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.

Implementation of remote sensing algorithms to estimate TOC, Chl-a, and TDS in a tropical water body; Sanalona reservoir, Sinaloa, Mexico.

The present study implements a methodology to estimate water quality values using statistical tools and remote sensing techniques in a tropical water body Sanalona. Linear regression models developed by Box-Cox transformations and processed data from LANDSAT-8 imagery (bands) were used to estimate TOC, TDS, and Chl-a of the Sanalona reservoir from 2013 to 2020 at five sampling sites measured every 6 months. A band discriminant analysis was carried out to statistically fit and optimize the proposed algorithms. Coefficients of determination beyond 0.9 were obtained for these water quality parameters (r2TOC = 0.90, r2TDS = 0.95, and r2Chl-a = 0.96). A comparison between the estimated and observed water quality was carried out using different data for validation. The validation of the models showed favorable results with R2TOC = 0.8525, R2TDS = 0.8172, and R2Chl-a = 0.9256. The present study implemented, validated, and compared the results obtained by using an ordered and standardized methodology proposed for the estimation of TOC, TDS, and Chl-a values based on water quality parameters measured in the field and using satellite images.

Modeling the effect of climate change scenarios on water quality for tropical reservoirs.

Impact of natural phenomena and anthropogenic activities on water quality is closely related with temperature increase and global warming. In this study, the effects of climate change scenarios on water quality forecasts were assessed through correlations, prediction algorithms, and water quality index (WQI) for tropical reservoirs. The expected trends for different water quality parameters were estimated for the 2030-2100 period in association with temperature trends to estimate water quality using historical data from a dam in Mexico. The WQI scenarios were obtained using algorithms supported by global models of representative concentration pathways (RCPs) adopted by the Intergovernmental Panel on Climate Change (IPCC). The RPCs were used to estimate water and air temperature values and extrapolate future WQI values for the water reservoir. The proposed algorithms were validated using historical information collected from 2012 to 2019 and four temperature variation intervals from 3.2 to 5.4 °C (worst forecast) to 0.9-2.3 °C (best forecast) were used for each trajectory using 0.1 °C increases to obtain the trend for each WQI parameter. Variations in the concentration (±30, ±70, and +100) of parameters related to anthropogenic activity (e.g., total suspended solids, fecal coliforms, and chemical oxygen demand) were simulated to obtain water quality scenarios for future health diagnosis of the reservoir. The results projected in the RCP models showed increasing WQI variation for lower temperature values (best forecast WQI = 74; worst forecast WQI = 71). This study offers a novel approach that integrates multiparametric statistical and WQI to help decision making on sustainable water resources management for tropical reservoirs impacted by climate change.

Assessment of Water Quality in A Tropical Reservoir in Mexico: Seasonal, Spatial and Multivariable Analysis.

Agricultural activities are highly related to the reduction of the availability of water resources due to the consumption of freshwater for crop irrigation, the use of fertilizers and pesticides. In this study, the water quality of the Adolfo López Mateos (ALM) reservoir was evaluated. This is one of the most important reservoirs in Mexico since the water stored is used mainly for crop irrigation in the most productive agricultural region. A comprehensive evaluation of water quality was carried out by analyzing the behavior of 23 parameters at four sampling points in the period of 2012-2019. The analysis of the spatial behavior of the water quality parameters was studied by spatial distribution graphs using the Inverse Distance Weighting interpolation. Pearson correlation was performed to better describe the behavior of all water quality parameters. This analysis revealed that many of these parameters were significantly correlated. The Principal Components Analysis (PCA) was carried out and showed the importance of water quality parameters. Ten principal components were obtained, which explained almost 90% of the total variation of the data. Additionally, the comprehensive pollution index showed a slight water quality variation in the ALM reservoir. This study also demonstrated that the main source of contamination in this reservoir occurs near sampling point one. Finally, the results obtained indicated that a contamination risk in the waterbody and further severe ecosystem degradations may occur if appropriate management is not taken.

