Water Contamination Levels Research Articles

Moodie and Evans Respond

Despite the charges by Stifelman et al., nowhere do we claim that blood lead levels (BLLs) were used as the sole criterion for cleanup actions at Bunker Hill. Rather, we argue that insofar as BLLs were one of the Remedial Action Objectives (RAOs) specified in the Record of Decision (ROD), this criterion was neither protective nor proactive in reducing risk. The threshold of concern (10 μg/dL) is far too high in light of a mounting body of evidence showing the adverse effect of lead at much lower levels.1–6 In addition, the other RAOs for environmental criteria (e.g., soil, dust, and water contaminant levels) were set at levels much higher than the Environmental Protection Agency’s (EPA’s) own standards.7 Although Stifelman et al. remain confident about the “protectiveness of the remedy,” this confidence does not equal valid and reliable data. The continued low participation in blood lead screening remains troublesome. In 2010, only 13 of 475 Medicaid children residing in the original Bunker Hill site (otherwise known as the “Box”) were screened; one had a BLL greater than 10 micrograms per deciliter. With less than three percent of Medicaid eligible children screened, let alone the broader population, safe lead exposure levels cannot be claimed. Although Stifelman et al. claim that “[a]chievement of BLLs below the RAO did not—and will not—stop remediation,” in February 2012 the EPA announced a massive scale back of the cleanup efforts at Bunker Hill.8,9 The EPA Region 10 director of environmental cleanup admitted that the work planned under this plan may not be sufficient. Finally, the social justice concerns raised by the use of BLLs (as well as other environmental criteria) as RAOs are not based on the distribution of exposure along socioeconomic lines. To the extent that the residents of Bunker Hill can be considered a vulnerable population (poverty, low educational achievement, and a background of poor health outcomes), exposure to lead increases the risk of adverse health outcomes compared with nondisadvantaged populations. The result is an exacerbation of the existing inequalities that threaten the health and well-being of Bunker Hill residents.

Phytoremediation Potential of Paragrass— An In Situ Approach for Chromium Contaminated Soil

The present in situ phytoextraction approach uses paragrass (Brachiaria mutica (Forssk) Stapf) as a hyper accumulator for attenuation of chromium level in soil and mine waste water at South Kaliapani chromite mine area of Orissa. The bioconcentration factor (BCF) for Cr was maximum (0.334) in 100 days grown paragrass weeds. Transportation index (Ti) i.e. 6.16 and total accumulation rate (TAR) i.e. 8.2 mg kg−1day−1 was maximum in 125 days old paragrass grown in Cr contaminated experimental cultivated plots. Cr bioaccumulation in roots was nearly 1000 times more than shoots. Paragrass showed luxuriant growth with massive fibrous roots when grown over Cr contaminated soils (11,170 mg/ kg dry soil). Cr bioaccumulation varies significantly with plant age, biomass and level of Cr contamination in irrigated mine waste water and soil. Paragrass could be used as hyperaccumulators as it showed rapid massive growth with a high tolerance to Cr.

Chemical Processing in High-Pressure Aqueous Environments. 9. Process Development for Catalytic Gasification of Algae Feedstocks

Through the use of a metal catalyst, gasification of wet algae slurries can be accomplished with high levels of carbon conversion to gas at relatively low temperature (350 °C). In a pressurized-water environment (20 MPa), near-total conversion of the organic structure of the algae to gases has been achieved in the presence of a supported ruthenium metal catalyst. The process is essentially steam reforming, as there is no added oxidizer or reagent other than water. In addition, the gas produced is a medium-heating value gas due to the synthesis of high levels of methane, as dictated by thermodynamic equilibrium. As opposed to earlier work, biomass trace components were removed by processing steps so that they did not cause processing difficulties in the fixed catalyst bed tubular reactor system. As a result, the algae feedstocks, even those with high ash contents, were much more reliably processed without plugging the feeding systems or the fixed catalyst bed. High conversions were obtained even with high slurry concentrations. Consistent catalyst operation in these short-term tests suggested good stability and minimal poisoning effects. High methane content in the product gas was noted with significant carbon dioxide captured in the aqueous byproduct in combination with alkali constituents and the ammonia byproduct derived from proteins in the algae. High conversion of algae to gas products was found with low levels of byproduct water contamination and low to moderate loss of carbon in the mineral separation step. Further development is required to demonstrate protection of the catalyst bed from sulfur poisoning.

