Risk,Liability, and Economic Issues with Long-Term CO<Subscript>2</Subscript> Storage—A Review

Given a scarcity of commercial-scale carbon capture and storage (CCS) projects, there is a great deal of uncertainty in the risks, liability, and their cost implications for geologic storage of carbon dioxide (CO₂). The probabilities of leakage and the risk of induced seismicity could be remote, but the volume of geologic CO₂ storage (GCS) projected to be necessary to have a significant impact on increasing CO₂ concentrations in the atmosphere is far greater than the volumes of CO₂ injected thus far. National-level estimates of the technically accessible CO₂ storage resource (TASR) onshore in the United States are on the order of thousands of gigatons of CO₂ storage capacity, but such estimates generally assume away any pressure management issues. Pressure buildup in the storage reservoir is expected to be a primary source of risk associated with CO₂ storage, and only a fraction of the theoretical TASR could be available unless the storage operator extracts the saltwater brines or other formation fluids that are already present in the geologic pore space targeted for CO₂ storage. Institutions, legislation, and processes to manage the risk, liability, and economic issues with CO₂ storage in the United States are beginning to emerge, but will need to progress further in order to allow a commercial-scale CO₂ storage industry to develop in the country. The combination of economic tradeoffs, property rights definitions, liability issues, and risk considerations suggests that CO₂ storage offshore of the United States may be more feasible than onshore, especially during the current (early) stages of industry development.     

Climate conditions and relative abundance of C<Subscript>3</Subscript> and C<Subscript>4</Subscript> vegetation during the past 40 ka inferred from lake sediments in Wudalianchi,northeast China

Paleoclimate and paleovegetation changes over the last 40 cal ka were recorded by multiple variables in a sediment core from Qingshi, Wudalianchi City, northeast China. The history of vegetation types inferred from n-C₂₇/n-C₃₁ and average chain length of n-alkanes indicates the paleovegetation went through several distinct stages, consistent with pollen records from the study area. Compound-specific carbon isotope composition was also determined for C₂₇, C₂₉ and C₃₁ n-alkanes in the Qingshi core sediments. The relative abundance of C₃ and C₄ plants was calculated using a binary model and indicates that C₃ plants were the dominant input during the last glacial and Holocene. There were, however, shifts in the ratio of C₃ to C₄ vegetation abundance that correspond to changes in climate conditions. Generally, the long-term trend towards greater C₄ plant abundance from the last glacial to Holocene correlated with an increase in pCO₂, higher temperature, greater precipitation and more growing season precipitation. Our results suggest that temperature and seasonality of precipitation played a strong role in altering the relative abundance of C₃ and C₄ plants in the study area. These results provide information for predicting future vegetation changes in response to on-going global warming.     

Territorial Development of Christianity in Africa in the 20<Superscript>th</Superscript>–Early 21<Superscript>st</Superscript> Centuries

The characteristic features of the transformation of the territorial geospace structure in the African Christianity religious geospace during 1910–2010 have been revealed. African countries within the boundaries of 2010 are used as territorial cells that have been fixed retrospectively over the course of the period analyzed. We used indicators, such as Ryabtsev’s index of relative structural shifts and the trajectory of the demographic center of the Christianity to assess changes in the inertia level of the territorial structure for the entire time interval as a whole and for each of the components of its 20-year long periods. It is found that to date the adherents of Christianity are extremely unevenly distributed in the countries of Africa; however, over the course of the period under consideration there was taking place a homogenization of their settlement. In accordance with changes of the values of the indicators used, we identified two development stages of geospace of African Christianity: colonial and post-colonial. It is determined that the colonial stage (1910–1970) is characterized by a “compression” of territorial structure from east and north, and by a predominance of the south-westward direction of movement of the demographic center because of a decrease in the proportion in the Christian population of East Africa first on account of Egypt and Ethiopia and Madagascar (1910–1930) and then North Africa on account of Egypt and Algeria (1930–1950). The territorial structure of Christianity’s geospace during the post-colonial stage is characterized by a higher degree of inertia at the background of the westward ”expansion” and the “compression” from the south as well as by a change of the vector of movement of the demographic center for north-westward.     

Landscape regularities of human colonization of the Tuva territory in the Scythian time (8<Superscript>th</Superscript>–3<Superscript>rd</Superscript> centuries B. C.)

