There is an intense and continuous growth of the world population living in cities. This increase in population means an increase in car traffic, an increase in new constructions and an increase in the production of waste that translates into an intensive use of land, particularly in terms of soil contaminants. Among other environmental contaminants, toxic metals, such as lead (Pb), cadmium (Cd), nickel (Ni) and chromium (Cr) represent a public health problem. In this study the content of toxic metals in Lisbon’s (Portugal) soils was determined. The study was conducted over approximately a decade in six city locations, with a total of about 700 samples. Each site has different urban characteristics: traffic zone, residential area, urban park and mixed areas. The study allowed to verify the heterogeneity of metal content values in the city soils and their dependence on local traffic. Metal contents were determined by graphite furnace atomic absorption spectroscopy (GFAAS). For each site the geo-accumulation index, pollution factor, degree of contamination, pollution load index and ecological risk factor were calculated. The mean concentrations of Cd, Cr, Ni and Pb in soils were 0.463, 44.0, 46.6 and 5.73 mg/kg of dry soil, respectively. In the last year of the study the values were 0.417, 51.5, 62.4 and 8.49 mg/kg of dry soil, respectively. Cd and Ni exceeded the typical content values of these metals in the earth’s crust, indicating their anthropogenic origin. The correlation analysis revealed a significant correlation between Cr and Ni, Cd and Ni and Cd and Pb contents in the city soils. Regarding the results obtained in this long monitoring campaign, Lisbon’s soils can be considered as having low levels of pollution by these metals.

The charge density wave (CDW) transition temperature in the quasi-one-dimensional (Q1D) organic material $\left(\mathrm{Per}{)}_2\mathrm{Au}\right(\mathrm{mnt}{)}_2$ is relatively low ${(T}_{\mathrm{CDW}}\sim 12\mathrm{K}).\mathrm{}$ Hence in a mean field BCS model, the CDW state should be completely suppressed in magnetic fields of order 30–40 T. To explore this possibility, the magnetoresistance of $\left(\mathrm{Per}{)}_2\mathrm{Au}\right(\mathrm{mnt}{)}_2$ was investigated in magnetic fields to 45 T for $0.5\mathrm{K}<T<\mathrm{}12\mathrm{}\mathrm{K}.$ For fields directed along the Q1D molecular stacking direction, $T_{\mathrm{CDW}}$ decreases with field, terminating at about $\sim 37\mathrm{T}$ for temperatures approaching zero. Results for this field orientation are in general agreement with theoretical predictions, including the field dependence of the magnetoresistance and the energy gap, ${\Delta }_{\mathrm{CDW}}.$ However, for fields tilted away from the stacking direction, orbital effects arise above 15 T that may be related to the return of un-nested Fermi surface sections that develop as the CDW state is suppressed. These findings are consistent with expectations that Q1D metallic behavior will return outside the CDW phase boundary.

The quasi-one-dimensional organic conductor $(\mathrm{P}\mathrm{e}\mathrm{r}{)}_2\mathrm{P}\mathrm{t}(\mathrm{m}\mathrm{n}\mathrm{t}{)}_2$ exhibits a charge density wave ground state below 8 K. Magnetoresistance and magnetization measurements show that the charge density wave is suppressed with magnetic fields of order 20 T, above which a high resistance state, with a cascade of subphases, appears. This new state, tentatively identified as a field induced charge density wave, reenters a low resistance state above 40 T. The results are presented in light of theoretical work [D. Zanchi et al. Phys. Rev. B 53, 1240 (1996).] involving field induced charge density wave ground states in high magnetic fields.