Geochemistry of leachates from the El Fraile sulfide tailings piles in Taxco, Guerrero, southern Mexico

Leachates from the El Fraile tailings impoundment (Taxco, Mexico) were monitored every 2 months from October 2001 to August 2002 to assess the geochemical characteristics. These leachates are of interest because they are sometimes used as alternative sources of domestic water. Alternatively, they drain into the Cacalotenango creek and may represent a major source of metal contamination of surface water and sediments. Most El Fraile leachates show characteristics of Ca–SO₄, (Ca+Mg)–SO₄, Mg–SO₄ and Ca–(SO₄+HCO₃) water types and are near-neutral (pH=6.3–7.7). Some acid leachates are generated by the interaction of meteoric water with tailings during rainfall events (pH=2.4–2.5). These contain variable levels of SO₄ ²⁻ (280–29,500 mg l⁻¹) and As (<0.01–12.0 mg l⁻¹) as well as Fe (0.025–2352 mg l⁻¹), Mn (0.1–732 mg l⁻¹), Zn (<0.025–1465 mg l⁻¹) and Pb (<0.01–0.351 mg l⁻¹). Most samples show the highest metal enrichment during the dry seasons. Leachates used as domestic water typically exceed the Mexican Drinking Water Guidelines for sulfate, hardness, Fe, Mn, Pb and As, while acidic leachates exceed the Mexican Guidelines for Industrial Discharge Waters for pH, Cu, Cd and As. Speciation shows that in near-neutral solutions, metals exist mainly as free ions, sulfates and bicarbonates, while in acidic leachates they are present as sulfates and free ions. Arsenic appears as As^(V) in all samples. Thermodynamic and mineralogical evidence indicates that precipitation of Fe oxides and oxyhydroxides, clay minerals and jarosite as well as sorption by these minerals are the main processes controlling leachate chemistry. These processes occur mainly after neutralization by interaction with bedrock and equilibration with atmospheric oxygen.     

A convenient and eco-friendly way to synthesize Pt(II) and Pd(II) porphyrins in ionic liquids by microwave activation

Due to the slow rate of incorporation of inert-metal ions into free-base porphyrins compared to other transition metals, several methods have been proposed to accelerate the rate of metalation. However, these methods have disadvantages such as low yields, difficulties of purification of final products, and environmental effects. To avoid those disadvantages, we reacted Pt(II) and Pd(II) salts with H₂(TPP), H₂(TMPyP)⁴⁺, and their β-pyrrole derivatives, H₂(Br₈TPP) and H₂(Br₈TMPyP)⁴⁺, in 1-butyl-3-methylimidazolium bromide ([bmim]⁺Br⁻) under microwave irradiation. The combination of microwave heating and ionic liquids provides efficient thermal energy transfer among the porphyrins and metal salts. In addition, ionic liquids stabilize charged species as well as their intermediates, due to their high dipole moment and high boiling point. This not only shortens the reaction time but also gives high yields of products at relatively low temperatures, of about 100°C compared to conventional synthesis methods: 150°C for DMF, 190°C for DMSO. Here, we demonstrate that Pt(II)/Pt(II) metalloporphyrins are synthesized at high rates, e.g. 6–30 min for 100% metalation, with high yields of 79–93% in [bmim]⁺Br⁻ by microwave activation.     

Greenhouse effect of clusterization of CO2 and CH4 with atmospheric moisture

Carbon dioxide and methane are major compounds involved in global warming. The process of CO₂ and CH₄ molecules absorption by water clusters was investigated by the molecular dynamics method. The frequency spectra of dielectric permittivity for systems consisting of (H₂O) _n , (CO₂) _i (H₂O)₁₀ and (CH₄) _i (H₂O)₁₀ clusters mixed in various proportions were determined. The IR radiation absorption spectra of these systems were calculated and compared. Also, the radiating power of these systems was established. The capture of greenhouse gases’ molecules by ultra disperse water media reduces the ability of the media to absorb the Earth’s radiation, i.e., it reduces the greenhouse effect.     

