Chromium in soil: environmental issues

Chromium (Cr) is a unique element in soil, because of (i) essentiality to human and animal life and non-essentiality for the vegetable kingdom and (ii) its possible presence in two main oxidation forms, trivalent (CrIII) and hexavalent (CrVI), which show opposite properties. The two forms have completely different effects on living organisms: the first (CrIII) is apparently useful or harmless at reasonable concentrations, while the second (CrVI) is extremely toxic. In addition, CrIII is not mobile in soil, therefore the risks of leaching are negligible, while CrVI, mainly present in the forms of chromates (CrO2− 4 ) and dichromates (Cr2O2− 7 ), is generally mobile and often is part of crystalline minerals (ophiolites, serpentines). Chromium-rich soils are common in many countries, where Cr minerals are diffuse and its content in natural soils (i.e. serpentine soils) may easily exceed 10,000 mg/kg. Conversion of CrIII to CrVI has been shown in some particular soils: rich in manganese (Mn) oxides, poor in organic matter and high redox potential. On the contrary, the reverse transformation of CrVI to CrIII is very common and easier, so that it is difficult to find hexavalent chromium forms in soil solution or in leaching waters. Chromium shows a soil-plant transfer factor (F) (\u201cF\u201d indicates the amount of metals that passes from the soil to the plants) very low (normally less than 5), so that Cr belongs to the less mobile elements of the soil-system. The main barrier to the income of Cr in plants is represented by the roots. CrIII is fixed on the roots and the amount that cross the cellular wall is negligible. The problem of Cr enrichment in soil has been often discussed not only in relation to the discharge of tannery wastes, but also to the possibility of Cr presence in soil amendments, mainly organics, and to the existence of excellent organic fertilizers produced from leather residues or wastes. Environmental or safety issues are often cited fearing the use of such fertilizers, generally without scientific support. As a matter of fact, the United States Environmental Protection Agency has withdrawn any limit to the presence of Cr in biosolids. The main aim of this session is to discuss updated positions of this problem, gathering the contribution of scientists who have devoted their study to chromium in recent years

Fanghi" in agricoltura, risorsa troppo spesso dimenticata

Solamente pochi agricoltori potrebbero essere a conoscenza del significato del termine perugino, de\la sua origine e del rispetto con cui, ancor oggi, \uece persone anziane di Lucca e provincia ne fanno memoria. ll termine perugino designa il contenuto del pozzo nero ed \ue8 stato coniato secoli fa per indicare l'attivit\ue0 di una cooperativa di imprenditori originari di Perugia periodicamente impegnata a svuotare i pozzineri di tutta la citt\ue0. Tale attivit\ue0 prevedeva il solo e r\uecconosciuto compenso da parte degli agricoltori che ne richiedevano f impiego come concime, usato del resto per fer\ufabzzare i campi fin dall'origine della storia dell'uomo. In Italia forse l'esempio di utilizz azione megl io or ganizzata dei pozzineri si \ue8 avuta nelle marcite, vere e proprie opere di ingegneria idraulica della bassa milanese. Molti ricorderanno che ancora nella seconda met\ue0 del secolo scorso le fogne venivano scaricate nelle campagne e andavano a lambire Ie superfici del terreno, sistemate in modo da agevolare un loro lento scorrimento e l'assorbimento di ci\uf2 che convogliavano. Da Melegnano in gi\uf9 la gente si lamentava bofonchiando che "A MiI\ue0n gh'en i c\ue8ss, a Melegn\ue0n i ud\uf9r" (a Milano ci sono i cessi, a Melegnano gli odori), ma gli effetti mirabili di tale pratica erano pi\uf9 che evidenti: il fieno che si raccoglieva nella pianura padana era costituito da d ue o tre tagli (maggengo,agostano e quando andava bene anche un rachitico terzuolo), mentre in tutta la bassa milanese e nell'attuale provincia di Lodi se ne contavano sette o otto o anche di pi\uf9, fino a undici o dodici, e di ottima qualita'. L'articolo esamina questi aspetti

Humic substances and therapeutic uses thereof

The present invention relates to the medical field, in particular to the use of natural organic polyanions, i.e. humic substances, HSs, in the treatment of neurodegenerative diseases, such as Prion disease, Alzheimer's and Parkinson's disease