We discuss the issues related to the human colonization of the Tuva landscapes in the Scythian time. An analysis is made of the spatial and landscape confinedness of archaeological sites having regard to the Late-Holocene rhythms of climate change in the mountains. For the historical-landscape analysis the MapInfo 12.0 GIS technologies were used in compiling the landscape map of the Tyva Republic, the scheme of physical-geographical regionalization and the schematic map of spatial distribution of archaeological sites from the Scythian time. The then most developed landscapes include the steppe mountain-valley and forest-steppe low- and mid-mountain landscapes, which was associated with the main economic sector, namely nomadic stockbreeding. The culture of the Scythian time existed under a colder and more humid climate than at present. An increase in humidity in originally dry areas led to an increase in steppe vegetation productivity growing in depressions and on slopes of mountain ranges. These factors created favorable conditions for the development of nomadic stockbreeding. A spatial analysis of the distribution of archaeological sites in the physical-geographical provinces of Tuva intimates that depression landscapes were colonized mostly in the Scythian time. The Tuvinian depression province (the archaeologically richest area of Tuva) and the Ubsunur depression account for 52 and 21% of the sites, respectively. The mountain landscapes were colonized to a considerably lesser extent; the largest number of sites are located in the Western-Tuva mountain province. In the Scythian time, the cores of development of the Tuva territory were represented by the intermontane depressions (Tuvinian and Ubsunur), the connections between which were provided by a small number of large valleys and mountain passes.     

Where Are the Women? Accounting for Discrepancies in Female Doctorates in U.S. Geography

Although there have been noticeable improvements in recent years, geography continues to be a predominantly male discipline. The percentage of women receiving PhDs in geography has tracked lower than the U.S. average of female PhDs. Previous studies of women's contribution to geography have focused on personal accounts or on the study of some of the most prominent practitioners, with a few studies using basic data on PhDs awarded and Association of American Geographers membership to determine trends. This article provides a comprehensive overview of doctoral degrees in geography by gender, over time, and across all universities in the United States by examining an alternative database, that of doctoral dissertations. The analysis yields three separate types of results. First, historical and contemporary variations among U.S. universities are examined. Second, data indicate that male and female doctoral students differ in the sex of their advisor. Third, a simple regression model explains some of the discrepancies in the proportion of female doctoral students by department. In sum, this article provides a comprehensive empirical study of the factors that might contribute to the continued disparities in female doctoral students in geography.     

The Ideology of U.S. Agriculture: How Are Integrated Management Approaches Envisioned?

The ease and affordability of the herbicide glyphosate and the development of glyphosate tolerant crops has encouraged a simplified weed management system in the U.S. However, the overuse of this technological package in recent years has led to an explosion in the number of herbicide resistant weeds and a decrease in the effectiveness of glyphosate. In addition to this bio-chemical problem, many growers appear to be stuck within a farming ideology that focuses on a reduction in time/labor, an increase in profitability and a vision of ever-increasing efficiencies of scale. This may prevent them from conceptualizing and implementing solutions that fall outside of a simple herbicide application plan. The objective of this paper is to begin describing the current ideology of industrial corn and soybean farmers in the United States, as well as how this ideology contributes to farmers’ resistance to complex weed management strategies.     

Washington Women: Practicing Geography in the U.S. Government, 1915–1970s

Histories of geography, especially those dealing with the twentieth century, tend to focus on geographic thought or academia rather than on practice in other arenas such as government agencies. In the United States during that period, however, the latter included a higher proportional representation of women professionals than did research-oriented universities. This article examines the careers of selected women geographers who had long-term and senior positions in Washington, DC, in agencies such as the Library of Congress, Bureau of the Census, the Department of State, and the Office of Naval Research. Drawing on sources including directories, the archives and oral history collections of the Society of Woman Geographers, and interviews conducted in the late 1980s and early 1990s, I explore four main themes: how these women came to government work, aspects of the intersections of personal and professional lives, ways in which economic and political contexts shaped their opportunities and experiences, and the nature of their contributions.     

