摘要:

Algal populations, either suspended in the water column (planktonic) or present on the walls of an enclosure (periphytic), develop differently depending upon the physical scale of the system. This study determined whether these variations altered the speciation and therefore exposure of polychlorinated biphenyls (PCBs) in estuarine mesocosms. Exposure was defined as the fraction of applied contaminant taken up by plankton after two hours. Using a three phase equilibrium model, the partitioning of a suite of PCBs within variously-sized mesocosms was predicted using laboratory derived distribution coefficients and measured levels of planktonic and periphytic algal biomass. in mesocosms having large wall surface area to volume ratios, sorption of hydrophobic PCBs to periphyton significantly decreased contaminant exposure. However, within the range of planktonic algal biomasses observed in this study, the regulation of PCB exposure was relatively invariant between variously-sized mesocosms. to minimize sorption of hydrophobic organic contaminants (HOCs) to periphyton and reduce artefacts inherent with this partitioning, we suggest using mesocosms with low wall surface area to volume ratios (less than or equal to 1). in addition, periphytic biomass should be quantified regularly and a three-phase equilibrium approach used to predict the actual exposure concentrations.

ISSN:0275-7540    

DOI:10.1080/02757549908037641

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Hypnum cupressiforme epiphytic moss and tree bark (elm and holm oak) samples have been collected in three sites of the city of Florence in the period 1995–1998. Lead, zinc, copper, and cadmium were determined by differential pulse anodic stripping voltammetry (DPASV) in about 200 samples collected at different heights above ground. A new clean-up procedure by nitrogen jet has been followed and its efficiency has been also verified by electron microscopy (SEM and ESEM techniques). Lead median contents in moss and bark samples fall within the ranges of 0.052–0.86 and 0.20–1.30 μmoles g−1(dry weight), resulting values for moss and bark are proportional to the vehicular traffic density. the increasing use of lead-free gasoline has not been followed by a decrease of lead moss concentration.

ISSN:0275-7540    

DOI:10.1080/02757549908037642

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Concentrations of HCH and DDT organochlorine insecticide residues were measured in blubber, muscle and oil samples from three specimens of river dolphins,Platanista gangetica, from the River Ganges, India. Concentrations of HCH and DDT ranged from 94 to 289 ng g−1and from 1324 to 9388 ng g−1on wet wt. basis respectively. Comparisons are made with other aquatic mammals and other studies on river dolphins.P. gangeticaappears to exhibit similar patterns of accumulation with age and with ß-HCH andp-p′-DDE being accumulated to higher levels than other HCH isomers and parent DDT and its other metabolites, respectively. These organochlorines may pose a health risk to river dolphin populations that are already showing evidence of environmental stress. Further studies are recommended.

ISSN:0275-7540    

DOI:10.1080/02757549908037643

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Seasonal and spatial changes in seston, (POC), particulate organic carbon, (PON) particulate organic nitrogen and chlorophyll-a concentrations were studied on a monthly basis in a Mediterranean shallow coastal area (Stagnone di Marsala, Western Sicily) in order to gather information on factors controlling particulate organic matter distribution and composition. Seston concentration and composition were connected to the main physicochemical and biological driving factors, such as temperature, salinity, dissolved oxygen, wind-speed and biomass of submerged vegetation. the Stagnone di Marsala is characterized by high temperatures with strong seasonality (range: 11–28°C), while values ranged from 33 to 45 salinity. Total suspended organic matter concentrations (by ignition loss) ranged from 2 mg l−1(in summer) to 12mgl−1(in winter) and chlorophyll-a concentrations from 0.02 to 2 μgl−1. Despite a low POC/PON ratios (ranging from 5 to 11), the ratio of POC to chlorophyll (CHL-a) displayed very high values (annual average of 647). the data reported in this study, highlighting the oligotrophy of the Stagnone di Marsala area, indicate that the trophic state of the basin was controlled by different degrees of wind exposure (mean monthly wind velocity at exposed sites ranged between 4.2 and 6.7 m s−1) and by gradients in vegetation cover. These two factors induced clear changes in the concentration and composition of the suspended particles, but played a different role in exposed and sheltered areas. Exposed areas with limited vegetation were characterized by large resuspension processes and wide temperature and salinity fluctuations caused by wind induced turbulence. in these areas, autotrophic biomass (as chlorophyll-a), due to phytoplankton and/or re-suspended microphytobenthos, appeared to play an important