Photosynthesis, respiration and calcification of a zooxanthellate scleractinian coral under submerged and exposed conditions

An experimental set-up was designed to investigate photosynthesis, respiration and calcification of zooxanthellate scleractinian corals under submerged and exposed conditions. The results of experiments to determine the effect of exposure to air on the metabolism of Stylophora pistillata (Esper, 1797) revealed that: (1) maximum gross photosynthesis ( p _{g max}) is 3.6 times higher in water than in air; (2) an indicator of photoadaptation (I _k ) does not reveal any difference between water and air; (3) the difference between submerged and aerial respiration is not statistically significant; (4) aerial photosynthesis–irradiance (P–I) curves display lower initial slopes (α) than aquatic P–I curves; (5) there is no calcification in air. Received: 7 February 1997 / Accepted: 4 March 1997     

Detection of metallothionein in the intestinal mucosa and brain with 109cadmium∗

Metallothionein (MT) has a great capacity of binding metal ions showing an interesting connection with metal toxicology, as a biochemical marker for environmental metal pollution.

To normal male Wistar rats (200±10 g) and other groups with ferropenic anemia, are administered 1 mg Cd/Kg/day, during 6 days, and MT labelled with the administration 2 h before sacrifice of 3 μCi ¹⁰⁹CdCl₂, also through intragastric catheter. The MT concentration in the intestinal mucosa is expressed in μg MT/g fresh tissue, being for control rats 1.4 ± 0.5; for rats administered with 6 doses of Cd 2.5 ± 0.6 (P<0.05); with ferropenic anemia 4.3±0.7 (P<0.001), and for anemic rats treated with 6 doses Cd 12 + 0,3 (P<0.001) μg MT/g fresh tissue respectively. PAGE 15% T, 2% C_Bis show for intestinal mucosa 2 MT peaks and for brain 3 MT peaks. Anemia induce MT accumulation and increases cadmium incorporation, being anemic subjects eligibles to be submitted first to control and detoxication than the rest of the population, and also MT should be studied as biochemical marker of the pollution.     

Ultrastructure of pedal muscle as a function of temperature in nacellid limpets

Temperature and mitochondrial plasticity are well studied in fishes, but little is known about this relationship in invertebrates. The effects of habitat temperature on mitochondrial ultrastructure were examined in three con-familial limpets from the Antarctic (Nacella concinna), New Zealand (Cellana ornata), and Singapore (Cellana radiata). The effects of seasonal changes in temperature were also examined in winter and summer C. ornata. Stereological methods showed that limpet pedal myocytes were 1–2 orders of magnitude smaller in diameter (≈3.5 μm) than in vertebrates, and that the diameter did not vary as a function of temperature. Mitochondrial volume density (Vv_(mt,f)) was approximately 2–4 times higher in N. concinna (0.024) than in the other species (0.01 and 0.006), which were not significantly different from each other. Mitochondrial cristae surface density (Sv_(im,mt)) was significantly lower in summer C. ornata (24.1 ± 0.50 μm² μm⁻³) than both winter C. ornata (32.3 ± 0.95 μm² μm⁻³) and N. concinna (34.3 ± 4.43 μm² μm⁻³). The surface area of mitochondrial cristae per unit fibre volume was significantly higher in N. concinna, due largely to the greater mitochondrial volume density. These results and previous studies indicate that mitochondrial proliferation in the cold is a common, but not universal response by different species from different thermal habitats. Seasonal temperature decreases on the other hand, leading preferentially to an increase in cristae surface density. Stereological measures also showed that energetic reserves, i.e. lipid droplets and glycogen in the pedal muscle changed greatly with season and species. This was most likely related to gametogenesis and spawning.     

Microbial activity and carbon, nitrogen, and phosphorus content in a subtropical seagrass estuary (Florida Bay): evidence for limited bacterial use of seagrass production

