Machine Learning Based Predictive Modeling of Debris Flow Probability Following Wildfire in the Intermountain Western United States

It has been recognized that wildfire, followed by large precipitation events, triggers both flooding and debris flows in mountainous regions. The ability to predict and mitigate these hazards is crucial in protecting public safety and infrastructure. A need for advanced modeling techniques was highlighted by re-evaluating existing prediction models from the literature. Data from 15 individual burn basins in the intermountain western United States, which contained 388 instances and 26 variables, were obtained from the United States Geological Survey (USGS). After randomly selecting a subset of the data to serve as a validation set, advanced predictive modeling techniques, using machine learning, were implemented using the remaining training data. Tenfold cross-validation was applied to the training data to ensure nearly unbiased error estimation and also to avoid model over-fitting. Linear, nonlinear, and rule-based predictive models including naïve Bayes, mixture discriminant analysis, classification trees, and logistic regression models were developed and tested on the validation dataset. Results for the new non-linear approaches were nearly twice as successful as those for the linear models, previously published in debris flow prediction literature. The new prediction models advance the current state-of-the-art of debris flow prediction and improve the ability to accurately predict debris flow events in wildfire-prone intermountain western United States.     

DDT in endangered Galapagos sea lions (Zalophus wollebaeki)

We characterize for the first time the presence of DDT and its metabolites in tropical Galapagos sea lions (Zalophus wolleabeki). ∑DDT concentrations in Galapagos sea lion pups sampled in 2005 and 2008 ranged from 16 to 3070 μg/kg lipid. Concentrations of ∑DDT in pups in 2008 averaged 525 μg/kg lipid and were 1.9 times higher than that (281 μg/kg lipid) detected in pups in 2005. These concentrations are lower than those reported in many pinnipeds elsewhere, comparable to those in Hawaiian monk seals, and higher than those in southern elephant seals. The health risk characterization showed that 1% of the male pups exceeded the p,p′-DDE toxic effect concentration associated with anti-androgenic effects reported in rats. The findings provide preliminary guidance on the relationship between DDT use and ecological impacts, serving as a reference point against which possible future impact of tropical DDT use can be assessed.     

Contaminant exposures at the 4H shell mounds in the Santa Barbara Channel

Remobilization, bioavailability, and potential toxicity of chemical contaminants were evaluated at the 4H shell mounds – the site of abandoned offshore oil and gas production platforms in the Santa Barbara Channel region of the Southern California Bight. Evaluations used a weight-of-evidence approach based on results from bulk phase chemical analyses and laboratory toxicity testing of shell mound cores, in situ field bioassays using caged mussels, and surficial sediment chemistry. Shell mound cores contained elevated concentrations of metals associated with drilling wastes (e.g., Ba, Cr, Pb, and Zn), as well as monocyclic and polycyclic aromatic hydrocarbons (PAHs). The highest concentrations along with pockets of free oil were associated with the middle “cuttings” stratum. Sediments composited from all core strata caused significant acute toxicity and bioaccumulation of Ba and PAHs in test organisms during laboratory exposures. In contrast, caged mussels placed at each of the shell mounds for a period of 57–58 days had greater than 90% survival, and there were no significant differences in survival of mussels placed at the shell mounds and corresponding reference sites. While all mussel samples exhibited increases in shell length, whole animal weight, and tissue lipid content, in some cases growth metrics for the shell mound mussels were significantly higher than those for the reference sites. Concentrations of metals, PAHs, and polychlorinated biphenyls (PCBs) in tissues of the shell mound mussels were not significantly different from those at reference sites. The presence of labile aromatic hydrocarbons in shell mound cores and absence of significant contaminant accumulation of tissues of caged mussels indicated that chemical contaminants are not being remobilized from the 4H shell mounds. Surficial bottom sediments near the shell mounds contained elevated Ba concentrations that probably were associated with drilling wastes. However, concentrations did not exhibit clear spatial gradients with distance from the shell mounds. Despite a number of storm events during the mussel exposures, maximum currents were 34 cm s⁻¹ and unlikely to erode materials from the shell mounds. Thus, Ba distributions in bottom sediments probably were due to episodic disturbance such as platform removal or trawling rather than ongoing erosion and dispersion of shell mound solids by near-bottom currents. These results suggest that, in the absence of physical disturbances, contaminants are expected to remain sequestered in the shell mounds.     

