From the utilization point of view, it is notable that the total element concentrations in the precipitated calcium carbonate (PCC) waste were significantly lower than the maximal allowable heavy metal concentrations for fertilizers used in agriculture and in forestry, set on the basis of the EU and Finnish legislation. The easily soluble Ca concentration of 168.5g kg(-1) (d.w.) in PCC waste was 105 times higher than the typical value of 1.6g kg(-1) (d.w.) in the coarse mineral soil in Finland indicates that the PCC waste is a potential agent for soil remediation and for improving soil fertility if it is used as fertilizer. According to a five-stage sequential extraction procedure, the highest concentrations of most of the elements occurred either in HF+HNO3+HCl or H2O2+CH3COONH4 fraction. This means that the major part of the elements retained in the PCC waste are not easy to extract (leach) under conditions normally found in nature. This is beneficial since, if inorganic materials and by-products are utilized in earth construction, the content of harmful compounds must be low and the harmful components must be tightly bound to the matrix. 相似文献
The official control programme for organochlorine (OC) contaminants in food producing animals in Sweden was used to study temporal and spatial trends of the polychlorinated biphenyl CB 153, hexachlorobenzene (HCB) and p,p′-DDE in adipose tissue from bovines and swine 1991–2004. Our results show that efforts to decrease OC contamination of animal feed and the environment have had a positive impact on the contamination of the animal production. OC concentrations declined significantly in almost all studied regions of Sweden. OC temporal trends were slower in bovines (6–8% per year) than in swine (10–12%). Power analyses showed that data from more than 10 years of sampling were needed for a detection of an annual OC level change of 5% in both species in the control programme, due to large within- and between-year variation in OC levels. CB 153 and p,p′-DDE levels were higher in southern than in northern Sweden. Levels decreased with age in milk cows, but not in young nulliparous cows (heifers) and bulls. Moreover, milk cows and bulls had significantly lower OC levels than heifers. Levels were not age-dependent among swine, but castrated male swine (barrows) had significantly lower OC levels than young female swine (gilts). Levels of the studied OCs are now in many cases below the LOQ of the analytical method used. Future time trend studies of these OCs thus depend on lowered LOQs in the control programme. 相似文献
Background, aim, and scope Degradation of the 16 US EPA priority PAHs in soil subjected to bioremediation is often achieved. However, the PAH loss is
not always followed by a reduction in soil toxicity. For instance, bioanalytical testing of such soil using the chemical-activated
luciferase gene expression (CALUX) assay, measuring the combined effect of all Ah receptor (AhR) activating compounds, occasionally
indicates that the loss of PAHs does not correlate with the loss of Ah receptor-active compounds in the soil. In addition,
standard PAH analysis does not address the issue of total toxicant bioavailability in bioremediated soil.
Materials and methods To address these questions, we have used the CALUX AhR agonist bioassay and the Comet genotoxicity bioassay with RTL-W1 cells
to evaluate the toxic potential of different extracts from a PAH-contaminated soil undergoing large-scale bioremediation.
The extracts were also chemically analyzed for PAH16 and PCDD/PCDF. Soil sampled on five occasions between day 0 and day 274
of biological treatment was shaken with n-butanol with vortex mixing at room temperature to determine the bioavailable fraction
of contaminants. To establish total concentrations, parts of the same samples were extracted using an accelerated solvent
extractor (ASE) with toluene at 100°C. The extracts were tested as inducers of AhR-dependent luciferase activity in the CALUX
assay and for DNA breakage potential in the Comet bioassay.
Results The chemical analysis of the toluene extracts indicated slow degradation rates and the CALUX assay indicated high levels of
AhR agonists in the same extracts. Compared to day 0, the bioavailable fractions showed no decrease in AhR agonist activity
during the treatment but rather an up-going trend, which was supported by increasing levels of PAHs and an increased effect
in the Comet bioassay after 274 days. The bio-TEQs calculated using the CALUX assay were higher than the TEQs calculated from
chemical analysis in both extracts, indicating that there are additional toxic PAHs in both extracts that are not included
in the chemically derived TEQ.
Discussion The response in the CALUX and the Comet bioassays as well as the chemical analysis indicate that the soil might be more toxic
to organisms living in soil after 274 days of treatment than in the untreated soil, due to the release of previously sorbed
PAHs and possibly also metabolic formation of novel toxicants.