Kinetics of a fixed bed reactor with immobilized microorganisms for the removal of organic matter and phosphorous.

The biodegradation of domestic wastewater contaminants has been carried out using microorganisms immobilized in sodium alginate gel (Alg-Na). A fixed bed reactor with immobilized microorganisms was used for the treatment of domestic wastewater. A wastewater pretreatment was carried out to remove the larger particulate matter, which consisted of a reactor packed with different materials (anthracite, zeolite, and activated carbon). Later, a second reactor packed with balls with immobilized microorganisms was used to eliminate organic matter and nutrients. 2.5% w/v of Alg-Na was used as a support to immobilize the microorganisms. According to the results, a total phosphorus (TP) and chemical oxygen demand (COD) removal of 94.26% and 78.25% was obtained, respectively. In addition, the degradation rate for both organic matter and phosphorous was studied by using the kinetic model for fix bed reactor. © 2020 Water Environment Federation PRACTITIONER POINTS: Phosphorous and organic matter removal by adsorption and immobilized microorganisms. High removal efficiency of phosphorous and organic matter was found. An innovative wastewater treatment alternative is proposed. Kinetic model for fixed bed reactor is also proposed for scaling-up purposes.

Assessment of intensive agriculture on water quality in the Culiacan River basin, Sinaloa, Mexico.

The percentage of agricultural land cover effect on water quality in Culiacan River basin is studied in this research. The basin contains only intensive cropland as primary economic activity with 60% of the total area. Mathematical relationships between percentages of cropland and total phosphorus (TP) and total nitrogen (TN) concentrations were established. Sampling sites in middle and lower basin and water quality information during 2013-2018 were considered, and percentages of cropland were obtained by geospatial methods including variable area buffers. During rainy season, coefficients of determination were less than 0.2, although quantified nutrient concentration was higher, related to point sources of pollution in the basin. During dry season, coefficients of determination were higher than 0.76 and 0.90 for TN and TP, respectively, with an exponential mathematical trend. Results suggest that intensive agriculture practices generate accelerated loss of soil consolidation, which is transported to water bodies. These soils are in continuous contact with fertilizers and pesticides, mostly organophosphates which have been transported by runoff and underground flows. Using the information generated will help to establish environmental management plans, and to improve environmental diagnosis and effect in countries where there is not enough historical cartographic information and/or water quality data.

Feasibility Study on the Use of Recycled Polymers for Malathion Adsorption: Isotherms and Kinetic Modeling.

In this study, the use of Polyvinylchloride (PVC) and High Density Polystyrene (HDPS) was demonstrated as an alternative for the adsorption of Malathion. Adsorption kinetics and isotherms were used to compare three different adsorbent materials: PVC, HDPS, and activated carbon. The adsorption capacity of PVC was three times higher than activated carbon, and a theoretical value of 96.15 mg of Malathion could be adsorbed when using only 1 g of PVC. A pseudo first-order rate constant of 1.98 (1/h) was achieved according to Lagergren kinetic model. The adsorption rate and capacity values obtained in the present study are very promising since with very little adsorbent material it is possible to obtain high removal efficiencies. Phosphorous and sulfur elements were identified through Energy Dispersive X-ray (EDX) analysis and evidenced the malathion adsorption on PVC. The characteristic spectrum of malathion was identified by the Fourier Transform Infrared (FTIR) Spectroscopy analysis. The Thermogravimetric and Differential Thermal Analysis (TG/DTA) suggested that the adsorption of malathion on the surface of the polymers was mainly determined by hydrogen bonds.

Emulating natural wetlands oxygen conditions for the removal of N and P in agricultural wastewaters.

