity. This paper investigates the complex structural matrix of riverine flocs over a large range of magnifications using correlative microscopic techniques. The significance of floc structural characteristics [(size, shape, porosity, density, inorganic composition, organic composition (bacteria and fibrils)] on the physical (eg. transport and settling), chemical (eg. adsorbing/transforming contaminants and nutrients), and biological (eg. biotransformation and habitat development) behaviour of a floc is investigated. Results suggest that it is the floe’s internal structure that has a significant impact on controlling the above floc behaviours. This internalstructure is complex and is often dominated by the existence of a three-dimensional matrix of fibrillar material secreted by the active microbial community within the floc. This matrix, in conjunction with the inorganic and bioorganic (active and inactive) constituents of a floc, provides an intricate pore structure that may result in water being an important bound component of a floc. These complex interactive structural and functional properties of a floe are considered to influence a floe’s behaviour both physically in how it is transported or settled, chemically in how it adsorbs/transforms contaminants and nutrients, and biologically in how it develops a diverse microhabitat capable of modifying the structural, chemical and biological makeup of the floc.

Rhizosphere microbial populations in contaminated soils

Abstract: Rhizosphere microbial populations may increase bioremediation of soil contaminated with organic chemicals. A growth chamber study was conducted to evaluate rhizosphere microbial populations in contaminated and non-contaminated soil. Alfalfa (Medicago sativa L.) and alpine bluegrass (Poa alpina L.) were grown in soil containing a mixture of organic chemicals for 14 weeks. The equal millimolar mixture of hexadecane, (2,2-dimethyl-propyl)-benzene, cis-decahydronaphthalene (decalin), benzoic acid, phenanthrene, and pyrene was added at levels of 0 and 2000 mg/kg. Organic chemical degrader (OCD) populations were assessed by a Most-Probable-Number technique, and bacteria and fungi were enumerated by plate count methods. Different methods for expressing OCD rhizosphere populations were investigated to determine the effect it had on interpretation of the results. At 9 weeks, the OCD numbers were significantly higher in rhizosphere and contaminated soils than in bulk and non-contaminated soils, respectively. Alfalfa rhizosphere OCD levels were 4 × 107/g for contaminated and 6 × 106/g for non-contaminated soils. Bluegrass rhizosphere OCD levels were 1 × 107/g and 1 × 106/g in contaminated and non-contaminated soils, respectively. Selective enrichment of OCD populations was observed in contaminated rhizosphere soil. Higher numbers of OCD in contaminated rhizospheres suggest potential stimulation of bioremediation around plant roots.

Fish Diet and Mercury Exposure in a Riparian Amazonian Population

Abstract: The incorporation of mercury into the food chain and its assimilation by humans is a universally recognized potential health hazard. Studies carried out in the Amazon Basin have shown that mercury (Hg) is present in fish and in humans, however, the relation between fish diet and human exposure has received limited attention in this region. The present study focused on a small village, Brasilia Legal (3°59′00″S, 55°30′00″W), situated on the banks of the Rio Tapajos. A total of 181 fish (40 species) were captured in March, 1995 and analysed for Hg concentration. Of these, 132 fish were among species consumed by the population during the rainy season (mid-November to mid-May) and the dry season (mid-May to mid-November). Wide intra- and inter-species variations in Hg concentrations were observed. Thirty four fish (25.8% of the consumed species) had levels above 0.5 µg/g Hg fresh weight; all were among the piscivorous and omnivorous species. Hair Hg concentrations (HHg), showed that villagers with a high fish diet (n=31; median HHg=16.1 µg/g) and mixed fish diet (n=36; median HHg=14.8 µg/g) had significantly higher HHg concentrations compared to the low fish diet group (n=29; mean HHg=7.8 µg/g). Time series function of HHg measurements, made for 26 persons with over 24 cm of hair, revealed sinusoidal variations, with peaks during the rainy season and troughs during the low water period, paralleling the seasonal shift in dietary habits. Piscivorous and omnivorous fish species, with higher mercury levels, are the main component of the fish diet during the rainy season, while herbivorous fish species predominate during the dry season. Preventive actions should take into account the risk to human health, particularly for fetal and neonatal development, the importance of fish in the riparian diet, the wide intra- and inter -species variations in mercury content and seasonal fluctuations in diet.

