Atmospheric trace metals and sulfate in the Greenland Ice Sheet

Chemical analyses of surface snow and dated deep ice core samples from central Greenland suggest that Zn, Pb and sulfate are presently being deposited there at two to three times the natural rates. No recent increases in Cd or V concentrations were observed. Pre-1900 ice shows no measurable effect of the activities of man and represents a good natural aerosol baseline. High enrichment factors relative to average crustal material were observed for Zn, Pb, Cd and sulfate in all samples indicating a natural source other than continental dust is responsible. A high temperature process or vapor phase origin for these enriched elements, possibly volcanism, seems likely.     

Man's impact on shorelines and nearshore environments: a geomorphological perspective

Man evolved late in terms of geologic history, yet he has become a major geomorphologic agent despite his short tenure on Earth. His ability to alter the materials, processes and forms along the world's shorelines are manifested in a variety of ways. Beginning with the indirect changes that resulted from early agriculture and animal husbandry, he progressed to direct modification through reclamation and harbor construction. Today, in the name of shoreline stabilization, thousands of kilometers of natural shoreline have been modified by the addition of artificial structures.     

Preliminary assessment of trace metals and polycyclic aromatic hydrocarbons in the sediments

Total concentrations of Cd, Cr, Co, Fe, Pb, Ni, Mn and Zn were determined by atomic absorption spectrophotometry in the surface sediments of Taylor Creek, Southern Nigeria. The most concentrated trace metals, ranging from 113.2 to 5160.7 mg/g-dry weights were Fe, Pb, Mn, Ni and Zn. There was no significant variation in sediment-associated metal levels (P>0.05). The metal pollution index was highest at Agbia/Nedugo and is attributed to local contamination of the Creek. The concentrations of low molecular weight polycyclic aromatic hydrocarbons (PAHs) were also detected and quantified in the sediments by capillary gas chromatography equipped with a flame ionization detector. The concentration levels of 178.1-1266.3 mg/g-wet weights were high for the PAHs. The results indicate that the pollutants, which are bio-accumulatable, could contribute to inferior biodiversity, and shifts in community composition from sensitive to tolerant taxa.     

Limits of solution of trace elements in minerals according to Henry's law: Review of experimental data

Results of a survey of experimental data on trace element partitioning between crystals and coexisting liquid and between crystals and coexisting aqueous fluid are reported. These studies involve combinations of elements such as Cs, Rb, K, Na, Li, Ba, Sr, Ni and Sm dissolved in minerals such as feldspars, micas, feldspathoids, garnets, pyroxenes, amphibole and olivine. It is shown that the concentration ranges of these elements in minerals with solution behavior according to Henry's law appear to extend to less than 1 wt.% and often to less than 100 ppm of the element in the crystalline phase.The available data indicate that the concentration ranges of solution in minerals according to Henry's law can be positively correlated with the difference of ionic radii between trace element and the host element for which the tracer is assumed to substitute. Furthermore, studies involving crystals and coexisting aqueous fluid have been used to determine whether Henry's law or Raoult's law adequately describes the solution. Based on the assumption that the aqueous fluid solution can be considered ideal, models have been proposed stating that if the difference between the ionic radii of the tracer and the host element in the crystalline phase is less than about 10% (relative to the host element), the solution is ideal (Raoult's law). With larger differences between the ionic radii, there is an excess free energy of mixing, although Henry's law is still obeyed in the concentration ranges where crystalliquid or crystal-fluid partition coefficients are independent of element concentration.     

Mobility and impact of trace metals in Barapukuria coal mining area, Northwest Bangladesh

Trace metals were analyzed in water and sediment samples from Barapukuria coal mine area of Bangladesh in order to evaluate their mobility and possible environment consequences. Cadmium is the most mobile element with an average partition coefficient (log K _d ) of 2.95 L/kg, while V is the least mobile element with a mean log K _d of 5.50 L/kg, and their order of increasing mobility is: V < As < Pb < Fe < Cr < Se < Mn < Ni < Zn < Cu < Ba < Sr < Cd. Contents of organic carbon in sediment samples shows strong positive correlations with most trace metals as revealed by the multivariate geostatistical analysis. The overall variation in concentration is mainly attributed to the discharge of effluents originating from the coal mining activities around the study area. Compared to their background, Ni and Cu are the most enriched while significant enrichment of As, Mn, Ba, Sr, Cr, and Pb is also observed in the sediments. Geoaccumulation indices (I _geo ) suggest sediments are moderately to heavily polluted with respect to Ni and Cu. The metal pollution index (MPI) varied from 91.91 to 212.01 and the highest value is found at site CM03 that is close to discharge point. The sediment quality guideline index (SQG-I _Intervention ) values (0.56–1.52) suggest that the sediments at the study area have moderate to high ecotoxicological risk.     