The aim of this research was to evaluate a constructed wetland system (CW) operated under aerobic-anoxic-aerobic conditions to remove C, N and P from water with high concentrations of the last two nutrients. A series of three CW were operated continuously for 190 days. An aerobic vertical CW was used in the first and third stages and an anoxic horizontal CW was used in the second stage. The total nitrogen (TN) removal efficiency was 70 ±â€¯1.5%. Similar removal efficiency behavior was observed in others nitrogen compounds, where a removal of 85 ±â€¯1.5% for NO3--N and 97 ±â€¯2.2% for NH3+N were achieved. The combination of different oxygen conditions enhanced oxidation of nitrates and the assimilation of ammonium by vegetation. On the other hand, 54 ±â€¯6.5% total phosphorus (TP) was removed in the entire system, which is higher than the reported in several investigations, including mechanized and controlled systems such as activated sludge. The phosphorous removal efficiency was attributed to the adequate design and configuration of CW, which facilitated dissolved oxygen (DO) conditions required for phosphorus capture. Despite in this investigation the CW was not designed for an optimal removal of organic matter the removal efficiency of this parameter was 64 ±â€¯7.5%. The successful results suggest that the combination of aerobic-anoxic-aerobic stages is a technically suitable option for the treatment of agricultural wastewater with high content of N and P.

Kinetics of Acid Orange 7 oxidation by using carbon fiber and reticulated vitreous carbon in an electro-Fenton process.

In this study, a micro-scale parallel plate reactor was built to electrochemically generate hydrogen peroxide (H2O2) and to develop the Fenton reaction in situ, for the treatment of toxic organic pollutants. Two types of carbon materials were compared and used as cathodes: unidirectional carbon fiber (CF) and reticulated vitreous carbon (RVC). As anode, a stainless steel mesh was used. The results of H2O2 were experimentally compared by means of electrogeneration process. RVC cathode with dimensions of 2.5 × 1 × 5 cm (170 mA and variable voltage V = 2.0-2.7) and 180 min produced 5.3 mM H2O2, with an H2O2 production efficiency of 54%. Unidirectional carbon fiber cathode produced 7.5 mM of H2O2 (96% of H2O2 production efficiency) when a voltage of 1.8 V was applied during 180 min to a total area of 480 cm2 of this material. Acid Orange 7 (AO7) was degraded to a concentration of 0.16 mM during the first 40 min of the process, which represented 95% of the initial concentration. Electrolysis process removed nearly 100% of the AO7 using both cathodes at the end of these experiments (180 min).

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.

Assessment of heavy metals in sediment of Aguamilpa Dam, Mexico.

The Aguamilpa Dam is part of the reservoir cascade system formed by four reservoirs in the middle and lower part of the Santiago River. For decades, this system has received urban and industrial wastewater from the metropolitan area of Guadalajara and the runoff of agricultural fields located in the river basin. The present study was carried out to obtain a preliminary assessment on the concentration distribution of heavy metals (Al, Ba, Cd, Cr, Cu, Fe, Hg, Mg, Ni, Pb, and Zn) in surface sediments of the Aguamilpa reservoir collected from 10 sampling stations. The metal concentrations (mg kg(-1)) in the sampling stations ranged as follows: Al, 27,600-7760; Ba, 190.0-15.9; Cd, 0.27-0.02; Cr, 18.30-0.22; Cu, 60.80-0.79; Fe, 15,900-4740; Hg, 0.04-0.01; Mg, 7590-8.05; Ni, 189.00-0.24; Pb, 13.6-1.64; and Zn, 51.8-14.8. Significant spatial variation in concentrations was observed for Al, Fe, and Pb. Sediment pollution was evaluated using the enrichment factor, the geo-accumulation index, the pollution load index, and sediment quality guidelines. Based on geo-accumulation and pollution load indexes, Aguamilpa sediments were found, in some sampling stations, as unpolluted to moderately polluted with Ni, Cd, Cu, and Mg. Enrichment factors showed that Cd is highly related to agricultural activities that take place in the surrounding areas of the Aguamilpa reservoir. Despite these results, none of the heavy metals evaluated exceeded international concentrations limits, indicating that the Aguamilpa reservoir surface sediments are not contaminated.