Phosphate-enhanced movement of arsenic out of lead arsenate-contaminated topsoil and through uncontaminated subsoil

Abstract: Past use of lead arsenate insecticides has resulted in elevated concentrations of lead (Pb) andarsenic (As) in topsoils of many existing and former deciduous tree fruit orchard sites throughoutthe world. Application of phosphate (PO4)-containing fertilizers to these soils can increase soil Assolubility, phytoavailability and downward mobility. A laboratory soil column experiment wasconducted to determine if As released by phosphate additions to a topsoil artificially contaminatedwith lead arsenate (1.65 mmol total Pb/kg; 1.10 mmol total As/kg) would be appreciably resorbedby the underlying uncontaminated subsoil. Treatments were a factorial combination of topsoilamendment with monoammonium phosphate (MAP, 0 or 16.67 mmol PO4/kg), and amount ofleaching (1, 5 and 10 pore volume displacements (PVD) with distilled water under saturated flowconditions). Soil As decreased in the topsoil with increasing amount of leaching and increased inthe subsoil. Addition of MAP substantially increased loss of topsoil. As, promoted As transportinto and through the subsoil, and increased dissolved As concentrations in the column leachates.After 10 PVDs, 95% of the initial soil As remained in the -MAP columns, while 56% of the initialsoil As remained the +MAP columns. Dissolved Pb concentrations were <0.05 µmol/Lin all column leachates. The data are consistent with a mechanism of PO4-enhanced release of Asin the topsoil and subsequent promotion of As movement through the subsoil by continuingcompetition of dissolved As and PO4 for ion adsorption sites. The experimental results indicatethat use of PO4-containing fertilizers on lead arsenate-contaminated soils has the potential togreatly enhance downward movement of soil As.

Ammonia stripping as a pretreatment for landfill leachate

Abstract: The effectiveness of ammonia stripping at different air flow rates (0, 1 and 5 L min−1) and lime dosages (0 and 10 000 mg L−1 calcium hydroxide) was investigated in aeration tanks in a laboratory as a pretreatment to remove ammoniacal-nitrogen and organic load (COD) in landfill leachate. Ammoniacal-nitrogen removal at 20°C after one day was 70% for 0 L min−1, 81% for 1 L min−1 and 90% for 5 L min−1 regardless of the origin of leachate. Ammonia loss was mainly due to desorption through water surface. The levels of phosphorus and COD were only reduced by lime precipitation, with 85% and 93% phosphorus removal and 24% and 47% COD removed for leachate from the Junk Bay Landfill (JB) and Gin Drinkers' Bay Landfill (GDB) respectively. The highly significant difference (P<0.05) of COD removal between JB and GDB might be due to the different age of the two landfills studied. Leachate quality and configuration of the treatment reactor were important factors affecting the efficiency of ammonia removal by stripping processes.

Effects of Bulk Density on Sediment Erosion Rates

Abstract: By means of a recently developed flume, sediment erosion rates as a function of shear stress and with depth in the sediments have previously been determined for relatively undisturbed sediments from several rivers and lakes. These experiments demonstrated that erosion rates depended on at least the following parameters: bulk density (or water content) of the sediments, particle size distribution as well as mean particle size, mineralogy, organic content, and amounts and sizes of gas bubbles. In order to isolate and quantify the effects of one of these parameters, the bulk density, additional experiments have been done with reconstructed sediments and are reported here. These experiments first determined the bulk density as a function of depth in the sediments for three different types of sediments, for three different sediment core lengths, and for compaction times varying from 1 to 60 days. For each of these sediment cores and compaction times, the erosion rate as a function of shear stress and with depth was then measured and related to the local bulk density of the sediment The results demonstrate that, for a particular sediment and shear stress, the erosion rate is a unique function of the bulk density and can be expressed as a product of powers of the shear stress and bulk density.

