Messung des Wasserdampfflusses in der konvektiven Grenzschicht mit DIAL und RADAR-RASS

In der vorliegenden Arbeit wird ein aktives, bodengebundenes Fernerkundungsverfah- ren zur Bestimmung von Wasserdampffliissen in der konvektiven Grenzschicht be- schrieben. Das Meßsystem besteht aus einem Wasserdampf-DIAL und einem RADAR- RASS-Gerät, mit denen simultan und hochaufgelöst Wasserdampf und Vertikalwind bestimmt werden. Daraus läßt sich mit Hilfe der Eddy-Correlation-Methode der vertikale turbulente Wasserdampffluß ermitteln. Der Meßbereich des DIAL-RASS- Systems in seinem derzeitigen Aufbau erstreckt sich von 400 bis 700 m Höhe. Die zeitliche und räumliche Auflösung des Meßsystems beträgt 60 s bzw. 75 m. Letzteres beschränkt die Einsatzmöglichkeiten des Systems auf die konvektive Grenzschicht, wo anzunehmen ist, daß die Skalen der für den Fluß relevanten Wirbel größer als die Systemauflösung sind. Es werden daher die Ergebnisse einer Messung vorgestellt, die im Juli 1991 unter konvektiven Bedingungen durchgeführt wurde. Aus den Daten werden für 3 Meßabschnitte zwischen 30 min und 3 h Dauer, die sich durch unterschiedlich starke Konvektion auszeichnen, Vertikalprofile des Wasserdampfflusses zwischen 400 und 700 m Höhe bestimmt und die mittlere Wasserdampfflußdivergenz ermittelt. Der statistische Fehler der Wasserdampfflußwerte liegt bei ca. 20 %, der Samplingfehler beträgt je nach Länge des Mittelungsintervalles 30-40%. Aufgrund der Größe der Wirbel in der konvektiven Grenzschicht und ihrer ausgeprägten zeitlichen und räum- lichen Variabilität können mit einem bodengebundenen Meßsystem bei Mittelungs- zeiten bis zu 3 h keine repnäsentativeren Meßwerte bestimmt werden. Eine Verringe- rung des Samplingfehlers läßt sich durch Mittelung über mehrere Meßabschnitte, die an verschiedenen Tagen unter ähnli.chen meteorologischen Bedingungen aufge- nommen wurden, erreichen. Einen zentralen Punkt nimmt die Klärung der Frage ein, ob die Systemauf- lösung ausreichend ist, um den Hauptbeitrag zum Wasserdampffluß in einer kon- vektiven Grenzschicht zu erfassen. Die Varianzspektren der Vertikalwind- und Feuchtedaten zeigen am hochfrequenten Ende einen fiir den Inertialbereich typischen Abfall f'5/3. Dies is;t,,ein deutlicher Hinweis darauf, daß die Wirbel, die vom Meß- system nicht mehr aufgelöst werden, im Inertialbereich liegen und somit keinen signifikanten Beitrag zum Wasserdampffluß leisten. Zusätzlich wird der Wasser- dampffluß im Höhenbereich zwischen 400 und 700 m mittels zweier indirekter Methoden abgeschätzt und mit den gemessenen Flußprofilen verglichen. Es zeigt sich, daß im Rahmen der statistischen Fehler und der Samplingfehler die gemessenen und abgeschätzten Flüsse in derselben Größenordnung liegen. Diese Ergebnisse demonstrieren, daß mit einer Kombination aus DIAL und RADAR-RASS die wesentlichen Beiträge zum Wasserdampffluß in der konvektiven Grenzschicht erfaßt werden können

In-depth investigation of the long-term strength and leaching behaviour of inorganic polymer mortars containing green liquor dregs

