Calculation of in situ acoustic sediment attenuation using off‐the‐shelf horizontal A DCPs in low concentration settings

2017 ◽  
Vol 53 (6) ◽  
pp. 5017-5037 ◽  
Author(s):  
Dan Haught ◽  
Jeremy G. Venditti ◽  
Scott A. Wright
Keyword(s):  
Low Concentration ◽  
Sediment Attenuation

scholarly journals Start-up Strategies for Anaerobic Ammonia Oxidation (Anammox) in In-Situ Nitrogen Removal from Polluted Groundwater in Rare Earth Mining Areas

2021 ◽  
Vol 13 (8) ◽  
pp. 4591
Author(s):  
Shuanglei Huang ◽  
Daishe Wu
Keyword(s):  
Rare Earth ◽  
Low Temperature ◽  
Removal Efficiency ◽  
Nitrogen Removal ◽  
Ex Situ ◽  
High Concentration ◽  
Low Concentration ◽  
Start Up ◽  
Anammox Activity

The tremendous input of ammonium and rare earth element (REE) ions released by the enormous consumption of (NH4)2SO4 in in situ leaching for ion-adsorption RE mining caused serious ground and surface water contamination. Anaerobic ammonium oxidation (anammox) was a sustainable in situ technology that can reduce this nitrogen pollution. In this research, in situ, semi in situ, and ex situ method of inoculation that included low-concentration (0.02 mg·L−1) and high-concentration (0.10 mg·L−1) lanthanum (La)(III) were adopted to explore effective start-up strategies for starting up anammox reactors seeded with activated sludge and anammox sludge. The reactors were refrigerated for 30 days at 4 °C to investigate the effects of La(III) during a period of low-temperature. The results showed that the in situ and semi in situ enrichment strategies with the addition of La(III) at a low-concentration La(III) addition (0.02 mg·L−1) reduced the length of time required to reactivate the sludge until it reached a state of stable anammox activity and high nitrogen removal efficiency by 60–71 days. The addition of La(III) promoted the formation of sludge floc with a compact structure that enabled it to resist the adverse effects of low temperature and so to maintain a high abundance of AnAOB and microbacterial community diversity of sludge during refrigeration period. The addition of La(III) at a high concentration caused the cellular percentage of AnAOB to decrease from 54.60 ± 6.19% to 17.35 ± 6.69% during the enrichment and reduced nitrogen removal efficiency to an unrecoverable level to post-refrigeration.

scholarly journals Mercury methylation in paddy soil: source and distribution of mercury species at a Hg mining area, Guizhou Province, China

2016 ◽  
Vol 13 (8) ◽  
pp. 2429-2440 ◽  
Author(s):  
Lei Zhao ◽  
Christopher W. N Anderson ◽  
Guangle Qiu ◽  
Bo Meng ◽  
Dingyong Wang ◽  
...  
Keyword(s):  
Paddy Soil ◽  
Surface Soil ◽  
Ambient Air ◽  
Rice Paddy ◽  
Guizhou Province ◽  
Mercury Species ◽  
Low Concentration ◽  
Paddy Water ◽  
Hg Mining

Abstract. Rice paddy plantation is the dominant agricultural land use throughout Asia. Rice paddy fields have been identified as important sites for methylmercury (MeHg) production in the terrestrial ecosystem and a primary pathway of MeHg exposure to humans in mercury (Hg) mining areas. We compared the source and distribution of Hg species in different compartments of the rice paddy during a complete rice-growing season at two different typical Hg-contaminated mining sites in Guizhou province, China: an abandoned site with a high Hg concentration in soil but a low concentration in the atmosphere and a current-day artisanal site with a low concentration in soil but a high concentration in the atmosphere. Our results showed that the flux of new Hg to the ecosystem from irrigation and atmospheric deposition was insignificant relative to the pool of old Hg in soil; the dominant source of MeHg to paddy soil is in situ methylation of inorganic Hg (IHg). Elevated MeHg concentrations and the high proportion of Hg as MeHg in paddy water and the surface soil layer at the artisanal site demonstrated active Hg methylation at this site only. We propose that the in situ production of MeHg in paddy water and surface soil is dependent on elevated Hg in the atmosphere and the consequential deposition of new Hg into a low-pH anoxic geochemical system. The absence of depth-dependent variability in the MeHg concentration in soil cores collected from the abandoned Hg mining site, consistent with the low concentration of Hg in the atmosphere and high pH of the paddy water and irrigation water, suggested that net production of MeHg at this site was limited. We propose that the concentration of Hg in ambient air is an indicator for the risk of MeHg accumulation in paddy rice.

scholarly journals Composition of dental plaque formed in the presence of sucrose and after its interruption