Ground- and space-based GPS data ingestion into the NeQuick model

This paper presents a technique for ingesting ground- and space-based dual-frequency GPS observations into a semi-empirical global electron density model. The NeQuick-2 model is used as the basis for describing the global electron density distribution. This model is mainly driven by the F2 ionosphere layer parameters (i.e. the electron density, N _m F2, and the height, h _m F2 of the F2 peak), which, in the absence of directly measured values, are computed from the ITU-R database (ITU-R 1997). This database was established using observations collected from 1954 to 1958 by a network of around 150 ionospheric sounders with uneven global coverage. It allows computing monthly median values of N _m F2 and h _m F2 (intra-month variations are averaged), for low and high solar activity. For intermediate solar activity a linear interpolation must be performed. Ground-based GNSS observations from a global network of ~350 receivers are pre-processed in order to retrieve slant total electron content (sTEC) information, and space-based GPS observations (radio occultation data from the FORMOSAT-3/COSMIC constellation) are pre-processed to retrieve electron density (ED) information. Both, sTEC and ED are ingested into the NeQuick-2 model in order to adapt N _m F2 and h _m F2, and reduce simultaneously both, the observed minus computed sTEC and ED differences. The first experimental results presented in this paper suggest that the data ingestion technique is self consistent and able to reduce the observed minus computed sTEC and ED differences to ~25–30% of the values computed from the ITU-R database. Although sTEC and ED are both derived from GPS observations, independent algorithm and models are used to compute their values from ground-based GPS observations and space-based FORMOSAT-3/COSMIC radio occultations. This fact encourages us to pursue this research with the aim to improve the results presented here and assess their accuracy in a reliable way.     

Macro benthic community assemblage before and after the 2007 tsunami and earthquake at Paracas Bay,Peru

Macrobenthic soft bottom community assemblages were studied from December 2006 to December 2007 at Paracas Bay (Atenas Beach, 13°45' S, 76°17' W, Peru), including the period of the tsunami of 15 August 2007, providing a unique opportunity to assess the effects of this type of natural disturbance in soft bottom marine ecosystems. The results show that the tsunami affected the soft bottom community assemblage by changing the sediment granulometry, the biomass and abundance of epifaunal species, and by increasing the silt proportion. The event affected all functional groups, resulting in an increased numbers and biomass of filter feeder and grazers that were followed soon after by predators during the post-tsunami period. A similar pattern was observed for biomass and the abundance of infaunal species without changing the functional groups. The slow recovery observed after four months was likely related to the loss of sediment stability. In summary, there were differences in the structure and composition of soft bottom macrofaunal assemblages before and after the earthquake and posterior tsunami disturbance, forcing benthic communities to initiate re-colonisation processes.     

Age and magnetic fabric of the Três Córregos granite batholith: evidence for Ediacaran transtension in the Ribeira Belt (SE Brazil)

Anisotropy of magnetic susceptibility (AMS) and U–Pb (SHRIMP) zircon ages in the eastern part of the Três Córregos batholith (Ribeira belt, SE Brazil) indicate a well-defined fabric pattern acquired between 600 and 595 Ma. The batholith consists mostly of porphyritic granites distributed in the Ribeirão Branco, Barra do Chapéu and Itaóca plutons. Late fluorite-bearing alkaline granites, some containing Sn-polymetallic greisen-type deposits, intruded the Ribeirão Branco pluton and the low-grade metasedimentary host rocks. The magnetic fabric of the Ribeirão Branco granite is dominantly oblate and oblique to the pluton elongation while that in Barra do Chapéu is mostly concentric. On both plutons, AMS records the preferred orientation of coarse, homogeneous Ti-poor magnetite grains. Such fabric patterns indicate a partitioned strain field dominated by strike-slip left-lateral shear deformation in the Ribeirão Branco and extension in the Barra do Chapéu pluton. The zircon ages of these plutons are 600 ± 6 Ma and 595 ± 4 Ma. Likewise, the ages of alkaline plutons were in the range of 597 and 595 Ma, registering a fast transition between the typical syntectonic batholithic magmatism to the late, highly evolved and specialized magmas. These results indicate that the Ribeira belt was deformed by transtension in the Middle Ediacaran. The geological setting is consistent with a continental arc with the Três Córregos batholith emplacing at the middle-upper crust.     