Green liquor dregs are the most challenging waste stream coming from the pulp and paper industry. Despite tremendous efforts, there are not currently any viable recycling alternatives for this massively produced waste (2 Mt/year), which inevitably ends up in landfills. Urgent actions must be undertaken to tackle this. In this work, a substantial amount of dregs was incorporated into eco-friendly, waste-based inorganic polymer (geopolymer) mortars as fine filler. Then, and for the first time, the long-term strength performance (up to 270 days) and heavy metals leaching behaviour of the dregs-containing mortars was evaluated. The effect of the mixture composition and dregs incorporation content on the fresh- and hardened-state properties of the mortars was also studied. Dregs were found to increase the initial and final setting time of the slurries, thus extending the open time before their in-situ application. The use of dregs as fine filler effectively enhances the compressive strength of the mortars, and decreases their water absorption levels. These eco-friendly building materials showed excellent long-term performance, as their strength continuously increases up to the 270th day (after mixture), and no signs of efflorescence formation were detected. Moreover, the heavy metals leaching levels of the mortars were well below the contamination limits in soil, which demonstrates the feasibility of this recycling methodology.publishe

Unravelling the Affinity of Alkali-Activated Fly Ash Cubic Foams towards Heavy Metals Sorption

In this work, alkali-activated fly ash-derived foams were produced at room temperature by direct foaming using aluminum powder. The 1 cm3 foams (cubes) were then evaluated as adsorbents to extract heavy metals from aqueous solutions. The foams’ selectivity towards lead, cadmium, zinc, and copper ions was evaluated in single, binary, and multicomponent ionic solutions. In the single ion assays, the foams showed much higher affinity towards lead, compared to the other heavy metals; at 10 ppm, the removal efficiency reached 91.9% for lead, 83.2% for cadmium, 74.6% for copper, and 64.6% for zinc. The greater selectivity for lead was also seen in the binary tests. The results showed that the presence of zinc is detrimental to cadmium and copper sorption, while for lead it mainly affects the sorption rate, but not the ultimate removal efficiency. In the multicomponent assays, the removal efficiency for all the heavy metals was lower than the values seen in the single ion tests. However, the superior affinity for lead was preserved. This study decreases the existing knowledge gap regarding the potential of alkali-activated materials to act as heavy metals adsorbents under different scenarios

Profiling the molecular destruction rates of temperature and humidity as well as the turbulent kinetic energy dissipation in the convective boundary layer

A simultaneous deployment of Doppler, temperature, and water-vapor lidars is able to provide profiles of molecular destruction rates and turbulent kinetic energy (TKE) dissipation in the convective boundary layer (CBL). Horizontal wind profiles and profiles of vertical wind, temperature, and moisture fluctuations are combined, and transversal temporal autocovariance functions (ACFs) are determined for deriving the dissipation and molecular destruction rates. These are fundamental loss terms in the TKE as well as the potential temperature and mixing ratio variance equations. These ACFs are fitted to their theoretical shapes and coefficients in the inertial subrange. Error bars are estimated by a propagation of noise errors. Sophisticated analyses of the ACFs are performed in order to choose the correct range of lags of the fits for fitting their theoretical shapes in the inertial subrange as well as for minimizing systematic errors due to temporal and spatial averaging and micro- and mesoscale circulations. We demonstrate that we achieve very consistent results of the derived profiles of turbulent variables regardless of whether 1 or 10 s time resolutions are used. We also show that the temporal and spatial length scales of the fluctuations in vertical wind, moisture, and potential temperature are similar with a spatial integral scale of ≈160 m at least in the mixed layer (ML). The profiles of the molecular destruction rates show a maximum in the interfacial layer (IL) and reach values of ϵm≃7×10-4 g2 kg−2 s−1 for mixing ratio and ϵθ≃1.6×10-3 K2 s−1 for potential temperature. In contrast, the maximum of the TKE dissipation is reached in the ML and amounts to ≃10-2 m2 s−3. We also demonstrate that the vertical wind ACF coefficient kw∝w′2‾ and the TKE dissipation ϵ∝w′2‾3/2. For the molecular destruction rates, we show that ϵm∝m′2‾w′2‾1/2 and ϵθ∝θ′2‾w′2‾1/2. These equations can be used for parameterizations of ϵ, ϵm, and ϵθ. All noise error bars are derived by error propagation and are small enough to compare the results with previous observations and large-eddy simulations. The results agree well with previous observations but show more detailed structures in the IL. Consequently, the synergy resulting from this new combination of active remote sensors enables the profiling of turbulent variables such as integral scales, variances, TKE dissipation, and the molecular destruction rates as well as deriving relationships between them. The results can be used for the parameterization of turbulent variables, TKE budget analyses, and the verification of large-eddy simulations.</p