Four Thousand Years of Atmospheric Pb, Cd and Zn Deposition Recorded by the Ombrotrophic Peat Bog of Penido Vello (Northwestern Spain)

Abstract: The Northwestern Iberian Peninsula is a mid-latitude oceanic region with areas where different types of bogs are frequent or abundant. The ombrotrophic nature of some bogs make them suitable for the study of accumulation patterns of heavy metals. One of these bogs, Penido Vello, was sampled to a depth of 2.5 m and analyzed in detail for its physico-chemical properties and Pb, Zn and Cd concentrations. Ash and organic carbon content, Ca/Mg molar ratios and a number of other characteristics support an ombrotrophic interpretation of the core. Concentrations of Pb, Zn and Cd were measured, showing important variations in the core. While Zn and Cd are concentrated mainly in the upper sections of the core with minor changes with depth, the Pb profile shows significant peaks in the deeper layers suggesting pre-industrial atmospheric pollution. Enrichment factors (EFs) calculated by normalising to Al correlate well with those calculated by normalising to Ti. Maximum EFs are 33, 56 and 52 for Pb, Zn and Cd respectively. While for Pb these values are comparable to those obtained by other authors, maximum Zn EFs are greater than those mentioned in the literature and may be attributed to the emissions of a nearby coal-burning power plant. At least for Pb the accumulation pattern suggests that atmospheric pollution can be dated back some 2800 years, and that pollution increased steadily since the Iron Age to reach considerably elevated levels, up to 5 times the ‘background’, during the Roman Empire. Changes in Pb emissions through time are in good accord with the prehistorical and historical record of the Iberian Peninsula.

Simultaneous sorption of Cd, Cu, Ni, Zn, Pb, and Cr on soils treated with sewage sludge supernatant

Abstract: Disposal of sewage sludge creates the potential for heavy metal accumulation in the environment. This study assessed nine soils currently used as Dedicated Land Disposal units (DLDs) for treatment and disposal of municipal sewage sludge in the vicinity of Sacramento, California. Adsorption characteristics of these soils for Cd, Cu, Ni, Zn, Pb, and Cr were studied by simultaneously mixing these elements in the range of 0–50μmol L−1 with sludge supernatant and reacting with the soil using a soil:supernatant ratio of 1:30, pH=4.5 or 6.5, and constant ionic strength (0.01M Na-acetate). The concentration of metals in the supernatant was determined after a 24 hr equilibration period. Adsorption isotherms showed that metal sorption was linearly related to its concentration in the supernatant solution. The distribution coefficient K d (K d = concentration on solid phase/concentration in solution phase) was computed as the slope of the sorption isotherm. The distribution coefficients were significantly correlated to soil organic matter content for Ni, Cu, Cd, and Pb at pH 4.5 and for Ni, Cu, Zn, and Cd at pH 6.5. There was also a correlation between K d and soil specific surface area but no relationship to other soil properties such as CEC, clay content, and noncrystalline Fe and Al materials. Therefore, soil organic carbon and surface area appear to be the most important soil properties influencing metal adsorption through formation of organo-metal complexes. The K d values for all elements were higher at pH 6.5 than at 4.5. Selectivity between metals resulted in the following metal affinities based on their K d values: Pb>Cu>Zn>Ni>Cd≈Cr at pH 4.5 and Pb>Cu≈Zn>Cd>Ni>Cr at pH 6.5.

Stable Isotope and Concentration Records of Atmospheric Lead Pollution in Peat and Lake Sediments in Sweden

Abstract: We compare lead concentration and stable lead isotope analyses from three peat bog and three lake sediment records in Sweden. Radiocarbon dated stratigraphies give evidence that trends in the concentration of Pb in the peat and sediment cores are very similar, and follow the general outline of historical global Pb production over several thousand years. Due to the large difference in the 206Pb/207Pb ratio between Sweden, about 1.5, and continental Europe (excluding Fennoscandia), ≤1.2, it is possible to distinguish external sources of Pb to Sweden. In the lake sediments, profiles of 206Pb/207Pb ratio mirror the Pb concentration until 1000 AD; increasing concentration is accompanied by decreasing ratios. After 1000 AD the ratio varies little at about 1.2 in sediments, because of the near total dominance of pollutant Pb. There is a further decline in the Pb ratio to about 1.14 in this century as a result of the addition of alkyl-Pb in petrol. The Pb concentration profiles in the peat match the lakes, but the isotope profiles do not. During the fen-to-bog transition there is a rapid decline in the 206Pb/207Pb ratio from >1.3 to about 1.2, and the ratio continues to decline to the present. We hypothesise that this is because externally-derived Pb from long-range transport of soil dust and atmospheric pollution has always been more important in the ombrotrophic peat than in lakes, which have a greater influx of catchment-derived Pb.