Conclusions Our results put focus on the issue of slow degradation rates and bioavailability of PAHs during large-scale bioremediation
treatments. The release of sorbed PAHs at the investigated PAH-contaminated site seemed to be faster than the degradation
rate, which demonstrates the importance of considering the bioavailable fraction of contaminants during a bioremediation process.
Recommendations and perspectives It has to be ensured that soft remediation methods like biodegradation or the natural remediation approach do not result in
the mobilization of toxic compounds including more mobile degradation products. For PAH-contaminated sites this cannot be
assured merely by monitoring the 16 target PAHs. The combined use of a battery of biotests for different types of PAH effects
such as the CALUX and the Comet assay together with bioavailability extraction methods may be a useful screening tool of bioremediation
processes of PAH-contaminated soil and contribute to a more accurate risk assessment. If the bioremediation causes a release
of bound PAHs that are left undegraded in an easily extracted fraction, the soil may be more toxic to organisms living in
the soil as a result of the treatment. A prolonged treatment time may be one way to reduce the risk of remaining mobile PAHs.
In critical cases, the remediation concept might have to be changed to ex situ remediation methods. 相似文献
Overexploitation of fish stocks causes concern not only to fisheries managers and conservation biologists, but also engages seafood consumers; more integrated product perspectives would be useful. This could be provided by life cycle assessment (LCA); however, further complements of present LCA methodology are needed to assess seafood production, one being by-catch impacts. We studied the scientific rationale behind using the IUCN Red List of Threatened Species? for assessment of impacts relating to fish species’ vulnerability. For this purpose, the current Red List status of marine fish in Sweden was compared to the advice given in fisheries as well as key life history traits known to indicate sensitivity to high fishing pressure. Further, we quantified the amount of threatened fish (vulnerable, endangered, or critically endangered) that was discarded in demersal trawl fisheries on the Swedish west coast. The results showed that not only did the national Red List of marine fish have a high consistency with advice given in fisheries and indices of vulnerability, the different fishing practices studied were also found to have vastly different amounts of threatened fish discarded per kilo landing. The suggested approach is therefore promising as a carrier of aggregated information on the extent to which seafood production interferes with conservation priorities, in particular for species lacking adequate stock assessment. To enable extensive product comparisons, it is important to increase coverage of fish species by the global IUCN Red List, and to reconsider the appropriate assessment unit (species or stocks) in order to avoid false alarms. 相似文献
Mixing inside an anaerobic digester is often continuous and is not actively controlled. The selected mixing regime can however affect both gas production and the energy efficiency of the biogas plant. This study aims to evaluate these effects and compare three different mixing regimes, 150 RPM and 25 RPM continuous mixing and minimally intermittent mixing for both digestion of fresh substrate and post-digestion of the organic fraction of municipal solid waste. The results show that a lower mixing intensity leads to a higher biogas production rate and higher total biogas production in both cases. 25 RPM continuous mixing and minimally intermittent mixing resulted in similar biogas production after process stabilization, while 150 RPM continuous mixing resulted in lower production throughout the experiment. The lower gas production at 150 RPM could not be explained by the inhibition of volatile fatty acids. Cumulative biogas production until day 31 was 295 ± 2.9, 317 ± 1.9 and 304 ± 2.8 N ml/g VS added during digestion of fresh feed and 113 ± 1.3, 134 ± 1.1 and 130 ± 2.3 N ml/g VS added during post digestion for the 150 RPM, 25 RPM and minimally mixed intensities respectively. As well as increasing gas production, optimal mixing can improve the energy efficiency of the anaerobic digestion process. 相似文献
A laminated sediment core collected in the southern part of the Baltic Proper was analysed for DDT compounds, polychlorinated biphenyls (PCB) including the coplanar congeners, polybrominated diphenyl ethers (PBDE) and polychlorinated naphthalenes (PCN). Two sewage sludge samples were also analysed for the same compounds.
The results of the sediment analyses indicate the presence of PCB, DDT and PBDE compounds in sediment layers dating from the 1950s and later. Neither coplanar PCB nor PCN were detected at any level of the sediment core. The PCB concentrations indicate a slight increase in levels during the last decades, while there were no changes in the levels of DDT compounds. In contrast, TeBDE levels increase 4- to 8-fold and one PeBDE congeners levels increase 10- to 20-fold. The results of sewage sludge analyses showed the concentration of the individual PBDE to be at about the same level as for the individual PCB congeners. The congener pattern in sludge samples indicates low-chlorinated products to be the main PCN source. 相似文献