氯乙酰苯胺除草剂及其降解产物在肯尼亚Nzoia流域的演变

采用气相色谱法对肯尼亚沿Nzoia河9个地点的水样和沉积物样中草不绿(也称杂草锁)(α'-氯-N-(2,6-二乙基苯基)-N-(甲氧基甲基)乙酰胺)、甲氧毒草安(α-氯6'-乙基-N-(2甲氧基-1-甲基乙基)乙酰邻甲苯胺)及它们各自环境稳定的苯胺类降解物2,6-二乙基苯胺、2-乙基-6-甲基苯胺进行分析.降解物在90%以上的沉积物样和水样中检出,而母体化合物只在不到14%的水样中检出.沉积物中的杀虫剂和它们的降解物比在水中浓度高很多(1.4～10 800倍),显示出化合物在沉积物中的积累.在研究时间内沉积物中降解物的普遍存在意味着这些化合物的持续性.可以假定在热带气候为主的条件下,促使杀虫剂快速分解为环境稳定的降解物,从而在研究区域内使后者成为比其母体更重要的污染物.     

Algal-bacterial interactions in metal contaminated floodplain sediments

The aim of the present study was to investigate algal-bacterial interactions in a gradient of metal contaminated natural sediments. By means of multivariate techniques, we related the genetic structure (denaturing gradient gel electrophoresis, DGGE) and the physiological structure (community-level physiological profiling, CLPP) of the bacterial communities to the species composition of the algal communities and to the abiotic environmental variables, including metal contamination. The results revealed that genetic and physiological structure of the bacterial communities correlated with the species composition of the algal community, but hardly to the level of metal pollution. This must be interpreted as an indication for a strong and species-specific linkage of algal and bacterial species in floodplain sediments. Metals were, however, not proven to affect either the algal or the bacterial communities of the Dutch river floodplains.     

Life cycle responses of the midge Chironomus riparius to polycyclic aromatic compound exposure

During acute exposure, polycyclic aromatic compounds (PACs) act mainly by narcosis, but during chronic exposure the same compounds may exert sublethal life cycle effects. The aim of this study was therefore to evaluate the chronic effects of sediment spiked PACs on the emergence of the midge Chironomus riparius. Three isomer pairs were selected, and 28-day LC50 values and 50% emergence times (EMt50) were determined. Concentration-response relationships were observed for phenanthrene, acridine, phenanthridine and acridone. Anthracene and phenanthridone had no effect on total emergence, but did cause a delay in emergence. Calculated porewater LC50 values correlated well with logKow values, suggesting narcosis as mode of action. In contrast, effect concentrations for delay in emergence (EMt50) deviated from narcosis, suggesting a specific mode of action during chronic exposure. It is concluded that emergence is a powerful endpoint to detect life cycle effects of PACs on a key sediment inhabiting invertebrate.     

Influence of light and temperature on the growth rate of estuarine benthic diatoms in culture

Four species of estuarine benthic diatoms: Amphiprora c. f. paludosa W. Smith, Nitzschia c. f. dissipata (Kützing) Grunow, Navicula arenaria Donkin, and Nitzschia sigma (Kützing) W. Smith were grown in unialgal cultures. The growth rates of the diatoms were determined as the rate of increase of the chlorophyll a content of the cultures. The diatoms were cultured at different combinations of temperture, daylength, and quantum irradiance. The highest growth rates of Navicula arenaria occurred at 16° to 20°C; the other 3 species had their optimum at 25°C or higher. The small-celled species had higher growth rates at their optimum temperature, but at lower temperatures the growth rates of all 4 species became very similar. The minimum daily quantum irradiance that could effect light-saturated growth at 12° and 20°C ranged from 2.5 to 5.0 E.m^-2.day^-1. At 12°C, two species had their highest growth rates under an 8 h daily photoperiod. At 20°C, the three species tested all had highest growth rates under 16 h daily photoperiod. The growth response of the benthic diatoms is comparable to that of several cultures of planktonic diatoms, as described in the literature. The influence of temperature and quantum irradiance on the diatoms in the present investigation was comparable to the influence of temperature and light intensity on the ¹⁴C-fixation of marine benthic diatoms (Colijn and van Buurt, 1975).     

Biological variation in sensitivity to N-heterocyclic PAHs; effects of acridine on seven species of micro-algae

The toxicity of the nitrogen (N) heterocyclic polyaromatic hydrocarbon (PAH) acridine was tested for seven species of microalgae: Scenedesmus acuminatus, Selenastrum capricornutum, Chlamydomonas eugametos, Staurastrum chaetoceras, Staurastrum manfeldtii, Navicula salinarum and Nitzschia sigma. The effect of acridine on the algae was studied in a 96-h growth test, in which growth rates were determined using cell numbers and biovolume. The obtained EC50 values (for growth rates based on cell numbers) ranged from 0.08 mg litre(-1) for N. sigma to 0.78 mg litre(-1) for C. eugametos and N. salinarum. Effect concentrations based on biovolume were slightly higher for most species. Metabolism of acridine was observed for one species (S. capricornutum), but this capacity did not result in a very different tolerance. Acridine toxicity was neither related to taxonomical background (green algae versus diatoms) nor to original habitat of the species (planktonic or benthic, eutrophic or oligo-mesotrophic). The presence of near-UV radiation during the incubation might explain the higher toxicity of acridine than is expected on basis of QSAR derived narcotic toxicity.     

