Hydrochemical and isotopic characterization of the hydrological budget of a MAB Reserve: Mar Chiquita lagoon,province of Buenos Aires,Argentina

Mar Chiquita is a coastal lagoon located in the Argentine Buenos Aires province in South America. The aim of this study was to perform a hydrochemical and stable isotopes characterization in order to better the understanding of the hydrology of the Mar Chiquita lagoon’s catchment and its water budget. Groundwater samples were taken from 144 wells and 21 samples from main streams, and seven lagoon water samples were also collected. Chemical analyses were carried out using standard laboratory methods, and isotopic determinations were made through laser spectroscopy using a DLT-100 liquid–water isotope analyzer. Hydrochemical analysis permits a general classification of groundwater and streamwater as sodium bicarbonate waters, while the lagoon chemical composition shows an evolution toward seawater composition, from the north to its mouth, which is located southerly. Isotopic data show a source of aquifer recharge from rainfall and a groundwater domain into the streams’ flow. Three main components can be recognized as end members in a plot of electrical conductivity (EC) versus δ¹⁸O: seawater, streamwater and groundwater. Obtained EC values for groundwater in the discharge zone (EC average value = 3,516 μS/cm) allow minimizing its direct contribution and to take into consideration two dominating end members: streamwater and seawater. Mar Chiquita lagoon’s water falls close to the line between streamwater and seawater end members according to its EC and δ¹⁸O. The obtained seawater proportion for these samples ranges from 84 % in the lagoon’s mouth to around 0 % in the more distal area.     

Experiments with condensation nucleus size spectrometers

Summary The paper presents the theory of an electrical method for resolving a polydisperse aerosol — brought up to charge equilibrium — usingBoltzmann's law of charge distribution which was suggested byT. A. Rich, and reports on experimental tests of this method and on a comparison of its results with those obtained by theL. W. Pollak & A. L. Metnieks' exhaustion method employing a diffusion battery without end-pieces or connecting tubing.The application of the novel diffusion battery without end-pieces or connecting tubing for determining the diffusion coefficient of nuclei stored in a balloon gasometer showed, as in the case of room air nuclei, that the apparent diffusion coefficient increases with increased flow rates and that the increase becomes bigger with decreasing size of nuclei; thus the dependence of the apparent diffusion coefficient on the air-flow is not caused by impaction and deposition of the nuclei in the end-pieces nor by losses in the tubing.No frictional electrical charges on the diffusion battery were, of course, detected when the battery constructed entirely of metal was earthed, and no influence on the diffusion coefficient as determined by the dynamic method was found when the insulated diffusion battery was charged to 52 volts.The resolution of polydisperse aerosols by determining the mobility spectrum of the charged components of the aerosol, brought up to charge equilibrium, showed that the electrical method is well suited for nucleus populations with large percentage of charged nuclei (rather big nuclei) and is sensitive enough to indicate the ageing, even over a few hours, of a stored aerosol. The equivalent radius as computed from the concentrations of the charged and uncharged nuclei of an aerosol under charge equilibrium conditions agrees very well indeed with the average radius of the size spectrum determined by the electrical method and represents so far the best single size characteristic of a polydiperse aerosol.The results obtained so far by the electricla and dynamic methods are in good agreement both with regard to the spectral distribution of the components and to the average size of the nuclei.