2003 ◽  
Vol 14 (3) ◽  
pp. 147-152 ◽  
Author(s):  
Jaime Aparecido Cury ◽  
Aline Soler Marques ◽  
Cíntia Pereira Machado Tabchoury ◽  
Altair Antoninha Del Bel Cury
Keyword(s):  
Crossover Study ◽  
Dental Plaque ◽  
Sucrose Solution ◽  
Inorganic Phosphorus ◽  
Deionized Water ◽  
The Other ◽  
Low Concentration ◽  
Human Enamel ◽  
Two Stages

Since dental plaque reservoirs of fluoride (F), calcium (Ca) and inorganic phosphorus (Pi) are susceptible to decreases in pH, this in situ crossover study was conducted to test the hypothesis that the low concentration of these ions in plaque, formed in the presence of sucrose, could be attributed merely to the fermentation of this sugar. Eleven volunteers wore palatal appliances containing 6 human enamel blocks during two stages. In each stage, the treatments were either 20% sucrose solution or distilled deionized water, which were dripped onto the blocks 8 times a day. After 28 days, in each stage, the dental plaque formed on two blocks was collected, the treatment was inverted and after a further 24 and 48 h, the biofilm formed was collected from the other blocks. The concentration of acid-soluble F, Ca and Pi, and the concentration of insoluble polysaccharide (IP) were determined in the dental plaque. Statistically lower concentrations of F, Ca and Pi, and a higher concentration of IP were found in the 28-day biofilm formed in the presence of sucrose than in its absence; after the treatment inversion the change in F, Ca and Pi was not statistically significant, but the IP concentration changed significantly. The hypothesis was rejected because change in concentration of F, Ca and Pi is not due to fermentation of the sucrose.

Through the years with on-a-chip gas chromatography: a review

Lab on a Chip ◽  
2015 ◽  
Vol 15 (12) ◽  
pp. 2559-2575 ◽  
Author(s):  
F. Haghighi ◽  
Z. Talebpour ◽  
A. Sanati-Nezhad
Keyword(s):  
Gas Chromatography ◽  
Small Volume ◽  
Microelectromechanical System ◽  
Low Concentration ◽  
Mems Technology

In recent years, the need for measurement and detection of samples in situ or with very small volume and low concentration (low and sub-parts per billion) is a cause for miniaturizing systems via microelectromechanical system (MEMS) technology.

scholarly journals Mercury Methylation in paddy soil: Source and distribution of mercury species at a Hg mining area, Guizhou Province, China

2016 ◽  
Author(s):  
L. Zhao ◽  
C. W. N. Anderson ◽  
G. L. Qiu ◽  
B. Meng ◽  
D. Y. Wang ◽  
...  
Keyword(s):  
Atmospheric Deposition ◽  
Paddy Soil ◽  
Soil Layer ◽  
Ambient Air ◽  
Rice Paddy ◽  
Mercury Species ◽  
Low Concentration ◽  
Paddy Water ◽  
Hg Mining

Abstract. Rice paddy plantation for human consumption is dominant land uses throughout Asia. Rice paddy fields have been identified as important sites for methylmerucry (MeHg) production in the terrestrial ecosystem, and a primary pathway of MeHg exposure to human in mercury (Hg) mining areas. We compared the source and distribution of Hg species in different compartments of the rice paddy during a complete rice-growing season at two different typical Hg-contaminated mining sites: an abandoned site with high Hg concentration in soil but low concentration in atmosphere, and a current-day artisanal site with low concentration in soil but high concentration in atmosphere. The contribution of new Hg to the ecosystem from irrigation and atmospheric deposition was insignificant relative to the pool of old Hg; the dominant source of MeHg to paddy soil is in situ methylation of inorganic Hg. Elevated MeHg concentrations jointly with the high proportion of Hg as MeHg in paddy water and the surface soil layer at the artisanal s ite demonstrated active Hg methylation at this site only. We propose that the in situ production of MeHg is dependent on elevated IHg in the atmosphere, and the deposition of new Hg into a low pH anoxic geochemical system. In contrast, the absence of depth-dependent variability in the MeHg concentration in soil cores collected from abandoned Hg mining site, consistent with the low concentration of Hg in atmospheric deposition and high pH of the paddy water/irrigation water, suggested that the net production of MeHg was limited. We also propose that the concentration of Hg in ambient air is an indicator for the risk of MeHg accumulation in paddy rice.

EOR by Low Salinity Water and Surfactant at Low Concentration: Impact of Injection and in Situ Brine Composition

2016 ◽  
Vol 30 (4) ◽  
pp. 2705-2713 ◽  
Author(s):  
Hamid Hosseinzade Khanamiri ◽  
Ida Baltzersen Enge ◽  
Meysam Nourani ◽  
Jan Åge Stensen ◽  
Ole Torsæter ◽  
...  
Keyword(s):  
Low Concentration ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water
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