Chemical,biological, and ecotoxicological assessment of pesticides and persistent organic pollutants in the Bahlui River,Romania

Background, aim, and scope

Current knowledge on environmental impacts of industrial activities in Romania, particularly persistent organic pollutants (POPs), indicates that environmental standards of the European Union are not systematically met. In our study area, additional sources of POPs are agriculture and domestic wastes. Very scarce information is available upon environmental contaminations and effects. In the present study, we investigated the chemical pollution and their eventual impact on the ecosystem by measuring POPs and by using biological indicators of pollution.

Materials and methods

The survey was carried out at six main sample sites along the Bahlui River. Sediments were chemically analysed for their content in polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs)—hexachlorocyclohexanes (HCHs) isomers and the dichlorodiphenyl trichloroethane (DDT) family. River water was biologically monitored at the level of phytoplankton and benthic invertebrates’ communities. Water samples from six locations have been analyzed for algal species composition and correspondence to various water quality indices. Biological samples have been taken from the same locations so as to calculate the macroinvertebrate indices. In the most polluted areas, as revealed by previous methods, toxicity was tested by exposing the green alga Pseudokirchneriella subcapitata and the cladoceran Daphnia magna to various dilutions of water sample.

Results

Important concentrations of POPs were identified only in sediments at river mouths (sites S5 and S6). Along the year, the sum of PCB concentrations ranged between 3 and 10 ng/g dw (S5), and between 4 and 26 ng/g dw (S6). Concentration of HCHs ranged between 0.4 and 3 ng/g dw (both S5 and S6) with a higher contribution of the gamma-HCH (30–70%), followed by beta-HCH (20–50%). The beta-HCH isomer was found at lower concentrations or even not detected in outer city sites. DDTs were found at higher concentrations than HCHs and ranged between 0.18 and 4 ng/g dw (S5) and between 0.56 and 18 ng/g dw (S6). The parent compound, p,p′-DDT, could be detected only in low concentrations (up to 5 ng/g dw) and contributed with less than 30% to the sum of DDTs in sediment. The principal contributors of the ΣDDTs in sediment were p,p′-DDE, and p,p′-DDD. The o,p′-DDD and DDT isomers were minor contributors to the sum of DDT. PAHs were found at higher concentrations than DDTs and ranged between 6 and 36 ng/g dw (S5) and between 36 and 155 ng/g dw (S6). Fluoranthene was predominant (up to 40%), followed by phenantrene (up to 30%), naphthalene (up to 35%), and benzo-(g,h,i)-perylene (up to 23%). The saprobity index and the diatom index increased from springs to river mouth, indicating a decrease in the water quality, but within the limits of moderate pollution. The saprobity index varied between 1.99 at spring to 2.70 at mouth. The diatom index varied from 3.48 to 3.14. The species’ richness in phytoplankton has a less clear pattern along the river, but in general, it appears to be negatively influenced by pollution. At the level of biological consumer species, the analyses of the macroinvertebrates confirm the situation and the tendency shown with algae. In addition, the Shannon–Wiener index, the Pielou evenness index, and the McNaughton dominance index indicate a peculiar pattern: invertebrate communities appear to a have a more stable structure along the river, with visible shifts at springs and at river mouths. Water toxicity testing indicates low toxicity of river waters around the city of Iasi, with two notable exceptions: the point pollution at the domestic wastewater treatment discharge and at the old open-air deposit of domestic solid wastes. Another important result was that tested algae appeared to be more readily affected than tested cladoceran: EC₅₀ (percent effluent) was 16 in algae and 28 in cladocerans. The slope of toxic effect was also much steeper in cladocerans (6) than in algae (1.8), which means that the toxic effect is more sudden on the tested invertebrates than on the tested algae.

Discussion

Pollutant concentrations reported herein are lower or similar than those reported for the sediments by earlier studies (RIZA 2000; Dragan et al., Int J Environ Anal Chem 86:833–842, 2006). Ratios of individual PAH compounds indicate important pyrolytic inputs and suggest that PAHs in the area are derived from the combustion of fossil fuels. Biologically, the waters appear to be beta-mesosaprobic towards alpha-mesosaprobic according to the saprobic index classification and undergo moderate pollution according to the diatom index classification. Water quality decreases from springs to river mouths. Algal species richness index has a less clear pattern along the river. Water toxicity is low, but certain sources of point pollution require increased attention.

