scholarly journals SEDIMENTOLOGICAL AND PALAEOENVIRONMENTAL CHARACTER OF LAKE KORONIA SEDIMENTS

2017 ◽  
Vol 50 (1) ◽  
pp. 295
Author(s):  
S. Doani ◽  
K. Albanakis ◽  
O. Koukousioura ◽  
K.K. Koliadimou
Keyword(s):  
Grain Size ◽  
Organic Matter ◽  
Environmental Conditions ◽  
Water Body ◽  
Fine Sand ◽  
Lake Bottom ◽  
Bottom Sampling ◽  
Palaeoenvironmental Conditions ◽  
Freshwater Ostracods ◽  
Ostracod Species

The aim of the present study is to investigate the sedimentological characteristics of Lake Koronia down to a depth of 3.5m below lake bottom. Sampling operations took advandage of a season that the lake bottom was exposed to subaerial conditions. The sedimentological analysis proved that sediments consist of mud to sandy mud, with 2 phases of very fine sand fractions. The proportion of dry organic matter contained into sediment, appears to be generally small while the rates of moisture and volatiles are relatively high. Furthermore, this study examines the distribution of ostracod populations in the sediments of the lake in relation to depth, grain size and other environmental conditions of this water body. Four ostracod species were identified: Candona neglecta, Darwinula stevensoni, Heterocypris spp. and Limnocythere inopinata. The study of freshwater ostracods provides information for the palaeoecological/palaeoenvironmental conditions during the sedimentation.

scholarly journals Recognition of Environmentally Vulnerable Depositional Facies in the Chacahua Lagoon, Oaxaca, Mexico

2005 ◽  
Vol 32 (2) ◽  
pp. 17 ◽  
Author(s):  
FELIPE RÍOS ◽  
GELIA SANDOVAL ◽  
ALFREDO FRÍAS
Keyword(s):  
Cluster Analysis ◽  
Grain Size ◽  
Organic Matter ◽  
Bottom Sediment ◽  
Environmental Conditions ◽  
Environmental Concern ◽  
Environmental Indicators ◽  
Depositional Facies ◽  
Sediment Samples ◽  
Insight Into

Over the years, human activity and environmental problems have impacted the Chacahua Lagoon in the State of Oaxaca, Mexico. In an attempt to gain more insight into the current environmental conditions of this lagoon, twenty-eight bottom sediment samples were collected in August 2003. Using depth, physical properties (grain-size and texture) and biological characteristics (organic matter and CaCO3 contents) of sediments as environmental indicators, three depositional facies were identified implementing cluster analysis, each facies seems to be under the influence of different processes. In terms of environmental concern, it was determined that the central part of the lagoon presents a high potential of pollutant sorption, thus this sector should be closely monitored.

scholarly journals Superficial sediments and their relation to polyehaete families in a subtropieal embayment, Mexico

2015 ◽  
pp. 237-238
Author(s):  
Nuria Méndez ◽  
María Green Ruiz
Keyword(s):  
Grain Size ◽  
Organic Matter ◽  
Organic Matter Content ◽  
Fine Sand ◽  
Matter Content ◽  
Pearson’S Correlation ◽  
Pearson's Correlation ◽  
Superficial Sediments ◽  
Soft Bottoms

The soft bottoms in front of Mazatlan Bay and "Isla de la Piedra" Peninsula were studied to produce maps (depth, grain size and organic matter content in sediments). Sixty samples were óbtained with a 30 x 30 van Veen grab (4-21 m depth) and polychaetes were extracted from 21 subsamples. Grain size ranged from -1.05 phi (gravel) to 3 .81 phi (very fine sand), with fme sand predominl\ting. Organic matter content in sediment was 0.91-3.06 % (most values = 1-2 %). Thirty polychaete families (905 individuals/m2 in mean) were found, and Cirratulidae, Spionidae, Onuphidae, and Pilargiidae were domiuant. Pearson's correlation of grain size.

scholarly journals Recognition of Environmentally Vulnerable Depositional Facies in the Chacahua Lagoon, Oaxaca, Mexico