Stable isotope (δ<Superscript>13</Superscript>C, δ<Superscript>15</Superscript>N, δ<Superscript>34</Superscript>S) analysis of sediment cores suggests sockeye salmon (<Emphasis Type="Italic">Oncorhynchus nerka</Emphasis>) did not historically spawn in Lake Roberta,Washington (USA)

Historically, the Sanpoil River, Washington (USA) produced spawning runs of chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (O. mykiss). Lake Roberta is connected to the Sanpoil River and local oral history suggests it may have supported anadromous sockeye salmon (O. nerka) until the completion of Grand Coulee Dam in the 1940s. Post-spawning mortality of anadromous salmon provides large pulses of marine-derived nutrients to aquatic and terrestrial ecosystems in the vicinity of spawning sites. Unique isotopic ratios of these marine-derived nutrients are often transferred to freshwater algae and archived in lake sediments. However, marine-derived isotope signatures may be overpowered by large inputs of other nutrient sources such as agricultural fertilizers, reactive nitrogen deposition, nitrogen fixation, or poor trophic transfer to freshwater algae. We compared nitrogen and sulfur isotope compositions for pre-1940 and post-1940 sediments to those collected from a control lake with no history of anadromy to investigate the possible historic presence of anadromous salmon in Lake Roberta. We also analyzed carbon isotopes, carbon:nitrogen ratios, and sediment accumulation rates to determine if changes in the lake sediments resulted from eutrophication rather than salmon exclusion. If sockeye did spawn in Lake Roberta historically, and if excessive nitrogen inputs did not overpower the marine-derived signal, we would expect pre-1940 sediment organic matter isotope compositions indicative of the large pulses of marine nutrients from decomposing salmon carcasses. Isotope results and land use in the Lake Roberta watershed present no conclusive evidence to support anecdotal accounts of anadromy. There is some evidence to suggest that marine-derived nutrients transferred to riparian communities within the lake’s watershed may have moved downstream to the lake. However, most of the evidence suggests eutrophication and a switch to increased autochthonous productivity are the main causes of changes in the lake sediment isotope composition.     

Lead pollution history from 256 BC to AD 2005 inferred from the Pb isotope ratio (<Superscript>206</Superscript>Pb/<Superscript>207</Superscript>Pb) in a varve record of Lake Korttajärvi in Finland

The lead pollution history, based on the accumulation rate of total Pb and ratio of stable isotopes (²⁰⁶Pb/²⁰⁷Pb), was studied in the annually laminated sediment of a small lake in Finland (62°20′ N; 25°41′ E). The sediment chronology based on varve counting provided a unique opportunity to explore and date signals of Pb emissions, including the ancient metallurgical activities of the Roman Empire at the beginning of the Current Era. Changes in the ratio of stable isotopes gave a pronounced signal of the atmospheric Pb fallout in AD 32–392, although this was not distinguishable in the accumulation rate of total Pb, as it was observed in previous work. Calculated accumulations of the ancient pollution Pb were low, the highest values being 0.2–0.3 mg m² a⁻¹ in AD 144–392, corresponding 14–21% of the accumulation of total Pb. The accumulation of pollution Pb collapsed in the fifth century and remained at or close to the background level up to the eleventh century. After this, the accumulation rate of pollution Pb began to increase and reached 1.2 mg m² a⁻¹ in AD 1420–1439, corresponding to 44% of the total Pb accumulation. During five centuries, from AD 1420–1895, the average accumulation of pollution Pb was 2.6 mg m² a⁻¹, the variation being from 0.8 to 4.8 mg m² a⁻¹. The accumulation of Pb started to increase exponentially in the early twentieth century, and the highest accumulations of pollution Pb (11–22 mg m² a⁻¹, corresponding 50–76% of the annual accumulation of total Pb) were dated to AD 1926–1985. The banning of the use of leaded fuel has led to a pronounced decrease in the accumulation of pollution Pb since the 1980s, and the present accumulation rate represents the level that prevailed 80–120 years ago.     

Elemental (C,N, H and P) and stable isotope (δ<Superscript>15</Superscript>N and δ<Superscript>13</Superscript>C) signatures in sediments from Zeekoevlei,South Africa: a record of human intervention in the lake

We used elemental carbon, nitrogen, phosphorus and hydrogen ratios (C/N, N/P and H/C) with total organic carbon (TOC) and total phosphorus (TP) as well as stable carbon and nitrogen isotopes (δ¹³C and δ¹⁵N) to investigate the source and depositional conditions of organic matter in sediments from Zeekoevlei, the largest freshwater lake in South Africa. Typical C/N (10–12), H/C ratios (≥1.7) and δ¹³C_organic values (−22 to −19‰) together with the increase in TOC concentration indicate elevated primary productivity in lower middle (18–22 cm) and top (0–8 cm) sections of the sediment cores. Seepage of nutrients from a nearby waste water treatment plant, rapid urbanization and heavily fertilized farming in the catchments are responsible for the increased productivity. Consistent with this, measured δ¹⁵N_organic values (∼11‰) indicate increased raw sewage input towards the top-section of the core. Although cyanobacterial blooms are evident from the low δ¹⁵N values (∼3‰) in mid-section of the core, they did not outnumber the phytoplankton population. Low N/P ratio (∼0) and high TP (100–2,200 mg l⁻¹) support cyanobacterial growth under N limited condition, and insignificant input of macrophytes towards the organic matter pool. Dredging in 1983, caused sub-aerial exposure of the suspended and surface sediments, and affected organic matter preservation in the upper mid-section (12–14 cm) of the core.     

