Quantifying septic nitrogen loadings to receiving waters: Waquoit Bay,Massachusetts

Abstract

Waquoit Bay, a shallow bay on Cape Cod, Massachusetts, is exhibiting symptoms of eutrophication, largely attributed to septic nitrogen inputs. This study assessed septic nitrogen inputs by linking a three-dimensional ground-water model, a geographic information system (GIS), and a customized spatio-temporal nitrogen loading program. Owing to the slow speed of ground-water movement, the bulk of septic nitrogen entering the bay lags behind development by nearly a decade. Even if residential development is held at 1989 levels, nitrogen input from septic systems wilt increase by 36% over the current levels. At full residential build-out (i.e., development), septic nitrogen loading will eventually increase to more than twice the current levels.     

Design of a view-based DSS for location planning

Abstract.

The traditional approach in DSS falls short of providing a highly interactive problem solving environment for planning. Often, cumbersome procedures are required to implement optional plans and obtain feedback information. In dynamic graphic systems, the user is able to view different linked graphic representations (e.g., spatial or statistical graphs) of statistical data and interact (e.g., selecting items) with these graphics. In this paper we describe the design of a DSS for planning facility locations, which uses principles of dynamic graphics to achieve a highly interactive problem solving environment. As in dynamic graphic systems, the user interacts with the DSS through active and linked views. However, where views in dynamic graphics are different representations of a given dataset, the views in the DSS are active data structures describing the facility system to be planned from different perspectives. The declarative and procedural forms of knowledge involved are identified by a logical analysis of planning problems. A frame-based formalism is proposed to represent the knowledge contained in the views. The main advantage of this view-based approach is that it offers the user a highly flexible and interactive environment for performing ‘what-if’ analyses.     

ENVIRONMENTAL CONSEQUENCES OF HUMAN ACTIVITY ON THE YELLOW RIVER AND ITS DELTA,CHINA

The Yellow River is unique among the major rivers of the world because of its extremely heavy sediment load in relation to its small discharge. The Yellow River has changed courses numerous times during the past 5000 to 6000 years. With its large sediment load, most of which comes from the Loess Plateau of central China, the river has created a number of deltas along the coast of northern China. The abandoned deltas are eroding, whereas the present delta being formed in Bohai Bay is growing rapidly. Human activity, including extensive agriculture, heavy water consumption, the use of river-control structures, and war, has been responsible for many of the changes occurring in the Yellow River and its delta. [Key words: hydrology, loess, floods, Yellow River, Bohai Bay, China.]     

DUST FALL IN THE TAKLA MAKAN DESERT OF CHINA

The Takla Makan Desert is one of the supposed sources of eolian deposits in the eastern China and the North Pacific Ocean. Lack of direct measurements hinders the theoretical interpretation of material exchange between the atmosphere and land surface as well as the sediment budget of the region. From 1992 to 1994, four measuring sites were established in the vicinity of 84°E meridian along a 380 km observation traverse from the northern margin to the central desert. Data were collected on quantities of dust fall and sedimentary characteristics of airborne sediments, including grain-size distributions as well as chemical and mineral compositions. The quantities of annual dust fall were 10² to 10³ tons km^-2 yr^-1, increasing from the margin toward the central desert. Monthly concentrations of particles finer than 0.02 mm in diameter ranged from 0.06 to 1.25 mg m^-3 over the three-year observation period. The elemental ratio and the element enrichment factor ruled out the Takla Makan Desert as possible sources of the dust in Hawaii and Alaska. The mean geometric diameter of airborne sediments in the 4 to 8 m surface layer from the Luntai oasis was 0.038 mm and from the interior ranged 0.064 to 0.067 mm being moderately to poorly sorted. Weight percent of particles finer than 0.063 mm in diameter were from 83.5% to 47.7%, decreasing toward the central desert. Distributions of the airborne particles were unimodal with peak diameters of 0.06 to 0.07 mm in the central desert and 0.02 to 0.06 mm in the sites toward the edge of the desert. [Key words: dust fall, sedimentary characteristics, Takla Makan Desert.]     