GEOTRACES - An international study of the global marine biogeochemical cycles of trace elements and their isotopes

Trace elements serve important roles as regulators of ocean processes including marine ecosystem dynamics and carbon cycling. The role of iron, for instance, is well known as a limiting micronutrient in the surface ocean. Several other trace elements also play crucial roles in ecosystem function and their supply therefore controls the structure, and possibly the productivity, of marine ecosystems. Understanding the biogeochemical cycling of these micronutrients requires knowledge of their diverse sources and sinks, as well as their transport and chemical form in the ocean.Much of what is known about past ocean conditions, and therefore about the processes driving global climate change, is derived from trace-element and isotope patterns recorded in marine deposits. Reading the geochemical information archived in marine sediments informs us about past changes in fundamental ocean conditions such as temperature, salinity, pH, carbon chemistry, ocean circulation and biological productivity. These records provide our principal source of information about the ocean's role in past climate change. Understanding this role offers unique insights into the future consequences of global change.The cycle of many trace elements and isotopes has been significantly impacted by human activity. Some of these are harmful to the natural and human environment due to their toxicity and/or radioactivity. Understanding the processes that control the transport and fate of these contaminants is an important aspect of protecting the ocean environment. Such understanding requires accurate knowledge of the natural biogeochemical cycling of these elements so that changes due to human activity can be put in context.Despite the recognised importance of understanding the geochemical cycles of trace elements and isotopes, limited knowledge of their sources and sinks in the ocean and the rates and mechanisms governing their internal cycling, constrains their application to illuminating the problems outlined above. Marine geochemists are poised to make significant progress in trace-element biogeochemistry. Advances in clean sampling protocols and analytical techniques provide unprecedented capability for high-density sampling and measurement of a wide range of trace elements and isotopes which can be combined with new modelling strategies that have evolved from the World Ocean Circulation Experiment (WOCE) and Joint Global Ocean Flux Study (JGOFS) programmes. A major new international research programme, GEOTRACES, has now been developed as a result of community input to study the global marine biogeochemical cycles of trace elements and their isotopes. Here, we describe this programme and its rationale.     

Geogenic sources and sinks of trace metals in the Larsemann Hills,East Antarctica: Natural processes and human impact

To evaluate the extent of human impact on a pristine Antarctic environment, natural baseline levels of trace metals have been established in the basement rocks of the Larsemann Hills, East Antarctica.From a mineralogical and geochemical point of view the Larsemann Hills basement is relatively homogeneous, and contains high levels of Pb, Th and U. These may become soluble during the relatively mild Antarctic summer and be transported to lake waters by surface and subsurface melt water. Melt waters may also be locally enriched in V, Cr, Co, Ni, Zn and Sn derived from weathering of metabasite pods. With a few notable exceptions, the trace metal concentrations measured in the Larsemann Hills lake waters can be entirely accounted for by natural processes such as sea spray and surface melt water input. Thus, the amount of trace metals released by weathering of basement lithologies and dispersed into the Larsemann Hills environment, and presumably in similar Antarctic environments, is, in general, not negligible, and may locally be substantial.The Larsemann Hills sediments are coarse-grained and contain minute amounts of clay-size particles, although human activities have contributed to the generation of fine-grained material at the most impacted sites. Irrespective of their origin, these small amounts of fine-grained clastic sediments have a relatively small surface area and charge, and are not as effective metal sinks as the abundant, thick cyanobacterial algal mats that cover the lake floors. Thus, the concentration of trace metals in the Larsemann Hills lake waters is regulated by biological activity and thawing–freezing cycles, rather than by the type and amount of clastic sediment supply.     