Bacterial abundance, production, and extracellular enzyme activity were determined in the shallow water column, in the epiphytic community of Thalassia testudinum, and at the sediment surface along with total carbon, nitrogen, and phosphorus in Florida Bay, a subtropical seagrass estuary. Data were statistically reduced by principle components analysis (PCA) and multidimensional scaling and related to T. testudinum leaf total phosphorus content and phytoplankton biomass. Each zone (i.e., pelagic, epiphytic, and surface sediment community) was significantly dissimilar to each other (Global R = 0.65). Pelagic aminopeptidase and sum of carbon hydrolytic enzyme (esterase, peptidase, and α- and β-glucosidase) activities ranged from 8 to 284 mg N m⁻² day⁻¹ and 113–1,671 mg C m⁻² day⁻¹, respectively, and were 1–3 orders of magnitude higher than epiphytic and sediment surface activities. Due to the phosphorus-limited nature of Florida Bay, alkaline phosphatase activity was similar between pelagic (51–710 mg P m⁻² day⁻¹) and sediment (77–224 mg P m⁻² day⁻¹) zones but lower in the epiphytes (1.1–5.2 mg P m⁻² day⁻¹). Total (and/or organic) C (111–311 g C m⁻²), N (9.4–27.2 g N m⁻²), and P (212–1,623 mg P m⁻²) content were the highest in the sediment surface and typically the lowest in the seagrass epiphytes, ranging from 0.6 to 8.7 g C m⁻², 0.02–0.99 g N m⁻², and 0.5–43.5 mg P m⁻². Unlike nutrient content and enzyme activities, bacterial production was highest in the epiphytes (8.0–235.1 mg C m⁻² day⁻¹) and sediment surface (11.5–233.2 mg C m⁻² day⁻¹) and low in the water column (1.6–85.6 mg C m⁻² day⁻¹). At an assumed 50% bacterial growth efficiency, for example, extracellular enzyme hydrolysis could supply 1.8 and 69% of epiphytic and sediment bacteria carbon demand, respectively, while pelagic bacteria could fulfill their carbon demand completely by enzyme-hydrolyzable organic matter. Similarly, previously measured T. testudinum extracellular photosynthetic carbon exudation rates could not satisfy epiphytic and sediment surface bacterial carbon demand, suggesting that epiphytic algae and microphytobenthos might provide usable substrates to support high benthic bacterial production rates. PCA revealed that T. testudinum nutrient content was related positively to epiphytic nutrient content and carbon hydrolase activity in the sediment, but unrelated to pelagic variables. Phytoplankton biomass correlated positively with all pelagic components and sediment aminopeptidase activity but negatively with epiphytic alkaline phosphatase activity. In conclusion, seagrass production and nutrient content was unrelated to pelagic bacteria activity, but did influence extracellular enzyme hydrolysis at the sediment surface and in the epiphytes. This study suggests that seagrass-derived organic matter is of secondary importance in Florida Bay and that bacteria rely primarily on algal/cyanobacteria production. Pelagic bacteria seem coupled to phytoplankton, while the benthic community appears supported by epiphytic and/or microphytobenthos production.     

Interactions between NH+4 and NO−3 uptake and assimilation: comparison of diatoms and dinoflagellates at several growth temperatures

Ammonium concentrations of ∼1 M are commonly cited as being the threshold for inhibition of NO₃ ⁻ uptake, but the applicability of this threshold to phytoplankton from different taxonomic classes has rarely been examined. Additionally, little is known about the influence of environmental variables (e.g. growth temperature) on the interaction between ambient NH₄ ⁺ and NO₃ ⁻ uptake. Four species of estuarine phytoplankton, two diatom [Chaetoceros sp., and Thalassiosira weissflogii (Grunow) Fryxell et Hasle] and two dinoflagellate [Prorocentrum minimum (Pavillard) Schiller, and Gyrodinium uncatenum Hulburt], were grown on NO₃ ⁻ at several different temperatures (4, 10, 15, or 20 °C), and the impact of NH₄ ⁺ additions on NO₃ ⁻ uptake/assimilation (non-TCA-extracted) and assimilation (TCA-extracted) was assessed. For all species at all temperatures, NO₃ ⁻ uptake/assimilation and assimilation rates decreased in a roughly exponential manner with increasing NH₄ ⁺ concentrations but were not completely inhibited even at elevated NH₄ ⁺ concentrations of 200 μM. Estimated half-inhibition concentrations (K _i) were significantly greater in the diatom species (mean ± SE; 2.70 ± 0.67 μM) than in the dinoflagellate species (1.26 ± 0.55 μM). Half-inhibition constants were positively related to temperature-limited relative growth rate although not significantly. The observed inhibition of NO₃ ⁻ uptake and assimilation, as a percentage of NO₃ ⁻ uptake in the absence of NH₄ ⁺, averaged about 80% and ranged from 49 to 100%. For all species, a significant (P < 0.001) positive correlation was found between percent inhibition of NO₃ ⁻ assimilation and temperature-limited relative growth rate. Two experiments on Chesapeake Bay phytoplankton during an April 1998 diatom bloom showed that in short-term (∼1 h) temperature manipulation experiments, percent inhibition of NO₃ ⁻ uptake/assimilation was also positively related (P = 0.05) to experimental temperature. The observed relationships between temperature-limited relative growth rate and percent inhibition of NO₃ ⁻ assimilation rates for the species tested suggest that at the enzyme level, the inhibitory mechanism of NO₃ ⁻ assimilation is similar among species, but at the whole cell level may be regulated by species-specific differences in the accumulation of internal metabolites. These findings add not only to our understanding of species-specific variability and the role of growth temperature, but also provide additional data with which to evaluate current models of NH₄ ⁺ and NO₃ ⁻ interactions. Received: 31 August 1998 / Accepted: 7 December 1998     

