Nitrate concentrations and nitrate reduction in acid groundwater/lake systems in southern Australia

We have analyzed nitrate in saline groundwaters from the Lake Tyrrell region of north-western Victoria and the Norseman-Salmon Gums region of south-eastern Western Australia. These are regions where acid (pH<4) groundwater exists naturally. The nitrate concentrations of these groundwaters are ∼5–10 times lower than nitrate concentrations from other arid and semi-arid regions around the world and in Australia. The source of the nitrate to the groundwater is soil organic matter, not anthropogenic activity. The data from the Lake Tyrrell system suggest that the gain and loss of fixed nitrogen are probably important biogeochemical processes in the early evolution of these waters. Nitrate reduction also occurs in the shallow groundwaters of Western Australia. Nitrate reduction is very low due to the low concentrations of organic matter present. Groundwaters in both of these systems eventually discharge along the edges of playas. This process may concentrate nitrate in the surficial salts of the playa.     

Simulation of surface urban heat islands under ‘IDEAL’ conditions at night part 1: Theory and tests against field data

Observations show that the urban heat island in the atmospheric layer below roof level is most strongly developed during calm, cloudless conditions at night. This paper outlines two versions of a numerical model to describe the cooling of rural and street canyon surfaces under these conditions using surface thermal and radiative properties and the radiative geometry of the canyons. One version uses a full system of differential equations and the other the simpler force-restore approach. The two approaches are shown to be in general agreement and the output of the simpler model is shown to give a faithful representation of cooling of rural and urban surfaces, and therefore heat islands, when compared with field observations.     

Changing Business Opportunities: The Geography Of Rapidly Growing Small U.S. Private Firms, 1982–1992*

The objective of this paper is to analyze the changing geography of the 500 fastest growing small, private companies, as defined by Inc magazine, in the United States from 1982 to 1992. The study focuses on rates of formation of these firms within types of metropolitan region, the impact of economic restructuring, and the locational dynamics of companies within the fastest growing economic sectors. Results suggest that there is little regional or hierarchical logic to the distribution of the firms, that the influence of economic restructuring is clearly evident, and that new rapidly growing high-technology firms are highly concentrated in San Francisco and Los Angeles, while higher-order service firms are dispersing down the urban hierarchy.     

The identification of radial velocity anomalies in the lower mantle using an interference method

A radial velocity anomaly in the lower mantle may cause a triplication in the travel-time curve for short-period P waves, but the first two arrivals may not be separable visually on seismograms over a distance range of about 4–10°. However, the changes of slowness and azimuth as a function of time can be used to infer the presence of interfering signals. Some of the interference effects that can be generated synthetically are often observed on seismograms of earthquakes recorded at the Yellowknife array at distances close to 50°, 80° and 90°. The data from Yellowknife provide evidence for the presence of regions of high velocity gradients at depths of about 1250, 2400 and 2730 km that also show rapid lateral variations. Numerous P arrivals from South American earthquakes that traverse the lowest 500 km of the mantle beneath the Caribbean region have been used to illustrate the main features of the interference method.     

Properties, origin and nomenclature of rodlets of the inertinite maceral group in coals of the central Appalachian basin, U.S.A.