Salinity tolerance of benthic estuarine diatoms as tested with a rapid polarographic measurement of photosynthesis

Measurements of net photosynthesis of benthic estuarine diatoms were made by polarographic registration of oxygen saturation. A measuring cell was constructed in which media with salinities of 2.0 to 100.7 were pumped over the algae between measurements. Diatoms from unialgal cultures and mixed populations from intertidal flats appeared to be highly tolerant of extreme salinities. During short-term exposures (20 min) the net photosynthesis of the algae did not drop below 70% of the initial values, within the salinity range 4.0 to 60.0. Prolonged exposure (up to 6 h) gave essentially the same results. Populations of benthic diatoms, sampled from field stations with mean salinities of about 30, 12, and below 5, showed only gradual differences in their tolerance of salinities between 2.0 and 33.7. Two species, Navicula arenaria and Nitzschia sigma, were cultured in media ranging in salinity from 8.0 to 45.0 and from 2.0 to 45, respectively. The tolerance to changing salinity was only slightly affected by the salinity of the medium in the preculture. The role of salinity in the production and distribution of intertidal diatoms is discussed.     

MODELING TO EVALUATE MACROPHYTE INDUCED IMPACTS TO DISSOLVED OXYGEN IN A TAILWATER RESERVOIR1

ABSTRACT: Effects of aquatic macrophytes are not considered in most standard water quality models. This study used field measurements and water quality models to help determine the effects of aquatic macrophytes on dissolved oxygen (DO) concentrations in a shallow tailwater reservoir. Installation of a hydropower plant and macrophytes (primarily Potamogeton and Chara) in a large shallow portion of the lake are possible causes of reduced DO levels in the tailwater reservoir. A water quality model (WASP5) was used to quantify the various DO sources and sinks and to evaluate the effects of the hydropower operations on DO levels in the lake. It was found that the macrophytes in Lake Ogallala had a significant effect on the DO levels in the lake. At an average macrophyte density of about 6,360 g/m² (wet weight) in 2000, the DO fluctuated daily from about 3 mg/l to about 12 mg/l. At an average macrophyte density of about 2,120 g/m² (wet weight) in 2002, the DO fluctuated from about 5 mg/l to about 9 mg/l daily. The model predicted that the DO would remain near 5 mg/l without macrophytes. The photo‐synthetic and respiration rates developed in the model (4.4 mg/g‐hr and 1.4 mg/g‐hr, respectively) agree well with literature values.     

Metal-induced tolerance in the freshwater microbenthic diatom Gomphonema parvulum

The benthic diatom Gomphonema parvulum Kützing is a common species in both clean and metal contaminated rivers. Our aim was to investigate whether metal-induced tolerance could explain the persistance of this taxon under metal polluted conditions. G. parvulum strains were isolated from a Zn- and Cd-contaminated stream and from a relatively clean ("reference") stream. The strains were cultured in synthetic medium as mono-specific biofilms to maintain their specific benthic growth features. Moreover, the strain from the metal polluted stream was cultured in plain and Zn- and Cd-enriched synthetic medium. Short-term (5 h) toxicity experiments with Zn were performed with the strains using pulse amplitude modulated (PAM) fluorometry. Zn lowered significantly the minimal chlorophyll fluorescence (F0) and the photon yield (phi(p)) of the exposed strains after 5 h exposure. The actual Zn concentrations that caused a 50% reduction (EC50's) of the phi(p) of the strain from the metal polluted stream were significantly higher than those of the isolate from the unpolluted stream. The absence of tolerance to Cu of the "polluted" strain indicated that Zn tolerance resulted from specific induction by chronic exposure to Zn in the field. Observations on field biofilms confirmed a higher tolerance of the G. parvulum population from the polluted stream than of the G. parvulum population from the reference stream. A genetic nature of this metal adaptation was supported by the persistance of the Zn tolerance of the polluted strain 2 years after isolation.     

Sensitivity of characteristic riverine insects, the caddisfly Cyrnus trimaculatus and the mayfly Ephoron virgo, to copper and diazinon

This study reports the effects of two model toxicants, copper and diazinon, on two characteristic riverine insect species, the caddisfly Cyrnus trimaculatus and the mayfly Ephoron virgo. It was demonstrated that these species are very sensitive to both compounds in comparison with aquatic insects traditionally used in ecotoxicity tests. For diazinon, the 96-h LC(50) value of Cyrnus trimaculatus (1.1 microg/l) is lower than for any other insect species known from the literature and for copper it was demonstrated that Ephoron virgo is among the most sensitive aquatic insect species. The observed low LC(50) values stress the importance of using these indigenous species in assessing the risk of environmental contaminants in large European rivers and in defining conditions for ecological recovery.     

Development and application of a sediment toxicity test using the benthic cladoceran Chydorus sphaericus

This study reports on the development and application of a whole sediment toxicity test using a benthic cladoceran Chydorus sphaericus, as an alternative for the use of pelagic daphnids. A C. sphaericus laboratory culture was started and its performance under control conditions was optimised. The test was firstly validated by determining dose-response relationships for aqueous cadmium and copper and ammonia, showing a sensitivity of C. sphaericus (96 h LC(50) values of 594 microg Cd/L, 191 microg Cu/L and 46 mg ammonia/L at pH 8) similar to that of daphnids. Next, sediment was introduced into the test system and a series of contaminated sediments from polluted locations were tested. A significant negative correlation between survival and toxicant concentrations was observed. It is concluded that the test developed in the present study using the benthic cladoceran C. sphaericus is suitable for routine laboratory sediment toxicity testing.