Assessing benthic impacts of organic enrichment from marine aquaculture

Abstract: Benthic observations were carried out at 22 stations in the Western Isles region of the Bay of Fundy on the east coast of Canada to evaluate impacts at salmon aquaculture sites. Eleven sites were located under salmon net-pens and 11 sites (reference or control locations) were at distances > 50 m from net-pens. Total S- and redox potential (Eh) in surface sediment and benthic O2 uptake and CO2 release were sensitive indicators of benthic organic enrichment. High variability between replicate measurements of sediment gas exchange could reflect spatial patchiness in sedimentation of fecal waste and food pellets under fish pens. Biomass of deposit feeders was significantly increased at cage sites but total macrofauna biomass was similar at cage and reference locations. Surface sediment water content, modal grain size, pore water salinity and sulfate, and total biomass of macrofauna were the least sensitive indicators of enrichment.

Barium and Other Trace Metals as Indicators of Vehicle Emissions

Abstract: In the Siena urban environment, unwashed Q. ilex leaves had a significantly higher Al, Ba, Cr, Fe, Mn, Na, Ni, Pb, Ti, and V content than samples from a neighbouring Mediterranean maquis. Significant relationships between element pairs indicated both the presence of metals emitted by motor vehicles and lithophilic elements, presumably from soil particles, resuspended by wind or turbulence generated by traffic. In order to minimize the effects of soil dust contamination and to seek clues to the metal sources, the estimated substrate contribution was subtracted from the raw concentrations of elements in Q. ilex leaves. Normalization for local soil composition confirmed that automotive emissions are the principal source of pollution in Siena. On the basis of a very significant relationship between normalized concentrations of Pb and Ba and the presence of the latter element in diesel and unleaded gasoline, Ba was recognized as a valuable tracer for vehicle emissions, in the place of Pb.

A Comparison of the Historical Lead Pollution Records in Peat and Freshwater Lake Sediments from Central Scotland

Abstract: The concentrations, inventories, fluxes and isotopic composition of Pb in four 210Pb-dated cores from the raised Flanders Moss peat bog are compared with corresponding data for two sediment cores from Loch Lomond, also in central Scotland. Although the inventories and fluxes of Pb revealed by the peat record for the past few hundred years are generally lower, the isotopic records are in good agreement, confirming a prevailing 206Pb/207Pb ratio of 1.17 for anthropogenic ("industrial") Pb in the atmosphere prior to the introduction of leaded petrol in the 1920s. The 206Pb-depleted nature of the latter has resulted in a decline of about -0.04 to -0.05 in the 206Pb/207Pb ratio of deposited Pb for both peat and lake sediments. Despite the time-resolution limitations of the peat record, car exhaust emissions of Pb appear to have contributed 35-50% over the past 20 years, 15-30% over the past 75 years, but no more than 27% overall to the peat Pb burden. The finding that 67-85% of anthropogenic Pb in the peat was apparently deposited post-1900 compared with 51% for the Loch Lomond sediments could be due to geographical variations in atmospheric deposition of Pb, other additional inputs to the sediments, or perhaps to some post-depositional loss of Pb from peat, although the integrity of the 206Pb/207Pb record does argue against any significant vertical mobility of Pb in peat.

