35 research outputs found
In Situ Measurement of Wall Thermal Properties: Parametric Investigation of the Heat Flow Meter Methods through Virtual Experiments Data
No full textEnergy retrofit of existing buildings is based on the assessment of the starting performance of the envelope. The procedure for the in situ measurement of thermal conductance is described in the ISO 9869-1:2014, which provides two techniques for data processing: the average method (AM) and the dynamic method (DM). This work studies their effectiveness using virtual data from numerical simulations based on a finite difference model applied to different wall kinds, considering winter and summer boundary conditions alternatively (Italian Milan-Linate TMY). The estimated thermal conductances are compared to the reference theoretical values. The main purposes are: (i) defining the shortest test duration that provides acceptable results; (ii) assess the reliability of the criteria provided by the standard to evaluate the measurement quality; (iii) evaluate the sensitivity of both methods to variables such as wall properties, boundary conditions and others more specific to the DM (namely, the number of time constants and linear equations). The AM always provides acceptable estimates in winter (-3.1% divided by 10% error), with better outcomes when indoor heat flux is considered, except for the highly insulated wall, but is not effective in summer, despite the fulfillment of the acceptance criteria for the highly insulated wall. The DM provides improvements in both seasons (0.05% divided by 8.6% absolute values of error), for most virtual samples, and requires shorter sampling periods, even below the 3 days limit suggested by the standard. The test on the confidence interval indicated by the ISO 9869-1:2014 is not reliable and measurements are sensitive to the number of linear equations, that is left to the user's discretion without strict indications. This work suggests a possible approach for overcoming this issue, which requires deeper future investigation
In Situ Measurement of Wall Thermal Properties: Parametric Investigation of the Heat Flow Methods Through Virtual Experiments Data
No full textEnergy retrofit of existing buildings is based on the assessment
of the starting performance of the envelope. The procedure
to evaluate thermal conductance through in situ
measurements is described in the technical standard ISO
9869-1:2014, which provides two alternative techniques to
process collected data: the Average Method (AM) and the
Dynamic Method (DM).
This work studies their effectiveness using virtual data
from numerical simulations of three kinds of walls, performed
using a Finite Difference model.
The AM always provides acceptable estimates in winter,
with better outcomes when indoor heat flux is considered
in every case except the highly insulated wall. Summer
conditions do not lead to acceptable measurements, despite
the fulfillment of the check required by the standard.
The DM results show acceptable estimations of the thermal
conductance in both climates, for most of the virtual
samples considered, although critically depending on
some parameters of the DM that are left to the user’s discretion,
without strict indications by the standard. This
work highlights a possible approach for overcoming this
issue, which requires deeper future investigation
Decomposition processes and trace metals in muds of the Gulf of Papua, Papua New Guinea
No full textMaintenance and Update Frequency: notPlannedStatement: Statement: Methods and sensors are described in:Alongi DM, Boyle S, Tirendi F and Payne C (1996) Composition and behaviour of trace metals in post-oxic sediments of the Gulf of Papua. Estuarine Coastal and Shelf Science 42: 197-211.andAlongi DM (1995) Decomposition and recycling of organic matter in muds of the Gulf of Papua, northern Coral Sea. Continental Shelf Research 15: 1319-1337.<b>Credit</b><br/>Alongi, Daniel M, Dr (Principal Investigator)Nutrient chemistry and rates of nutrient regeneration were examined in muds of the Gulf of Paupa, Papua New Guinea. Samples were taken from 3 new sites (IGP1, IGP2, IGP3) and 2 sites previously sampled in 1990 (D9, GP8).Sedimentary variables were: temperature; grain size; salinity; porosity; and percent sand, silt and clay.Dissolved solute (DON, DOP, ammonium, nitrite, nitrate, phosphate, silicate, DOC, Fe, Mn) flux measurements and primary production (O2 flux) were made for each site.Cores were taken for measurements of solid-phase elements (TOC, TN, TP, TS) and porewater nutrients at each site.The concentrations of solid-phase and dissolved trace metals (Al, Fe, Mn, Mo, Ni, Cu, Co), including sediment-water interface, were measured.<br/> To describe rates of bacterial composition and recycling of organic matter in the upper sediment layers (0-20 cm) of these inner shelf muds and their contribution to primary pelagic production.To assess the role of post-oxic muds in the flux of trace metals into the Coral Sea.<br/> This research project was a component of a larger project to determine the influence of freshwater and detrital export from the Fly River system on adjacent pelagic and benthic systems
Benthic infauna and organism-sediment relations in a shallow, tropical coastal area: influence of outwelled mangrove detritus and physical disturbance
No full textCarbon and nutrient cycling in seagrass meadows, Sulawesi, Indonesia
No full textMaintenance and Update Frequency: notPlannedStatement: Statement: Methods and sensors as described in:Alongi DM, Trott LA, Undu MC and Tirendi F (2008) Benthic microbial metabolism in seagrass meadows along a carbonate gradient in Sulawesi, Indonesia. Aquatic Microbial Ecology 51: 141-152.<b>Credit</b><br/>Alongi, Daniel M, Dr (Principal Investigator)The study was conducted in 3 seagrass beds in Awerange Bay during the dry season (September 2006) and the wet season (March 2007).Densities of seagrass (shoots m-2) and production in(g DW m-2 d-1) were calculated.pH and redox potential were measured. Water content, total C, total N, TOC and total P were determined, and total inorganic carbon calculated.Rates of sulfate reduction were measured.Solute fluxes of DIC, O2, and dissolved inorganic nutrient and other solute (Ca, Fe, Mn, hydrogen sulphide) across the sediment-water interface were measured.Net ammonium production was measured from each site.Denitrification was measured using the N2-gas technique. Fluxes of methane and N2O were measured. Nitrogen fixation in sediments was also measured.Benthic microaglal production was measured by oxygen fluxes in the dry and wet seasons.<br/> To examine sediment carbon and nitrogen cycling in seagrass meadows across a gradient of increasing cabonate content
Timor-Leste: Preliminary assessment of a rapidly eroding landscape in the Coral Triangle
No full textContext
Sedimentation in the rivers and on the coasts of Timor-Leste has increased since deforestation, affecting floods and probably living aquatic resources.
