Economic Development Threatens Groundwater in Puerto Rico: Results of a Field Study

Abstract

This report addresses the question of groundwater quality in a context of economic development and heterogeneous land use. Seven wells, each actively producing for the public water supply, and together providing 37 percent of the total aquifer production of four municipios, were tested in three topographic basins. Major land use categories, including agriculture, urbanization, and industry, were identified throughout the basins. Well samples were drawn three times during a six-month period and analyzed for a set of 15 water quality parameters including biological indicators. The most common pollutants detected were heavy metals, nitrate, arsenic, and semivolatile organic compounds. Wells surrounded by agricultural and commercial activities were contaminated by nitrate, mercury, lead, and phthalates. Wells in mixed residential and industrial settings had concentrations of semivolatile organic compounds and lead. The presence of noxious chemicals in the public water supply, even in relatively small amounts, threatens the viability of the groundwater reservoir. Both operational and policy aspects of water quality should be discussed in the context of urban and economic development.     

Estimation of undiscovered deposits in quantitative mineral resource assessments—examples from Venezuela and Puerto Rico

Quantitative mineral resource assessments used by the United States Geological Survey are based on deposit models. These assessments consist of three parts: (1) selecting appropriate deposit models and delineating on maps areas permissive for each type of deposit; (2) constructing a grade-tonnage model for each deposit model; and (3) estimating the number of undiscovered deposits of each type. In this article, I focus on the estimation of undiscovered deposits using two methods: the deposit density method and the target counting method.In the deposit density method, estimates are made by analogy with well-explored areas that are geologically similar to the study area and that contain a known density of deposits per unit area. The deposit density method is useful for regions where there is little or no data. This method was used to estimate undiscovered low-sulfide gold-quartz vein deposits in Venezuela.Estimates can also be made by counting targets such as mineral occurrences, geophysical or geochemical anomalies, or exploration plays and by assigning to each target a probability that it represents an undiscovered deposit that is a member of the grade-tonnage distribution. This method is useful in areas where detailed geological, geophysical, geochemical, and mineral occurrence data exist. Using this method, porphyry copper-gold deposits were estimated in Puerto Rico.     

Spatial distribution of tropical cyclone rainfall and its contribution to the climatology of Puerto Rico

This study explores two different tropical cyclone rainfall (TCR) problems: first, the identification of areas where TCR is highly concentrated and, second, the contribution of tropical cyclones (TCs) to the climatology of Puerto Rico for the period 1970–2010. A total of 86 storms within a 500-km radius of Puerto Rico were analyzed. Daily and monthly rainfall data from 32 weather stations were used to generate interpolated surfaces. Two geostatistical interpolation techniques were implemented: ordinary kriging and ordinary cokriging. Results show that rainfall from most TCs tends to be clustered in the eastern, southeastern, and central regions of the island, with a decrease in values toward the west. TCs closer to Puerto Rico (≤230 km) and embedded in high moisture environments (≥44.5 mm) exhibited the highest rainfall values, with most concentrated in the high elevation areas of the southeastern region of the island. Months with the largest TC contributions to rainfall (20–30%) were August and September, while the lowest contributions were found in June and November. For August, stations in the southern and eastern portions of the island had TCR contributions of >20%, with some stations in the southern coastal plains exhibiting 30%.     

IMPACT OF NEOTECTONICS ON THE RECORD OF GLACIER AND SEA LEVEL FLUCTUATIONS, STRAIT OF MAGELLAN, SOUTHERN CHILE

ABSTRACT. This paper presents evidence for a neotectonic influence on Late Pleistocene/Holocene records of environmental change in the southern Strait of Magellan. We concentrate on one site, Puerto del Hambre, a key location for reconstructing palaeoenvironmental change in southernmost South America. We report geomorphological, structural geological, seismic and topographic data that all show the site has been affected by postglacial faulting. There is also indirect evidence from the site stratigraphy that the site has been displaced. Also, recent faulting explains some of the puzzles associated with interpretation of the palaeoenvironmental record at Puerto del Hambre. The implication of this work is that neotectonic faulting had a pervasive influence in the southern part of the Strait of Magellan and southernmost Tierra del Fuego, and thus affects glacial or sea level reconstructions in the area.     

Reduced channel morphological response to urbanization in a flood‐dominated humid tropical environment

Urbanization through the addition of impervious cover can alter catchment hydrology, often resulting in increased peak flows during floods. This phenomenon and the resulting impact on stream channel morphology is well documented in temperate climatic regions, but not well documented in the humid tropics where urbanization is rapidly occurring. This study investigates the long‐term effects of urbanization on channel morphology in the humid sub‐tropical region of Puerto Rico, an area characterized by frequent high‐magnitude flows, and steep coarse‐grained rivers. Grain size, low‐flow channel roughness, and the hydraulic geometry of streams across a land‐use gradient that ranges from pristine forest to high density urbanized catchments are compared. In areas that have been urbanized for several decades changes in channel features were measurable, but were smaller than those reported for comparable temperate streams. Decades of development has resulted in increased fine sediment and anthropogenic debris in urbanized catchments. Materials of anthropogenic origin comprise an average of 6% of the bed material in streams with catchments with 15% or greater impervious cover. At‐a‐station hydraulic geometry shows that velocity makes up a larger component of discharge for rural channels, while depth contributes a larger component of discharge in urban catchments. The average bank‐full cross‐sectional area of urbanized reaches was 1.5 times larger than comparable forested reaches, and less than the world average increase of 2.5. On average, stream width at bank‐full height did not change with urbanization while the world average increase is 1.5 times. Overall, this study indicates that the morphologic changes that occur in response to urban runoff are less in channels that are already subject to frequent large magnitude storms. Furthermore, this study suggests that developing regions in the humid tropics shouldn't rely on temperate analogues to determine the magnitude of impact of urbanization on stream morphology. Copyright © 2012 John Wiley & Sons, Ltd.     