Finding shortest paths on real road networks: the case for A*

The problem of identifying the shortest path along a road network is a fundamental problem in network analysis, ranging from route guidance in a navigation system to solving spatial allocation problems. Since this type of problem is solved so frequently, it is important to craft an approach that is as efficient as possible. Based upon past research, it is generally accepted that several efficient implementations of the Dijkstra algorithm are the fastest at optimally solving the ‘one‐to‐one’ shortest path problem (Cherkassky et al. 1996 Cherkassky, B. V., Goldberg, A. V. and Radzik, T. 1996. Shortest paths algorithms: theory and experimental evaluation.. Mathematical Programming: Series A and B, 73: 129–174. [Crossref], [Web of Science ®] , [Google Scholar]). We show that the most efficient state‐of‐the‐art implementations of Dijkstra can be improved by taking advantage of network properties associated with GIS‐sourced data. The results of this paper, derived from tests of different algorithmic approaches on real road networks, will be extremely valuable for application developers and researchers in the GIS community.     

The Sustainable Global Energy Economy: Hydrogen or Silicon?

A sustainable global silicon energy economy is proposed as a potential alternative to the hydrogen economy. This first visualization of a silicon energy economy is based on large-scale and carbon-neutral metallic silicon production from major smelters in North Africa and elsewhere, supplied by desert silica sand and electricity from extensive solar generating systems. The resulting “fuel silicon” is shipped around the world to emission-free silicon power stations for either immediate electricity generation or stockpiling. The high energy density of silicon and its stable storage make it an ideal material for maintaining national economic functioning through security of base load power supply from a renewable source. This contrasts with the present situation of fossil fuel usage with its associated global warming and geopolitical supply uncertainties. Critical technological requirements for the silicon economy are carbon-neutral silicon production and the development of efficient silicon-fired power stations capable of high-temperature rapid oxidation of fuel silicon. A call is made for the development of research effort into these specific engineering issues, and also with respect to large-scale economical solar power generation.     

Geomorphic constraints on the active tectonics of southern Taiwan

Taiwan is a region of rapid active tectonics, yet the study of the tectonic processes that shape the interior of the island is difficult due to the high rates of erosion and dense vegetation. We use digital topography to look for indications of active deformation preserved in the local geomorphology. In particular, anomalies in the regional pattern of drainage are used to infer zones of enhanced tectonic activity. The apparent anticlockwise rotation of major river systems in plan view indicates the presence of a diffuse zone of left-lateral shear running down the southeastern side of Taiwan. Asymmetries in the catchments of individual drainage basins show the influence of varying rates of uplift across southern Taiwan, with the most rapid uplift close to Taitung at the indentation point of the Luzon arc with the Chinese continental margin. Our interpretations, though based predominantly on remote-sensing observations, are consistent with the available field evidence. This study demonstrates the usefulness of drainage basins as tectonic markers in the quantification of regional strain and uplift, which may have wider applicability in other deforming parts of the world.     

Progress in isotope paleohydrology using lake sediment cellulose

Recent advances in sample preparation techniques and mass spectrometry have fostered more routine oxygen isotope analysis of aquatic cellulose in lake sediment cores, a proxy for lake water oxygen isotope history. These methodological developments have significantly increased the feasibility of incorporating this approach into high-resolution, multi-site, and multi-proxy studies, which are frequently necessary to answer complex hydrological, hydroecological and hydroclimatic questions requiring a paleoenvironmental perspective. Direct translation of lake sediment aquatic cellulose oxygen isotope composition into lake water oxygen isotope composition offers appreciable opportunity for quantitative paleohydrological reconstructions, as evidenced by studies conducted over the past 15 years that span Holocene and pre-historical timescales.     

Evaluation of ostracod-based palaeoenvironmental reconstruction with instrumental data from the arid Faiyum Depression,Egypt

The utility of ostracod-based palaeoenvironmental reconstruction was evaluated using instrumental data for Lake Qarun, Egypt. The euryhaline ostracod Cyprideis torosa was the only species found in the lake’s recent sediment record. This species is known to tolerate salinity levels and water solute compositions that may prevent colonisation by other species. Oxygen and carbon isotope ratios of ostracod carbonate from lake sediments covary with changes in instrumental values for lake level and salinity for the period 1890–1974. δ¹³C-values correlate negatively with lake water salinity (r ² = 0.87) and δ¹⁸O-values correlate negatively with measured lake level changes (r ² = 0.41). Other ostracod proxy data provide qualitative information on lake level trends. Fossil assemblage data (juvenile/adult and valve/carapace ratios and valve preservation) provide information on wave energy. Ecophenotypic variation of C. torosa valves provided some useful palaeolimnological information. Sr/Ca and Mg/Ca ratios in ostracods were not found to reflect water composition, due to the uncoupling of these ratios with salinity in Lake Qarun. Overall, our results highlight the need to calibrate ostracod proxy data in modern systems prior to their use for palaeoenvironmental reconstruction.