Structure in fluctuations of large-scale soil moisture climate due to external random forcing and internal feedbacks

Large-scale fields of soil moisture are forced by atmospheric precipitation and radiative forcing. When these forcing factors are themselves influenced by surface and soil moisture processes, the result is a nonlinear land-atmosphere system with inherent feedback mechanisms that may strongly modulate variability in climate. Given such feedbacks, simple randomness in the forcing factors may be manifested as a complex statistical signature in the surface hydrology. In this paper, we investigate the impacts of non-Gaussian and colored-noise on the probability distribution of soil moisture resulting from the statistical-dynamical land-atmosphere interaction model of Rodriguez-Iturbe et al. (1991). Persistence of hydroclimatologic anomalies as characterized by the correlation time scale of soil moisture is discussed.     

Use of sequential extraction procedure for assessing the environmental impact at regional scale of the São Domingos Mine (Iberian Pyrite Belt)

São Domingos is one of the most emblematic Portuguese mining districts in the Iberian Pyrite Belt (IPB). The beginning of mining exploitation in the area has been dated back to pre-Roman times, remaining in activity until 1966 when it was definitely halted. The intense mining labours are reflected in the presence of a huge amount of sulphide-mining wastes and downstream production of acid mine drainage (AMD). The mining wastes in the area are highly heterogeneous, and numerous different types may be recognized, including slags, iron oxides, smelting ashes, brittle and blocks of pyrite, leaching tank refuses, industrial landfill and other residues coming from ore extraction (gossan wastes and country rocks). The chemical speciation of potentially toxic elements (As, Cd, Cr, Cu, Fe, Mn, Pb, S, Sb and Zn) in all mine wastes from São Domingos was determined by modified BCR-sequential extraction procedure (European Community Bureau of Reference) and combined with the mass/volume proportions of each waste to quantify the potential risk of this mining district at regional scale. Analytical recoveries by sequential extraction, with respect to a pseudo-total metal content digestion, were generally acceptable (100 ± 17%). The oxidizable fraction corresponds with metals bound to sulphides and released easily under oxidizing conditions in AMD production processes. This is the most polluting fraction for the environment in this type of residues. Part of this fraction is retained by precipitation of soluble secondary minerals in warm periods, moving to the bio-available fraction that is dissolved in rainy periods. Just considering the bio-available fraction, all mine wastes from São Domingos may leach up to 172514 ton of Fe, 10564 ton of S, 6644 ton of Pb, 2610 ton of Zn, 1126 ton of Mn, 1032 ton of Cu, 183 ton of Cr, 109 ton of As, 34 ton of Sb and 0.9 ton of Cd. The process of precipitation and re-dissolution of efflorescent salts formed directly by oxidation of the oxidizable fraction is seasonally repeated, which causes an annual self-feeding and releasing of the bio-available fraction. Thus, the present study shows the pollutant potential of this IPB mining district and explains the spoiled state of the fluvial courses in the region.     

Numerical modelling of surfacewater/groundwater flows for freshwater/saltwater hydrology: the case of the alluvial coastal aquifer of the Low Guadalhorce River, Malaga, Spain

This applied research deals with the numerical modelling and transient simulation of the joint surfacewater/groundwater flows that characterize the freshwater/saltwater hydrology of the coastal alluvial valley of the Low Guadalhorce River, Malaga, Spain. The MELEF model used was mainly adapted and calibrated for a simulation period of two hydrological years 1989/1990–1990/1991, before the current channelling of the river, where floods and low precipitations have been recorded. The model calibration process was performed with the aid of phreatic levels measured in numerous wells and piezometers, as well as recharges from precipitation and irrigation on the alluvial surface, which was also assessed by the hydrologic model SSMA-2. The present numerical approach can predict the forthcoming hydrology of the coastal alluvial of the Guadalhorce River after its final channelling.     

Kinematic constraints between stellar systems in superposition

Some kinematic consequences of a superposition of two stellar systems are studied. Chandrasekhar's axially-symmetric model has been adopted for each one of the subsystems. The solution of Chandrasekhar's equations provides us with a potential function, which must be shared by both stellar subsystems and, thus, some relationships between the kinematic parameters of both, subsystems are obtained. In the case of a stationary potential function the whole set of second-order centred moments may be explained.Gotta serve somebody... (Bob Dylan) may be U may be ₂.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

Comparative agroenvironmental risks of pesticides in different cropping systems: application of the I-Phy indicator

The green revolution laid the foundations of modern agriculture, by using science and technology to produce more from same resources. The pesticides contributed to agricultural output in the last decades; however, their use has resulted in environmental pollution, health problems, soil and water contamination and negative impact on biota. The impacts of agricultural activities to the environment depended on the practices adopted during the production process. Measurement tools to assess the impacts of those practices are necessary to improve agricultural systems and must be evaluated in different ecosystems. Different soils, climates and crops impose many phytosanitary arrangements. This complex network and the fact that most of the indicators and measurement tools are developed for temperate climates makes it difficult to quantify the environmental impacts under subtropical regions. The I-Phy index is a predictive indicator that assesses the risks of pesticide usage in agriculture and identifies as to which practices generate the main environmental impacts of pesticides. The objective of this study was to test the suitability of the I-Phy index for subtropical conditions and, if suitable, compare the pesticide risk between two regions. Five crops were assessed under three different cropping systems: no-tillage, minimal tillage and conventional tillage. The I-Phy index was sensitive in both regions and capable of identifying that no-tillage generally presented risks of environmental pollution slightly lower than the other tillage systems. The results of I-Phy index showed that high environmental vulnerability of the fields and the numerous applications of active ingredients with high risks resulted in high risks of general contamination. The application of I-Phy on these two case studies showed the indicator can be useful as a support tool to farmers, research and extension institutions pursuing management practices with lower impact on the environment.