Sommella, Alessia (2014) Sustainability in food production: the effects and the risks of the arsenic contamination in soil and irrigation water. [Tesi di dottorato]

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Abstract

Arsenic (As) is ubiquitous in many environments and highly toxic to all forms of life. Sources of As contamination are both natural and anthropogenic and the scale of contamination ranges from local to regional. Arsenic has been detected in groundwater in several countries of the world with concentration levels exceeding the WHO drinking water guideline value of 10 μg/L. For instance, in the Bengal Delta Plain of Bangladesh and West Bengal, India, As in groundwater has emerged as the largest environmental health disaster putting at least 100 million people at risk of cancer and other As-related diseases. Food and drinking water are the major routes of As exposure for humans. It occurs predominantly in inorganic form as arsenate (AsV) and arsenite (AsIII), whereas the organic species most common are monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA). The inorganic species are more acutely toxic than organic species. Arsenate is an analogue of phosphate and thus interferes with essential cellular processes such as oxidative phosphorylation and ATP synthesis, whereas the toxicity of As(III) is due to its propensity to bind to sulfhydryl groups, with consequent effects on protein functions. Due to the toxicity and potential environmental risks related to the mobility of As, it is of quite importance in agriculture, investigate for minimize the transfer from contaminated agricultural soils and/or contaminated water to the crop plants. It is necessary to limit entering in food chain and reduce the economic damage linked to productivity. There are many areas of research that are being actively pursued to address the As contamination problem. My Ph.D: projet was focus on the possible strategies to reduce the translocation of this element to the plant using of amendments and / or microorganisms and investigations on As exposure in food. During the first year of my Ph.D., I conducted a study on influence of phosphatic fertilization in tomato plants (Lycopersicum esculentum L. cv piennolo), grown on uncontaminated soil and irrigated with solutions containing increasing concentrations of arsenic (0, 0.5, 2,4 mg L - 1). It was found that the total biomass of the plants decreases significantly with increasing concentration of arsenic. Plants grown without phosphorus (P- ) showed a decrease in biomass of 17% , 42% and 58 % with increasing concentration of As compared to the control , while plants that have had phosphorus (P +) showed a significantly lower equal to 13%, 30% , and 42% more than the control. The concentration of arsenic in tomato plants increases as the concentration of arsenic in irrigation water. This fact is particularly evident in the roots is that of the P- P +. The concentration of arsenic in fruit is very low in both the P- than in P + (P- 0.18 to 0.28 mg kg -1, P + 0.15 to 0.22 mg kg -1). During the second year, my main research was carried out at Aberdeen University ( Scotland, UK) , and had as its objective the qualitative and quantitative study of arsenic and trace elements in samples of rice purchased in Italy , with particular attention to the quantification and speciation of arsenic. The total concentration of As in the samples analyzed according to the variety, includes a range of average values from 0.18 (Ribe) and 0.28 mg kg -1 (Vialone Nano). The results analyzed according to the region of provenience showed that the highest concentration of total As was recorded in Emilia Romagna (0.28 mg kg -1), the lowest in Calabria (0.11 mg kg -1). The data indicate that the speciation of inorganic arsenic concentration varies between 0.08 and mg kg -1 (Ribe, Rome) 0.11 mg kg -1 (Vialone Nano ) and between 12.06 (Calabria) mg kg- 1 and 0.10 (Lombardia) based on the origin. For organic species on the other hand, the concentration varies between 0:02 to 12:08 mg kg-1 depending on variety, and between 0.01 to 0.08 mg kg-1 on the basis of geographical origin. We also had interesting results for chromium (individual values range between 0.11 to 1.51 mg kg-1, and for cadmium (individual values range 0.001-0.16 mg kg-1). In the third year of my PhD, research had as objective to evaluate the effectiveness of Trichoderma in alleviating the toxic effects of arsenic in plants of lettuce (Lactuga sativa L.). Were tested two different strains of Trichoderma: T. harzianum (T22) and T. atroviride (P1). The plants are grown in pots with uncontaminated soil but irrigated with solutions containing 0-5-10 mg As L-1. In plants not inolculate, the toxic effect of arsenic was revealed especially in reduced root growth and leaf. Inoculated plants, however, with both strains of Trichoderma have shown a significant increase in total biomass compared to the control. In particular, the inoculum with the T22, has increased biomass production compared to the control total of 30.1 % (As0), 39 % (As5) and 52.5 % (As10). Lettuce has a great sensitivity to As, in fact during our studies we have it detected a high concentration both in the roots than in leaves, compared to the control. The highest concentration was found in the roots. The control -T where has not been used or contaminated water or inoculum of Trichoderma, has a concentration of As equal to 0.160 mg kg- 1 in the roots, instead of in plants irrigated with contaminated water but not inoculated , we have a concentration equal to 3.84 (As5) and of 7.30 (1 As) mg kg- 1 . In plants inoculated instead of As concentration measured is lower compared to the control: 2.95 (As5) and 6.13 (As10) mg kg-1 for those inoculated with T22 and 3.14 (As5) and 6.25 (As10) mg kg-1 with P1. Treatment with T22 and P1 in the leaves also showed a lower absorption of As compared to the control (1.24 mg kg-1 for AS5 and 2.66 mg kg-1 for As10). In fact, for plants inoculated with T22 we found a concentration of 2.95 (5As), 6.13 (As10) mg kg-1, for those inoculated with P1 3.14 (5As) and 6.24 (As10) mg kg-1.

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