Search results for "Dredging"
showing 10 items of 11 documents
Letter to the editor regarding the article “Taking advantage of seagrass recovery potential to develop novel and effective meadow rehabilitation meth…
2020
Alagna et al. (2019) suggest new transplantation methods for Posidonia oceanica (Linnaeus) Delile, inspired by its natural recovery process after disturbance due to dredging operations for gas-pipelines. They observe that P. oceanica vegetative fragments naturally settled only on loose calcareous stones deployed to fill the trenches of the gas-pipeline. No recovery was noted on dead matte, sand and large calcarenitic boulders. Following a new pilot restoration project currently ongoing in the same area, we demonstrate that natural recovery also occurs on dead matte. After examining other alternative transplantation methods for P. oceanica, the Authors suggest using their "habitat enhancemen…
Trace element storage capacity of sediments in deadPosidonia oceanicamat from a chronically contaminated marine ecosystem
2016
Posidonia oceanica mat is considered a long-term bioindicator of contamination. Storage and sequestration of trace elements and organic carbon (Corg) were assessed in dead P. oceanica mat and bare sediments from a highly polluted coastal marine area (Augusta Bay, central Mediterranean). Sediment elemental composition and sources of organic matter have been altered since the 1950s. Dead P. oceanica mat displayed a greater ability to bury and store trace elements and Corg than nearby bare sediments, acting as a long-term contaminant sink over the past 120?yr. Trace elements, probably associated with the mineral fraction, were stabilized and trapped despite die-off of the overlying P. oceanica…
Catastrophic effects of sand mining on macroinvertebrates in a large shallow lake with implications for management
2019
Sand mining is a human activity that is increasing in inland waters and has profound effects on entire aquatic ecosystems. However, current knowledge of the effects of sand mining on freshwater lake ecosystems remains limited, especially for biotic communities. Here, we investigated the responses of macroinvertebrates to indiscriminate sand mining in a large shallow lake of China. Our results indicated that sand mining significantly increased the content of suspended particulate matter, total nitrogen, total phosphorus and chlorophyll a in the water column both in the sand mining area and the area adjacent to the dredging activities. While there was significantly lower total nitrogen and th…
Incidence of persistent contaminants through blue mussels biomonitoring from Flekkefjord fjord and their relevance to food safety
2020
Dredging activities can lead to the re-suspension of contaminated sediments, resulting in a potential hazard for the whole ecosystem and also for human health. Six-month active biomonitoring was performed in order to monitor the trends of different classes of both legacy (organochlorine – OCPs – and organophosphate (OPs) compounds and polychlorinated biphenyls – PCBs) and emerging (polybromodiphenyl ethers – PBDE – and per- and polyfluoroalkyl substances – PFASs) organohalogen compounds, as well as polycyclic aromatic hydrocarbons (PAHs), in blue mussel (Mytilus edulis spp.) specimens transplanted at different depths in the Flekkefjord fjord. Such biomonitoring was performed to evaluate the…
Macrofaunal colonization of mine tailings impacted sediments
2020
An experiment was conducted to study and compare macrofaunal colonization of thin layers of mine tailings. Experimental boxes filled with marine sediments capped with mine tailings were placed on the seabed and subject to colonization for six and twelve months. Three Norwegian mine tailings, representative of major production processes, were used. In addition, one set of boxes served as control and was not treated with tailings. The layer thickness of the tailings was supposed to represent the thickness in the transition zone between the sea deposit itself and unaffected sediments. The most fine-grained tailings, which also contained flotation chemicals, showed a significantly lower coloniz…
Evaluation of organic compound source and natural attenuation, Liepaja Latvia
2004
Liepaja harbor is a former Soviet military site. Remediation of the harbor basin, including dredging of the sediments heavily contaminated with petroleum hydrocarbons and heavy metals is necessary to convert the harbor for civilian use. Abandoned pollution sources on land still continue to leach contaminants into the harbor basin. Our long-term research objective therefore is to identify transport pathways into the harbor sediments and to assess the in-situ degradation of pollutants in the system. The Liepaja harbor is treated as a complex system, where processes in the water column interact with the sediments and the nepheloid sediment boundary layer. For this research PAHs are used as the…
Chemical speciation of metals from marine sediments : assessment of potential pollution risk while dredging, a case study in southern Sweden
2020
Abstract Contamination associated with metals is a critical concern related to their toxicity, persistence, and bio-accumulation. Trace elements are partitioned into several chemical forms, which some are more labile during fluctuations in the environment. Studying the distribution of metals between the different chemical fractions contributes to assess their bioavailability and to identify their potential risk of contamination to surrounding environments. This study concerns the speciation of metals (Pb, Cr, Ni, Zn and Fe) from sediments coming out from Malmfjarden bay, Sweden. The aim was to assess the potential risk of metal pollution during present and future dredging as well as while u…
COMPOSITION AND QUALITY OF FRESHWATER LAKE SEDIMENTS (BALVU AND PĒRKONU LAKES)
2019
Water quality, watershed basin and urbanization are key factors from the perspective of freshwater management; however, actual depth of waterbodies is often an overlooked element. Actual depth represents the overall depth of lake bed and depth of sediments. Some cases have been reported, where with increase of average depth of lake , it is possible to expect improvements of water quality when sediments are removed. If lakes are eutrophic, shallow, overgrown with macrophytes and contain high concentrations of biogenic elements water and lake ecosystem quality can be endangered. Removal of sediments can be an expensive procedure and also depends on the composition, structure, local conditions…
Rehabilitation of two northern river lamprey (Lampetra fluviatilis) populations impacted by various anthropogenic pressures : lessons learnt in the p…
2019
The pioneering work done during the past three decades in the regulated Rivers Perhonjoki and Kalajoki, Finland, to study and rehabilitate river lamprey populations is presented. The effects of various anthropogenic activities and rehabilitation measures are evaluated based on habitat surveys and long-term monitoring of larval densities, numbers of adults migrating upstream and of transformers migrating downstream. Telemetric tracking and tagging experiments were used to determine the efficacy of fishways. Lamprey populations in both rivers decreased in the 1980s and 1990s. This was linked to obstructed upstream migration of adults and deterioration of habitats for different life stages due…
Contaminated sediments from dredging activities as modern turbidites: geochemical signatures in box-core sediments from the Augusta area, Ionian Sea,…
2009
The Augusta area (SE Sicily) is one of the most industrialized and contaminated coastal environments in the Mediterranean region, having a relatively high influx of unregulated industrial effluents. Valuable sets of geochemical data (major elements and trace metals), obtained from box-core sediments collected along a transect from the Sicilian coastal zone seawards of Augusta and dated via 210Pb and 137Cs, indicated increased metal contamination (notably Hg) since ca 1940-1950, related to the industrial development of the area. Metal enrichment is considerable in the coastal sediments, being significantly in excess (for Hg and Pb) of background values estimated for the Strait of Sicily. Mor…