Green additives to enhance silica dissolution during water treatment

The effect of various environmentally friendly chemical additives on the dissolution of colloidal silica is systematically studied. These silica scale dissolvers are principally polycarboxylates with one to five –COOH groups, mixed polycarboxylates/phosphonates and aminoacids. Based on these results, an effort is made to link their dissolution performance to structural features in this structure/function study. Presence of additional groups (eg. –PO₃H₂, –NH₂, or –OH) in the dissolver molecule augments the dissolution process.     

Differential effects of UV-B radiation fluence rates on growth,photosynthesis, and phosphate metabolism in two cyanobacteria under copper toxicity

This work was undertaken to ascertain the impact of different fluence rates of ultraviolet-B (UV-B) radiation on two cyanobacterial biofertilizers, Phormidium foveolarum and Nostoc muscorum, growing under copper toxicity. Copper (2 and 5?µmol?L^?1) and high UV-B fluence rate (UV-B_H; 1.0?µmol?m^?2?s^?1) decreased the growth, pigment content, photosynthetic oxygen yield, phosphate uptake, and acid phosphatase activity in both the strains analyzed after 24 and 72?h of experiments, and combined exposure further enhanced the toxic effects. Respiration and alkaline phosphatase activities were stimulated appreciably. The damaging effect was shown on the order on pigments: phycocyanin?>?chlorophyll a?>?carotenoids, and on photosystems: whole chain photosynthetic reaction?>?photosystem II?>?photosystem I. Partial recovery in the photosystem II activity in the presence of artificial electron donors; diphenyl carbazide (DPC), hydroxylamine (NH₂OH), and manganese chloride (MnCl₂) pointed out the interruption of electron flow on the oxidation side of photosystem II. Unlike UV-B_H, low UV-B fluence rate (UV-B_L; 0.1?µmol?m^?2?s^?1), rather than causing damaging effect partially, alleviated the toxic effects of Cu. This study suggests that the cyanobacterium P. foveolarum is less sensitive against UV-B_H and excess Cu (2 and 5?µmol?L^?1), thus P. foveolarum may be used as a biofertilizer for sustainable agriculture.     

Effects of diurnal variations in phytoplankton photosynthesis obtained from natural fluorescence

Effects of diurnal variation in phytoplankton photosynthesis on estimating daily primary production (DPP) were examined using field data from Sagami Bay, Japan. DPP at 5 m depth was calculated from the continuous data of chlorophyll a (Chl a) and light intensity monitored by a natural fluorescence sensor with and without considering time-dependent changes in the photosynthesis–irradiance (P–E) relationship. Chl a could be estimated from natural fluorescence examining the variations in the quantum yield of fluorescence (φ _f) and Chl a-specific light absorption coefficient (a*_ph), and relating them to Chl a. The P–E relationship was determined by water sampling three times daily. A distinct diurnal pattern was observed for the maximum photosynthetic rate (P*_max), being maximal at noon, while periodicity of the maximum light utilization coefficient (α*) was less obvious. The actual DPP was calculated by interpolating the P–E parameters from those obtained at dawn, noon, and dusk. For comparison, DPP was calculated by fixing the P–E parameters as the constants measured at dawn, noon or dusk for a day. The difference from the actual DPP was small when the P–E parameters measured at dawn (3% on average) and noon (5%) were used as the constants for a day. The difference was largest when the values at dusk were used (−43%). The medium values of P*_max at dawn, its low values at dusk, and the fact that a major part of the DPP was produced around noon were responsible for these results. The present study demonstrates that measurement of the P–E parameters at dawn or noon can give a good estimation of DPP from natural fluorescence.     

