Avaliação espacial e temporal dos teores de sais nas águas subterrâneas no município de Boa Vista-PB.

Abstract

The objective of the research was to evaluate, spatially and temporal, the salinity of the underground waters of the municipality of Boa Vista-PB. The study had as a field of investigation the municipality of Boa Vista - PB, totaling an area of 446.30 km2 located in the coordinates 7º10'11,5 "and 7º22'1,6" south latitude and 36º04'19" and 36º19'17" west longitude. The climate of the region, according to the classification of Köppen, is BSh type, which means hot semiarid, with average precipitation of 416 mm/year. The research began on October 2014, extending until August 2015, with the systematic collection of water samples to obtain the mean of the salt contents of the tubular wells surveyed. For this, two steps were obeyed. The first stage, 86 samples were collected from the sources, throughout the city, carried out an assessment of the underground water quality. The second stage was collected 76 water samples, occurring reductions, since some wells were dried and others were broken, finally the 76 wells were georeferenced. The points were georeferenced using a GPS 12 XL and photographed with a digital camera. The collection was performed at the point where the flow of water flows, avoiding to the maximum contaminated reservoirs (drinker), obtained directly from the pumping. The contents of salts were analyzed in the Irrigation and Salinity Laboratory (UFCG) by reading the electrical conductivity of the water (CEa), determining the salts - 4 cations and 3 anions, hydrogenation potential (pH) and obtaining the sodium adsorption ratio RAS). For the other parameters, formulas were used to obtain the alkalinity, the total dissolved salts (STD), CSR, ISL, RSI and the hardness of the waters of the municipality of Boa Vista, PB. The waters of the region of Boa Vista-PB were characterized, for the most part, as chlorinated sodas. Most of the pH values are in normal values, for human consumption, animal and irrigation. For alkalinity and hardness values, they were accepted in more than 50% of the samples. The electrical conductivity of the region is quite high, unfit for its multiple uses; in both collections the values of chloride were well above the recommended for human consumption, animal and irrigation. According to the total dissolved solids, water is considered saline. According to Richards (1954) they are C4 waters with very high salinity. These waters should only be used for salt tolerant crops. According to residual sodium carbonate, the water quality is suitable for irrigation practice. They were classified with moderate inlay and strong corrosion in the first data collection and in the second as balanced and strong corrosion. Having as technical recommendation the construction of cisterns for the dilution of these waters with high conductivity that will be offered to the animals, the irrigation with saline waters should be made for tolerant crops and the implantation of tanks for the creation of tilapia and shrimp.