Innovation and the dynamics of global warming

Global warming and the carbon cycle are a dynamic system with positive feedbacks. Fossil fuels are exhaustible resources. These two facts mean that innovation in clean energy technology, rather than mitigating global warming, can lead to a permanently higher temperature path. This paper explores the impact of innovation in the simplest model linking the economic theory of exhaustible resources with positive feedback dynamics in the carbon cycle.     

In situ seagrass photosynthesis measured using a submersible, pulse-amplitude modulated fluorometer

Assessments of photosynthetic activity in marine plants can now be made in situ using a newly developed, submersible, pulse-amplitude modulated (PAM) fluorometer: Diving-PAM. PAM fluorometry provides a measure of chlorophyll a fluorescence using rapid-light curves in which the electron-transport rate can be determined for plants exposed to ambient light conditions. This technique was used to compare the photosynthetic responses of seagrasses near Rottnest Island, Western Australia. Several fluorescence parameters were measured as a function of time of day and water depth; electron-transport rate (ETR), quantum yield, photochemical quenching and non-photochemical quenching and Photosystem II (PSII) photochemical efficiency (F _v :F _m ratio) were measured. Results indicate that recent light-history plays a crucial role in seagrass photosynthetic responses. Maximum ETR of Posidonia australis, Amphibolis antarctica and Halophila ovalis is influenced by the irradiance during the diurnal cycle, with low rates at dawn and dusk (<10 μmol electron m⁻² s⁻¹), highest rates in late morning (40 to 60 μmol electron m⁻² s⁻¹) and a mid-day depression. Maximum ETR and PSII photochemical efficiency varied widely between seagrass species and were not correlated. A comparison of photochemical to non-photochemical quenching indicated that seagrasses in shallow water receiving high light have a high capacity for non-photochemical quenching (e.g. light protection) compared to seagrasses in deep water. These results indicate that in situ measurements of photosynthesis will provide new insights into the mechanisms and adaptive responses of marine plants. Received: 26 May 1997 / Accepted: 27 May 1998     

Analyse von Quecksilber in Seeadlerfedern aus Mecklenburg-Vorpommern mit Hilfe der Hamburger Protonenmikrosonde

With the aid of the Hamburg proton micro-probe, we examined the concentration of mercury in sea eagle feathers collected over the course of several decades in the Mecklenburg-Vorpommern area. Based on the sites where these feathers were collected and the data of these findings, it is possible to get a differential picture of mercury contamination related both temporally and regionally to the mercurial pollution of seed mordants used agriculturally. We compared the concentrations found with a basic “geogenic” contamination which was also to be seen in the feather samples from the last century as detected in museum animal specimens.     

Projecting Large-Scale Area Changes in Land Use and Land Cover for Terrestrial Carbon Analyses

One of the largest changes in US forest type areas over the last half-century has involved pine types in the South. The area of planted pine has increased more than 10-fold since 1950, mostly on private lands. Private landowners have responded to market incentives and government programs, including subsidized afforestation on marginal agricultural land. Timber harvest is a crucial disturbance affecting planted pine area, as other forest types are converted to planted pine after harvest. Conversely, however, many harvested pine plantations revert to other forest types, mainly due to passive regeneration behavior on nonindustrial private timberlands. We model land use and land cover changes as a basis for projecting future changes in planted pine area, to aid policy analysts concerned with mitigation activities for global climate change. Projections are prepared in two stages. Projected land use changes include deforestation due to pressures to develop rural land as the human population expands, which is a larger area than that converted from other rural lands (e.g., agriculture) to forestry. In the second stage, transitions among forest types are projected on land allocated to forestry. We consider reforestation, influences of timber harvest, and natural succession and disturbance processes. Baseline projections indicate a net increase of about 5.6 million ha in planted pine area in the South over the next 50 years, with a notable increase in sequestered carbon. Additional opportunities to expand pine plantation area warrant study of landowner behavior to aid in designing more effective incentives for inducing land use and land cover changes to help mitigate climate change and attain other goals.     