An Overall Water Quality Index (WQI) for a Man-Made Aquatic Reservoir in Mexico

A Water Quality Index (WQI) is a useful statistical tool for simplifying, reporting and interpreting complex information obtained from any body of water. A simple number given by any WQI model explains the level of water contamination. The objective was to develop a WQI for the water of the Luis L. Leon dam located in the state of Chihuahua, Mexico. Monthly water samples were obtained in 2009; January 10, February 12, March 8, May 20, June 10, July 9, August 12, September 10, October 11, November 15 and December 13. Ten sampling sites were randomly selected after dividing the study area using a geographic package. In each site, two samples at the top depth of 0.20 m and 1.0 m were obtained to quantify physical-chemical parameters. The following 11 parameters were considered to calculate the WQI; pH, Electrical Conductivity (EC), Dissolved Oxygen (DO), color, turbidity, ammonia nitrogen, fluorides, chlorides, sulfates, Total Solids (TS) and phosphorous (P). The data analysis involved two steps; a single analysis for each parameter and the WQI calculation. The resulted WQI value classified the water quality according to the following ranges: <2.3 poor water; from 2.3 to 2.8 good water; and >2.8 excellent water. The results showed that the WQI values changed from low levels (WQI < 2.3) in some points during autumn time to high levels (WQI > 2.8) most of the year and the variation was due to time of sampling generally rainy season.

Evaluation of Naocl 0,2% Solution for Disinfection of Dental Equipment Waterlines

Objetivo: Avaliar o efeito do hipoclorito de sodio a 0,2% na desinfeccao da tubulacoes de agua de equipos odontologicos, previamente contaminadas. Metodo: Foram obtidas amostras de agua dos reservatorios, das mangueiras que suprem as turbinas de alta-rotacao e das seringas triplice de 34 equipos com tubulacoes desinfetadas com hipoclorito de sodio a 0,2% e de 31 equipos do grupo controle. As amostras foram semeadas em “Plate Count Agar” (ACOMIDIA®) e incubadas em aerobiose a 35oC, durante 48 horas, para avaliar a presenca e contagem das unidades formadoras de colonias (UFC) de bacterias heterotroficas por mililitro de agua.Utilizou-se como parâmetro para a avaliacao das amostras as normatizacoes do Ministerio da Saude referentes a presenca dessas bacterias na agua de consumo para humanos. Foram comparados os niveis de contaminacao da agua dos diversos pontos de coleta e entre os equipos com e sem sistema de desinfeccao, atraves do teste qui-quadrado de Pearson com significância de 5%. Resultados: Nos equipos que sofreram desinfeccao das tubulacoes de agua, as amostras estavam contaminadas em 41,2% dos reservatorios, 67,7% das mangueiras alta-rotacao e 64,7% das seringas triplices. Nao houve diferenca significativa na contaminacao entre os diversos pontos de coleta e entre os equipamentos com e sem sistema de desinfeccao (p maior que 0,05). Conclusao: O metodo proposto foi ineficaz na desinfeccao das tubulacoes de agua de equipos odontologicos, previamente contaminadas. Com base nos resultados obtidos, sugere-se novos estudos para o desenvolvimento de um protocolo padrao para a desinfeccao das tubulacoes de agua de equipos odontologicos.

Considering the Risk of Infection by Cryptosporidium via Consumption of Municipally Treated Drinking Water from a Surface Water Source in a Southwestern Ontario Community

Through the use of case-control analyses and quantitative microbial risk assessment (QMRA), relative risks of transmission of cryptosporidiosis have been evaluated (recreational water exposure vs. drinking water consumption) for a Canadian community with higher than national rates of cryptosporidiosis. A QMRA was developed to assess the risk of Cryptosporidium infection through the consumption of municipally treated drinking water. Simulations were based on site-specific surface water contamination levels and drinking water treatment log₁₀ reduction capacity for Cryptosporidium. Results suggested that the risk of Cryptosporidium infection via drinking water in the study community, assuming routine operation of the water treatment plant, was negligible (6 infections per 10¹³ persons per day--5th percentile: 2 infections per 10¹⁵ persons per day; 95th percentile: 3 infections per 10¹² persons per day). The risk is essentially nonexistent during optimized, routine treatment operations. The study community achieves between 7 and 9 log₁₀ Cryptosporidium oocyst reduction through routine water treatment processes. Although these results do not preclude the need for constant vigilance by both water treatment and public health professionals in this community, they suggest that the cause of higher rates of cryptosporidiosis are more likely due to recreational water contact, or perhaps direct animal contact. QMRA can be successfully applied at the community level to identify data gaps, rank relative public health risks, and forecast future risk scenarios. It is most useful when performed in a collaborative way with local stakeholders, from beginning to end of the risk analysis paradigm.