2004 ◽  
Vol 31 (2) ◽  
pp. 17
Author(s):  
Felipe RÍOS ◽  
Gelia SANDOVAL ◽  
Alfredo FRÍAS
Keyword(s):  
Cluster Analysis ◽  
Grain Size ◽  
Organic Matter ◽  
Bottom Sediment ◽  
Environmental Conditions ◽  
Environmental Concern ◽  
Environmental Indicators ◽  
Depositional Facies ◽  
Sediment Samples ◽  
Insight Into

Over the years, human activity and environmental problems have impacted the Chacahua Lagoon in the State of Oaxaca, Mexico. In an attempt to gain more insight into the current environmental conditions of this lagoon, twenty-eight bottom sediment samples were collected in August 2003. Using depth, physical properties (grain-size and texture) and biological characteristics (organic matter and CaCO3 contents) of sediments as environmental indicators, three depositional facies were identified implementing cluster analysis, each facies seems to be under the influence of different processes. In terms of environmental concern, it was determined that the central part of the lagoon presents a high potential of pollutant sorption, thus this sector should be closely monitored.

Holocene climate recorded by magnetic properties of lake sediments in the Northern Rocky Mountains, USA

The Holocene ◽  
2019 ◽  
Vol 30 (3) ◽  
pp. 479-484
Author(s):  
Daniel P Maxbauer ◽  
Mark D Shapley ◽  
Christoph E Geiss ◽  
Emi Ito
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Rocky Mountains ◽  
Future Research ◽  
Magnetic Minerals ◽  
Holocene Climate ◽  
Northern Rocky Mountains ◽  
The North ◽  
Lake Bottom ◽  
Northern Rockies

We present two hypotheses regarding the evolution of Holocene climate in the Northern Rocky Mountains that stem from a previously unpublished environmental magnetic record from Jones Lake, Montana. First, we link two distinct intervals of fining magnetic grain size (documented by an increasing ratio of anhysteretic to isothermal remanent magnetization) to the authigenic production of magnetic minerals in Jones Lake bottom waters. We propose that authigenesis in Jones Lake is limited by rates of groundwater recharge and ultimately regional hydroclimate. Second, at ~8.3 ka, magnetic grain size increases sharply, accompanied by a drop in concentration of magnetic minerals, suggesting a rapid termination of magnetic mineral authigenesis that is coeval with widespread effects of the 8.2 ka event in the North Atlantic. This association suggests a hydroclimatic response to the 8.2 ka event in the Northern Rockies that to our knowledge is not well documented. These preliminary hypotheses present compelling new ideas that we hope will both highlight the sensitivity of magnetic properties to record climate variability and attract more work by future research into aridity, hydrochemical response, and climate dynamics in the Northern Rockies.

scholarly journals Stability of Fe-oxide nanoparticles coated with natural organic matter under relevant environmental conditions

2014 ◽  
Vol 70 (12) ◽  
pp. 2040-2046 ◽  
Author(s):  
L. Chekli ◽  
S. Phuntsho ◽  
L. D. Tijing ◽  
J. L. Zhou ◽  
J.-H. Kim ◽  
...  
Keyword(s):  
Organic Matter ◽  
Natural Organic Matter ◽  
Environmental Conditions ◽  
Divalent Cations ◽  
Oxide Nanoparticles ◽  
Fe Oxide ◽  
Coated Nanoparticles ◽  
Aggregation Behaviour ◽  
Physico Chemical ◽  
The Stability

Manufactured nanoparticles (MNPs) are increasingly released into the environment and thus research on their fate and behaviour in complex environmental samples is urgently needed. The fate of MNPs in the aquatic environment will mainly depend on the physico-chemical characteristics of the medium. The presence and concentration of natural organic matter (NOM) will play a significant role on the stability of MNPs by either decreasing or exacerbating the aggregation phenomenon. In this study, we firstly investigated the effect of NOM concentration on the aggregation behaviour of manufactured Fe-oxide nanoparticles. Then, the stability of the coated nanoparticles was assessed under relevant environmental conditions. Flow field-flow fractionation, an emerging method which is gaining popularity in the field of nanotechnology, has been employed and results have been compared to another size-measurement technique to provide increased confidence in the outcomes. Results showed enhanced stability when the nanoparticles are coated with NOM, which was due to electrosteric stabilisation. However, the presence of divalent cations, even at low concentration (i.e. less than 1 mM) was found to induce aggregation of NOM-coated nanoparticles via bridging mechanisms between NOM and Ca2+.

