The objective of this study was to determine the seasonal and downstream water quality variations of the San Pedro River in Chihuahua, Mexico. Water samples were collected monthly from October 2005 to August 2006 in triplicate, totaling 165 water samples. The five sampling locations were: below the Francisco I. Madero dam (LP); between Rosales and Delicias (RD); Meoqui (M); El Torreon (ET), and Julimes (LJ). The levels of As, Be, Ca, Cd, Co, Cu, Cr, Fe, Li, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sr, Ti, Ta, V and Zn were measured using an Inductively Coupled Plasma- Optical Emission Spectrometry (ICP-OES) Perkin Elmer 2100. In addition, temperature, pH, electrical conductivity and total and fecal coliformes were determined. The statistical analysis considered a factorial treatment design; where factor A was the location point and factor B was sampling date. In addition, a multivariate technique looking for principal components was performed. The results indicated that some samples exceeded Mexican standards for As, Be, Ca, Cd, Co, Cr, Fe, Mn, Ni, Pb, Sb, Se, Sr and Zn. The As level must be considered for a red flag to the communities along the Rio San Pedro because both the monthly average level (0.10 mg L-1) and location (0.10 mg L-1) exceeded the Mexican and International norms. The multivariate analysis showed a predominant aggregation at the LP location, meaning that there was a predominance of As, Sr, Fe and Li. At the rest of the locations the elements did not present a tendency for aggregation. Statistics applied to sampling month showed that December, January, March and April were aggregated in a negative quadrant of component 1 indicating a predominance of V, Ni, Be, Fe and As. Overall, the results confirmed that this stretch of the San Pedro River is contaminated with heavy metals and other contaminants that might affect human health as well as the health of the ecosystem.

/pdf/heavy-metals-in-water-of-the-san-pedro-river-in-chihuahua-4jd2m2elsr.pdf

Heavy metals in water of the San Pedro River in Chihuahua, Mexico and its potential health risk.

An area near the city of Chihuahua has been traditionally irrigated with wastewater to grow forage crops. It has been hypothesized that metal levels could be found in these soils high enough to cause potential health problems to the population. The objective of this study was to determine heavy metal concentrations in different soils due to irrigation practices. Four soil types were evaluated; a soil with a past and present history of wastewater irrigation (S1), a soil with a history of wastewater irrigation until 2003 (S2), a soil with no irrigation history (S3), and a soil similar to S1 and adjacent to the river where the wastewater is transported (S11). Three soil depths were evaluated; 0-15, 15-30 and 30-50 cm. Consequently, a total of 150 soil samples were analyzed evaluating pH, EC, OM and the following elements; Na, K, Cd, Pb, Ni, Cr, Cu and Fe. The pH (P=0.000) and EC (P=0.000) were different for each soil type but no differences were noted for soil depth and the interaction. Maximum pH levels were noted in S3 with a value of 8.74 while maximum EC was observed in S1 with a value of 0.850 dSm-1. The OM level was different for soil type (P=0.000), soil depth (P=0.005) and the interaction (P=0.014). S1 and S11 obtained maximum levels of OM while minimum levels were noted in S3. Maximum OM levels were observed at the 0-15 cm depth followed by the 15-30 cm depth and finally at the 30-50 cm depth. The highest concentration of metals was as follows: K in S1 (359.3 mg kg-1); Cd in S1 (4.48 mg kg-1); Pb in S11 (155.83 mg kg-1); Ni in S1 (10.74 mg kg-1); Cu in S1 (51.36 mg kg-1); B in S3 (41.5 mg kg-1); Fe in S3 (20,313.0 mg kg-1), Cr in S3 (44.26 mg kg-1) and Na in S3 (203.0 mg kg-1). The conclusion is that some metals are present in the soils due to anthropogenic activities but others are present in natural forms.

https://www.mdpi.com/1660-4601/5/5/441/pdf

Heavy Metal Content in Soils under Different Wastewater Irrigation Patterns in Chihuahua, Mexico

A Water Quality Index (WQI) is a simple numeric expression reflecting the quality of water in any ecosystem at a given time. The objective of this study was to develop a WQI for the man-made dam Francisco I. Madero located in Chihuahua, Mexico. Eight points were randomly selected in the dam area and at each point water samples were collected monthly from March 2011 to February 2012 at three depths; 0.30 m, 5 m and 10 m. The following physical-chemical variables were measured: potential hydrogen (pH), electrical conductivity (EC), dissolved oxygen (DO), temperature (T), turbidity, total dissolved solids (TDS), total hardness (TH) and chlorides (Cl-). In a first step for data analysis, an analysis of variance (ANOVA) was performed for each variable considering a factorial treatment design 12 × 3 in which factor A was the month with 12 levels (sampling months) and factor B was the depth with three levels (0.30 m, 5 m and 10 m). In a second statistical step, the WQI was calculated for each month only for the surface sampling (0.30 m) and the resulting value was classified under three categories; 2.5 as excellent water. The results showed the following ranges for single variables: pH of 7.63 - 10.65, EC of 190 - 320 μS·cm-1, DO of 1.30 - 12.1 mg·L-1, T of 11.30°C - 30°C, Turbidity of 0-1, 120 NTU, TDS of 170 - 220 mg·L-1, TH of 240 - 900 mg·L-1 and Cl- of 7.28 - 7034 mg·L-1. The calculated WQI demonstrated that water quality varies seasonally and was classified as poor in the rainy season to good in winter season. We conclude that in general the water from the dam is acceptable and suitable for ecological and a broad spectrum of other purposes.