From Fearsome Pollution to Fukushima: Environmental Activism and the Nuclear Blind Spot in Contemporary Japan

On September 19, 2011, sixty thousand people gathered in Tokyo to protest against nuclear power and radiation pollution after reactor meltdowns at the Fukushima Daiichi Nuclear Power Plant. Their protest evoked memories of the 1960s when Japan was among the most polluted locations on the planet with hazardous levels of air, water, and ground contamination. Observers at the time described the country as a polluters' paradise and advised tourists to pack a gas mask. By the early 1970s, however, the Japanese had addressed many their thorniest pollution problems and the country possessed some of the strictest regulatory standards in the world. In this article I analyze the activities of an influential group of natural and social scientists, the Pollution Research Committee, which spearheaded the struggle against pollution. I make two claims. First, on the positive side, the committee played a decisive role in Japan's pollution turnaround through its field research, pollution victim advocacy, and extensive international activities. But, second, the reactive victim-centered environmental agenda of the committee and other contemporary groups never developed into a preventive movement capable of identifying and scrutinizing potential forms of pollution such as radiation. The result was a nuclear blind spot in Japanese environmental activism only made visible with the Fukushima disaster of 2011.

Relationship between size-fractionated Chlorophyll a and environmental factors in Lake Baiyangdian, China

Abstract Eutrophication results from an acumulation of nutrients such as nitrogen, phosphorus and carbon in a waterbody in turn leading to high levels of plant growth. To investigate the correlations between plant growth and eutrophication in Lake Baiyangdian, the levels of size-fractionated Chlorophyll a (Chl a ) from phytoplankton and nutrients in the water were determined in 2010. Two typical stations, a eutrophic station Nanliuzhuang and a non-eutrophic station Caiputai, were selected for this study. Results showed that Chl a from nano-phytoplankton was the main contributor to total Chl a levels at both the stations. Moreover, the percentage of net phytoplankton and nano-phytoplankton was closely correlated to water contamination levels. Therefore, the percentage of size-fractionated Chl a can be considered as an important indicator to evaluate the eutrophic level of a lake.

Impact of municipal solid waste (MSW) dumping on ground water quality at Muthi Jammu -A Case Study

The present paper deals with the physico -chemical analysis of ground water quality near a municipal solid waste dumping site at Muthi, Jammu. The impact of MSW dumping on ground water quality varies in different seasons and at different distances from the waste dumping sites .The depth of ground water also indicates the level of ground water contamination. Ground water analysis was carried for a period of seven months during (June to Dec. 2007) and thirteen parameters viz., pH, Turbidity, EC, TDS, DO, Free CO2 , HCO3, Total hardness,Ca++, Mg2+ , NO3-, SO42-, Cl- were analysed for present studies. Results revealed that in some samples pH, turbidity, DO , HCO3, total hardness, Ca++, Mg2+, NO3- were not within the standards prescribed by WHO, 1993 and BIS, 1992.

English

Life on earth depends on water. However, there is scarcity of portable water supplies in South Africa especially in rural areas. This results to the consumption of untreated water that may be contaminated with microbial species such as Klebsiella . The aim of the study was to investigate Klebsiella contamination levels in water from the Modimola dam situated adjacent the Modimola village, in the North West Province, Mafikeng – South Africa. Nine water samples (three each) were collected from the upstream, middle-stream and down-stream of the dam. The samples were analyzed by plating on mFC and Eosin methylene blue agar plates. The blue isolates on mFC were counted and results recorded. The identities of metallic sheen colonies on EMBA were determined using Gram staining, preliminary (TSI and oxidase test) and confirmatory (API 20E, gapA specific PCR) tests. A total of 504 presumptive isolates were screened and 28 (35.9%) Klebsiella species were positively identified. Despite the fact that faecal coliform bacteria were not detected in tap water, the level of faecal contamination was higher in samples obtained from the upstream than the middle stream and; than the downstream. All water samples collected from the different sites of the Setumo dam contained Klebsiella species and this indicates the risk that water from this dam can pose threat to the inhabitants of the Modimola community who use the water for fishing and some daily activities.

