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.

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−1. The Cr was different for months (P < 0.001) and the interaction years x months (P < 0.001), noting the highest value of 0.25 mg L−1. The Cu, Fe, Mn, Va and Zn were different for years, months, and their interaction. The highest value of Cu was 2.50 mg L−1; for Fe, it was 16.36 mg L−1; for Mn it was 1.66 mg L−1; V was 0.55 mg L−1; and Zn was 0.53 mg L−1. For Ni, there were differences for years (P = 0.030), months (P < 0.001), and locations (P = 0.050), with the highest Ni value being 0.47 mg L−1. The Li level was the same for sampling month (P < 0.001). This information can help prevent potential health risks in the communities established along the river watershed who use this natural resource for swimming and fishing. Some of the contaminant concentrations found varied from year to year, from month to month and from location to location which necessitated a continued monitoring process to determine under which conditions the concentrations of toxic elements surpass existing norms for natural waters.

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.

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; <2.0 as poor water, in a range of 2.0 to 2.5 as good water and, >2.5 as excellent water. The results showed the following ranges for single variables:

This study was conducted in a major agricultural area in the state of Chihuahua, Mexico. Sediment samples were collected from five sites in the San Pedro River basin with the objective of detecting levels of cadmium (Cd), arsenic (As) and lead (Pb). Site 1 was located near the Presa las Virgenes dam (PV), site 2 near the locations of Delicias-Rosales (RD), site 3 near the town of Meoqui (M), site 4 in the community of El Torreon (ET) and site 5 near the communities of Junta de los Rios Conchos and San Pedro (LJ). The metals analysis was conducted using an Inductively Couplet Plasma Atomic Emission Spectrometer (ICP-OES) Perkin Elemer 2000. The results were compared with NOM-147-SEMARNAT/SSA1-2004. Cd levels were not determined in any soil sample. The results indicated that Pb levels were below the established NOM-147 and that location M had the highest value with a mean of 9.15 mg kg -1 . The highest concentration levels of arsenic were found in the RD locale with 14.56 mg kg -1 during the December sampling. In conclusion, lead and arsenic levels in mud from the San Pedro River basin are below the norm. Still, As levels might be significant to human health, especially for the communities established along the San Pedro River.