Diet induced differences in carbon isotope fractionation between sirenians and terrestrial ungulates

Carbon isotope differences (Δ¹³C) between bioapatite and diet, collagen and diet, and bioapatite and collagen were calculated for four species of sirenians, Dugong dugon (Müller), Trichechus manatus (Linnaeus), Trichechus inunguis (Natterer), and the extinct Hydrodamalis gigas (Zimmerman). Bone and tooth samples were taken from archived materials collected from populations during the mid eighteenth century (H. gigas), between 1978 and 1984 (T. manatus, T. inunguis), and between 1997 and 1999 (D. dugon). Mean Δ¹³C values were compared with those for terrestrial ungulates, carnivores, and six species of carnivorous marine mammals (cetaceans = 1; pinnipeds = 4; mustelids = 1). Significant differences in mean δ¹³C values among species for all tissue types were detected that separated species or populations foraging on freshwater plants or attached marine macroalgae (δ¹³C values < −6‰; Δ¹³C_{bioapatite–diet} ∼14‰) from those feeding on marine seagrasses (δ¹³C values > −4‰; Δ¹³C_{bioapatite–diet} ∼11‰). Likewise, Δ¹³C_{bioapatite–collagen} values for freshwater and algal-foraging species (∼7‰) were greater than those for seagrass-foraging species (∼5‰). Variation in Δ¹³C values calculated between tissues and between tissues and diet among species may relate to the nutritional composition of a species’ diet and the extent and type of microbial fermentation that occurs during digestion of different types of plants. These results highlight the complications that can arise when making dietary interpretations without having first determined species-specific Δ¹³C_{tissue–diet} values. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mercury accumulation in soils and plants in the Almadén mining district, Spain: one of the most contaminated sites on Earth

Although mercury (Hg) mining in the Almadén district ceased in May 2002, the consequences of 2000 years of mining in the district has resulted in the dissemination of Hg into the surrounding environment where it poses an evident risk to biota and human health. This risk needs to be properly evaluated. The uptake of Hg has been found to be plant-specific. To establish the different manners in which plants absorb Hg, we carried out a survey of Hg levels in the soils and plants in the most representative habitats of this Mediterranean area and found that the Hg concentrations varied greatly and were dependent on the sample being tested (0.13–2,695 μg g⁻¹ Hg). For example, the root samples had concentrations ranging from 0.06 (Oenanthe crocata, Rumex induratus) to 1095 (Polypogon monspeliensis) μg g⁻¹ Hg, while in the leaf samples, the range was from 0.16 (Cyperus longus) to 1278 (Polypogon monspeliensis) μg g⁻¹ Hg. There are four well-differentiated patterns of Hg uptake: (1) the rate of uptake is constant, independent of Hg concentration in the soil (e.g., Pistacia lentiscus, Quercus rotundifolia); (2) after an initial linear relationship between uptake and soil concentration, no further increase in Hg_plant is observed (e.g., Asparagus acutifolius, Cistus ladanifer); (3) no increase in uptake is recorded until a threshold is surpassed, and thereafter a linear relationship between Hg_plant and Hg_soil is established (e.g., Rumex bucephalophorus, Cistus crispus); (4) there is no relationship between Hg_plant and Hg_soil (e.g., Oenanthe crocata and Cistus monspeliensis). Overall, the Hg concentrations found in plants from the Almadén district clearly reflect the importance of contamination processes throughout the study region.     

Microsensor studies of photosynthesis and respiration in larger symbiotic foraminifera. I The physico-chemical microenvironment of Marginopora vertebralis, Amphistegina lobifera and Amphisorus hemprichii

