The Pedagogical Benefits of Participatory GIS for Geographic Education

In this article, participatory GIS (PGIS) is explored and established as a powerful platform for geographic education. PGIS pedagogy can help educators meet diverse learning objectives pertaining to: (1) local knowledge and place-based thinking; (2) community engagement; (3) field mapping with geospatial technologies; (4) mixed-methods research; and (5) fostering of critical reflexivity in students. The discussion is supported with insights from multiple student-facilitated PGIS projects organized in rural Tanzania. There also is a thorough discussion of the challenges and caveats associated with involving students in PGIS projects, and a call for new research for assessing and advancing PGIS pedagogy.     

Cyclic and seismic response of single piles in improved and unimproved soft clays

Presented in this paper are results of two centrifuge tests on single piles installed in unimproved and improved soft clay (a total of 14 piles), with the relative pile–soil stiffness values varying nearly two orders of magnitude, and subjected to cyclic lateral loading and seismic loading. This research was motivated by the need for better understanding of lateral load behavior of piles in soft clays that are improved using cement deep soil mixing (CDSM). Cyclic test results showed that improving the ground around a pile foundation using CDSM is an effective way to improve the lateral load behavior of that foundation. Depending on the extent of ground improvement, elastic lateral stiffness and ultimate resistance of a pile foundation in improved soil increased by 2–8 times and 4–5 times, respectively, from those of a pile in the unimproved soil. While maximum bending moments and shear forces within piles in unimproved soil occurred at larger depths, those in improved soil occurred at much shallower depths and within the improved zone. The seismic tests revealed that, in general, ground improvement around a pile is an effective method to reduce accelerations and dynamic lateral displacements during earthquakes, provided that the ground is improved at least to a size of 13D × 13D × 9D (length × width × depth), where D is the outside diameter of the pile, for the pile–soil systems tested in this study. The smallest ground improvement used in these tests (9D × 9D × 6D), however, proved ineffective in improving the seismic behavior of the piles. The ground improvement around a pile reduces the fundamental period of the pile–soil system, and therefore, the improved system may produce larger pile top accelerations and/or displacements than the unimproved system depending on the frequency content of the earthquake motion.     

How the Distribution of Anthropogenic Nitrogen Has Changed in Narragansett Bay (RI,USA) Following Major Reductions in Nutrient Loads

Over the past decade, nitrogen (N) loads to Narragansett Bay have decreased by more than 50%. These reductions were, in large part, the direct result of multiple wastewater treatment facility upgrades to tertiary treatment, a process which employs N removal. Here, we document ecosystem response to the N reductions and assess how the distribution of sewage N in Narragansett Bay has changed from before, during, and shortly after the upgrades. While others have observed clear responses when data were considered annually, our seasonal and regional comparisons of pre- and post-tertiary treatment dissolved inorganic nitrogen (DIN) concentrations and Secchi depth data, from bay-wide surveys conducted periodically from the early 1970s through 2016, resulted in only a few subtle differences. Thus, we sought to use stable isotope data to assess how sewage N is incorporated into the ecology of the Bay and how its distribution may have changed after the upgrades. The nitrogen (δ¹⁵N) and carbon (δ¹³C) stable isotope measurements of particulate matter served as a proxy for phytoplankton, while macroalgae served as short-term integrators of water column bio-available N, and hard clams (Mercenaria mercenaria) as integrators of water column production. In contrast to other estuarine stable isotope studies that have observed an increased influence of isotopically lower marine N when sewage N is reduced, the opposite has occurred in Narragansett Bay. The tertiary treatment upgrades have increased the effluent δ¹⁵N values by at least 2‰. The plants and animals throughout Narragansett Bay have similarly increased by 1–2‰, on average. In contrast, the δ¹³C values measured in particulate matter and hard clams have declined by about the same amount. The δ¹⁵N results indicated that, even after the N reductions, sewage N still plays an important role in supporting primary and secondary production throughout the bay. However, the δ¹³C suggests that overall net production in Narragansett Bay has decreased. In the 5 years after the major wastewater treatment facilities came on-line for nutrient removal, oligotrophication has begun but sewage remains the dominant source of N to Narragansett Bay.     

Stratigraphy and chronology of Provo shoreline deposits and lake‐level implications,Late Pleistocene Lake Bonneville,eastern Great Basin,USA

The Provo shoreline of Lake Bonneville formed following the Bonneville flood, and, based on previous dating, was formed during a period of overflow from about 17.5 to 15.0 cal. ka. In many places the Provo shoreline consists of a pair of distinct shorelines, one ～3 m higher than the other. We present data from two cuts through double beaches to show that the upper beach is younger and represents sedimentation after a lake‐level rise. In addition, the lower beach deposits are internally stratified by beds that suggest three more lake‐level rises during its development. The Provo beach complex thus appears to have been built during rising lake levels, which can be explained by rises in the overflow threshold by sequential landslide deposition. Evaluation of beach altitudes demonstrates that the two beach crests throughout the Bonneville basin experienced equivalent rebound from removal of the lake load, and therefore they formed after the rebound associated with the Bonneville flood occurred in early Provo time. However, radiocarbon ages on gastropods collected within the beach deposits suggest both that the sequence of five beach deposits formed from c.18.1 to c. 17.0 cal. ka, and that the Bonneville flood occurred before 18 cal. ka. These ages are discordant with previous dates on shells within offshore sands, and raise questions about the validity of radiocarbon ages for shells in Lake Bonneville as well as about the age of the Bonneville flood and Provo shoreline. The timing for maximum Provo lake depths and its association with climate stages during deglaciation remain unresolved.     