SOIL DEVELOPMENT AND SPATIAL VARIABILITY ON GEOMORPHIC SURFACES OF DIFFERENT AGE

Twenty-four soil pedons on each of four sandy lake terraces in northwestern lower Michigan that ranged in age from 3000 to 11,000 years BP were studied to assess trends in soil morphological variability with time. After verifying the general uniformity of parent materials within and between the four surfaces, we examined temporal trends in the spatial variability of soil color, cementation, horizon thickness and development. E horizons attained high color values (lightness) by 3000 years and changed little after that time, whereas B horizons continued to get darker with time. Cementation within B horizons increased in strength and amount with time, as did B horizon thickness. Soils ≥4000 years old had deeper eluvial zones but much greater variabilities in the thickness of that zone than did younger soils. Soil development increased with time, but spatial variability in degree of development also increased with time. These patterns are best explained by invoking spatially random soil mixing upon a surface that is otherwise undergoing podzolization. [Key words: podzolization, chronofunction, Michigan, soil variability, soil genesis.]     

Relationships between environmental factors and Donax denticulatus populations in Puerto Rico

Donax denticulatus population density and size distribution were studied in five different Puerto Rican beaches for a one year period in order to determine relationships between the densities and size distributions of the clam, and twelve different physico-chemical parameters of sediments and water. Maní beach exhibits significantly higher population densities followed by Luquillo, Esperanza and Ballenas. No clams were found in Crashboat. Luquillo and Esperanza had similar population fluctuations, having peak densities in August and January. Maní had higher densities in September and May, and Ballenas in June. The only major settlement period appeared during January at Esperanza. The bigger clams (30 mm) were found in Maní only. Higher population density and bigger clams in Maní are related to waters having high concentrations of total organic carbon, particulate organic carbon and nitrates. The clam was absent from Crashboat where very low levels of phosphates and nitrates were observed. These studies indicate relationships between water and sediment quality, and densities of D. denticulatus.     

Compound[ing] disasters in Puerto Rico: Pathways for virtual transdisciplinary collaboration to enhance community resilience

Puerto Rico has been subject to complex and compounding effects of multiple disasters, exacerbated by sociopolitical, climactic, and geographical challenges that complicate relief and resilience. Interdisciplinary teams are uniquely suited to traverse emerging challenges in post-disaster settings, but there are few studies that leverage transdisciplinary skill sets and virtual co-production of knowledge to build on local autonomous responses. Communities are key sources of information and innovation which can serve as a model for recovery amidst disaster. Thus, an interdisciplinary team of emerging scholars collaborated with Caras con Causa, a local organization in Cataño, Puerto Rico, to develop processes for enhancing autonomous responses to disaster events through participatory pathways, specifically highlighting local knowledge and preferences. The results of this collaboration include: (1) an iterative process model for transdisciplinary co-production in virtual settings and (2) key highlights from post engagement reflections including community-scale definitions of disaster, and limitations to virtual collaboration amidst disaster. Together, these results yielded critical insights and lessons learned, including recommendations for improved project communication methods within transdisciplinary and virtual collaborations. Collectively, the process, it’s resulting products, and the post-engagement reflections demonstrate a pathway for scholars and community members to engage disaster resilience challenges. These strategies are most effectively practiced through focused collaboration with community stakeholders and are paramount in solving real-world challenges related to the increasing complex of compounding disasters.     

Significance of Landscape Age,Uplift, and Weathering Rates to Ecosystem Development

The combined roles of chemical and physical weathering have profound effects on the development of terrestrial ecosystems. Landscapes which are tectonically active are rapidly denudated and continually produce nutrient solutes from fresh bedrock. The chemical weathering yields are related to climate, but also to geologic factors such as uplift rates. Long-term nutrient production and the phase of ecological development are closely related to geological setting. Until recently, this relationship has not been seriously considered by ecologists. Our analysis of existing information suggests, however, not only that the nature and type of geologic processes provide significant insights into landscape, but also to ecological development. In this paper, we describe the impact of geologic uplift on the long term generation of soluble nutrients from bedrock by evaluating long-term data from a number of forested sites and comparing it to newly collected data from Taiwan, an area undergoing rapid tectonic uplift.     

When Fields Revert to Forest: Development and Spontaneous Reforestation in Post-War Puerto Rico

During the past 50 years forests have recolonized extensive areas of Puerto Rico. Between 1950 and 1990 forest cover increased from 9% to 37% of the island's land area. In proportional terms more land has reverted to forest in Puerto Rico than anywhere else on earth during the second half of the twentieth century. This paper explores the geography of this process by matching changes in land cover with the characteristics of the land and communities in Puerto Rico. The reversion of agricultural lands to forest occurred most frequently in humid, upland, coffee-growing regions characterized by heavy out-migration and populations of smallholders who earned some of their income from off-farm sources. These findings suggest that changes in non-farm labor markets, as well as changes in the political economy of agriculture, have important impacts on the prospects for converting agricultural lands into forests.