---

Zusammenfassung Die Theorie einer elektrischen Methode zur Zerlegung eines heterogenen Aerosols in seine Komponenten, welche vonT. A. Rich vorgeschlagen wurde, wird entwickelt. Die Kerne des Aerosols werden in Ladungsgleichgewicht gebracht undBoltzmann's Gesetz der Ladungsverteilung benützt. Über eine experimentelle Prüfung dieser Methode und die Vergleichung ihrer Resultate mit jenen der Exhaustions-Methode nachL. W. Pollak & A. L. Metnieks, die eine Diffusionsbatterie benützt, wird berichtet.Die Anwendung der neuartigen Diffusionsbatterie ohne Endstücke oder Verbindungsröhren zur Bestimmung des Diffusionskoeffizienten von Kondensationskernen, welche in einem Gasometer gespeichert waren, zeigt — wie im Falle von Kernen in Laboratoriumsluft —, dass der virtuelle Diffusionskoeffizient mit zunehmender Luftstromgeschwindigkeit wächst und dass der Zuwachs mit abnehmender Grösse der Kerne grösser wird; die Abhängigkeit des virtuellen Diffusionskoeffizienten vom Luftstrom ist daher nicht durch das Aufprallen und die Ablagerung der Kerne in den Endstücken oder durch Verluste in den Verbindungsröhren verursacht.Es wurden natürlich keine reibungs-elektrischen Ladungen an der Diffusionsbatterie festgestellt, wenn die ganz aus Metall konstruierte Diffusionsbatterie geerdet war, und es wurde ferner kein Einfluss auf den mittels der dynamischen Methode bestimmten Diffusionskoeffizienten gefunden, wenn die isolierte Diffusionsbatterie auf 52 Volt geladen wurde.Die Bestimmung des Beweglichkeitsspektrums der geladenen Komponenten eines polydispersen Aerosols, welches mittels eines Alphastralers in Ladungsgleichgewicht gebracht wurde, zeigte, dass die elektrische Methode zur Zerlegung von Aerosolen mit hohem Prozentsatz geladenerr Kerne (ziemlich grossen Kernen) wohl geeignet und dass sie hinreichend empfindlich ist, die Alterung eines in einem Gasometer gespeicherten Aerosols während weniger Stunden erkennen zu lassen.Der aequivalente Radius, wie er aus der Konzentration der geladenen und ungeladenen Kerne eines im Ladungsgleichgewicht befindlichen Aerosols berechnet werden kann, stimmt sehr gut mit dem mittleren Radius überein, wie er sich aus dem elektrisch bestimmten Grössenspektrum ergibt. Der aequivalente Radius stellt die bis jetzt beste durch eine einzige Zahl ausgedrückte Grössencharakteristik eines polydispersen Aerosols dar.Die bisher mit der elektrischen und dynamischen Methode erhaltenen Resultate stimmen gut überein, sowohl rücksichtlich der spektralen Verteilung der Komponenten als auch bezüglich der aus ihnen abgeleiteten mittleren Kerngrösse.

     

Estimation of average size of submicron particles from the number of all and uncharged particles

Summary Recently one of the authors introduced for a polydisperse aerosol the useful concept of the equivalent radius which is computed from a monodisperse substitute aerosol with the same fraction of charged nuclei as the actual.In this paper the result of a theoretical and experimental investigation into the agreement between equivalent and average radius of polydisperse aerosols are presented. It is shown that for normal conditions as is to be expected in practice the equivalent radius represents a very good estimate of the average size of submicron particles in polydisperse aerosols.

---

Zusammenfassung Einer der Authoren hat jüngst den nützlichen Begriff des äquivalenten Radius für polydisperse Aerosole eingeführt, welcher für ein monodisperses Ersatz-Aerosol mit dem gleichen Bruchteil von geladenen Teilchen als das wirkliche Aerosol berechnet wird.In der vorliegenden Arbeit werden die Resultate einer theoretischen und experimentellen Untersuchung der Uebereinstimmung des äquivalenten und mittleren Radius für polydisperse Aerosole mitgeteilt. Es wird gezeigt, dass unter normalen Bedingungen, wie sie in der Praxis zu erwarten sind, der äquivalente Radius eine sehr gute Abschätzung für den mittleren Radius von sub-mikroskopischen Teilchen in polydispersen Aerosolen vorstellt.