Palaeoclimatic cycles, global environmental changes and new glacial periods induced by the impact of extraterrestrial bodies

In terms of Earth-Sun geometry, the Milankovitch theory has successfully explained most of the cyclic palaeoclimatic variations during the history of the Earth, especially in the Quaternary. In this paper, the authors suggest that the impact of extraterrestrial bodies on the Earth may be another mechanism to cause palaeoclimatic cycles, global environmental changes and new glacial periods. Based on geological and geochemical records in the boundary layers produced by six huge Cenozoic bolide-impact events (65, 34, 15, 2.4, 1.1, 0.73 Ma B.P.), including those at 34, 15, 1.1 and 0.73 Ma B. P. which are represented by four famous tektite-strewn fields, the process and mechanics of palaeoclimatic cycles and global environmental catastrophes induced by extraterrestrial impact are discussed in detail. Impact-generated dust, soot and aerosol floating in the stratosphere could result in short-term (<1 year), rapid drop in temperature immediately after impact. Through self-regulation of the Earth’s climate system, the temperature at the surface slowly went up within 100a and maintained stable for a long time at 250K. If there were no other factors leading to the break-down of the newly-established equilibrium, a new glacial pound would be initiated. Estimating from the thickness of δ¹³C and δ¹⁸O anomalies in sediments across the impact boundary layer and deposition rate, the duration of two stages of the palaeoclimate cycle in the form of cold weather—greenhouse effect—normal weather was 10⁴ – 10⁵a, respectively. The conclusion deduced from the above model is supported by palaeotemperature change recorded by oxygen isotope in sediments across the impact boundary layer. The study was granted by the Scientific and Technological Bureau of Resources and Environment, Chinese Academy of Sciences (KZ952-J1-031) and the National Natural Science Foundation of China.     

The contribution of constructive geography to the problem of optimization of society's impact on the environment

The paper defines the notion of ‘constructive geography’. It traces its development in Soviet geography and attempts to evaluate its contribution to the development of the U.S.S.R.     

Chemical balance of the Earth's crust

The chemical composition and lithologic proportions of average sedimentary and igneous rocks are analyzed by a linear least squares regression. The best set of internally consistent data for sediments in geosynclines, continental platforms, deep ocean basin and the average igneous and sedimentary rock are shown below. These results are based on published estimates of the chemical composition of igneous and sedimentary rocks and the relative volume of sediments on the continents and in the deep ocean basins.

$\text{SiO}{}_2\text{A1}{}_2\text{O}{}_3\text{Fe(total)}\text{MgO}\text{CaO}\text{Na}{}_2\text{O}\text{K}{}_2\text{O}\text{CO}{}_2\text{Geosynclines}\text{55.2}\text{12.0}\text{3.6}\text{3.2}\text{8.3}\text{1.0}\text{2.4}\text{8.6}\text{Platforms}\text{49.5}\text{10.7}\text{3.2}\text{3.3}\text{12.3}\text{0.9}\text{2.2}\text{10.8}\text{Av. sed.}\text{55.9}\text{13.8}\text{4.4}\text{3.6}\text{5.8}\text{1.2}\text{2.6}\text{5.2}\text{Av. ig.}\text{59.0}\text{15.0}\text{5.0}\text{3.6}\text{7.0}\text{3.4}\text{3.2}$

The lithologic proportions are: geosyncline—24% sandstone, 58% shale, and 16% carbonate; platform—23% sandstone, 49% shale and 26% carbonate; average sedimentary rock—13% sandstone, 33% shale, 12% carbonate, and 41% pelagic; average igneous rock is approximately 2/3 granodiorite and 1/3 tholeiite. These data indicate a chemical balance of major elements in the Earth's upper crust during the last 1.5 b.y.     

Thermochemical redox equilibria of ZoBell's solution

The redox potential of ZoBell's solution, consisting of $\text{3.33 × 10}{}^{\mathrm{?3}}$ molar K₄Fe(CN)₆, $\text{3.33 × 10}{}^{\mathrm{?3}}$ molar K₃Fe(CN)₆ and 0.10 molar KCl, has been measured by a polished platinum electrode vs a saturated KCl, Ag/AgCl reference electrode. Measurements in the temperature range 8–85°C fit the equation $\text{E(}\text{volts}\text{) = 0.23145 ? 1.5220 × 10}{}^{\mathrm{?3}}\text{(t ? 25) ? 2.2449 × 10}{}^{\mathrm{?6}}\text{(t ? 25)}{}^2$ where $\text{t}$ is in degrees Celsius. Evaluation of literature data was necessary to obtain a reliable value for the Ag/AgCl half-cell reference potential as a function of temperature. Combining the measurements from this study with the literature evaluation of the Ag/AgCl reference potential yields the temperature dependent potential for ZoBell's solution: $\text{E(}\text{volts}\text{) = 0.43028 ? 2.5157 × 10}{}^{\mathrm{?3}}\text{(t ? 25) ? 3.7979 × 10}{}^{\mathrm{?6}}\text{(t ? 25)}{}^2$ relative to the standard hydrogen potential. From these data the enthalpy, entropy, free energy and heat capacity for the ferro-ferricyanide redox couple have been calculated. The temperature equation for the potential of ZoBell's solution may be used for checking potentiometric equipment in the determination of the redox potential of natural waters.     