Comparison of Hg and Pb fluxes to hummocks and hollows of ombrotrophic big heath bog and to nearby Sargent Mt. Pond, Maine, USA

Abstract: Two hummock cores (separated by I m), two hollow cores (separated by 1 m and both within 5 m of the hummock) from ombrotrophic Big Heath,and a single core from Sargent Mountain Pond (12 km north-northeast of the bog), Mt. Desert Island, Acadia National Park Maine, USA were collected in 1983 and dated using 210 Pb and analyzed for a suite of major and trace metals. The hummock cores correspond closely in terms of dating profiles, concentrations of Hg and Pb, and thus trends and values for accumulation rates. The hollow cores agree generally with each other but give more subdued peaks in concentration and lower integrated anthropogenic burdens of Hg and Pb and 50% lower unsupported 210 Pb than the hummock cores. Σ 210 Pb uns. (Bq/cm 2 ), ΣHg anth. (ng/cm 2 ), and ΣPb anth. (μg/cm 2 ) for the two hummock cores were 0.744 and 0.773, ≃ 130 and 130 (ng/cm 2 ), and ≃ 159 and 138 (μg/cm 2 ), respectively. The values for Sargent Mountain Pond were 0.411, 269, and 72, respectively. Hummock cores agree closely with the lake sediment core with respect to timing of maximum accumulation rates which occurred in the 1970s; Background atmospheric deposition rates of Hg and Pb to coastal Maine appear to have been about 2.5 to 3 ng/cm 2 /yr and <0.2 μg/cm 2 /yr, respectively. Atmospheric deposition of Hg and Pb increased to as much as 20 ng/cm 2 /yr and 2 μg/cm 2 /yr, respectively, by the 1970s and has decreased since then. Probably more than 50% of the Hg and Pb are deposited in dry and occult deposition.

Lead-210 Age Dating of Three Peat Cores in the Jura Mountains, Switzerland

Abstract: Peat cores collected from three sites in the Jura region of Switzerland, La Tourbiere des Genevez, Etang de la Gruere and Praz Rodet, were analysed for the fallout radionuclides 210Pb, 137Cs, 134Cs and 241Am, and the minerogenic radionuclide 226Ra. Unsupported 210Pb inventories of the cores were all in the range 3900-4784 Bq m-2 and are consistent with their having largely retained the atmospheric flux (ca. 130 Bq m-2y-1). In contrast, comparisons with earlier (1986) cores from these sites suggest that there have been significant losses of fallout 137Cs. Samples from all three sites had low but significant levels of supported 210Pb (226Ra) activity, the origin of which is presumably wind blown soil dust. 210Pb dates calculated using the CRS model were independently validated by 241Am and pollen stratigraphy. The core from La Tourbiere des Genevez had a fairly conventional 210Pb activity versus depth profile indicating more or less constant net accumulation during the past 100 years. At the other two sites however the 210Pb profiles contained significant deviations from simple exponential decline that may record episodes in the bog during which there were major variations in the net dry mass accumulation rate. These episodes are dated 1930-50 (Etang de la Gruere) and 1960-80 (Praz Rodet). Although the depths at which total 210Pb reaches equilibrium with the supporting 226Ra range widely, from ca.37 cm in Etang de la Gruere to ca.60 cm in Praz Rodet, mean net dry mass accumulation rates for the past 100 years are remarkably similar, the values for all three sites are in the range 0.023-0.027 g cm-2y-1.

Lead in Three Peat Bog Profiles, Jura Mountains, Switzerland: Enrichment Factors, Isotopic Composition, and Chronology of Atmospheric Deposition

Abstract: One metre cores were taken from three peat bogs in the Jura Mountains of Switzerland: Etang de la Gruere (EGr), La Tourbiere des Genevez (TGe), and Praz Rodet (PRd). Dried peat samples were analyzed for lead (Pb) using the EMMA XRF and scandium (Sc) using INAA. Enrichment factors (EF) were calculated by normalizing to the background Pb/Sc ratio at EGr. Age dates were obtained using 210Pb (CRS Model) and confirmed using pollen chronostratigraphic markers in replicate cores. The isotopic composition of Pb in selected peat samples from EGr and TGe was determined using TIMS. Two pronounced peaks in Pb EF occur in the uppermost sections of all three bogs: the upper one corresponds to the late 1960's to late 1970's and the lower one to approximately 1900 to 1920. At EGr, sample 2f5 (11 cm, 86 µg/g Pb, EF = 91, and dated at A.D. 1967 ± 2) has an isotopic composition similar to that of leaded gasoline used in Berne in the 1970's. For comparison, the older peak at EGr (sample 2fl 1 at 29 cm, 84 µg/g Pb, EF = 79 and dated at A.D. 1905 ± 6) is significantly different. In contrast to these two samples, the isotopic composition of sample 2fl 5 (41 cm, 30 µg/g Pb, EF = 13 and pre-dating ca. A.D. 1800) approaches the present day "average terrestrial lead" and is likely to be predominately lithogenic. Therefore, the isotopic data show that the Pb introduced to the bog from leaded gasoline has not penetrated to this depth in the profile. A simple mass balance using the measured Pb concentrations and the isotopic compositions shows that vertical migration of gasoline Pb cannot explain the deeper, older peak in Pb EF. A more likely explanation is that the older peak reflects the rates of atmospheric Pb deposition during the first two decades of the 20th century. Taken together, the Pb concentrations, age dates, and isotopic data suggest that these peat profiles have preserved the record of changing rates of atmospheric Pb deposition. In addition, the results indicate that the isotopic composition of Pb deposited on the surface of the bogs gradually shifted away from lithogenic ratios as long ago as the middle of the 19th century, a change which clearly pre-dates the introduction of leaded gasoline.