Resin rodlets, sclerenchyma strands and woody splinters, which are collectively called rodlets, were studied by chemical, optical petrographic, and scanning-electron microscopic (SEM) techniques. A study was made of such rodlets from the bituminous coal beds of the central Appalachian basin (Pennsylvanian; Upper Carboniferous) of the United States. Comparisons were made with rodlets from coal beds of the Illinois basin, the Southern Anthracite Field of Pennsylvania, the St. Rose coal field of Nova Scotia, and European and other coal fields. In order to determine their physical and chemical properties, a detailed study was made of the rodlets from the Pomeroy coal bed (high volatile A bituminous coal; Monongahela Formation; Upper Pennsylvanian) of Kanawha County, West Virginia. The origin of the rodlets was determined by a comparative analysis of a medullosan (seed fern) stem from the Herrin (No. 6) coal bed (high volatile C bituminous coal; Carbondale Formation) from Washington County, Illinois. Rodlets are commonly concentrated in fusain or carbominerite layers or lenses in bituminous coal beds of the central Appalachian basin. Most of the rodlets examined in our study were probably derived from medullosan seed ferns. The three types of rodlets are distinguished on the basis of cellularity, morphology and fracture.The resin rodlets studied by us are noncellular and appear to be similar in properties and origin to those found in coal beds of the Middle and Upper Pennsylvanian of the Illinois basin. The resin rodlets extracted from the Pomeroy coal bed exhibit high relief and high reflectance when polished and viewed in reflected light; they are opaque in transmitted light. In cross section, the resin rodlets are oval to round and have diameters ranging from 60 to 450 μm. Many are solid, but some have vesicles, canals or cavities, which are commonly filled with clay, probably kaolinite. Typically, they have distinct fracture patterns (“kerfs”) in longitudinal and cross sections and many are characterized by dense (probably oxidized) rims. The orientation and amounts of void space and mineralization of resin rodlets in coal have resulted in much confusion in their recognition and classification. The resin rodlets are petrographically recognized as sclerotinites of the inertinite maceral group. We here propose that resin rodlets be assigned to the maceral variety of sclerotinites termed “resino-sclerotinite” because of their presumable resinous origin. Other investigators have confused some fusinitized resin rodlets with fungal masses, which have different morphological properties and which probably have different chemical properties. We here propose that such fungal masses be assigned to the maceral variety of sclerotinites termed “fungo-sclerotinite.”The sclerenchyma strands examined in our study are cellular, thick-walled, and crescent-shaped in cross section. They exhibit high reflectance and high relief and belong to semifusinite and fusinite of the inertinite maceral group. Sclerenchyma strands are commonly associated with resin canals in Medullosa and related seed-fern genera, which are common in coal balls of the Illinois basin. We here propose adoption of the maceral varietal terms “sclerenchymo-fusinite” and “sclerenchymo-semifusinite” for these bodies.The woody splinters in the Pomeroy coal bed are cellular and thin-walled and have scattered pits as much as a few microns in diameter. They are dark brown to black in transmitted light and commonly have a lower reflectance than the resino-sclerotinite and sclerenchymo-fusinite of the Pomeroy coal. The woody splinters belong to semifusinite and fusinite of the inertinite maceral group. The maceral varietal terms “xylemo-semifusinite” and “xylemo-fusinite” are here proposed for these bodies.Elemental chemical data for the resin rodlets of the Pomeroy coal bed of the central Appalachian basin indicate that resin rodlets have significantly lower atomic H/C and O/C ratios than do sclerenchyma strands and woody splinters. The lower atomic H/C and O/C ratios of the resin rodlets correlate with the highest reflectance. In the coal ball medullosan seed-fern stem from the Herrin (No. 6) coal bed of the Illinois basin, the reflectances of the resin rodlets, woody splinters and sclerenchyma strands are similar and comparable to those of associated vitrinite in the coal ball stem and in the attached coal. However, resin rodlets and sclerenchyma strands in the attached coal have significantly higher reflectances, similar to those of the Pomeroy coal.     

Further evidence for radial velocity anomalies in the lower mantle

Summary Wright andLyons (1981) used a least-squares matching technique (LMM) and an adaptive processing method (ADP) to study the behaviour of slowness and azimuth measurements made on two synthetic interfering wavelets having different arrival vectors and onset times. We have applied these results to the analysis of real array seismograms. Some of the effects generated synthetically are frequently observed on real seismograms of earthquakes recorded at Yellowknife at distances close to 50° and 90°. We have also processed sufficient data to illustrate how the interference phenomenon can be used to confirm the presence of radial velocity anomalies in the lower mantle. NumerousP arrivals from South American earthquakes at distances between 78° and 98° suggest the presence of two radial velocity anomalies at depths close to 2400 and 2730 km below the Caribbean region; these anomalies also appear to vary laterally.Contribution No. 864 from the Earth Physics Branch.     

