| 1. |
- Chauvet, Eric, et al.
(författare)
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Litter decomposition as an indicator of stream ecosystem functioning at local-to-continental scales : insights from the European RivFunction project
- 2016
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Ingår i: Large-scale ecology. - London : Academic Press. - 9780081009352 ; 55, s. 99-182
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Bokkapitel (refereegranskat)abstract
- RivFunction is a pan-European initiative that started in 2002 and was aimed at establishing a novel functional-based approach to assessing the ecological status of rivers. Litter decomposition was chosen as the focal process because it plays a central role in stream ecosystems and is easy to study in the field. Impacts of two stressors that occur across the continent, nutrient pollution and modified riparian vegetation, were examined at > 200 paired sites in nine European ecoregions. In response to the former, decomposition was dramatically slowed at both extremes of a 1000-fold nutrient gradient, indicating nutrient limitation in unpolluted sites, highly variable responses across Europe in moderately impacted streams, and inhibition via associated toxic and additional stressors in highly polluted streams. Riparian forest modification by clear cutting or replacement of natural vegetation by plantations (e.g. conifers, eucalyptus) or pasture produced similarly complex responses. Clear effects caused by specific riparian disturbances were observed in regionally focused studies, but general trends across different types of riparian modifications were not apparent, in part possibly because of important indirect effects. Complementary field and laboratory experiments were undertaken to tease apart the mechanistic drivers of the continental scale field bioassays by addressing the influence of litter, fungal and detritivore diversity. These revealed generally weak and context-dependent effects on decomposition, suggesting high levels of redundancy (and hence potential insurance mechanisms that can mitigate a degree of species loss) within the food web. Reduced species richness consistently increased decomposition variability, if not the absolute rate. Further field studies were aimed at identifying important sources of this variability (e.g. litter quality, temporal variability) to help constrain ranges of predicted decomposition rates in different field situations. Thus, although many details still need to be resolved, litter decomposition holds considerable potential in some circumstances to capture impairment of stream ecosystem functioning. For instance, species traits associated with the body size and metabolic capacity of the consumers were often the main driver at local scales, and these were often translated into important determinants of otherwise apparently contingent effects at larger scales. Key insights gained from conducting continental scale studies included resolving the apparent paradox of inconsistent relationships between nutrients and decomposition rates, as the full complex multidimensional picture emerged from the large-scale dataset, of which only seemingly contradictory fragments had been seen previously.
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| 2. |
- Chauvet, Eric, et al.
(författare)
-
Litter decomposition as an indicator of stream ecosystem functioning at local-to-continental scales : insights from the European RivFunction project
- 2016
-
Ingår i: Large-scale ecology. - London : Academic Press. ; 55, s. 99-182
-
Bokkapitel (populärvet., debatt m.m.)abstract
- RivFunction is a pan-European initiative that started in 2002 and was aimed at establishing a novel functional-based approach to assessing the ecological status of rivers. Litter decomposition was chosen as the focal process because it plays a central role in stream ecosystems and is easy to study in the field. Impacts of two stressors that occur across the continent, nutrient pollution and modified riparian vegetation, were examined at > 200 paired sites in nine European ecoregions. In response to the former, decomposition was dramatically slowed at both extremes of a 1000-fold nutrient gradient, indicating nutrient limitation in unpolluted sites, highly variable responses across Europe in moderately impacted streams, and inhibition via associated toxic and additional stressors in highly polluted streams. Riparian forest modification by clear cutting or replacement of natural vegetation by plantations (e.g. conifers, eucalyptus) or pasture produced similarly complex responses. Clear effects caused by specific riparian disturbances were observed in regionally focused studies, but general trends across different types of riparian modifications were not apparent, in part possibly because of important indirect effects. Complementary field and laboratory experiments were undertaken to tease apart the mechanistic drivers of the continental scale field bioassays by addressing the influence of litter, fungal and detritivore diversity. These revealed generally weak and context-dependent effects on decomposition, suggesting high levels of redundancy (and hence potential insurance mechanisms that can mitigate a degree of species loss) within the food web. Reduced species richness consistently increased decomposition variability, if not the absolute rate. Further field studies were aimed at identifying important sources of this variability (e.g. litter quality, temporal variability) to help constrain ranges of predicted decomposition rates in different field situations. Thus, although many details still need to be resolved, litter decomposition holds considerable potential in some circumstances to capture impairment of stream ecosystem functioning. For instance, species traits associated with the body size and metabolic capacity of the consumers were often the main driver at local scales, and these were often translated into important determinants of otherwise apparently contingent effects at larger scales. Key insights gained from conducting continental scale studies included resolving the apparent paradox of inconsistent relationships between nutrients and decomposition rates, as the full complex multidimensional picture emerged from the large-scale dataset, of which only seemingly contradictory fragments had been seen previously.
