Modelling solute transport in structured soils: performance evaluation of the ADR and TRM models

The movement of chemicals through the soil to the groundwater or discharged to surface waters represents a degradation of these resources. In many cases, serious human and stock health implications are associated with this form of pollution. The chemicals of interest include nutrients, pesticides, salts, and industrial wastes. Recent studies have shown that current models and methods do not adequately describe the leaching of nutrients through soil, often underestimating the risk of groundwater contamination by surface-applied chemicals and overestimating the concentration of resident solutes. This inaccuracy results primarily from ignoring soil structure and nonequilibrium between soil constituents, water, and solutes. A multiple sample percolation system (MSPS), consisting of 25 individual collection wells, was constructed to study the effects of localized soil heterogeneities on the transport of nutrients (NO&minus;3, Cl&minus;, PO3&minus;4) in the vadose zone of an agricultural soil predominantly dominated by clay. Very significant variations in drainage patterns across a small spatial scale were observed (one-way ANOVA, p &lt; 0.001 indicating considerable heterogeneity in water flow patterns and nutrient leaching. Using data collected from the multiple sample percolation experiments, this paper compares the performance of two mathematical models for predicting solute transport, the advective-dispersion model with a reaction term (ADR), and a two-region preferential flow model (TRM) suitable for modelling nonequilibrium transport. These results have implications for modelling solute transport and predicting nutrient loading on a larger scale.<br /

Groundwater waves in a coastal aquifer: A new governing equation including vertical effects and capillarity

Groundwater waves, that is, water table fluctuations, are a natural phenomenon in coastal aquifers. They represent an important part of the interaction between the ocean and aquifer and affect the mass exchange between them. This paper presents a new groundwater wave equation. Because it includes the effects of vertical flows and capillarity, the new equation is applicable to both intermediate-depth aquifers and high-frequency waves. Compared with the wave equation derived by Nielsen ed al. [1997], the present equation provides a closer representation of groundwater waves. In particular, it predicts high-frequency water table fluctuations as observed in the field. A validation of the new equation has been carried out by comparing the analytical solutions to it with predictions from direct simulations using the numerical model SUTRA. The effects of various physical parameters and their relative importance are also discussed

A possible cause of misdiagnosis in tumors of the axilla: schwannoma of the brachial plexus

The Authors report a rare case of a 57 years old man affected by a left radial nerve schwannoma that occurred as an asymptomatic lesion of the axilla. At clinical examination the lump was undistinguishable from the most common axillary lymphadenopathy. A lymphoadenopathy was erroneously diagnosed with ultrasonography (US). This mistake was due to the low specificity of the instrumental methodology and to the rarity of an asymptomatic schwannoma of the infraclavicular brachial plexus. The neoplasia was excised without using the microscope. In the early post-operative follow up, a “falling” attitude of the wirst, the hand and the fingers appeared, peculiar for a lesion of the radial nerve. Furthermore a hypoaesthesia of the skin of first finger and of the first interosseus space was associated. The sensitive and motor electromyography showed a radial nerve suffering. The “stupor” of the nerve trunk was treated with steroid therapy for 7 days and the patient underwent to some series of neuro-rehabilitative physical therapy for 12 weeks. The postoperative total body CT, showed that the lesion was unique: therefore it was possible to exclude the diagnosis of neurofibromatosis. After 28 months electromyography and axillary US were performed showing the complete resolution of the motor and sensitive deficit and the absence of local recurrence

Insolita causa di addome acuto in paziente adulto: l’ileo biliare

L’ileo biliare è una condizione morbosa rara descritta tra le complicanze della litiasi della colecisti. È causa dell’1-3% delle ostruzioni meccaniche del piccolo intestino. Interessa più frequentemente pazienti di età compresa tra 63 e 85 anni. La diagnosi pre-operatoria è generalmente posta con ritardo variabile da 1 a 10 giorni per l’assenza di una sintomatologia specifica. Caso clinico. Gli Autori riportano il caso di un uomo di 50 anni in cui è stata posta diagnosi di occlusione meccanica del piccolo intestino da voluminosa concrezione litiasica. L’occlusione ileale è stata dimostrata con la TC. Il paziente è stato sottoposto in urgenza ad intervento chirurgico, in un unico tempo, di enterolitotomia, colecistectomia e riparazione della fistola duodenale. Il decorso clinico è stato regolare e il paziente è stato dimesso in XIV giornata. Discussione. Nel nostro caso la diagnosi di ileo biliare è stata posta con un ritardo di 5 giorni. L’ecotomografia del fegato e delle vie biliari non è stata in grado di visualizzare la colecisti. La diagnosi è stata posta con la TC che si conferma gold standard diagnostico. Conclusioni. Lo stato clinico del paziente influenza la strategia chirurgica. Nel nostro paziente, considerato a basso rischio, è stato possibile l’intervento chirurgico in un unico tempo. La procedura in due tempi, enterolitotomia e successiva colecistectomia con riparazione della fistola, va riservata ai pazienti ad alto rischio