/pdf/development-of-a-water-quality-index-wqi-of-an-artificial-5g0effhucb.pdf

Development of a Water Quality Index (WQI) of an Artificial Aquatic Ecosystem in Mexico

Presently, water contamination issues are of great concern worldwide. Mexico has not escaped this environmental problem, which negatively affects aquifers, water bodies and biodiversity; but most of all, public health. The objective was to determine the level of water contamination in six tributaries of the Conchos River and to relate their levels to human health risks. Bimonthly samples were obtained from each location during 2005 and 2006. Physical-chemical variables (temperature, pH, electrical conductivity (EC), Total solids and total nitrogen) as well as heavy metals (As, Cr, Cu, Fe, Mn, Ni, V, Zn, and Li) were determined. The statistical analysis considered yearly, monthly, and location effects, and their interactions. Temperatures differed only as a function of the sampling month (P < 0.001) and the pH was different for years (P = 0.006), months (P < 0.001) and the interaction years x months (P = 0.018). The EC was different for each location (P < 0.001), total solids did not change and total nitrogen was different for years (P < 0.001), months (P < 0.001) and the interaction years x months (P < 0.001). The As concentration was different for months (P = 0.008) and the highest concentration was detected in February samples with 0.11 mg L

/pdf/contamination-of-the-conchos-river-in-mexico-does-it-pose-a-1aai8y2a6q.pdf

Contamination of the Conchos River in Mexico: Does It Pose a Health Risk to Local Residents?

A geochemical characterization of the middle Rio Conchos basin is presented based on two contaminants, salts (Ca and Na) and toxic metalloids (As and Sb). Their content in surface water and sediment samples was determined, and their spatial distribution was mapped to show the relationship to each other, to the geology and hydrology, and to other potential factors affecting their distribution (i.e., prevailing winds). Correlation analyses between salts, toxic metalloids, and associated elements, and their spatial distribution aided in determining their sources, which included mines, rock outcrops, urban centers, irrigation waste water, and agricultural runoff. The salinity of the Rio Conchos reached a critical level after receiving waters of its contaminated tributary Rio Chuviscar and irrigation drain returns from the Irrigation District 005, but further downstream the water quality improved when it mixed with Ca-rich water, signifi cantly reducing its Na concentration. Based on its spatial distribution, the content of As in alluvial material was found to be associated with the presence of Ag-Pb mines and to a lesser degree to Oligocene ignimbrites. A correlation of As with Sb, Cu, and Bi suggests that natural sources are the dominant contribution of As within the area, although concentrations above permissible level for water were found in river water samples at a few places where sewage was also present, suggesting an additional (anthropogenic) important source of As. A characterization of natural sources affecting the chemistry of surface waters is a fi rst step toward understanding the natural processes taking place and for documenting natural background levels that are needed to predict the response of the environment to various human activities.

/pdf/geochemical-processes-contributing-to-the-contamination-of-3go6q6ejpf.pdf

Geochemical processes contributing to the contamination of soil and surface waters in the Rio Conchos basin, Mexico

The water of the Rio Conchos is a vital resource for approximately one million inhabitants of the state of Chihuahua, and is the main tributary of the Rio Bravo. With the purpose of determining the water quality, six samplings were carried out during 2004: February 20, March 19, April 23, May 21, June 18 and July 23. The following 30 elements were measured using ICP optical emission spectrometry: Ag, As, Al, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Sb, Se, Si, Sr, Ti, Tl, Va, Yb and Zn, together with physical (temperature, EC and total solids) and chemical parameters (pH, total N, ammonia-N, organic-N, chloride and total P). The results were compared with the Mexican standards (the Mexican Normatividad and those of the Secretaria de Desarrollo y Ecologia) and the USA Environmental Protection Agency standards. Elements that were higher than one or more standards for potable water were Al, Fe, Mn, Tl, Ba, Ni, Be, Zn and Na. Those that were higher than at least one standard for potable water were Al, Ba, Fe and Tl. None of the elements were above the standards for agriculture and animal production. The elements that exceeded most standards were Al (4), Mn, Fe and Tl (3), and Ba, Be, Na, Ni and Zn (1). The concentration of some elements is at levels that can cause damage to humans at the medium and/or long term, to a degree related to the people’s daily contact with these elements.

Calidad del agua del río Conchos en la región de Ojinaga, Chihuahua: parámetros fisicoquímicos, metales y metaloides

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Calidad del agua del río Conchos en la región de Ojinaga, Chihuahua: parámetros fisicoquímicos, metales y metaloides