The Fires, Asian, and Stratospheric Transport-Las Vegas Ozone Study (FAST-LVOS)

The Fires, Asian, and Stratospheric Transport&ndash;Las Vegas Ozone Study (FAST-LVOS) was conducted in May and June of 2017 to study the transport of ozone (O3) to Clark County, Nevada, a marginal non-attainment area in the southwestern United States (SWUS). This 6-week (20&nbsp;May&ndash;30&nbsp;June 2017) field campaign used lidar, ozonesonde, aircraft, and in situ measurements in conjunction with a variety of models to characterize the distribution of O3 and related species above southern Nevada and neighboring California and to probe the influence of stratospheric intrusions and wildfires as well as local, regional, and Asian pollution on surface O3 concentrations in the Las Vegas Valley (&asymp;&thinsp;900&thinsp;m above sea level, a.s.l.). In this paper, we describe the FAST-LVOS campaign and present case studies illustrating the influence of different transport processes on background O3 in Clark County and southern Nevada. The companion paper by Zhang et al.&nbsp;(2020) describes the use of the AM4 and GEOS-Chem global models to simulate the measurements and estimate the impacts of transported O3 on surface air quality across the greater southwestern US and Intermountain West. The FAST-LVOS measurements found elevated O3 layers above Las Vegas on more than 75&thinsp;% (35 of 45) of the sample days and show that entrainment of these layers contributed to mean 8&thinsp;h average regional background O3 concentrations of 50&ndash;55 parts per billion by volume (ppbv), or about 85&ndash;95&thinsp;&micro;g&thinsp;m&minus;3. These high background concentrations constitute 70&thinsp;%&ndash;80&thinsp;% of the current US National Ambient Air Quality Standard (NAAQS) of 70&thinsp;ppbv (&asymp;&thinsp;120&thinsp;&micro;g&thinsp;m&minus;3 at 900&thinsp;m&thinsp;a.s.l.) for the daily maximum 8&thinsp;h average (MDA8) and will make attainment of the more stringent standards of 60 or 65&thinsp;ppbv currently being considered extremely difficult in the interior SWUS. &nbsp;</p

The California baseline ozone transport study (CABOTS)

Ozone is one of the six criteria pollutants identified by the U.S. Clean Air Act Amendment of 1970 as particularly harmful to human health. Concentrations have decreased markedly across the United States over the past 50 years in response to regulatory efforts, but continuing research on its deleterious effects have spurred further reductions in the legal threshold. The South Coast and San Joaquin Valley Air Basins of California remain the only two extreme ozone nonattainment areas in the United States. Further reductions of ozone in the West are complicated by significant background concentrations whose relative importance increases as domestic anthropogenic contributions decline and the national standards continue to be lowered. These background concentrations derive largely from uncontrollable sources including stratospheric intrusions, wildfires, and intercontinental transport. Taken together the exogenous sources complicate regulatory strategies and necessitate a much more precise understanding of the timing and magnitude of their contributions to regional air pollution. The California Baseline Ozone Transport Study was a field campaign coordinated across Northern and Central California during spring and summer 2016 aimed at observing daily variations in the ozone columns crossing the North American coastline, as well as the modification of the ozone layering downwind across the mountainous topography of California to better understand the impacts of background ozone on surface air quality in complex terrain