Evidencing anthropogenic pollution of surface waters in a tropical region: a case study of the Culiacan River basin.

Nowadays, one of the most critical challenges is reduced access to water. Climate change, industrialization, and population growth have caused many countries to suffer from water crises, especially in arid and semi-arid areas. The Culiacan River basin in Sinaloa is a region of great importance in Mexico due to its intensive agricultural activity. Hence, water quality assessment has become a necessity to ensure sustainable water use. This study describes the spatiotemporal water quality features of the Humaya, Tamazula, and Culiacan Rivers within the Culiacan River basin and their sources of contamination. Twenty-two water quality parameters were analyzed from samples taken every 6 months from 2012 to 2020 at 19 sampling sites in the basin. A multivariate statistical analysis revealed significant correlations (r > 0.85) between the water quality parameters. The modified Integrated Water Quality Index (IWQI) identified severe pollution in samples from the urban river section of the basin, while good water quality conditions were found upstream. Severe contamination was observed in 26.32% of the samples, whereas only 13.45% evidenced good water quality. The Water Quality Index (WQI) indicated that 94.74% of the samples presented fair water quality, suggesting that the surface waters of the Culiacan River Basin are suitable for agricultural irrigation. This study provides insights into the current water quality status of the surface waters in the Culiacan River Basin, identifying significant pollution sources and areas of concern. The spatiotemporal dynamics of water quality in the Culiacan River basin revealed the importance of continuous monitoring and effective water management practices to improve water quality and achieve sustainable agricultural practices.

Efficiency of Opuntia ficus in the phytoremediation of a soil contaminated with used motor oil and lead, compared to that of Lolium perenne and Aloe barbadensis.

Industrial pollutants such as heavy metals and hydrocarbons in soils represent a serious concern due to their persistence and negative effects on the environment, affecting cellular processes in living organisms and even causing mutations and cancer. The main objectives of this work were to evaluate the efficiency of Opuntia ficus in the phytoremediation of a soil polluted with used motor oil. Two other species, one with different and one with similar characteristics, relatively, were used for comparison purposes: Lolium perenne and Aloe barbadensis. The effect of the plants on lead solubility and bioaccumulation, the biomass production of each specie and the microbial counts and bacterial identification for each experiment was studied. Total petroleum hydrocarbons (TPH) were measured every 5 weeks throughout the 20-week phytoremediation experiment. At the end of the experiment soluble Pb, Pb extracted by the plant species, microbiological counts, total biomass and bacterial species in soil were analyzed. Even though Lolium perenne showed the highest TPH removal (47%), Opuntia ficus produced the highest biomass and similar removal (46%). Since Opuntia ficus requires low amounts of water and grows fast, it would be a suitable option in the remediation of soils polluted with hydrocarbons and/or heavy metals.

Treatment of industrial effluents by electrochemical generation of H2O2 using an RVC cathode in a parallel plate reactor.

Electrochemical techniques have been used for the discolouration of synthetic textile industrial wastewater by Fenton's process using a parallel plate reactor with a reticulated vitreous carbon (RVC) cathode. It has been shown that RVC is capable of electro-generating and activating H2O2 in the presence of Fe(2+) added as catalyst and using a stainless steel mesh as anode material. A catholyte comprising 0.05 M Na2SO4, 0.001 M FeSO4.7H2O, 0.01 M H2SO4 and fed with oxygen was used to activate H2O2.The anolyte contained only 0.8 M H2SO4. The operating experimental conditions were 170 mA (2.0 V < ΔECell < 3.0 V) to generate 5.3 mM H2O2. Synthetic effluents containing various concentrations (millimolar - mM) of three different dyes, Blue Basic 9 (BB9), Reactive Black 5 (RB5) and Acid Orange 7 (AO7), were evaluated for discolouration using the electro-assisted Fenton reaction. Water discolouration was measured by UV-VIS absorbance reduction. Dye removal by electrolysis was a function of time: 90% discolouration of 0.08, 0.04 and 0.02 mM BB9 was obtained at 14, 10 and 6 min, respectively. In the same way, 90% discolouration of 0.063, 0.031 and 0.016 mM RB5 was achieved at 90, 60 and 30 min, respectively. Finally, 90% discolouration of 0.14, 0.07 and 0.035 mM AO7 was achieved at 70, 40 and 20 min, respectively. The experimental results confirmed the effectiveness of electro-assisted Fenton reaction as a strong oxidizing process in water discolouration and the ability of RVC cathode to electro-generate and activate H2O2 in situ.