ISSN:0275-7540    

DOI:10.1080/02757549908037644

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Above-ground biomass biomass ofMolinia caeruleafrom 36 sites throughout Britain was analysed for concentrations of elements (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn and Na), with matching analyses of soil nutrients, together with pH and LOI. Between-year and seasonal variation in the nutrients was also studied at one of the sites. the grass was found on acid sites ranging between pH 3.1 and 5.8. the soil humus content varied widely, and there were significant correlations between that and elements (N, P, K, Ca, Mg and Na) in the soil. Concentrations of calcium, magnesium, zinc and manganese in the plant material were significantly correlated with extractable levels in the soils. Between year variation in the plant nutrient concentrations at one site was of a similar order to variation between the sites. Generally there was less variation in nitrogen, phosphorus and potassium tissue levels than in calcium, magnesium, zinc and copper. Iron and sodium were the most variable. Tissue concentrations of nitrogen, phosphorus, potassium and copper declined throughout the growing season, whereas magnesium, calcium and iron built up until August/September after which a decline set in as the leaves senesced. the results are discussed in relation to the importance of standardizing the time of sampling, in comparison with concentrations of tissue levels in other plants and the growth strategy of this deciduous grass.

ISSN:0275-7540    

DOI:10.1080/02757549908037645

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Organochlorine contaminants (HCHs, DDTs and PCBs) in the muscle tissues of 12 bird species collected from Vellar River watershed areas (S. India) were determined. the accumulation pattern of organochlorine residues in birds of different feeding groups for HCHs and PCBs was: scavengers > inland piscivores > coastal piscivores > insectivores. the pattern for DDTs was: coastal piscivores > scavengers > insectivores > inland piscivores. Scavengers accumulated all the three organochlorines to a higher degree than the other groups of birds. Marked variations in the accumulation pattern by different species and individuals of birds to the same and different organochlorine residues were observed. the differences in the accumulation pattern of residues in different species of birds with similar feeding habits could be attributed to different feeding areas and because migrants are exposed to contaminants in different geographical locations. HCH residues were generally found in higher concentrations than DDTs, reflecting increasing use of HCH pesticides since banning of DDT for agriculture. Levels of PCBs were lower than in birds in developed countries. Results are discussed in relation to future pest control and industrialisation in India.

ISSN:0275-7540    

DOI:10.1080/02757549908037646

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The origin and distribution of suspended organic matter, the trophic features and the stable carbon isotopic composition of particulate organic carbon (POC) were studied monthly in a Western Mediterranean semi-enclosed basin. Sampling stations were selected as a function of wind-exposure and the degree of vegetation cover and then compared with an adjacent unvegetated site. the predominant vegetation was seagrass (Posidonia oceanicaandCymodocea nodosa) andCaulerpa prolifera.Water samples were analyzed for total suspended matter (inorganic and organic fractions), photosynthetic pigments (chlorophyll-a and phaeopigments), dissolved organic carbon, particulate organic carbon and their isotopic composition. Temperature and salinity were also measured at the same sampling sites within range of Mediterranean limits. the suspended organic matter concentration was 1.77 ± 1.55 mg l−1; the chlorophyll-a concentration was low (0.35 ± 0.24 μg l−1); the disolved organic carbon concentration was 2,140 ± 2,010 μg l−1; the particulate organic carbon concentration was 212 ± 106 μg l−1and the isotopic composition was 18.77 ± 2.51%°. There were significant temporal differences except for phaeopigments, POC and its POC isotopic composition, and there were no spatial differences other than for δ13C. This picture highlighted a general seasonal trend and trophical features similar to adjacent sea.

ISSN:0275-7540    

DOI:10.1080/02757549908037647

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The seasonal changes in the concentrations of aluminium (Al), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), magnesium (Mg), manganese (Mn), lead (Pb), and zinc (Zn) in the leaves ofTaraxacum officianale, Plantago lanceolataandPlantago majorare investigated. the most convenient periods for sampling are established when the elemental concentrations have minimal variation and are independent on the development of the plant itself. On this basis, the presumption is made that the most appropriate sampling period for herbaceous species for biomonitoring processes is the end of blossoming of the plant or immediately after that.

ISSN:0275-7540    

DOI:10.1080/02757549908037648

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0275-7540    

DOI:10.1080/02757549908037640

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor