2,4-Dichlorophenoxyacetic acid (2,4-D) sorption and degradation dynamics in three agricultural soils

The fate and transport of 2,4-dichlorophenoxyacetic acid (2,4-D) in the subsurface is affected by a complex, time-dependent interplay between sorption and mineralization processes. 2,4-D is biodegradable in soils, while adsorption/desorption is influenced by both soil organic matter content and soil pH. In order to assess the dynamic interactions between sorption and mineralization, 2,4-D mineralization experiments were carried using three different soils (clay, loam and sand) assuming different contact times. Mineralization appeared to be the main process limiting 2,4-D availability, with each soil containing its own 2,4-D decomposers. For the clay and the loamy soils, 45 and 48% of the applied dose were mineralized after 10 days. By comparison, mineralization in the sandy soil proceeded initially much slower because of longer lag times. While 2,4-D residues immediately after application were readily available (>93% was extractable), the herbicide was present in a mostly unavailable state (<2% extractable) in all three soils after incubation for 60 days. We found that the total amount of bound residue decreased between 30 and 60 incubation days. Bioaccumulation may have led to reversible immobilization, with some residues later becoming more readily available again to extraction and/or mineralization.     

A medical geology study of an arsenic-contaminated area in Kouhsorkh, NE Iran

High concentrations of arsenic were determined in sediments from the Kouhsorkh area, Khorasan province, NE Iran. The main rock formations in the area consist of Tertiary volcanic rocks as Tuffaceous sandstone, polymictic conglomerate and andesite. Furthermore, some As–Sb–Au mineralization occurred in this area. Concentrations of arsenic in sediments were determined to range between 4.2 and 268.2 ppm, exceeding US EPA (2004) limits. It seems that young volcanic activity is one of the most important factors for arsenic contamination in this area. The first stage of this medical geology study was done at 2 villages in the Kouhsorkh area in which the arsenic concentration in water is high. People in this residential area suffer from skin diseases including hyperpigmentation, hypopigmentation, keratosis on head, hands, and feet. The 24-h urine specimens were tested for arsenic, the level of total arsenic in urine were determined to range between 13.66 and 75.92 μg/l day, exceeding permissible limits from 5 to 40 μg/day. More systematic studies are needed to determine the link between As exposure and its related diseases.     

Pyrolysis of lemon peel waste in a fixed-bed reactor and characterization of innovative pyrolytic products

Journal of Material Cycles and Waste Management - Lemon peel waste (LPW) were pyrolysed in a laboratory fixed-bed reactor at final temperature of 300&nbsp;°C, 400&nbsp;°C and...     

Water demand of central pivot-irrigated areas in Bahia,Brazil: management of water resources applied to sustainable production

When performed without technical criteria, the rapid expansion of irrigated agricultural frontiers can result in overexploitation of water, causing worrying impacts on the balance of agroecosystems. This study proposes a model applied to the state of Bahia, to estimate the water demand of areas irrigated by a central pivot, in order to contribute to information that will subsidize the inspection and planning of water resources in the promotion of sustainable agriculture. The irrigated areas were identified and measured by photointerpretation using orbital images from the Landsat-8 satellite. With a historical series of data, the reference evapotranspiration was calculated and monthly water balance was elaborated. The data obtained were spatialized by kriging, and with punctual values of water deficit (mm), the water demand of the irrigated perimeter of the equipment was estimated. The results were described considering strategic planning units, proposed from municipalities, hydrographic basins and biomes. A total of 4075 pivots were quantified, covering an irrigated area of 265,896.30 ha and with an average annual consumption of 1,333,473,208.02 m³ of water. Areas of high demand were identified, especially in the western region of Bahia, which includes the hydrographic basin of the São Francisco River and the Cerrado biome, concentrating 80.85% and 75.47% of the state water demand for pivots, respectively. Considering possible points of water vulnerability and continuity of this expansion, the results provide the primary information needed to encourage the adoption of public policies aimed at the management of water resources. The study method proposes guidelines that condition the application in any region of interest in the world.

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