 The physico-chemical microenvironment of larger benthic foraminifera was studied with microsensors for O₂, CO₂, pH, Ca²⁺ and scalar irradiance. Under saturating light conditions, the photosynthetic activity of the endosymbiotic algae increased the O₂ up to 183% air saturation and a pH of up to 8.6 was measured at the foraminiferal shell surface. The photosynthetic CO₂ fixation decreased the CO₂ at the shell down to 4.7 μM. In the dark, the respiration of host and symbionts decreased the O₂ level to 91% air saturation and the CO₂ concentration reached up to 12 μM. pH was lowered relative to the ambient seawater pH of 8.2. The endosymbionts responded immediately to changing light conditions, resulting in dynamic changes of O₂, CO₂ and pH at the foraminiferal shell surface during experimentally imposed light–dark cycles. The dynamic concentration changes demonstrated for the first time a fast exchange of metabolic gases through the perforate, hyaline shell of Amphistegina lobifera. A diffusive boundary layer (DBL) limited the solute exchange between the foraminifera and the surrounding water. The DBL reached a thickness of 400–700 μm in stagnant water and was reduced to 100–300 μm under flow conditions. Gross photosynthesis rates were significantly higher under flow conditions (4.7 nmol O₂ cm⁻³ s⁻¹) than in stagnant water (1.6 nmol O₂ cm ⁻³ s⁻¹), whereas net photosynthesis rates were unaffected by flow conditions. The Ca²⁺ microprofiles demonstrated a spatial variation in sites of calcium uptake over the foraminiferal shells. Ca²⁺ gradients at the shell surface showed total Ca²⁺ uptake rates of 0.6 to 4.2 nmol cm⁻² h⁻¹ in A. lobifera and 1.7 to 3.6 nmol cm⁻² h⁻¹ in Marginopora vertebralis. The scattering and reflection of the foraminiferal calcite shell increased the scalar irradiance at the surface up to 205% of the incident irradiance. Transmittance measurements across the calcite shell suggest that the symbionts are shielded from higher light levels, receiving approximately 30% of the incident light for photosynthesis. Received: 6 July 1999 / Accepted: 28 April 2000     

Decrease of Pb bioavailability in solis by addition of phosphate ions

Bioavailability of Pb in contaminated soils can be highly decreased by conversion of labile Pb species into pyromorphite Pb₅(PO₄)₃Cl, induced by amendment with a phosphate source. However, PO₄ ³⁻ can be specifically adsorbed on goethite α-Fe(OH)₃ present in soils. We demonstrate that despite the stability of phosphate ions adsorbed on goethite surface, the reaction between goethite-adsorbed phosphates and aqueous lead in the presence of Cl⁻ results in crystallization of pyromorphite. Two morphological forms of pyromorphite formed on goethite were observed: 1) incrustations, indicating direct reaction of Pb and Cl ions with PO₄ ³⁻ adsorbed on goethite surface, and 2) aggregates of pyromorphite crystals indicating that the reaction with PO₄ ³⁻ ions took place in the volume of the solution. This suggests that precipitation of pyromorphite is faster than desorption of phosphates and that aqueous Pb may serve as a sink for phosphate ions by shifting the equilibrium and inducing PO₄ ³⁻ desorption.     

S–O–C isotopic picture of sulphate–methane–carbonate system in freshwater lakes from Poland. A review

Microbial oxidation of organic compounds (including methane), in freshwater sediments, may result in precipitation of carbonates, which may become an important geochemical archive of paleoenvironmental variations. Most probably low δ¹³C value in calcite in eutrophic systems results from an advanced oxidation of organic compounds in turbulent or/and sulphate-rich conditions. Likewise, high δ¹³C value in calcite from organic-rich sediments may evidence low redox potential of the freshwater system. Oxidation of methane and organic matter results in significant isotope effects in sulphates dissolved in water. Therefore, to better understand the origin of carbon isotope signal in carbonates, concentration and stable isotope measurements in dissolved sulphate (water column), bubble methane and calcite (freshwater sediments) have been carried out in 24 lakes, 2 ponds and 4 rivers in Poland. The highest concentration of sulphate has been detected in rivers (85.47 SO₄ ²⁻ mg/l) and an artificial lake (70.30 SO₄ ²⁻ mg/l) located in the extremely SO₄ ²⁻-polluted region called the “Black Triangle”. The lowest concentration of sulphate is found in dystrophic and mountain lakes (from 0.5 SO₄ ²⁻ to about 3 mg/l). The lowest δ³⁴S(SO₄ ²⁻) and δ¹⁸O(SO₄ ²⁻) values occur in unpolluted lakes in eastern Poland (−0.94 and 1.38‰, respectively). The highest S and O isotopic ratios are found in a polluted lake in western Poland (δ¹⁴S(SO₄ ²)=12.95‰) and in a dystrophic lake in eastern Poland (δ¹⁸O(SO₄ ²) = 16.15‰) respectively. It is proposed that δ³⁴SO₄ ²⁻ and (¹⁸O(SO₄ ²⁻) values in lakes represent a good tool to assess and quantify anthropogenic impact by acid precipitation and to monitor variations in the trophic state and redox processes controlled by biodegradation of organic compounds in sediments and water column. In general, increasing depth (up to 12 m) of the water column is associated with decreasing trend the δ¹³C(CH₄) value from about –35 to about –78‰. However, δ¹³C value in sedimentary calcite (δ¹³C vary from –10 to 0.5‰) shows opposite trends as compared to the corresponding methane. This is probably due to redox processes and distribution of heavy isotopes between methane and calcite. Likewise, turbulent water (river) show high δ¹³C value in methane and low δ¹³C value in calcite—this is probably due to an enhanced oxidation of methane producing ¹³C-depleted CO₂. In contrast to clean lakes, it is observed that an increase of the δ¹³C(CH₄) value occurs with increasing depth of the water column in a strongly SO₄ ²⁻-contaminated lake. This is probably due to a loss of biological buffering potential of the lake accompanied by an active oxidation of methane precursors.     