Investigation of the reaction products of unsymmetrical dimethylhydrazine with potassium permanganate by gas chromatography-mass spectrometry

The gas chromatography-mass spectrometry technique was used to investigate the composition of the reaction products of unsymmetrical dimethylhydrazine with a potassium permanganate and potassium permanganate-hydrogen peroxide mixture. If the water contamination level is within 50 threshold limit values (TLV) (1 mg/ml), the proposed detoxication method utilizing potassium permanganate in combination with hydrogen peroxide allows for the reduction of the UDMH concentration to a safe level without the accumulation of transformation products. The detoxication of aqueous solutions with significant UDMH concentrations (up to 50000 TLV) (1 g/l) with potassium permanganate alone or in combination with hydrogen peroxide reduces the UDMH concentration to a safe level, but UDMH transformation products, including the extremely toxic nitrozodimethylamine, are accumulated in the solution.

Application of physicochemical data for water-quality assessment of watercourses in the Gdansk Municipality (South Baltic coast)

The paper presents water-quality evaluation based on an 8-year monitoring programme in the Gdansk Municipality region, on the Southern coast of the Baltic Sea. The studies were carried out from 2000 to 2007 by surface water analysis at 15 various sites within eight watercourses. Sampling sites included rather urbanized or developed lands, farming fields and non-polluted city recreational areas such as parks and forests. Most of the watercourses were sampled monthly at two locations, one within the upper course of the watercourse and the other near its mouth. In all samples, eight parameters of water quality were determined: total suspended solids, dissolved oxygen, water temperature, oxygen saturation, 5-day biochemical oxygen demand, chemical oxygen demand, total phosphorus and total nitrogen concentration. Interpretation of the obtained results revealed that examination of those basic physicochemical parameters permits to discriminate initially watercourses with respect to level of water contamination. During the research, a large dataset was obtained and it was described by both basic statistical parameters and chemometric method of cluster analysis. The paper presents relations between analysed parameters and influence of land exploitation mode on water quality and describes variation of the results both in space and time.

Response of hydroponic tomato to daily applications of aqueous ozone via drip irrigation

Recycling of greenhouse irrigation water in hydroponic tomato production requires a water remediation process to reduce the risk of pathogen proliferation and the accumulation of other chemical compounds. The dissolution of ozone into bulk irrigation solutions is an effective technology for reducing chemical contaminant and pathogen levels in greenhouse irrigation water. Greenhouse managers utilizing ozonation typically remove residual ozone prior to distribution to the crop. Removal of the active compound in this treatment process has been deemed a prudent measure intended to prevent ozone-based plant damage. This said, although atmospheric ozone has been extensively studied with respect to its phytotoxicity, there are very few studies available on ozone in the aqueous phase in which evidence to support the removal of ozone (on the basis of phytotoxicity) is provided. Furthermore, removal limits the overall efficacy of the treatment as the ozone is not available to treat distribution lines and emitters. The purpose of this study was to determine if aqueous ozone impacts tomato ( Lycopersicon esculentum Mill. cv Matrix F1) productivity when applied directly to a mineral wool growth substrate via drip irrigation. At the highest aqueous ozone treatment level (3.0 mg L −1) significant increases in leaf area, shoot dry matter, and stem thickness were observed. There were no differences across all treatments in terms of net CO 2 assimilation rate, stomatal conductance, internal leaf CO 2 concentration, chlorophyll content index, and fruit production. A qualitative assessment of algae growth on the substrate surface was conducted. Both ozone treatments resulted in a visually discernible reduction in algae prevalence on the substrate surface. The results of this study do not support the removal of aqueous ozone (at the concentrations examined) prior to distribution when the solution is applied via drip irrigation in mineral wool hydroponic tomato production.