The Metazoan Meiofauna in Its Biogeochemical Environment: The Case of an Antarctic Coastal Sediment

1998 ◽  
Vol 78 (2) ◽  
pp. 411-434 ◽  
Author(s):  
S. Vanhove ◽  
H.J. Lee ◽  
M. Beghyn ◽  
D. Van Gansbeke ◽  
S. Brockington ◽  
...  
Keyword(s):  
Organic Matter ◽  
Standing Stock ◽  
Austral Summer ◽  
Fine Sand ◽  
Coastal Sediment ◽  
Feeding Guild ◽  
Fresh Organic Matter ◽  
Benthic Environment ◽  
Metazoan Meiofauna ◽  
Deposit Feeding

The metazoan meiobenthos was investigated in an Antarctic coastal sediment (Factory Cove, Signy Island, Antarctica). The fine sands contained much higher abundances compared to major sublittoral sediments worldwide. Classified second after Narrangansett Bay (North Atlantic) they reached numbers of 13 × 106ind m-2. The meiofauna was highly abundant in the surface layers, but densities decreased sharply below 2 cm. Vertical profiles mirrored steep gradients of microbiota, chloropigments and organic matter and were coincident with chemical stratification. Spatial patchiness manifested especially in the surface layer. Nematodes dominated (up to 90%), andAponema, Chromctdorita, Diplolaimella, Daptonema, MicrolaimusandNeochromadoraconstituted almost the entire community. Overall, the nematode fauna showed a strong similarity with fine sand communities elsewhere. The dominant trophic strategies were epistrarum and non-selective deposit feeding, but the applied classification for feeding guild structure of the nematodes of Factory Cove is discussed. High standing stock, low diversity and shallow depth distribution may have occurred because of the high nutritive (chlorophyll exceeded lOOOmgm-2and constituted almost 50% of the organic pool) and reductive character of the benthic environment. These observations must have originated from the substantial input of fresh organic matter from phytoplankton and microphytobenthic production, typical for an Antarctic coastal ecosystem during the austral summer.

scholarly journals Marine substrate response from the analysis of seismic attributes in CHIRP sub-bottom profiles

2017 ◽  
Vol 65 (3) ◽  
pp. 332-345 ◽  
Author(s):  
Larissa Felicidade Werkhauser Demarco ◽  
Antonio Henrique da Fontoura Klein ◽  
Jorge Antonio Guimarães de Souza
Keyword(s):  
Grain Size ◽  
Seismic Reflection ◽  
Ground Truth ◽  
Fine Sand ◽  
Seismic Attributes ◽  
Coarse Sand ◽  
Unconsolidated Sediments ◽  
Shallow Gas ◽  
Size Classes ◽  
Seismic Reflection Profiles

Abstract This paper presents an evaluation of the response of seismic reflection attributes in different types of marine substrate (rock, shallow gas, sediments) using seafloor samples for ground-truth statistical comparisons. The data analyzed include seismic reflection profiles collected using two CHIRP subbottom profilers (Edgetech Model 3100 SB-216S), with frequency ranging between 2 and 16 kHz, and a number (38) of sediment samples collected from the seafloor. The statistical method used to discriminate between different substratum responses was the non-parametric Kruskal-Wallis analysis, carried out in two steps: 1) comparison of Seismic Attributes between different marine substrates (unconsolidated sediments, rock and shallow gas); 2) comparison of Seismic Attributes between different sediment classes in seafloors characterized by unconsolidated sediments (subdivided according to sorting). These analyses suggest that amplitude-related attributes were effective in discriminating between sediment and gassy/rocky substratum, but did not differentiate between rocks and shallow gas. On the other hand, the Instantaneous Frequency attribute was effective in differentiating sediments, rocks and shallow gas, with sediment showing higher frequency range, rock an intermediate range, and shallow gas the lowest response. Regarding grain-size classes and sorting, statistical analysis discriminated between two distinct groups of samples, the SVFS (silt and very fine sand) and the SFMC (fine, medium and coarse sand) groups. Using a Spearman coefficient, it was found that the Instantaneous Amplitude was more efficient in distinguishing between the two groups. None of the attributes was able to distinguish between the closest grain size classes such as those of silt and very fine sand.

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