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The increasing population in urban areas in the last decades requires an effort to understand the geochemistry of contaminant elements in urban soil. Topsoil plays a crucial role in the exposure of Potentially Toxic Elements (PTEs) to humans through ingestion, dermal contact, and inhalation. In Chile, the last census revealed that 88.6% of people live in cities or towns and only 11.4% in rural areas. This study presents the first systematic geochemical survey of urban soil in the city of Valdivia, in the South of Chile. Topsoil samples (0–10 cm depth) were collected in less disturbed locations within the city at 130 sampling sites using a grid of 0.25 km2 squares covering a total area of approximately 30 km2. The concentrations of Al, Fe, Na, Ca, Mg, K, Ti, Be, V, Cr, Mn, Co, Ni, Cu, Zn, As, Mo, Sn, Cd, Se, Pb and Hg were measured. The results showed that high concentrations of Cu, V, Zn and Pb are located mainly in the city's northern area and exceed international soil quality legislation for agricultural use. Data processing comprised plotting of individual spatial distribution maps and the use of a combination of multivariate statistical methods. Hierarchical cluster analysis and principal component analysis identified three element associations. The two element groups V–Al–Ti–Fe–Cr–Co–Mn–Be–Ni and Ca–Na–K–As–Mg are interpreted as a dominant lithological origin related to the most pristine soil conditions in less populated areas. By contrast, the Sn–Pb–Zn–Mo–(Cu–Hg) association presents a significant correlation with urbanization indicators, including vehicular traffic and industrial activities developed since the end of the nineteenth century in Valdivia. [ABSTRACT FROM AUTHOR]

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Wheat (Triticum aestivum L.) is the major crop in terms of planted area and presents the largest distribution in the country covering a wide range of climatic regions. This study assesses the changes of various agronomic traits of winter wheat cultivars released in Chile between 1920 and 2000. A total of 117 winter accessions, representing 45 old and 72 modern cultivars were tested in a humid Mediterranean-type climate, with irrigation, in 2003. Old cultivars were those released before 1960 and modem ones were those released after 1960. Principal component (PC) analysis using 10 agronomic traits clearly separate modem from old cultivars of winter wheat. Comparing modem cultivars with old ones, plant height have been reduced by 25.6%, but others traits have increased, like harvest index (21.1%), number of grains per ear (42.6%), sedimentation value (103%), and grain hardness (32.0%). The variation in plant height was negatively correlated with harvest index (r = -0.30, p < 0.001). Grain yield, a trait not included in PC analysis, was highly correlated with the second PC (r = 0.81, p < 0.0001). Significant (p < 0.01) correlations were found between the year of release of cultivars and agronomic traits: plant height (r = -0.82), harvest index (r = 0.40), number of grain per ear (r = 0.69), sedimentation value (r = 0.64), and kernel weight (r = -0.46). Those correlations were mostly a consequence of absence or presence of dwarfing genes in the germplasm. Finally, the yield progress was calculated from yield data of yield trial with 15-25 cultivars and advanced lines of winter wheat tested almost every year from 1965 to 2001, showed no increase in yield between 1965 and 1975, but an increment of 246 kg ha-1 per year between 1976 and 1998, representing an annual increase of 2.6%. [ABSTRACT FROM AUTHOR]