Organic nitrogen uptake and growth by the chrysophyte Aureococcus anophagefferens during a brown tide event

The quantitative importance of light-mediated, dissolved organic nitrogen (DON) utilization in relation to overall nitrogen-assimilation in Aureococcusanophagefferens Hargraves et Sieburth was assessed during a brown tide event in Shinnecock Bay, Long Island, 24 through 26 July 1995. The growth response of A. anophagefferens was maximal in organic-rich Bay water and decreased proportional to the organic:inorganic nutrient ratio of the water. Short-term uptake measurements with six nitrogenous substrates revealed that reduced nitrogen could potentially represent 95% of overall nitrogen uptake of which 70% was due to organic nitrogen alone. Potential uptake of urea by the A. anophagefferens-dominated bloom was substan tially greater than uptake of the other substrates tested during the study, contributing the largest percentage of total nitrogen uptake (58 to 64%; ρ^′ _max(urea) 4.4 μg  atom N l⁻¹ h⁻¹), followed by NH₄ ⁺ (18 to 26%; ρ′_max(NH4+) 2 μg atom N l⁻¹ h⁻¹). The combined rates of uptake of algal extract, lysine and glutamic acid contributed between 11 and 16% of total uptake, whereas NO₃ ⁻contributed 5 to 8%. Based on the kinetic determinations from this study we suggest an ecological framework for the events leading to the dominance and abundance of A. anophagefferens in coastal bays. Received: 29 March 1997 / Accepted: 24 April 1997     

Determination of volatile organic sulfur compounds in contaminated groundwater

A practical method for the quantification of total purgeable organic sulfur (POS) in highly contaminated groundwater is described. Volatile organic sulfur compounds (VOSC) are purged from the water samples by a stream of oxygen and combusted. The emerging sulfur dioxide is absorbed in H₂O₂ and converted to sulfate which is quantified by ion chromatography and reported as mass sulfur equivalent. The overall limit of quantification is 0.03 mg l⁻¹. The content of POS is balanced with the total VOSC determined by GC-AED after liquid–liquid extraction. Separate determination of the non-volatile organic sulfur compounds by direct combustion of the water sample and adsorption to charcoal yielded a mass balance of the total sulfur content. Semi-quantitative GC-MS after purge & trap accumulation revealed that the VOSC mixture is composed of C₁–C₄ alkyl sulfides. The implementation of the developed methodology for the quantification of VOSC as potential catalyst poison in a cleaning plant for groundwater contaminated with volatile haloorganics (VOX) is presented.     

Assessment of the chemical components of Famenin groundwater,western Iran

The Faminin area in the semi-arid Hamadan state, western Iran is facing a serious deficiency in groundwater resources due to an increasing demand associated with rapid population growth and agricultural development. The chemical composition of 78 well samples throughout the Faminin area was determined with the aim of evaluating the concentration of the background ions and identifying the major hydrogeochemical processes that control the groundwater chemistry. The similarity between rock and groundwater chemistries in the recharge area indicates a significant rock-water interaction. The hydrochemical types Na–HCO₃ and Na–SO₄ are the predominate forms in the groundwater, followed by water types Ca–HCO₃ and Na–Cl. The high values of electrical conductivity and high concentrations of Na⁺, Cl⁻, SO₄²⁻ and NO₃⁻ in the groundwater appeared to be caused by the dissolution of mineral phases and would appeared to be caused by anthropogenic activities, such as intense agricultural practices (application of fertilizers, irrigation practice), urban and industrial waste discharge, among others.