Aims
To provide scientifically based estimates of long-term and short-term erosion rates to assess the apparent role of deforestation, a topic that has not received sufficient quantitative attention in the Coral Triangle.
Methods
Short-term erosion rates have been estimated from regional relationships between river sediment yield and catchment areas and cosmogenic nuclides for long-term rates. An attempt has also been made to estimate changes in rates of delta progradation to determine whether recent increases have occurred following deforestation.
Key results
The major scientific finding is that reduction in vegetation cover for agriculture and timber harvesting, particularly in the mountains, increased sediment yield by factors up to 120, mainly by landsliding. And there has been a large amount of sediment exported to the delta and offshore from river-channel change.
Implications
Impacts on living resources are likely both in rivers and on the coast, but require assessment. Revegetation of hillslopes is likely to reduce these impacts and improve the livelihoods of local people.Full Tex
Benthic decomposition rates and pathways in plantations of the mangrove Rhizophora apiculata in the Mekong delta, Vietnam
No full textCarbon and nitrogen budgets in shrimp ponds of extensive mixed shrimp-mangrove forestry farms in the Mekong delta, Vietnam
No full textMass balance estimates of carbon and nitrogen flux through two extensive shrimp ponds in the Mekong delta, Vietnam, were constructed to identify major sources and sinks of organic matter potentially available for shrimp production. Nutrient transformations in the sediments were measured to further assess rates of decomposition and burial and quality of organic matter. Tidal exchange was the major pathway for inputs and outputs of carbon and nitrogen in both ponds, with net primary production, nitrogen fixation and precipitation being minor inputs. No fertilizers or artificial feeds were added to either pond. The nutrient budgets identified burial and respiration as the next most important outputs after tidal exchange losses of particulate and dissolved carbon and nitrogen. There was no measurable denitrification in either pond, and NH4 + volatilization was negligible. Mineralization efficiency of carbon in the water column was high (> 100%) in pond 23 reflecting rapid respiration rates; efficiency was lower (36%) in pond 12 waters. Mineralization efficiency of sediment nutrients averaged 34% for C and 41% for N in the pond with a higher annual shrimp yield (pond 12); lower mineralization efficiencies (11% for C, 10% for N) were calculated for the lower yield pond (pond 23). High burial efficiencies for both C (66-89%) and N (59-90%) in the sediments of both ponds suggest that little organic matter was shunted into biological production. Conversion efficiency for shrimp averaged 16% for C and 24% for N from pond 12, and 6% for C and 18% for N from pond 23. The high quantity but low quality of organic matter entering the ponds coupled with other factors, such as poor water quality, limits shrimp productivity. On average, nutrient outputs were greater than inputs in both ponds. This imbalance partly explains why shrimp yields are declining in these ponds
Carbon and nitrogen processes in a mangrove creek receiving shrimp farm effluent
No full textIn order to quantify the fate of nutrients originating from shrimp pond waste, mass balances of carbon (C) and nitrogen (N) were compared from a mangrove creek that received shrimp farm effluent to those in an adjacent control creek that did not receive effluent. The annual C input from the shrimp farm exceeded carbon metabolism in creek water and sediments, indicating high sedimentation and burial of excess organic material in the upper reaches of the effluent creek. The rate of natural N flow was small compared with the rate of N supply from pond effluent. Ammonium uptake in creek water and sediment denitrification each accounted for less than 10% of the annual effluent N supply. Immediately downstream from the farm discharge point, mineralisation and release of dissolved inorganic and organic N from the sediments were not greatly enhanced compared to the control creek, despite 25% of the annual N supply and 10% of the annual C supply depositing in proximity to the discharge point. Further downstream, rapid bacterial growth and high rates of primary production were controlled by very high micro-zooplankton grazing rates. The remaining nutrients were exported from the upper reaches to the seaward end of the effluent creek via tidal flushing. On an annual basis, the upper reaches of the creek appeared to mineralise only a small fraction of the nutrients derived from the shrimp farm wastes. However, discharge of pond waste C and N during shrimp harvest periods did not cause eutrophication further downstream, probably due to a combination of physical mechanisms (intensive tidal flushing) and biological nutrient transformations by pelagic microbes and their subsequent grazing by micro-zooplankton and fish.No Full Tex
Primary production and nutrients in a tropical macrotidal estuary, Darwin Harbour, Australia
No full textGriffith Sciences, Griffith School of EnvironmentNo Full Tex
