Search

The Yaqui River Irrigation District is a region in Mexico with intensive agricultural production; thus, large quantities of fertilizers are used, and excess fertilizer can affect the quality of water bodies. The aim of this work was to estimate the water budget and nitrogen (N) and phosphorous (P) mass budgets to evaluate possible contamination of a littoral water body (Tóbari Bay) and leachates into an aquifer (Yaqui Valley aquifer). Wheat and corn crops were studied, climate information was compiled, and soil and water samples were collected for analysis. The water budget showed excess irrigation occurred due to the need for soil washing to prevent salinization. A total of 24% of all irrigation water was used for crops, 60% was discharged into the bay through runoff of the drainage system, and 16% corresponded to effective infiltration (aquifer recharge). The N budget showed that of the 100% N input, the highest percentage was used by plants (63%), and only minimal loss occurred through runoff (11%) and leachate into the aquifer (7%). The remaining N stayed in the soil (18%) or was volatilized (1%). These results indicate that the drainage system prevented large amounts of N from entering the aquifer; thus, the N concentrations in the groundwater did not exceed the regulated maximum limit for drinking water (10 mg N-NO 3 /L). In terms of the water pollution level in the bay, the presence of NO 3 - was minimal (concentrations below the quasintifiable limit). Of the 100% of P that was applied, 55% was used by the plants, and 40% remained in the soil; therefore, the P that was transported by runoff or was leached was minimal (3 and 2%, respectively). However, this minimal amount of P ranged from 0.1 to 0.2 mg/L in the bay, and these values exceeded the suggested values for the protection of aquatic life (0.01 mg/L). The administrators of the irrigation district must pay special attention to phosphate fertilizer management and implement irrigation techniques that increase water use efficiency., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

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.

This study assessed the spatial and temporal nutrient variability in the El Fuerte River basin in northwestern Mexico, considering its effects on the water trophic status as well as the nutrient loading to the Gulf of California. Physicochemical parameters, inorganic species of nitrogen, phosphate, total nitrogen, total phosphorus, and chlorophyll-a (chl-a) were quantified at 16 selected sites along the river in April (dry season) and October (rainy season) 2017. Mean concentrations of nutrients during dry and rainy seasons were 36.3 ± 24.1 and 55.1 ± 74.6 μg L -1 of total ammonia nitrogen, 3.4 ± 3.6 and 4.5 ± 3.5 μg L -1 of NO 2 - -N, 190.8 ± 256.0 and 163.6 ± 261.0 μg L -1 of NO 3 - -N, 42.4 ± 44.2 and 104.9 ± 76.2 μg L -1 of PO 4 3- -P, 1.0 ± 1.3 and 691 ± 2242 mg L -1 of TN, 0.06 ± 0.06 and 0.08 ± 0.09 mg L -1 of TP, and 0.9 ± 0.6 and 2.0 ± 0.9 μg L -1 of chl-a with significant differences (p < 0.05) between sites and seasons. When waters are transported downstream, nutrient levels are enriched by 4 to 35 times compared to those upstream due to increased population and agriculture downstream, confirming the hypothesis of the study. The calculated TN and TP fluxes were 1.23 × 10 4 and 3.57 × 10 1 ton year -1 , respectively. Factor analysis indicated that inorganic nitrogen species and phosphorus are the main factors affecting the river water quality. Despite N excess during the rainy season, the river reached mesotrophic waters due to phosphorus limitation. This suggests the need to establish a water quality monitoring program to understand the vulnerability of the river course to changes in its trophic state.

Water quality in the Mexican Caribbean is affected by increases in tourism infrastructure and poor wastewater treatment. Additionally, karst geomorphology facilitates the infiltration of organic matter to subterranean water and coastal fresh water that originates from submarine groundwater discharges (SGDs), altering the environment. The tourism infrastructure grows at different rates along the Caribbean coast, characterizing zones with diverse levels of tourism impact. The aim of this work was to measure nutrient concentrations in superficial coastal water and fresh water to evaluate the water quality through different zones along a gradient from intermediate- (Riviera Maya) to low-tourism (Costa Maya) development regions. Furthermore, this study aimed to compare the measured nutrient concentrations with the Mexican ecological criteria of water quality 001/89 (CE-CCA-001/89), detect possible contributions by SGDs, and determine whether the nitrogen (N) sources are anthropogenic using stable nitrogen isotopes in the seagrass Thalassia testudinum. According to the results, nutrient concentrations (ammonium, nitrate, nitrite, and orthophosphate) differed significantly between the Riviera Maya and Costa Maya (P = 0.0001). Sites such as Shambala, Chávez, Tankah, Mahahual 2, Tulum, Akumal, and Xahuayxol exceeded the upper levels set by the CE-CCA-001/89. Tankah, Shambala, and Chávez were influenced by SGDs. The nitrogen isotope ratio in Akumal and Tulum coast water shows that they are under N loading derived to the sewage percentage of δ 15 N in Akumal, Tulum, and Mahahual, showing that these sites suffer N loading due to sewage. Our study recommends continuous monitoring and coastal characterization to detect SGD and to regulate, treat, and dispose of sewage.