     

A Universal Diffusion Battery

Summary In order to examine the explanation put forward to us privately that the marked influence of the air-flow on the value of the diffusion coefficient as determined by the dynamic method is due to unequal flow through the channels of the diffusion apparatus used hitherto, a novel diffuser — called Universal Diffusion Battery — has been constructed in which the air-flow through each channel can be equalised.The new diffusion battery is described and its advantages outlined. Its application also shows that with equal flow through each channel the dependence of the diffusion coefficient on the air-flow (i.e. that higher diffusion constants with higher flow rates are obtained) still exists. A comparison of the diffusion coefficients as measured with the diffusion batteries of the old and new types is given.The explanation based on irrefutable theoretical considerations that this dependence of the diffusion coefficient on the air-flow is caused by the heterogeneity of the condensation nuclei in the aerosol, as given byPollak & Metnieks some time ago, is apparently the correct one or it accounts at least for the greatest part of the phenomenon.

---

Zussamenfassung Um die Erklärung, welche uns privat mitgeteilt wurde, zu prüfen, dass der ausgesprochene Einfluss der Luftstromgeschwindigkeit auf die Grösse des mit der dynamischen Methode bestimmten Diffusionskoeffizienten der verschiedenen Durchströmung der Kanäle des bisher verwendeten Diffusionsapparates zuzuschreiben ist, wurde ein neuartiger Diffusionsapparat, den wir «Universelle Diffusions Batterie» nennen, konstruiert, in welchem die Luftstromgeschwindigkeit durch jeden Kanal gleichgemacht werden kann.Die neue Diffusionsbatterie und ihre Vorteile werden beschrieben. Ihre Anwendung zeigt, dass auch mit gleicher Luftstromgeschwindigkeit durch jeden Kanal die Abhängigkeit der Diffusionskoeffizienten von der Luftstromgeschwindigkeit — nämlich, dass höhere Diffusionskonstanten mit grösseren Luftstromgeschwindigkeiten erhalten werden — doch besteht. Es werden die Resultate einer Vergleichung der Werte des Diffusionskoeffizienten, wie siebei Benützung der Diffusionsapparate der alten und neuen Bauart erhalten werden, mitgeteilt.Die Erklärung, welche sich auf unwiderlegbare theoretische Überlegungen stützt, dass die Abhängigkeit des Diffusionskoeffizienten von der Luftstromgeschwindigkeit durch die Heterogenität der Kondensationskerne verursacht wird — wie sie vor einiger Zeit vonPollak & Metnieks, gegeben wurde — scheint die richtige zu sein oder erfasst wenigstens den grössten Teil der Erscheinung.

---

---

The research reported in this article has been sponsored and supported in part by the Geophysics Research Directorate of the Air Force Cambridge Research Center, Air Research and Development Command, United States Air Force, under Contract AF 61(052)-26, through the European Office, ARDC in Brussels.     

Secondary Production of Macrobenthic Communities in Seagrass (<Emphasis Type="Italic">Zostera marina</Emphasis>, Eelgrass) Beds and Bare Soft Sediments Across Differing Environmental Conditions in Atlantic Canada

In nearshore ecosystems, habitats with emergent structure are often assumed to have higher ecosystem functioning than habitats lacking structure. However, such habitat-specific differences may depend on the surrounding environment. In this study, I examine the robustness of habitat-specific differences in ecosystem functioning for seagrass (Zostera marina) and adjacent bare soft sediments across varying environmental conditions on the Atlantic Coast of Nova Scotia, Canada, using secondary production as a metric. I also examine relationships of community secondary production and faunal structure with measured environmental variables (water depth, temperature, exposure, sediment, and plant properties). Benthic secondary production (invertebrates ≥500 μm) was higher in seagrass compared to bare sediments only at exposed sites with sandy sediments low in organic content, deep and cool water, and high belowground plant biomass. A regression relating community secondary production to the environmental variables explained 56% of the variance, while a constrained ordination explained 16% of the community structure. Important environmental determinants of community production were shoot density, temperature, depth, exposure, sediment organic content, and belowground plant biomass. Community structure was influenced by these variables plus sediment sand content and canopy height. This study shows that habitat-specific differences in secondary production may not be consistent across varying environmental conditions. Furthermore, seagrass beds are not always associated with higher ecosystem functioning than adjacent bare sediment. Both the surrounding environmental conditions and the presence of habitat structure should be considered for optimal management of nearshore ecosystems.     

