Microbial dechlorination of hexachlorobenzene in a sedimentation area of the Rhine River

In sedimentation areas of polluted rivers, microbial dechlorination of chlorinated aromatics may be of great environmental significance. This reaction may take place in the deeper, anaerobic sediment layers and involves replacement of a chlorine in the pollutant molecule by hydrogen. In this study, the microbial dechlorination of hexachlorobenzene in a sedimentation area of the Rhine River is evaluated by using Rhine water pollution data, concentrations in historical sediment samples and in recent sediment cores, and the results of anaerobic laboratory incubations with Lake Ketelmeer sediment. The various data support the conclusion that microbial dechlorination of hexachlorobenzene has occurred in the anaerobic sediment. Up to 80% of the hexachlorobenzene deposited in the early 1970s has been dechlorinated. The maximum half-life of hexachlorobenzene in the sediment is found to be 7 years.Two limitations of microbially mediated dechlorination in the natural environment have become clear. In the first place, a residual concentration of about 40 g/kg remains unaltered in the sediment or transformation rates of this fraction are at least extremely low. Secondly, the lower chlorinated benzenes that are produced from hexachlorobenzene appear to accumulate in the anaerobic sediment.     

Reproductive success of Coregonus species in areas loaded by effluents from paper mills

The annual reproductive success of Coregonus albula and C. lavaretus in some polluted and clean areas of the central parts of L. Päijänne was estimated in 1981–90 on the basis of occurrence of larvae in shore seine and seine net samples after the ice melted. In polluted areas (0–5 km from Kaipola paper mill) larvae of coregonids were found only occasionally. In semipolluted areas (5–15 km from the paper mill) the densities of larvae were usually less than 0.1 ind m^–2. In clean areas the mean densities of larvae ranged from 0.45 to 5.34 inds m^–2. A relatively high reproductive success of vendace was observed in 1984–85, moderate success in 1982–83 and low success in 1986–90. The larvae of whitefish were scarce in both polluted and semipolluted areas and their density ranged from 0.01 to 0.15 ind m^–2 in clean shores. The highest density was observed in 1989. In spite of the improvement of the quality of water in the area in the 1980s, the reproductive success of coregonids is still low in a great part of the basin which may depend on adverse oxygen conditions of the hypolimnion and sediment and the toxic effects of the effluents.     

The anthropogenically stressed periphyton of Lake Orta,Italy

A long history of discharge of industrial wastes has left Lake Orta contaminated with high concentrations of acid, ammonia and copper. To study the effect of this chronic pollution on periphyton, I sampled epilithic algae and associated invertebrates at several sites from 1987 to 1988. Although biomass varied both spatially and seasonally, the taxonomic composition of these communities remained relatively stable. The dominant algae were chlorophytes and the dominant invertebrates were trichopterans. Comparisons with nearby unpolluted Lake Mergozzo, and with general equations developed for neutral lakes in North America indicate that these anthropogenic stresses are more clearly reflected by changes in the taxonomic composition and size distribution of the community than by changes in its biomass.Contribution No 375 from the Groupe de recherches en Ecologie des Eaux douces, Université de Montréal.Contribution No 375 from the Groupe de recherches en Ecologie des Eaux douces, Université de Montréal.     

Effects of lindane and deltamethrin on zooplankton communities of experimental ponds

Two insecticides, lindane (321 µg l^–1) and deltamethrin (13 µg l^–1) were employed in a four mesocosm experiment (two ponds of 10 m³ and two of 16 m³) to asses the impact of water pollution by pesticides. Resistance of the different zooplankton species was variable and depended upon both the group and the insecticide concentration. No effect of lindane was observed on macrozooplancton such as Cladocera and Copepoda. In the deltamethrin-treated pond, all species of zooplankton were found dead a day after the treatment. The microzooplankton (Rotifera and copepod nauplii) were highly susceptible to both insecticides. Although the larvae of Chaoborus were present in the ponds after the treatments, their density decreased (less than 1 individual l^–1). The elimination of filter-feeding zooplankton by deltamethrin was followed by an increase of the concentration of chlorophyll a in the post-treatment period. Two months later the original zooplankton population recovered, with the addition of a new and dominant species: Ceriodaphnia reticulata.     

Plastics from household waste as a source of heavy metal pollution

An inventory study to the levels of cadmium in the plastic component of household waste was carried out utilizing INAA as the analytical technique. In a 2-h irradiation, 2-d decay, and 1-h measurement, protocol adequate sensitivities could be obtained for Cd, but also for a group of other metals: Cr, Co, Ni, Cu, Sr, Zn, As, Se, Mo, Sn, Sb, Ba, and Hg. Red-, orange-, and yellow-colored plastics either contain Cd at high levels (over 1000 mg/kg) or have relatively low Cd concentrations (<50 mg/kg). High concentrations were also occasionally found for Sr, Se, Ba, Sb, and Hg. INAA appeared very well to be routinely usable for such analysis because of the absence of a destruction step, adequate sensitivity, high accuracy, and multielement results.     

