A CSM-BASED PROCEDURE FOR IDENTIFYING SEGMENTS OF AGRICULTURAL DRAINAGE DITCHES TO BE PRIORITIZED IN MAINTENANCE WORK

Productive agricultural land is vital for food production. To help secure the productivity of drained agricultural soils, diches need to be intermittently maintained. Maintenance work is costly, however, so ditch segments in most need of maintenance should be prioritized. Here, we present a procedure for identifying drainage ditch segments likely to need maintenance based on susceptibility to soil erosion by water flowing in the ditch, evaluated using a cohesive strength meter (CSM). An important part of the procedure is to relate the pressure of the CSM jets to pressures acting on the soil. The relationship between CSM jet pressure and pressures at the soil surface was established based on measurements made with a pressure sensor plate and was applied to obtain several values for pressure at the surface, which were used in turn to estimate critical shear stress for erosion. The results showed that the CSM-based method was able to identify differences in critical shear stress for erosion for different field soils. This information can be useful in identifying drainage ditch segments that should be prioritized for maintenance work

Josep Sancho, «Artur Bladé, escriure la memòria (1907-1995)», Valls, Cossetània Edicions / Centre d?Estudis de la Ribera d?Ebre, 2018, 488 p.

Ressenya sobre el llibre de Josep Sancho, Artur Bladé, escriure la memòria (1907-1995), Valls, Cossetània Edicions / Centre d?Estudis de la Ribera d?Ebre, 2018, 488 pp., ISBN: 978-84-9034-752-2

Nitrogen fixation in the Mediterranean Sea

The Mediterranean Sea is an oligotrophic basin characterized by low nutrient levels and unusually high NO3/PO4 molar ratios in the deeper layers, that reach the maximum (N/P = 28) in the Eastern Mediterranean. An external nitrogen source needs to be claimed in order to explain the nitrogen excess. Pantoja et al. (2002) found that the 15N/14N natural abundance in particulate and in dissolved inorganic nitrogen display low values, suggesting an important role of a "light" nitrogen source. Two hypotheses can be invoked: (i) nitrogen compounds from atmospheric deposition and/or(ii)atmospheric molecular nitrogen throughout nitrogen fixation . During TRANSMED oceanographic cruise carried out in the framework of Italian project VECTOR(June 2007), N2 fixation experiments have been carried out all over the Mediterranean Sea and outside the Gibraltar Strait. Surprisingly, very low rates (< 0.10 nmol N2*l-1*d-1) have been observed in different areas of the basin, while higher values have been observed in Atlantic Ocean according with literature data. These preliminary results suggest a major role for nitrogen atmospheric deposition in shaping the NO3/PO4 anomaly of the basin. Pantoja, S., D. J. Repeta, J. P. Sachs, and D. M. Sigman (2002). Stable isotope constraints on the nitrogen cycle of the Mediterranean Sea water column, Deep Sea Res., Part I, 4, 1609- 1621

Molecular biomarkers and toxic consequences of impact by organic pollution in aquatic organisms

Organic contaminants are readily bioaccumulated by aquatic organisms. Exposure to and toxic effects of contaminants can be measured in terms of the biochemical responses of the organisms (i.e. molecular biomarkers). The hepatic biotransformation enzyme cytochrome P4501A (CYP1A) in vertebrates is specifically induced by organic contaminants such as aromatic hydrocarbons, PCBs and dioxins, and is involved in chemical carcinogenesis via catalysis of the covalent binding of organic contaminants to DNA (DNA-adducts). Hepatic CYP1A induction has been used extensively and successfully as a biomarker of organic contaminant exposure in fish. Fewer but equally encouraging studies in fish have used hepatic bulky, hydrophobic DNA-adducts as biomarkers of organic contaminant damage. Much less is known of the situation in marine invertebrates, but a CYPlA-like enzyme with limited inducibility and some potential for biomarker application is indicated. Stimulation of reactive oxygen species (ROS) production is another potential mechanism of organic contaminant-mediated DNA and other damage in aquatic organisms. A combination of antioxidant (enzymes, scavengers) and pro-oxidant (oxidised DNA bases, lipid peroxidation) measurements may have potential as a biomarker of organic contaminant exposure (particularly those chemicals which do not induce CYP1A) and/or oxidative stress, but more studies are required. Both CYP1A- and ROS-mediated toxicity are indicated to result in higher order deleterious effects, including cancer and other aspects of animal fitness

Recorregut geològic i mineralògic per les comarques de la Terra Alta i de la Ribera d'Ebre: des de Gandesa a Mora la Nova, Miravet, Pinell de Brai i a Prat de Compte

En aquesta ocasió, el recorregut del present itinerari discorrerà per una zona en la qual conflueixen tres unitats geològiques netament diferenciades: la Depressió Geològica de l´Ebre, la Serralada Prelitoral Catalana (integrant del Sistema Mediterrani) i la Serralada Ibèrica. Tot i així, els primers trams es faran per entre els afloraments cenozoics de la Depressió Geològica de l´Ebre i més concretament, per les immediacions de la denominada Zona de l´Avant – país plegat. Tot aquest recorregut es farà entre la població de Gandesa i la Venta de Camposines. Tot seguit es tallaran breument els afloraments mesozoics de la Branca Externa de la Serralada Prelitoral Catalana, per arribar després a trobar de nou els afloraments cenozoics que reblen la Depressió de Mora (situades ambdues dintre del Sistema Mediterrani). Aquest recorregut s´efectuarà entre Camposines i les immediacions de la població de Miravet Immediatament després, el recorregut transitarà per la Serralada Prelitoral Catalana (concretament per la denominada Branca Externa, de nou), per aquesta unitat geològica s´arribarà primer a les immediacions de Miravet, per on es tocarà la Serralada Prelitoral Catalana (però ara la seva Branca Interna). Tot i així, s´anirà circulant pel contacte entre aquesta i la ja esmentada Depressió de Mora, fins arribar a trobar la Serra de Cavalls – Serra de Pàndols, tot anant cap a Prat de Compte. Així, haurem tornat a penetrar a la Serralada Prelitoral Catalana (concretament per la denominada Branca Externa, per on ja hem circulat abans). Per d´altra banda, el recorregut de l´itinerari, discorrerà fonamentalment per dues de les comarques que formen part de les Terres de l´Ebre o Regió de Tortosa, concretament per la del la Terra Alta i per la de la Ribera d´Ebre