Temporal variation in abundance and fecundity of the invading copepod Eurytemora americana in Bahía Blanca Estuary during an unusual year

Eurytemora americana has been only reported as invader in Bahía Blanca Estuary, Argentina within the South Hemisphere. There are a few experimental researches under laboratory conditions done with this species and its reproductive behaviour around the world is very scarce. Consequently, it is still not possible to completely understand its population dynamics. In the present study, E. americana reproductive temporal behaviour and relationships among abundance, female size, egg production and hatching success were examined in the Bahía Blanca Estuary, during 2007 pulse. In order to determine the potential relationships between these variables and the environmental variables, experimental incubations were conducted in the laboratory simulating natural conditions. Spearman’s rank correlation was used to analyze the relationships among all variables. Temporal change of biotic and environmental variables was corroborated by a Mann–Whitney/Kruskal–Wallis non-parametric tests, with significant differences (p ? 0.01) in all variables throughout the study. Abundance population results showed very high values in relation to those recorded in recent years in Bahía Blanca Estuary. This response could be due to the unusual combination of environmental factors (polar wave with temperatures ≤6 °C and a drought period with high salinities, 32.7–36.6) recorded during the studied winter period. Significant positive correlations between abundance and salinity (p < 0.01, n = 226), and hatching success (p < 0.01, n = 25) as well as a significant negative correlation between abundance and chlorophyll a (p < 0.01, n = 226) were found. Although E. americana shows a k-strategy within its annual pulse, it presented two markedly distinct behaviours depending on temporal environmental variability. From July to early september, when the estuary evidenced high salinity, low temperature and high food availability, E. Americana showed large females, large clutch size and high hatching success. When environmental conditions became unfavorable from September to October, small females, small clutch size and very low hatching success were observed. The latter is associated with diapause egg laying which ensures population recruitment. According to our findings the particular combination of low temperatures, high salinities and high available food (i.e. variables which each year modulate its pulse) during 2007 winter–spring, favored the great development of E. americana. This invading species in its opportunistic role has managed to exploit a vacant niche in the estuary, developing two different behaviours within the k-strategy depending on change in environmental conditions.     

Carbon capture and storage policy in the United States: A new coalition endeavors to change existing policy

Carbon capture and storage (CCS) is considered by some to be a promising technology to reduce greenhouse gas emissions, and advocates are seeking policies to facilitate its deployment. Unlike many countries, which approach the development of policies for geologic storage (GS) of carbon dioxide (CO₂) with nearly a blank slate, the U.S. already has a mature policy regime devoted to the injection of CO₂ into deep geologic formations. However, the existing governance of CO₂ injection is designed to manage enhanced oil recovery (EOR), and policy changes would be needed to manage the risks and benefits of CO₂ injection for the purpose of avoiding GHG emissions. We review GS policy developments at both the U.S. federal and state levels, including original research on state GS policy development. By applying advocacy coalition framework theory, we identify two competing coalitions defined by their beliefs about the primary purpose of CO₂ injection: energy supply or greenhouse gas (GHG) emission reductions. The established energy coalition is the beneficiary of the current policy regime. Their vision of GS policy is protective: to minimize harm to fossil energy industries if climate policy were to be enacted. In contrast, the newly formed climate coalition seeks to change existing GS policy to support their proactive vision: to maximize GHG reductions using CCS when climate policy is enacted. We explore where and at what scale legislation emerges and examine which institutions gain prominence as drivers of policy change. Through a detailed textual analysis of the content of state GS legislation, we find that the energy coalition has had greater success than the climate coalition in shaping state laws to align with its policy preferences. It has enshrined its view of the purpose of CO₂ injection in state legislation, delegated authority for GS to state agencies aligned with the existing policy regime, and protected the EOR status quo, while creating new opportunities for EOR operators to profit from the storage of CO₂ The climate coalition's objective of proactively putting GS policy in place has been furthered, and important progress has been made on commonly held concerns, such as the resolution of property rights issues, but the net result is policy change that does not significantly revise the existing policy regime.