Revista de contaminación

High-level nuclear waste such as Caesium (Cs), Strontium (Sr), Tellurium (Te) and Ruthenium (Ru) was fixed in sodium zirconium phosphate (NZP) at very low temperature by adopting microwave synthesis. The quantity of substituted elements in the matrix was confirmed by dissolving doped NZP in a mixture of acids along with fusion mixture at 1073 K. The results obtained are not satisfactory for the elements like Cs and Te which are considerably volatile at this temperature. Hence microwave digestion method was adapted to obtained comparative data. Quantitative analysis of the solution was done by Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS). Results acquired revealed that microwave dissolution method gives more accurate and appropriate result compare to conventional dissolution method.
This work describes not only fixation of elements in the matrix but also detection of the exact amount of element that got fixed in the NZP ceramic, which will open the new path in the field of the fixation of nuclear waste in the ceramic matrix.

Dakar, like most African capitals, is characterized by a high human density, a dense transport network where motor vehicles are old and a high concentration of industries. Significant quantities of hydrocarbons are consumed daily to meet the energy needs of the economy; the combustion of hydrocarbons in engines and boilers in the presence of oxygen in the air produces various pollutants including carbon oxides (COx) and nitrogen oxides (Nox) found in the lower atmosphere. This work investigates the radiative forcing by Modtran6 following the concentrations of these two types of pollutants measured in the city of Dakar. Thus, this study has shown slight changes in the total radiance and a no less negligible place of ozone (especially in the dry season) whose peak absorption is 1040 cm-1 in the infrared. Atmospheric transmittance decreases throughout the width of the spectral band used during the rainy season; the most important jumps of this transmittance are observed around the wave numbers 800 cm-1 and 1050 cm-1.

The Bamenda Regional Hospital, like most hospitals in Cameroon, lacks an appropriate wastewater treatment system. The main objective of this work was to evaluate the state of the existing sanitation infrastructures in the Bamenda Regional Hospital and design a decentralized wastewater treatment system for the Hospital. The research methodology involved pre-research preparations, field data collection via semi-direct interviews with officials of the hospital, field observations and data analysis. Results obtained from semi-direct interviews and field observations revealed that the existing sanitation infrastructures in the hospital are inappropriate for the treatment of the hospital’s wastewaters due to their deteriorating state and poor design. We therefore designed in this paper a decentralized wastewater treatment system made up of a sewer network constituted of 12 main PVC pipes (S1, S2, S3, S4, S5, S6, S7, S8, PS, PS1, PS2 and PS3) and four treatment units: a settling tank (volume=13.25 m3, area=3.68 m2, depth=3.60 m, width=1.84 m and length=2.00 m); two 6-chambered anaerobic baffled reactors placed in series (each having a working volume of 317.95 m3, compartment up-flow area of 22.08 m2, total compartment area of 29.44 m2, reactor depth of 3.00 m, reactor width of 7.28 m and a reactor length of 14.56 m) ; two 3-chambered anaerobic filters placed in series (each having volume of filter of 66.24 m3, volume of packed bed of 41.4 m3, area of 27.6 m2, depth of 2.40 m, width of 5.25 m and a length of 5.25 m); and a horizontal planted gravel bed (with a cross-sectional area of 8.83 m2, total length of 7.00 m, width of 1.26 m, height of 1.5 m and 36 plants). A pump with an effective power of 0.03 KW was also designed. The choice of the system proposed in this work was governed by the fact that: the cost of construction, operation and maintenance of the different treatment units is relatively low compared to other technologies; the construction materials are locally available; the system does not require large area since the units are constructed underground; the system energy requirement is very low or almost zero; reports from researchers reveal that the different units combined in the chosen system have individually shown good treatment efficiencies.

Groundwater pollution has become an issue of great concern in rural China. Consequently, a series of policies to control groundwater pollution and improve the groundwater quality have been implemented in China. However, these policies rarely provided suggestions on how to manage and protect groundwater in rural areas. In this paper, we illustrate many consequences of groundwater pollution in rural China, and suggest that environmental researchers need to work out a set of solutions for tackling the growing problem of groundwater pollution in rural China. Several viewpoints are suggested to be taken into consideration at least when formulating projects for the prevention and control of rural groundwater pollution in the future.

The spatial and temporal variability, trend of visibility, frequency of occurrence (FOO) of ‘thick dust haze’ (TDH) and of ‘light dust haze’ (LDH) during the Harmattan season (November to February) were examined, using 27-year visibility data for 8 synoptic stations located in northern Nigeria. Visibility target used to differentiate TDH and LDH occurrence is that when visibility ≤ 1,000 m (Vx ≤ 1,000 m), which indicates Thick Dust Haze (TDH); while visibility range of ˃1,000 m and ≤ 5,000 m (1,000 m ˂ Vx ≤ 5,000 m) indicates Light Dust haze (LDH). The visibility pattern showed a decreasing trend throughout the study period as lowest visibility was observed in the month of January. Highest FOO of TDH and LDH conditions were also observed in this month, identifying January as the month of poorest visibility conditions and high occurrence of dust haze. The average frequency of TDH days observed was about 2– 4 days and LDH days from 2 – 11 days. The FOO of LDH days increases southwards which could be attributed to the predominance of fine dust particles and lower wind speed towards the south. TDH days follows a decreasing trend all through the study period, while LDH follows an increasing trend. TDH and LDH occurrences showed an inverse in relationship with respect to latitude. Visibility deterioration during the harmattan period is largely caused by the prevalence of dust particles in the atmosphere.