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| 3. |
- Djerf, Henric, et al.
(författare)
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Can wetlands reduce humic substances in forested streams : combining two approaches to characterize efficiency
- 2018
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Ingår i: Book of abstracts. - 9789188898289
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Establishing statistical significance in assessing wetland performance can be quite challenging when reduction in the monitored substance is very small and temporarily variable. Assessing colour changes associated with humic substances is such a situation. One of the most important parameters of any evaluation of wetland treatment performances is the retention time of the water before it exit the wetland. This can be theoretically estimated, but even better measured directly with the help of a tracing agent. In this research, the approach is based on the simultaneously assessment of hydraulic retention time using conservative tracing (Rhodamine WT) and a mass balance based removal efficiency assessment (regression slope of the summation mass-in vs. summation mass-out).
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| 4. |
- Djerf, Henric, et al.
(författare)
-
Can wetlands reduce humic substances in forested streams : combining two approaches to characterize efficiency
- 2018
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Ingår i: Book of abstracts. - Aalborg.
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Bokkapitel (populärvet., debatt m.m.)abstract
- Establishing statistical significance in assessing wetland performance can be quite challenging when reduction in the monitored substance is very small and temporarily variable. Assessing colour changes associated with humic substances is such a situation. One of the most important parameters of any evaluation of wetland treatment performances is the retention time of the water before it exit the wetland. This can be theoretically estimated, but even better measured directly with the help of a tracing agent. In this research, the approach is based on the simultaneously assessment of hydraulic retention time using conservative tracing (Rhodamine WT) and a mass balance based removal efficiency assessment (regression slope of the summation mass-in vs. summation mass-out).
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| 5. |
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Minh Tran, Thao, et al.
(författare)
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Capacity of Vitiver grass in treatment of a mixture of labaratory and domestic wastewaters
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this study, laboratory wastewater containing organic matters, heavy metals and aromatic compounds, was treated by vetiver grass (Vetiveria zizanioides) as a phytoremediation method to remove the above three groups of pollutants. Sewage effluent, as a source of nutrient supply for plant growth, was firstly fed to two wetland systems: mini horizontal subsurface flow (HSSF) and floating raft (FR) wetlands. Next, laboratory wastewater was added gradually to mix with sewage. Nominal hydraulic retention time in both wetlands are 12 hours. Pollutants removal efficiencies were monitored. Microbial community change corresponding with each stages of sewage only and mixture with laboratory wastewater was also examined. The examined microbial community includes Nitrogen-fixing (N-fixing) bacteria, Phosphate-solubilizing (P-solubilizing) microorganism, Pseudomonas sp., and Zoogloea sp. In HSSF wetland, base materials (gravel and sand), algae, and vetiver root were in turn investigated for pollutant removal efficiencies. The results reveal that even with the presences of heavy metals and aromatic compounds, vetiver presented reasonable removal efficiencies of about 62%, 68.6%, and 58.3% for BOD, TN, and TP removal, respectively. Base materials showed almost no effect on pollutant removal. Algae was slightly responsible for approximate 6.3%, 16.6%, and 19.7% of BOD, TN, and TP removals, respectively. On the other hand vetiver roots, in term of heavy metals, had an impressive removal efficiencies of 99.2, 95.8, 96.2, and 96.7% of Cr+6 (in K2Cr2O7), Mn (MnSO4), Fe (FeSO4), and Cu (CuSO4), respectively. For aromatic compounds, the wetland is responsible for 96.8 and almost 100% of correspondingly phenol and benzene removal efficiencies. For microbial aspect, N-fixing microorganisms (e.g. Azospirillum sp., Azotobacter sp.) and Phosphate-solubilizing bacteria (Bacillus sp.) increased gradually in population during domestic wastewater feeding stage. When laboratory wastewater was added, N-fixing and P-solubilizing bacteria were quantitatively decreased slightly while population of Pseudomonas sp. increased. Besides, Zoogloea sp. was also found increasing through out the experiment and keeping a stable growth even during laboratory wastewater adding. In FR wetland, both algae and vetiver root were also investigated for BOD and aromatic compounds and heavy metals. The outcomes show similar tendencies in treatment and microbial behaviours as in HSSF wetland. Vetiver grass, mainly responsible for organic matters and nutrients removal, presented slightly lower removal efficiencies than those in HSSF wetland. The average values of removal efficiencies are 59%, 63.5%, and 53.0% for BOD, TN, and TP removal, respectively. Algae, also, took minor responsibility for approximate 3.3%, 9.1%, and 8.9% of BOD, TN, and TP removals, respectively. Heavy metals of Cr+6 (in K2Cr2O7), Mn (MnSO4), Fe (FeSO4), and Cu (CuSO4) were found removing less than in HSSF wetland with average removal efficiencies values of 92.4, 85.1, 91.8, and 91.5%, respectively, by vetiver root. Algae show almost no effect on heavy metals and aromatic removals. The vetiver root likewise plays important role in phenol and benzene removals with values of 91.5 and 96% in efficiency, respectively. N-fixing and P-solubilizing microorganisms, Pseudomonas sp., and Zoogloea sp. presented similar responses tendencies to different living condition when domestic and laboratory wastewaters, in turn, were fed.