Long-term transformations and redistribution of potentially toxic heavy metals in arid-zone soils incubated: I. Under saturated conditions

Abstract: Solid-phase transformations of Cd, Cu, Cr, Ni and Zn, added as soluble salts at several levels to two arid-zone soils, were studied over a period of one year. The soils were maintained under a saturated-paste regime and sampled periodically. A selective sequential dissolution procedure was employed to determine the changes in metal distribution among six operationally defined solid-phase fractions. A function, Uts was introduced to measure the fractional attainment of equilibrium of the soils following a perturbation. The direction and rate of redistribution of the added metals in the soils were affected by the nature of the metal, the soil properties and the metal loading level. Cd added to the soils was transferred from the exchangeable (EXC) into the carbonate (CARB) fraction. When soluble Cu, Cr, Ni and Zn were added at low loading levels, metals were transferred from the reducible oxides(RO) bound and easily reducible oxides (ERO) bound fractions and the EXC fraction, into the CARB fraction. However, at the higher loading level, metals were transferred from the EXC and CARB fractions into the organic matter bound (OM), ERO and RO fractions. The Uts function approached lower values as incubation continued but remained removed from 1. The overall flux of metals among fractions was the combined result of the readjustment of the metals in the native soil to changing conditions due to saturation, and the transfer of added soluble metals to the less labile fractions.

highway stormwater runoff quality: development of surrogate parameter relationships

Abstract: The development of relationships for predicting the impact of highway stormwater runoff is described. The predictive relationships are regression-based equations reflecting variations in the magnitude of the constituents of interest. The objective is to identify a subset of constituents that can be used as surrogates for the remaining constituents as a means of decreasing the costs of collection and measurement of highway stormwater runoff quality data.

Atmospheric Lead Deposition from 12,400 to ca. 2,000 yrs BP in a Peat Bog Profile, Jura Mountains, Switzerland

Abstract: The bog at Etang de la Gruere (Jura Mountains, Switzerland) consists of 420 cm of Sphagnum-dominated bog peat overlying 230 cm of Carex-dominated fen peat. One hundred cm below the bog surface, there is a pronounced peak in lead (Pb) concentration (approx. 10 µg/g) which has been dated at 2110 ± 30 BP and can be attributed to Roman Pb mining and smelting.

Remobilization of trace elements from polluted anoxic sediments after resuspension in oxic water

Abstract: Polluted sediments are periodically subjected to resuspension processes resulting from natural events (e.g. storms, strong waves) as well as from anthropogenically induced activities (e.g. dredging). The main part of the resuspended material is initially in an anoxic state and will be reoxidized more or less quickly in the oxic water column.

Accumulation of inorganic and organic pollutants by biofilms in the aquatic environment

Abstract: In a partly urbanized catchment to the south of Trier, Germany, short term variations in river sediment compounds as well as the bioaccumulation of pollutants on surface associated microbial coatings (biofilms) were investigated weekly during a period of six months. Concentrations of selected heavy metals (Cu, Zn, Pb), polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB) and for microbial characterisation protein, carbohydrate and uronic acid were analyzed. Sorption processes on biofilms were determined by temporal variations in pollutants and microbial parameters and through the comparison of sorbed substances in biofilms and sediments. The results show, that sorption events on biofilms play an important and dynamic role in spring and summer for transport and accumulation of the investigated pollutants in the aquatic environment. The amount of pollutants sorbed on sediment particles is not only dependent on the particulate bound or solved pollutants in the river water, but is strongly controlled by the changing conditions of the biofilms.