Accumulation of lead and associated metals (Cu and Zn) at different growth stages of soybean crops in lead-contaminated soils: food security and crop quality implications

The Pb, Cu and Zn content, the physicochemical parameters in soils (EC, OM%, soil texture and pH) and the metal accumulation of Glycine max plants at different growth stages were evaluated. Topsoil and soybean samples were collected in the vicinity of a former battery-recycling plant, with the results showing that only the concentrations of Pb in soils corresponding to sites located near to the lead emission source were above the maximum permissible levels. However, soybean crops accumulated Pb above the permitted levels at all studied sites, revealing a potential toxicological risk for direct consumption. Thus, the accumulation of Pb in soybean was directly related to the translocation factor of the metal from roots to aerial parts of the plant. This was evidenced as a lower accumulation at early growth stages and a higher accumulation at maturity, with the distribution between organs coinciding with nutrient incorporation and remobilization in the plant. Moreover, the bioconcentration factor revealed that the bioaccumulation of lead in soybean was a consequence of the lead-recycling plant activity in the past. Taken together, results of the present study demonstrated that soybean crops can incorporate and accumulate potentially toxic metals, such as lead.     

Sedimentary provenance of the Late Paleozoic metamorphic basement,south-central Chile: Implications for the evolution of the western margin of Gondwana

ABSTRACT

U-Pb detrital zircon age patterns are presented for nine samples of metapelites from the metamorphic basement of south-central Chile between 37° and 40°S, along with detrital zircon ages for a sample from the Piedra Santa metamorphic complex and a crystallization age of the Chachil plutonic complex, farther east in Argentina. Two distinct zircon age patterns are identified. One is a pattern with a dominant population of zircons at ca. 470 Ma (Ordovician), a widespread presence of Mesoproterozoic ages (1200 ? 1000 Ma), and a Carboniferous maximum deposition age indicated by the youngest zircon population. The second pattern is drastically different, with a main population of Permian zircons, a 290–250 Ma maximum deposition age, and a minor contribution of Pennsylvanian age zircons. Our results, coupled with previously reported metamorphic ages, show that the patterns reflect the presence of different tectonic blocks separated by the Mocha-Villarrica Fault Zone at 39°S. Metapelites north of this structure have the Ordovician-dominated pattern characteristic of the Western Series of the Paleozoic basement, and those south of the fault show the Permian-dominated pattern observed in the younger high-pressure metapelites from the Bahía Mansa metamorphic complex. The Piedra Santa metamorphic complex also shows the Ordovician-dominated pattern and was intruded by the Chachil plutonic complex dated here at ca. 303 Ma. Therefore, the Piedra Santa complex is interpreted as coeval with the Chilean metamorphic basement. The present dislocation of blocks with different ages is attributed to continental-scale dextral strike-slip tectonics along the Huincul Fault Zone, Argentina, which extends to the west as the Mocha-Villarrica Fault Zone in Chile.     

Anomalous Diffuse CO2 Emission prior to the January 2002 Short-term Unrest at San Miguel Volcano, El Salvador, Central America

On January 16, 2002, short-term unrest occurred at San Miguel volcano. A gas-and-steamash plume rose a few hundred meters above the summit crater. An anomalous microseismicity pattern, about 75 events between 7:30 and 10:30 hours, was also observed. Continuous monitoring of CO₂ efflux on the volcano started on November 24, 2001, in the attempt to provide a multidisciplinary approach for its volcanic surveillance. The background mean of the diffuse CO₂ emission is about 16 g m^-2 d^-1, but a 17- fold increase, up to 270 g m^-2 d^-1, was detected on January 7, nine days before the January 2002 short-term unrest at San Miguel volcano. These observed anomalous changes on diffuse CO₂ degassing could be related to either a sharp increase of CO₂ pressure within the volcanic-hydrothermal system or degassing from an uprising fresh gas-rich magma within the shallow plumbing system of the volcano since meteorological fluctuations cannot explain this observed increase of diffuse CO₂ emission.     

Self-generated aperiodic behaviour in a simple climate model

Climatic variability arising from the coupling between ocean temperature and sea-ice extent is studied in a spatially distributed system. A spatial degree of freedom is crudely introduced by the coupling, through energy transfer, of two box models each of which describes a different space region. The evolution equations are cast into a normal form and some qualitative features of this general class of models are predicted. It is shown, both analytically and numerically, that internally generated complexity in the form of aperiodic behaviour can be a natural consequence of spatially distributed systems.