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| 10. |
- Minh Tran, Thao, et al.
(författare)
-
Capacity of Vitiver grass in treatment of a mixture of labaratory and domestic wastewaters
- 2015
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this study, laboratory wastewater containing organic matters, heavy metals and aromatic compounds, was treated by vetiver grass (Vetiveria zizanioides) as a phytoremediation method to remove the above three groups of pollutants. Sewage effluent, as a source of nutrient supply for plant growth, was firstly fed to two wetland systems: mini horizontal subsurface flow (HSSF) and floating raft (FR) wetlands. Next, laboratory wastewater was added gradually to mix with sewage. Nominal hydraulic retention time in both wetlands are 12 hours. Pollutants removal efficiencies were monitored. Microbial community change corresponding with each stages of sewage only and mixture with laboratory wastewater was also examined. The examined microbial community includes Nitrogen-fixing (N-fixing) bacteria, Phosphate-solubilizing (P-solubilizing) microorganism, Pseudomonas sp., and Zoogloea sp. In HSSF wetland, base materials (gravel and sand), algae, and vetiver root were in turn investigated for pollutant removal efficiencies. The results reveal that even with the presences of heavy metals and aromatic compounds, vetiver presented reasonable removal efficiencies of about 62%, 68.6%, and 58.3% for BOD, TN, and TP removal, respectively. Base materials showed almost no effect on pollutant removal. Algae was slightly responsible for approximate 6.3%, 16.6%, and 19.7% of BOD, TN, and TP removals, respectively. On the other hand vetiver roots, in term of heavy metals, had an impressive removal efficiencies of 99.2, 95.8, 96.2, and 96.7% of Cr+6 (in K2Cr2O7), Mn (MnSO4), Fe (FeSO4), and Cu (CuSO4), respectively. For aromatic compounds, the wetland is responsible for 96.8 and almost 100% of correspondingly phenol and benzene removal efficiencies. For microbial aspect, N-fixing microorganisms (e.g. Azospirillum sp., Azotobacter sp.) and Phosphate-solubilizing bacteria (Bacillus sp.) increased gradually in population during domestic wastewater feeding stage. When laboratory wastewater was added, N-fixing and P-solubilizing bacteria werequantitatively decreased slightly while population of Pseudomonas sp. increased. Besides, Zoogloea sp. was also found increasing through out the experiment and keeping a stable growth even during laboratory wastewater adding. In FR wetland, both algae and vetiver root were also investigated for BOD and aromatic compounds and heavy metals. The outcomes show similar tendencies in treatment and microbial behaviours as in HSSF wetland. Vetiver grass, mainly responsible for organic matters and nutrients removal, presented slightly lower removal efficiencies than those in HSSF wetland. The average values of removal efficiencies are 59%, 63.5%, and 53.0% for BOD, TN, and TP removal, respectively. Algae, also, took minor responsibility for approximate 3.3%, 9.1%, and 8.9% of BOD, TN, and TP removals, respectively. Heavy metals of Cr+6 (in K2Cr2O7), Mn (MnSO4), Fe (FeSO4), and Cu (CuSO4) were found removing less than in HSSF wetland with average removal efficiencies values of 92.4, 85.1, 91.8, and 91.5%, respectively, by vetiver root. Algae show almost no effect on heavy metals and aromatic removals. The vetiver root likewise plays important role in phenol and benzene removals with values of 91.5 and 96% in efficiency, respectively. N-fixing and P-solubilizing microorganisms, Pseudomonas sp., and Zoogloea sp. presented similar responses tendencies to different living condition when domestic and laboratory wastewaters, in turn, were fed.
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