Conclusions

The water quality is better than expected, probably because of the drop in pollution intensity following the collapse of local agricultural and industrial activity following the fall of communism in 1989. Nevertheless, further studies will be needed to confirm and refine our results. While this study draws no strident alarm, it appeals for high attention, particularly because the economic activity in the area is expected to increase.

Recommendations and perspectives

Future close monitoring will be necessary for insuring compliance with the Water Framework Directive, and for refining standards and understanding of the local situation, but with relevance for the wider international community. On the basis of the situation described in the present study, we recommend that future studies dedicate specific efforts to point pollution and effluent toxicity, particularly around the city of Iasi. For a better understanding of pollution and its effects, we recommend pursuing the type of multidisciplinary investigations proposed by the present study: chemical, ecotoxicological, and ecological. We also recommend that new methods should be developed and/or refined, like the empirical determination of partitioning coefficients in water and soils, process-based toxicity methods in ecotoxicological assessments, searching for interactions between pollution, producers, and consumers in aquatic ecosystems. We also recommend preference for cheaper survey methods, as these will be more applicable locally.

     

Treatment process for MSW combustion fly ash laboratory and pilot plant experiments

Fly ash from combustion of municipal solid waste sometimes contains large amounts of soluble salts, such as NaCl, even though the content of soluble toxic metal compounds is relatively low. Removal of the salts by washing with water has been suggested as a method to increase the stability of this type of ash. In the work presented here, a simple washing process was studied and evaluated. The process includes three steps: leaching with water, filtration and displacement washing. Basic data were obtained in laboratory experiments and used in the construction of pilot plant equipment at a full size fluidized bed boiler, where a side-stream of the cyclone ash was treated. The process was designed to minimize the water consumption while obtaining an effective removal of salts and a stable ash residue. In order to achieve this, recirculation of leaching liquor was used and the displacement washing was adjusted to become close to ideal. The results showed that an ash/water slurry with a liquid to solid ratio as low as 3 could be handled without difficulty in the mixing, pumping and filtration units. Washing of the filter cake at a liquid to solid ratio of 0.5 removed the major part of the remaining dissolved salts in the pore liquid. About 90% of the chloride content was removed from the ash, whereas the contents of Na, K, Ca, Cd, Pb and a number of other minor elements were removed by 10-30%. Before treatment, the results of ash leaching tests were sometimes too high for chloride (2003/33/EC), but the treatment reduced the amount of soluble chlorides to far below the limit values. The leachability of most metals was reduced or unaffected by the ash treatment. For Na, K and Cl, it was less than 10% of the value for the untreated ash. However, the results showed that some ash components may be mobilized by the washing. Antimony is the most important due to its toxicity.     

Spatial distribution,population dynamics and productivity of <Emphasis Type="Italic">Spisula subtruncata</Emphasis>: implications for <Emphasis Type="Italic">Spisula</Emphasis> fisheries in seaduck wintering areas