A 15.4-ka paleoclimate record inferred from δ<Superscript>13</Superscript>C and δ<Superscript>15</Superscript>N of organic matter in sediments from the sub-alpine Daping Swamp,western Nanling Mountains,South China

We inferred past climate conditions from the δ¹³C and δ¹⁵N of organic matter (OM) in a sediment core (DP-2011-02) from the sub-alpine Daping Swamp, in the western Nanling Mountains, South China. In the study region, a 1000-m increase in altitude results in a ~0.75‰ decrease in δ¹³C and a ~2.2‰ increase in δ¹⁵N. Organic carbon stable isotope (δ¹³C) values of the dominant modern vegetation species, surface soils, and the core samples taken in the swamp exhibit a strong terrestrial C3 plant signature. Comprehensive analysis of the core indicates both terrestrial and aquatic sources contribute to the OM in sediment. Temperature and precipitation are most likely the critical factors that influence δ¹³C: warm and wet conditions favor lower δ¹³C, whereas a dry and cool climate leads to higher δ¹³C values. Higher δ¹⁵N values may result from greater water depth and increased primary productivity, promoted by large inputs of dissolved inorganic nitrogen, induced by high surface runoff. Lower δ¹⁵N values are associated with lower lake stage and reduced productivity, under drier conditions. Therefore, stratigraphic shifts in these stable isotopes were used to infer past regional climate. Measures of δ¹³C and δ¹⁵N in deglacial deposits, in combination with total organic carbon (TOC) and nitrogen (TN) concentrations, the TOC/TN ratio, coarse silt and sand fractions, dry bulk density and low-frequency mass magnetic susceptibility, reveal two dry and cold events at 15,400–14,500 and 13,000–11,000 cal a BP, which correspond to Heinrich event 1 and the Younger Dryas, respectively. A pronounced warm and wet period that occurred between those dry episodes, from 14,500 to 13,000 cal a BP, corresponds to the Bølling–Allerød. The δ¹³C and δ¹⁵N data, however, do not reflect a warm and wet early Holocene. The Holocene optimum occurred between ~8000 and 6000 cal a BP, which is different from inferences from the nearby Dongge cave stalagmite δ¹⁸O record, but consistent with our previous results. This study contributes to our understanding of climate-related influences on δ¹³C and δ¹⁵N in OM of lake sediments in South China.     

A Retrospective of Oil and Gas Field Development in the U.S. Outer Continental Shelf Gulf of Mexico, 1947–2017

Natural Resources Research - The U.S. Gulf of Mexico is a world-class hydrocarbon basin and industry has an impressive track record of advancing its capabilities in the region. From 1947 to 2017,...     

And Did the Walls Come Tumbling Down? Ethnic Residential Segregation in Four U.S. Metropolitan Areas 1980-2000

The initial releases of data from the 2000 U.S. Census allow exploration of the extent of change, if any, in residential segregation in four major cities, where substantial population growth has continued to generate increased ethnic diversity. Using a recently established method of classifying residential areas according to their ethnic composition which facilitates comparative study over time and space, this paper examines segregation trends in Chicago, Los Angeles, New York, and Miami over the period 1980-2000 in the context of recent discussions of the nature of residential patterns there. It finds that though there has been some reduction in the extent of extreme segregation areas that are predominantly either White or African American with consequent greater ethnic mixing at the census tract level, nevertheless cores of extreme segregation remain, and these are being extended with greater segregation of the Hispanic population. Ethnic residential segregation in United States' metropolitan areas attracted much research throughout the 20th century, with each census providing new impetus for mapping and analysis. The 2000 census will be no exception, providing data with which the extent of change can be assessed after a further decade in which discrimination on the grounds of race and color was illegal. This paper provides an initial exploration for four metropolitan areas that have experienced substantial recent multi-ethnic in-migration. Using a method for classifying residential areas designed to facilitate comparative studies over space and time, it explores the extent of desegregation during the previous 20 years for each of the four main census ethnic groups.     