Stratigraphic framework for the Leichhardt and Calvert Superbasins: Review and correlations of the pre‐ 1700 Ma successions between Mt Isa and McArthur River

New stratigraphic, geochemical and palaeomagnetic data from the Peters Creek Volcanics are used to revise the correlations of part of the Palaeoproterozoic of northern Australia. The revised geological history for these cover rocks of the Murphy Inlier is extrapolated into the 1800–1700 Ma successions of the McArthur Basin and Mt Isa regions. New stratigraphic subdivisions and relationships are contrasted with the established lithostratigraphic schemes and also with conflicting published tectono‐stratigraphic interpretations. For the first time, a plethora of stratigraphic units can be rationalised into two major superbasins, the Leichhardt and Calvert Superbasins, and into eight pseudo‐chronostratigraphic basin phases (Associations A‐H). There are few absolute age constraints, but lateral correlations of the units in these eight basin phases are proposed. Results from the overlying Isa Superbasin (<1670 Ma) suggest that these eight associations probably represent second‐order supersequences. Mixed non‐marine and marine coarse clastics, deposited between about 1790 and 1780 Ma dominate Associations A and B. In the Mt Isa region these were deposited in an initial rift then a thermal relaxation or sag phase. To the northwest, however, the succession is dominated by rift facies. Association C is a widespread flood basalt and immature clastic suite that was deposited in clearly defined, north‐trending half‐grabens in the Mt Isa region. Along the southern edge of the Murphy Inlier, however, geophysically defined half‐grabens, filled with magnetic rocks (basalt), trend orthogonal to those at Mt Isa. North of the inlier Association C is much thinner, and little can be deduced about its palaeogeography. Association D is only present in the Mt Isa region as the Myally Subgroup. Differing views on its tectonic setting and environments of deposition, as presented in recent papers, are reviewed. Association E, deposited around 1755 Ma, is a regional sag phase with mixed clastic‐carbonate, shallow‐marine lithofacies in all areas. There is a major gap in the rock record between about 1750 and 1735 Ma which is probably related to widespread basin inversion. The Mid‐Tawallah Compressional Event (McArthur River area) and the Wonga Extension Event (Eastern Succession, Mt Isa) are both about this age. The overlying Association F is a thin, laterally uniform, upward‐fining succession that commences with shallow‐marine clastics and evolves through deeper marine clastics and ends in evaporitic facies. There are broad similarities between Associations F and E so interpretation as a third regional sag is favoured. The absence of Association F at Mt Isa may indicate that basin inversion was longer lived in the southeast. The youngest associations, G and H, are complex interstratified mixtures of felsic‐mafic igneous rocks and immature clastics. U–;Pb zircon SHRIMP ages appear to cluster around 1725 Ma and 1710 Ma, but they may all be part of one thermal event. These eight associations may represent the tectono‐magmatic response of the lithosphere during and after the Strangways Orogeny (1780–1730 Ma).     

Five years’ central pacific sea level from in situ array,satellite altimeter and numerical model: Research note

Abstract

Temporal and spatial features of central equatorial Pacific Ocean sea‐level variation appear similar, in measurements from two very different systems (one in the ocean and one carried on a satellite), and in results from a numerical model of the region. In particular, there is an interannual cycle: during El Nino, Kelvin waves appear at the equator, and the sea‐surface ridge associated with the equatorial current system shifts southward; in non‐El Nino years, instability waves appear at 6°N (strongest around the end of each calendar year), and the ridge shifts to the north. This three‐way comparison gives support to both measurement systems and to the numerical model.     

Occurrence and characteristics of inorganic ions and microorganisms in potable water from Jamaica

Water samples were collected from seven areas across Jamaica and they were analyzed for inorganic ions using the Graphite Furnace Atomic Absorption (GF-AA) analytical technique. The samples were tested for the presence of ions and microbes followed by gel electrophoresis. Iron and phosphate concentrations were higher in urban areas. Increased concentration of these inorganic ions has been linked to hemachromatosis, hypertension, tachycardia and central nervous system defects. The alkaline values in the pH may favor the growth of gram negative organisms. An increase in total chlorine concentration in Mandeville has implications for the incidence of diseases of the cardiovascular system. The values of the Lead and Cadmium that were detected in St. Thomas and St. Elizabeth exceeded acceptable concentrations. Copper concentration was highest in the urban areas. Five gram negative pathogens were identified which caused urinary tract infections and gastrointestinal diseases. EcoRI and HindIII digests showed varying banding patterns with a common band of 2,060 bps. The results of the study indicate that the potable water samples taken from selected urban and rural areas were contaminated with chemicals and microbes which are known to have a significant impact on the occurrence of various diseases in the population. Effective water treatment methods should be implemented in order to reduce this health risk to the population. Further studies should be done to determine the origin of the contamination and the types of groups at risk.