The roving palate: North America's ethnic restaurant cuisines

Although patterns of food consumption, and foodways in general, have profound social, cultural and economic implications, geographers and other social scientists have accorded the topic minimal attention. By examining the identity, number and location of restaurants in the United States and Canada offering self-consciously ‘ethnic’ and regional cuisines, i.e. a form of gastronomic tourism, to largely non-ethnic and extra-regional patrons, we can begin to explore the shifting connotations of ethnicity and the general transnationalization of culture in recent years, as well as changing food preferences. The information available in classified telephone directories for 271 metropolitan areas (the SMSAs of the U.S. and their Canadian equivalents) enables us to chart the larger outlines of the North American ethnic restaurant scene ca. 1980. Analysis of all recent Pennsylvania directories and those of Philadelphia over the period 1920–1980 provides insight into the nonmetropolitan and historical dimensions of the phenomenon. Ethnic restaurant cuisines are now both quite numerous and widespread throughout the continent, and contain dietary items from virtually all the many immigrant groups present, be they major or minor. But the incidence of the cuisines relative to total number of inhabitants or restaurants varies greatly among regions and by category of metropolis. Furthermore, there is usually at best only a weak relationship between the geographic pattern of a given cuisine and that of the related immigrant stock. On the other hand, socioeconomic class, regional culture and volume of affluent visitors seem to be significant determinants. Of special interest are the patterns for the three dominant cuisines, Chinese, Italian and Mexican, and their variants, and the two most important élite cuisines, the French and Japanese.     

冻融循环作用下黄土孔隙率变化规律

冻融循环作用通过破坏黄土颗粒的大小和土体的骨架及组构影响黄土的孔隙率. 通过颗粒分析实验发现冻融循环后土体颗粒有变小趋势,且集中分布在0.01～0.05 mm,在冻融10次后颗粒大小趋于稳定. 对经历冻融循环后的黄土进行压汞实验,发现随着冻融次数的增加,土体孔隙中的大孔径先减少,后增多;小孔径先增多,后减少,最后向5～10 μm范围内集中. 土的孔隙率也随冻融次数的增加而发生变化. 原状黄土的孔隙率在冻融5次时达到最小值,在冻融10次时达到最大值,冻融10次之后原状黄土的孔隙率在40%上下波动,达到稳定状态. 重塑黄土在冻融3次时孔隙率减少了6%并达到最小值,在冻融5次时孔隙率增加3%并达到最大值,最后在40%上下波动,达到稳定状态. 渗透系数的变化曲线与通过压汞实验获得的孔隙率变化曲线相似,印证了随着冻融次数的增加黄土的孔隙率呈先减小,后增大,然后趋于稳定的变化规律.     

Historical changes of the regional and global hydrological cycles

The gradual accumulation of the Earth's hydrosphere, the land-to-water ratio, the periodic change of orogenesis and peneplanization stages, the timely and spatial change of the incoming solar energy determined the periodic changes of the major global hydrological cycles with the development of continental glaciations and permafrost of great pluvial epochs of a global warming in the geological past.Within a relatively short historical period various reasons for periodic and non-periodic heat and water transfer have led to changes in the hydrological cycle and to land moisture fluctuations.At present global hydrological processes are going through quite drastic changes as a result of the fluctuations of a number of geophysical processes (natural energy factors, in the first place). The global warming of the climate has resulted in the increase in the intensity of surface water exchange, in the drying up of continents and in the filling of the World Ocean. These changes are accompanied by an increase in the anthropogenic impact on water balance by the strenghthening of hydrologic exchange and the slowing down of river water exchange.