Comparative assessment of toxicity of phenol, formaldehyde, and industrial wastewater to aquatic organisms

Abstract: The toxicity of pure phenol, formaldehyde, and industrial wastewater, containing phenol and formaldehyde, from a resin production plant was evaluated using aquatic organisms from different taxonomic groups Test organisms included mixed bacterial culture, unicellular green algae Scenedesmus quadricauda (Turp) Breb, crustacea Daphnia pulex de Geer (daphnids), and fish Oncorhynchus mykiss Call, 1990 (rainbow trout)

Follow-up of mercury levels in fish, human hair and urine in the Madeira and Tapajós basins, Amazon, Brazil

Abstract: Informal economy of gold mining has contaminated some important river basins in Amazon. Follow-up studies on critical compartments showed some areas with high Hg levels in fish as well as in human hair samples. Average Hg in piscivorous fish in the Madeira river itself was 846 ppb (N=284) with a maximum of 3921 ppb. Mercury in fish from non polluted areas in this basin shows high variability, even for single species. A seasonal variation in Hg content was observed, with higher values at the end of the dry season. In the upper Tapajos basin comparable values were found for fish but with a definite decreasing trend downstream. Average value for piscivorous fish in the whole Tapajos basin is 482 ppb (N=122) with a maximum value of 3770 ppb. Hair Hg was higher in fishing villages in the Tapajos (average: 17 ppm; with N=432 and maximum value of 176 ppm) than in the Madeira (average: 9 ppm; N=169; maximum 71 ppm), and data from some areas of the Tapajos suggest a decrease with time. Mercury was much higher in urine of goldshop workers in Santarem (low Tapajos) than in Alta Floresta (high Tapajos) and show a decreasing trend in both cases, probably related to the significant decline in gold mining activities during the study period (1986-1994).

Transport of bacteria and bacteriophages in irrigated effluent into and through an alluvial gravel aquifer

Abstract: The movement of bacteria and bacteriophages into and through an alluvial gravel aquifer was investigated at a bordered strip effluent irrigation scheme near Christchurch, New Zealand. Irrigation of one set of strips resulted in the contamination, by faecal coliform bacteria, and somatic and F-RNA coliphages, of two bores, approximately 60 m and 445 m downstream of the centre of the strips. F-RNA coliphages showed the greatest attenuation between the soil surface and the first bore, and faecal coliforms the least. Estimates of percolation times through the 13 m vadoze zone (based on times to peak concentration in the groundwater) ranged from 1.6 to 10.5 hr, with travel times for the bacteriophages being 1.4–3.4 times longer than for the bacteria. Injection of oxidation pond effluent containing rhodamine WT dye into the first bore resulted in contamination of the second bore (385 m downstream) by the dye, F-RNA coliphages, and faecal coliforms. In a second experiment, injection (into the same bore) of a mixture of phage MS-2, the bacterial tracerEscherichia coli J6-2, and rhodamine WT dye, produced a similar result in the downstream bore and in a newly-installed bore, 401 m downstream. In both injection experiments, the phages exhibited the shortest times to peak concentrations in the downstream bore(s), followed by the bacteria, and then the dye. Attenuation of the bacteria and phages was similar, but the microbes exhibited 100-fold greater reduction than the dye. Flow direction and longitudinal dispersivity were determined in a preliminary analysis using an idealised 2-D dispersion model. This information, and other measured and reported data, were then used as inputs in a 3-D dispersion model. The predicted concentration curves were matched to the observed curves by trial and error adjustment of the decay constant (λ). The best curve fits were obtained with λ values higher than those reported elsewhere. It is suggested that many of the reported microbial decay values underestimate microbial reductions in groundwater because they do not account for other removal mechanisms, such as filtration, sedimentation and irreversible adsorption.