Plant Resistance Mechanisms to Air Pollutants: Rhythms in Ascorbic Acid Production During Growth Under Ozone Stress

Relationships between ozone (O₃) tolerance and leaf ascorbic acid concentrations in 0₃-susceptible (O₃S) 'Hark' and O₃-resistant (O₃R) 'Hood'soybean, Glycine max (L.) Merr., cultivars were examined with high-performance liquid chromatography (HPLC). Leaf samples were analyzed at 4 h intervals during a 24 h period. Soybean cultivars grown in the greenhouse with charcoal filtered (CF) and nonfiltered (NF) air showed daily oscillations in ascorbic acid production. Highest ascorbic acid levels in leaves during light coincided with highest concentrations of photochemical oxidants in the atmosphere at 2:00 p.m. The resistant genotype produced more ascorbic acid in its trifoliate leaves than did the corresponding susceptible genotype. Under CF air (an O₃-reduced environment) O₃-S and O₃-R cultivars showed rhythms in ascorbic acid production. In NF air (an O₃ stress environment) the O₃-R cultivar alone showed rhythms in ascorbic acid production. Results indicated that superior O₃ tolerance in the Hood soybean cultivar (compared with Hark) was associated with a greater increase in endogenous levels of ascorbic acid. Ascorbic acid may scavenge free radicals and thereby protect cells from injury by O₃ or other oxyradical products. Plants defend themselves against photochemical oxidant stress, such as O₃, by several mechanisms. Experimental evidence indicates that antioxidant defense systems existing in plant tissues may function to protect cellular components from deleterious effects of photochemical oxidants through endogenous and exogenous controls.     

A model system to study the effect of SO2 on plant cells

Fumigation with 0.05 μl/l SO₂ decreased the germination rate of fern spores ofAdiantum capillus-veneris L. and influenced greatly the rhizoid development for abnormities such as apical swelling. Even 10 μM sulfite derived from SO₂ fumigation was influential. These SO₂ effects on germination and following rhizoid development were proved to be independent of each other, and could be induced separately by pulse treatment with K₂SO₃ solution given at different timings. According to the analysis using a time-lapse video recorder, growth retardation and apical swelling of rhizoid occurred just after the application of sulfite. It became clear that the fern gametophytes are very sensitive to SO₂, (that is sulfite) as compared with other plants used for air pollutant experiments so far.     

Sulfur accumulation in western wheatgrass exposed to three controlled SO2 concentrations

Summary Sulfur concentrations of western wheatgrass tillers and individual leaves were measured from plants exposed to four SO₂ concentrations (9, 52, 105 and 183 g·m^–3). Sulfur concentration of plants was a linear function of either time of exposure or concentration.Young leaves and the youngest portion of leaves contained less sulfur than their older counterparts irregardless of whether they had or had not been exposed to SO₂.Current hypotheses which relate plant sensitivity to amount of sulfur taken up do not apply for western wheatgrass.     

Evaluation of antibiotic resistance analysis and ribotyping for identification of faecal pollution sources in an urban watershed

AIMS: The accuracy of ribotyping and antibiotic resistance analysis (ARA) for prediction of sources of faecal bacterial pollution in an urban southern California watershed was determined using blinded proficiency samples. METHODS AND RESULTS: Antibiotic resistance patterns and HindIII ribotypes of Escherichia coli (n = 997), and antibiotic resistance patterns of Enterococcus spp. (n = 3657) were used to construct libraries from sewage samples and from faeces of seagulls, dogs, cats, horses and humans within the watershed. The three libraries were analysed to determine the accuracy of host source prediction. The internal accuracy of the libraries (average rate of correct classification, ARCC) with six source categories was 44% for E. coli ARA, 69% for E. coli ribotyping and 48% for Enterococcus ARA. Each library's predictive ability towards isolates that were not part of the library was determined using a blinded proficiency panel of 97 E. coli and 99 Enterococcus isolates. Twenty-eight per cent (by ARA) and 27% (by ribotyping) of the E. coli proficiency isolates were assigned to the correct source category. Sixteen per cent were assigned to the same source category by both methods, and 6% were assigned to the correct category. Addition of 2480 E. coli isolates to the ARA library did not improve the ARCC or proficiency accuracy. In contrast, 45% of Enterococcus proficiency isolates were correctly identified by ARA. CONCLUSIONS: None of the methods performed well enough on the proficiency panel to be judged ready for application to environmental samples. SIGNIFICANCE AND IMPACT OF THE STUDY: Most microbial source tracking (MST) studies published have demonstrated library accuracy solely by the internal ARCC measurement. Low rates of correct classification for E. coli proficiency isolates compared with the ARCCs of the libraries indicate that testing of bacteria from samples that are not represented in the library, such as blinded proficiency samples, is necessary to accurately measure predictive ability. The library-based MST methods used in this study may not be suited for determination of the source(s) of faecal pollution in large, urban watersheds.     

Enumeration and speciation of enterococci found in marine and intertidal sediments and coastal water in southern California

AIMS: To determine the levels and species distribution of enterococci in intertidal and marine sediments and coastal waters at two beaches frequently in violation of bacterial water standards. METHODS AND RESULTS: Faecal indicator bacteria were extracted from sediment and enumerated using membrane filtration. High levels of enterococci were detected in intertidal sediments in a seasonal river and near a storm drain outlet. Low levels were found in marine sediments at 10 m depths and in surf zone sand. Bacterial isolates presumptively identified as Enterococcus on mEI media were speciated. The predominant species found in both water and sediment included Enterococcus faecalis, Enterococcus faecium, Enterococcus hirae, Enterococcus casseliflavus and Enterococcus mundtii. A number of isolates (11-26%) from regulatory water samples presumptively identified as enterococci on mEI media were subsequently identified as species other than Enterococcus. At both study sites, the distribution of species present in water was comparable with those in sediments and the distribution of species was similar in water samples passing and exceeding bacterial indicator standards. CONCLUSIONS: High levels of Enterococcus in intertidal sediments indicate retention and possible regrowth in this environment. SIGNIFICANCE AND IMPACT OF THE STUDY: Resuspension of enterococci that are persistent in sediments may cause beach water quality failures and calls into question the specificity of this indicator for determining recent faecal contamination.