The Changing Geography of U.S. Hispanics from 1990–2006: A Shift to the South and Midwest

Abstract

Between 1990 and 2000 the U.S. Hispanic population increased by 14 million, which is the largest decadal population rise in United States history. This increase was not spread evenly throughout the United States, nor was it isolated to locations that already had large Hispanic populations. On the contrary, areas that previously had a relatively small Hispanic population experienced large percentage increases. In this article the regional variability in Hispanic population growth is explored, along with an emphasis on the economic pull factors driving those demographic changes. This analysis illustrates how restructuring in the meatpacking industry, and the associated economic impacts, have created a dependence on a low wage, illegal labor force that has shaped the recent demographic trend in the South and Midwest.     

Do spectrally inferred determinations of chlorophyll <Emphasis Type="Italic">a</Emphasis> reflect trends in lake trophic status?

Visible reflectance spectroscopy (VRS) has been used to reconstruct lake sediment chlorophyll a concentrations. Despite good concordance between inferred and measured chlorophyll a values, questions remain as to whether this spectral technique is tracking past changes in aquatic primary production, or simply recording a diagenetic signal. In this study, we critically evaluate how well VRS chlorophyll a determinations track past trends in aquatic primary production using sediment cores from several lake systems with well-known trophic histories. Our study sites include Arctic, boreal and prairie lakes that encompass a gradient of trophic states. In general, our spectrally inferred chlorophyll a values tracked past trends in lake trophic status consistent with historical measurements of production, or as inferred by independent proxies of primary production. We conclude that VRS chlorophyll a inferences indeed track histories of lake production trends and that this method is widely applicable as a rapid, inexpensive and non-destructive alternative to wet-chemical analyses of sediment chlorophyll a concentrations.     

Foreign-Area Expertise in U.S. Geography: An Assessment of Capacity based on Foreign-Area Dissertations, 1977–1991∗

Interpretations of a decline in foreign-area specialization have raised concerns about the capacity of geography in the United States to serve the expected increase in demands for foreign-area expertise. An assessment of foreign-area dissertations awarded by U.S. geography programs over a 15-year period (1977–1991) fails to support the concerns raised. No significant declines, if any at all, are found for early career interest and research in foreign areas. Several caveats are warranted, however. Geography has lost three doctoral programs with strong foreign-area dissertation records for the period in question. Also, non-U.S. citizens, many of whom do not remain in the United States after completion of their doctorate work, account for a significant proportion of foreign-area dissertations. Various questions that must be addressed to analyze the capacity question more broadly are identified.     

Spain. Regional differences in population density in 1986: the end of a process of increasing internal disequilibrium?

This is an analysis of regional differences in population trends in Spain during the twentieth century. Data are from a variety of official sources, including the censuses of 1900, 1960, 1970, and 1981. The author notes that up until 1975, interregional migration flows had acccentuated regional economic differences. However, the economic problems that have occurred since 1975, coupled with the political changes associated with greater regional autonomy, have resulted in new trends in internal migration that could have significant effects on the future distribution of the country's population.     

Reconstruction of <Emphasis Type="Italic">Lu</Emphasis>-level cropland areas in the Northern Song Dynasty (AD976–1078)

Based on data on taxed-cropland area and on the number of households in historical documents, a probabilistic model of cropland distribution and a cropland area allocation model were designed and validated. Cropland areas for the years AD976, 997, 1066, and 1078 were estimated at the level of Lu (an administrative region of the Northern Song Dynasty). The results indicated that (1) the cropland area of the whole study region for AD976, 997, 1066, and 1078 was about 468.27 million mu (a Chinese unit of area, with1 mu=666.7m²), 495.53 million mu, 697.65 million mu, and 731.94 million mu, respectively. The fractional cropland area (FCA) increased from 10.7% to 16.8%, and the per capita cropland area decreased from 15.7 mu to 8.4 mu. (2) With regard to the cropland spatial pattern, the FCA of the southeast, north, and southwest regions of the Northern Song territory increased by 12.0%, 5.2%, and 1.2%, respectively. The FCA of some regions in the Yangtze River Plain increased to greater than 40%, and the FCA of the North China Plain increased to greater than 20%. However, the FCA of the southwest region (except for the Chengdu Plain) in the Northern Song territory was less than 6%. (3) There were 84.2% Lus whose absolute relative error was smaller than 20% in the mid Northern Song Dynasty. The validation results indicate that our models are reasonable and that the results of reconstruction are credible.