Anthropogenic activities can deteriorate the quality of groundwater destined for human use and consumption due to the fact that human activities cause changes in groundwater chemistry. The changes are induced by chemical species coming from industrial waste, which interacts with rocks and minerals. These trigger agents (phosphorus and nitrogen nutrients) which can incorporate trace elements (As, Fe, Mn, Pb, Cd, Ni, Zn). The main objective of the present work was to study the phosphate ions' and nitrogenous species' effects on the incorporation of trace elements into groundwater used for human consumption and to determine the physicochemical processes that participate in the incorporation of trace elements. The physicochemical analysis and elemental analysis by ICP of the groundwater that supplies the study area showed that the phosphorus (P) activity contributes in the incorporation of trace elements into the water. Significant correlations between the activities of P and Fe (0.516), Mn (0.553), Pb (0.756), and As (- 0.747) as well as the correlation of NH 4 + with As indicate that the presence of chemical species such as PO 4 3- (2.50-32.20 mg L -1 ), NO 3 - (0.89-30.80 mg L -1 ), and NH 4 + (0.2-12.70 mg L -1 ) are triggering agents that favor the dissolution and mobility of As (0.014-0.020 mg L -1 ), Fe (0.020-1.14 mg L -1 ), Mn (0.007-0.254 mg L -1 ), Ni (0.002-0.0141 mg L -1 ), Zn (0.009-0.459 mg L -1 ), and Pb (0.009-0.0170 mg L -1 ), species with adverse health effects because they are considered carcinogenic. Adequate control of the nitrogenous and phosphated material prevents the dissolution and mobility of trace elements into the water.

Since nutrients are emitted and mobilized in river basins, causing eutrophication of water bodies, it is important to reduce such emissions and subsequent nutrient loads. Due to processes of attenuation, nutrient loads are reduced during their mobilization in river basins. At the mouth of the Río Verde basin in western Mexico, the El Purgatorio dam is being constructed to supply water to the metropolitan area of the second most populated city in the country, Guadalajara. To analyze situations that allow protecting this future dam from eutrophication, nutrient loads in the mouth of the river basin were determined and their reduction scenarios evaluated by using the NEWS2 (Nutrient Export from Watersheds) model. For this, a nutrient emissions inventory was established and used to model nutrient loads, and modeling results were compared to an analysis of water quality data from two different monitoring sites located on the river. The results suggest that 96% of nitrogen and 99% of phosphorus emissions are attenuated in the watershed. Nutrient loads reaching the mouth of the river basin come mainly from wastewater discharges, followed by livestock activities and different land uses, and loads are higher as emissions are located closer to the mouth of the river basin. To achieve and maintain mesotrophic state of water in the future dam, different nutrient emission reduction scenarios were evaluated. According to these results, the reduction of 90% of the phosphorus loads in wastewater emissions or 75% of the phosphorus loads in wastewater emissions and at least 50% in emissions from livestock activities in the river basin are required.

Human activities have altered the balance of ecosystems to the detriment of natural environments. Eutrophication is a serious risk in Yucatán, a state in the eastern peninsula of México where groundwater supplies the only freshwater to a karst shelf environment. While economic development in Yucatán is increasing, environmental awareness is lagging, and efficient waste treatment systems are lacking. To assess potential nitrogen and phosphorus inputs into the coastal zone of Yucatán, we analyzed government reports and the chemical composition of groundwater and aquaculture wastewater. Swine, poultry, and tourism are revealed as the main continental nutrient sources, while groundwater with high nitrate concentrations is the principal coastal nutrient source, a pattern similar to other river discharges around the world. This study demonstrates that environmental risk management practices must be implemented in the Yucatán region to protect groundwater quality.

N cycling in tropical dry forests is driven by rainfall seasonality but the mechanisms involved are not well understood. We studied the seasonal variation in N dynamics and microbial biomass in the surface litter of a tropical dry forest ecosystem in Mexico over a 2-year period. Litter was collected at 4 different times of the year to determine changes in total, soluble, and microbial C and N concentrations. Additionally, litter from each sampling date was incubated under laboratory conditions to determine potential C mineralization rate, net N mineralization, net C and N microbial immobilization, and net nitrification. Litter C concentrations were highest in the early-dry season and lowest in the rainy season, while the seasonal changes in N concentrations varied between years. Litter P was higher in the rainy than in the early-dry season. Water-soluble organic C (WSOC) and water-soluble N concentrations were highest during the early- and late-dry seasons and represented up to 4.1 and 5.9% of the total C and N, respectively. NH (4) (+) and NO (3) (-) showed different seasonal and annual variations. They represented an average 23% of soluble N. Microbial C was generally higher in the dry than in the wet seasons, while microbial N was lowest in the late-dry and highest in the early-rainy seasons. Incubations showed that lowest potential C mineralization rates and C and N microbial immobilization occurred in rainy season litter, and were positively correlated to WSOC. Net nitrification was highest in rainy season litter. Our results showed that the seasonal pattern in N dynamics was influenced by rainfall seasonality and labile C availability, and not by microbial biomass. We propose a conceptual model to hypothesize how N dynamics in the litter layer of the Chamela tropical dry forest respond to the seasonal variation in rainfall.