Bivalves are important in shallow marine habitats, not at least being the major food resource for seaducks such as the common scoter (Melanitta nigra), thousands of which are wintering on the Western Coastal Banks, near the Belgian-French border (North Sea). Next to this ecological importance, fishable stocks of one of these bivalves, Spisula subtruncata, occur in the area. This study aimed at investigating S. subtruncata’s spatial distribution, population dynamics and productivity and its implications for a sustainable Spisula fishery in seaduck wintering areas. The spatial distribution of S. subtruncata was studied in 1994 and 1997 in two areas of the Belgian Western Coastal Banks. The population dynamics and production were investigated by monthly sampling of two stations between April 1995 and April 1996 and a seasonal sampling between April 1996 and April 1998. Spisula subtruncata had a patchy distribution in the deeper (6 m), fine sandy (200 ± 20 μm) sediments of the Abra alba community, mainly found in the western most part of the Western Coastal Banks. In August 1995, an overwhelming and successful recruitment was observed in this area: local densities were as high as 150,000 ind m⁻². Minor, non-successful recruitments were detected in August 1996 and 1997. Due to space limitation, high densities of S. subtruncata are hypothesized to be responsible for the occurrence of aberrant shapes as observed from August 1996 onwards. Growth was described by a seasonally oscillating version of the von Bertalanffy growth function (VBGF): a growth stop was observed from late autumn till early spring. The VBGF parameters K (growth constant) and L _∞ (asymptotic length) were estimated at 0.7–0.9 and 31–33 mm. A combination of length and individual biomass increment showed: (1) a faster length increment of smaller individuals during the second growing period (catching-up phenomenon), (2) a constant length combined with a decreasing individual biomass during the suboptimal winter periods (except for the first winter, when the individual biomass slightly increased), (3) a positive relationship between the individual biomass decrease and the seawater temperature during the winter periods, and (4) a strong increase of the individual biomass in early spring (April 1997 and 1998) because of gametogenesis, followed by a decrease because of spawning (August 1997). The extremely high total production of the 1995 year class in the tidal gully (Potje) during the study period was estimated at approximately 1,500 g ash-free dry weight (ADW) m⁻² or 600 g ADW m⁻² on average per year. Shellfisheries for S. subtruncata within seaduck wintering areas, such as the Western Coastal Banks, should be carefully deliberated since (1) an important food resource for the seaducks will decrease, (2) the ecologically most diverse and rich macrobenthic A. alba community will be heavily affected, and (3) the recovery of Spisula populations after depletion is expected to be erratic.     

A model of nematode dynamics in the Westerschelde Estuary

We developed a time dynamic model to investigate the temporal dynamics of nematode community in the brackish zone of the Westerschelde Estuary. The biomass of four nematode feeding groups observed from March 1991 to February 1992 is used to calibrate the model. Using environmental data as the input, the model predicts the temporal modification and interrelation of four nematode feeding groups. Nematodes achieve a dominant position in the community because of their lower loss rate (in respiration, excretion and natural death). Predators which are deposit-feeding macrobenthos control the variations of dominant nematodes, such as omnivores and non-selective deposit feeders. Food availability causes modification only for rare nematodes such as epigrowth feeders and selective deposit feeders. Temperature is a factor affecting both predation death and a loss including respiration, excretion and natural death. Overall, the modification of nematode community by food availability is much lower than by predator. The macrobenthos in the Westerschelde Estuary decrease from upstream to the estuarine mouth. The stability and standing stock of nematode population follow the opposite gradient of their predators. They increase from upstream to the estuarine mouth.     

Combining modelling tools to evaluate a goose management scheme

Many goose species feed on agricultural land, and with growing goose numbers, conflicts with agriculture are increasing. One possible solution is to designate refuge areas where farmers are paid to leave geese undisturbed. Here, we present a generic modelling tool that can be used to designate the best locations for refuges and to gauge the area needed to accommodate the geese. With a species distribution model, locations are ranked according to goose suitability. The size of the area to be designated as refuge can be chosen by including more or less suitable locations. A resource depletion model is then used to estimate whether enough resources are available within the designated refuge to accommodate all geese, taking into account the dynamics of food resources, including depletion by geese. We illustrate this with the management scheme for pink-footed goose Anser brachyrhynchus implemented in Norway. Here, all geese can be accommodated, but damage levels appear to depend on weather, land use and refuge size.     

Metabolic responses of Eisenia fetida after sub-lethal exposure to organic contaminants with different toxic modes of action

Nuclear magnetic resonance (NMR) - based metabolomics has the potential to identify toxic responses of contaminants within a mixture in contaminated soil. This study evaluated the metabolic response of Eisenia fetida after exposure to an array of organic compounds to determine whether contaminant-specific responses could be identified. The compounds investigated in contact tests included: two pesticides (carbaryl and chlorpyrifos), three pharmaceuticals (carbamazephine, estrone and caffeine), two persistent organohalogens (Aroclor 1254 and PBDE 209) and two industrial compounds (nonylphenol and dimethyl phthalate). Control and contaminant-exposed metabolic profiles were distinguished using principal component analysis and potential contaminant-specific biomarkers of exposure were found for several contaminants. These results suggest that NMR-based metabolomics offers considerable promise for differentiating between the different toxic modes of action (MOA) associated with sub-lethal toxicity to earthworms.