SYNTHESIS OF DATA FROM STUDIES BY THE NATIONAL IRRIGATION WATER-QUALITY PROGRAM1

ABSTRACT: From 1986 to 1993, the National Irrigation Water-Quality Program (NIWQP) of the U.S. Department of the Interior studied whether contamination was induced by irrigation drainage in 26 areas of the Western United States. In 1992, a study to evaluate and synthesize data collected during these 26 investigations began. Selenium, boron, and molybdenum are the trace elements and DDT the pesticide most commonly found in surface water at concentrations exceeding chronic criteria for the protection of aquatic life. In six of the areas, the median selenium concentration exceeded the criterion. Aquatic-life criteria have not been developed for uranium, but the median uranium concentration exceeded the proposed Maximum Contaminant Level for drinking water in seven areas. A principal components analysis indicates that severity of selenium contamination is not related to the severity of contamination by boron, molybdenum, and arsenic. Arsenic, boron, molybdenum, and selenium concentrations are nearly the same in both filtered and unfiltered samples, which indicates that contaminant concentrations in filtered samples can be directly compared with biological-effects data developed using unfiltered samples. At a given site, selenium concentrations in surface water can change by an order of magnitude during the course of a year and from one year to another.     

Phytoremediation experimentation with the herbicide bentazon

An experiment was performed on six species of trees to determine the feasibility of remediating groundwater contaminated with an agricultural herbicide, bentazon, at a site in southern Louisiana. Fate studies on bentazon support that it is translocated to the plant leaves where it is degraded by photolysis to lower-order derivative compounds within short periods of time. Both transpiration observations and dosing tests suggest that the most favorable phreatophyte and tolerant specie of tree to bentazon exposure was the black willow (Salix nigra).     

PHYTOPLANKTON PRODUCTIVITY AND BIOMASS IN THE CHARLOTTE HARBOR ESTUARINE SYSTEM,FLORIDA1

ABSTRACT: Phytoplankton carbon-14 productivity at a depth of 50 percent of surface light and chlorophyll-α concentrations were measured every other month from November 1985 through September 1986 at 12 stations in the Charlotte Harbor estuarine system. Maximum productivity and chlorophyll-α concentrations occurred during summer or early autumn near the mouths of tidal rivers. Most of the variability in light-normalized productivity and chlorophyll-α could be attributed to two factors derived from Principal Component Analysis of ambient water-quality characteristics. One factor related to seasonal variability and the other to spatial variability. The seasonal factor incorporated the interaction of temperature and nutrients. The spatial factor incorporated the interaction of salinity, nutrients, and water color that resulted from the mixing of freshwater inflow and seawater. Although freshwater inflow increased the availability of nutrients in low salinity (less than 10‰) waters, the highly colored freshwater restricted light penetration and phytoplankton productivity. Maximum productivity and biomass occurred where color associated with the freshwater inflow had been diluted by seawater so that light and nutrients were both available. Concentrations of inorganic nitrogen were often at or below detection limit throughout most of the high salinity (greater than 20‰) waters of the estuary and was probably the most critical nutrient in limiting phytoplankton productivity.     

Fetal akinesia/hypokinesia sequence: Prenatal diagnosis and intra-familial variability

Intrauterine fetal movement plays a key role in normal embryonic and fetal development (Moessinger, 1983). When movement is absent or decreased, abnormal development takes place which can be appreciated in newborns and/or fetuses with the fetal akinesia/ hypokinesia sequence. This sequence is caused by a number of heterogeneous entities which result in decreased fetal movements by the action of intrinsic or extrinsic factors. Prenatal diagnosis of the akinesia/hypokinesia sequence may be possible during the second trimester through the use of real-time ultrasonographic evaluation of fetal movement. We report a family with three consecutive affected pregnancies in which the prenatal presentation of this sequence varied. Based on the phenotypic findings of the three affected fetuses, we believe that although they superficially resemble those features found in the New–Laxova syndrome, they are probably affected with a distinctly different lethal form of akinesia/ hypokinesia transmitted in an autosomal recessive fashion.     

Factors affecting heavy-duty diesel vehicle emissions

Societal and governmental pressures to reduce diesel exhaust emissions are reflected in the existing and projected future heavy-duty certification standards of these emissions. Various factors affect the amount of emissions produced by a heterogeneous charge diesel engine in any given situation, but these are poorly quantified in the existing literature. The parameters that most heavily affect the emissions from compression ignition engine-powered vehicles include vehicle class and weight, driving cycle, vehicle vocation, fuel type, engine exhaust aftertreatment, vehicle age, and the terrain traveled. In addition, engine control effects (such as injection timing strategies) on measured emissions can be significant. Knowing the effect of each aspect of engine and vehicle operation on the emissions from diesel engines is useful in determining methods for reducing these emissions and in assessing the need for improvement in inventory models. The effects of each of these aspects have been quantified in this paper to provide an estimate of the impact each one has on the emissions of diesel engines.