The measurement of reactive silicate in saline-hypersaline lakes: examples of the problem

The analysis of reactive silicate or H₄SiO₄ in saline lake waters using the silicomolybdic acid method developed by Mullin and Riley (1955) suffers from a rather severe salt interference. Our data show that the interference occurs in waters where both chloride and sulfate are the major anions. The interference leads to lower than actual values (by as much as 50 per cent). Until the chemical mechanism of the interference is quantitatively understood, dilution with deionized water appears to be the best approach to obtaining reliable data. This may limit the technique's usage in waters of high TDS, and low reactive silicate.     

The solubility control of rare earth elements in natural terrestrial waters and the significance of PO 4 3− and CO 3 2− in limiting dissolved rare earth concentrations: A review of recent information

Rare earth element (REE) concentrations in alkaline lakes, circumneutral pH groundwaters, and an acidic freshwater lake were determined along with the free carbonate, free phosphate, and free sulfate ion concentrations. These parameters were used to evaluate the saturation state of these waters with respect to REE phosphate and carbonate precipitates. Our activity product estimates indicate that the alkaline lake waters and groundwaters are approximately saturated with respect to the REE phosphate precipitates but are significantly undersaturated with respect to REE carbonate and sulfate precipitates. On the other hand, the acidic lake waters are undersaturated with respect to REE sulfate, carbonate, and phosphate precipitates. Although carbonate complexes tend to dominate the speciation of the REEs in neutral and alkaline waters, our results indicate that REE phosphate precipitates are also important in controlling REE behavior. More specifically, elevated carbonate ion concentrations in neutral to alkaline natural waters tend to enhance dissolved REE concentrations through the formation of stable REE-carbonate complexes whereas phosphate ions tend to lead to the removal of the REEs from solution in these waters by the formation of REE-phosphate salts. Removal of REEs by precipitation as phosphate phases in the acid lake (pH=3.6) is inconsequential, however, due to extremely low [PO ₄ ^3– ] _F concentrations (i.e., 10^–23 mol/kg).     

Late holocene paleoclimatic and paleobiologic records from sediments of Devils Lake,North Dakota

An 84 cm sediment core collected from the center of Devils Lake, North Dakota, was analyzed at 1-cm intervals for,²¹⁰Pb,¹³⁷Cs, sediment conductivity, the concentrations of, biogenic silica, total organic carbon, carbon to nitrogen ratio, and the carbon and nitrogen isotopic composition of the organic fraction. Variations in²¹⁰Pb activities in the upper 20 centimeters indicate that sediment accumulations rates in Devils Lake are not constant, and that accumulation rates were highest during periods of high lake level. The mean sedimentation accumulation rate was calculated as 0.24 cm^–1 yr. The¹³⁷Cs profile is characterized by near-surface maximum concentrations, possibly the result of redistribution of¹³⁷Cs during salinity excursions.Biogenic silica is strongly correlated to lake level in Devils Lake. Periods of low lake level (characterized by high sediment conductivity) correspond to low biogenic silica concentrations. The trends in biogenic silica are attributed to variations in diatom productivity in the lake and to variations in sediment accumulation rates. Based on biogenic silica content and the composition of organic matter in the sediment (total organic carbon, carbon:nitrogen ratio and the ¹³C and ¹⁵N composition of total organic matter), paleobiologic conditions of Devils Lake during low lake stands were characterized by, (1) decreased primary productivity, (2) decreased input of detrital organic matter, and (3) increased nitrogen availability.During the 350 years of sediment accumulation represented by the 84-cm sediment core Devils Lake has experienced two periods of sustained high lake level; one between about 130 and 170 years ago (1820 to 1860 A.D.) and the second between 270 and 310 years ago (1680 to 1720 A.D.). Devils Lake experienced a period of intense drying about 260 years ago (1720 A.D.).