Novel approach for assessing heavy metal pollution and ecotoxicological status of rivers by means of passive sampling methods

In order to study the pollution of fluvial ecosystems, it is necessary to analyze not only the levels of chemical contaminants in water, but also those accumulated in the sediment matrix, as well as to assess its ecotoxicological status. Eleven Catalan (Spain) river sections (one sampling point per river) located near urban and industrial areas were sampled during winter of 2009. Water pollutants were collected by using passive samplers as Diffusive Gradient in Thin-Films (DGTs) and Semi-Permeable Membrane Devices (SPMDs). Point water samples were also collected. The concentrations of potentially toxic elements (PTE) in water, filtered water, DGTs and sediment samples were analyzed. Aqueous and organic solvent extracts of sediments samples and organic extracts of SPMDs were performed to assess acute toxicity to Vibrio fischeri by Microtox ®, and chronic toxicity to the green alga Pseudokirschneriella subcapitata. Microtox ® test was also performed with DGT extracts. The results show that metals content of Catalan river waters are below the freshwater screening US EPA benchmarks, excepting some industrial areas (for Hg, Pb, and Zn). In contrast, sediments levels of some rivers were far above freshwater sediment screening US EPA benchmarks (for Zn, As, Cr, Pb, Ni, Hg, and Mn), particularly in the most industrialized areas. A good correlation was found between toxicity values of extracts (from sediments and DGTs) and PTE levels in sediments. The current results support the suitability of using combined point and passive sampling methods for assessing the chemical and ecotoxicological status of aqueous environments.

Simultaneous semi-sequential testing of dual alternatives for pattern recognition

In this paper, we propose a new nonparametric simultaneous test for dual alternatives. Simultaneous tests for dual alternatives are used for pattern detection of arsenic contamination level in ground water. We consider two possible patterns, namely, monotone shift and an umbrella-type location alternative, as the dual alternatives. Pattern recognition problems of this nature are addressed in Bandyopadhyay et al. [5], stretching the idea of multiple hypotheses tests as in Benjamini and Hochberg [6]. In the present context, we develop an alternative approach based on contrasts that helps us to detect three underlying pattern much more efficiently. We illustrate the new methodology through a motivating example related to highly sensitive issue of arsenic contamination in ground water. We provide some Monte-Carlo studies related to the proposed technique and give a comparative study between different detection procedures. We also obtain some related asymptotic results.

The anthropogenic transformation of the water bodies of the European North of Russia

Water bodies of the European North of Russia are classified according to the water contamination level. The high degree of contamination of particular river sections in the European North is shown to be caused by the accumulation of toxic heavy metal compounds and other pollutants. The values of the anthropogenicaltered natural background of water bodies were estimated. It was shown the content of phenol and of copper compounds, of iron and of nickel to exceed the maximum allowable concentrations dozens of times.

Evaluation of hexachlorocyclohexane contamination from the last lindane production plant operating in India

α-Hexachlorocyclohexane (HCH), β-HCH, and lindane (γ-HCH) were listed as persistent organic pollutants by the Stockholm Convention in 2009 and hence must be phased out and their wastes/stockpiles eliminated. At the last operating lindane manufacturing unit, we conducted a preliminary evaluation of HCH contamination levels in soil and water samples collected around the production area and the vicinity of a major dumpsite to inform the design of processes for an appropriate implementation of the Convention. Soil and water samples on and around the production site and a major waste dumpsite were measured for HCH levels. All soil samples taken at the lindane production facility and dumpsite and in their vicinity were contaminated with an isomer pattern characteristic of HCH production waste. At the dumpsite surface samples contained up to 450g kg(-1) Σ HCH suggesting that the waste HCH isomers were simply dumped at this location. Ground water in the vicinity and river water was found to be contaminated with 0.2 to 0.4mg l(-1) of HCH waste isomers. The total quantity of deposited HCH wastes from the lindane production unit was estimated at between 36,000 and 54,000t. The contamination levels in ground and river water suggest significant run-off from the dumped HCH wastes and contamination of drinking water resources. The extent of dumping urgently needs to be assessed regarding the risks to human and ecosystem health. A plan for securing the waste isomers needs to be developed and implemented together with a plan for their final elimination. As part of the assessment, any polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) generated during HCH recycling operations need to be monitored.

Use of diatom life-forms and ecological guilds to assess pesticide contamination in rivers: Lotic mesocosm approaches

The persistence of pesticides in the environment and their effects are a cause of concern to more and more people, and so in 2009 the French government announced plans to reduce pesticide use in agriculture over the next 10 years. Water managers are to monitor the beneficial impact of this reduction on aquatic environments. It has been suggested that diatoms may be good indicators of pesticides, and more particularly of herbicides, in water. Diatoms have been routinely used to assess organic and nutrient pollution for more than 10 years. The general approach is to develop a diatom-based tool to assess pesticide contamination. Diatom indices are usually based on specific pollution sensitivity. Other metrics, such as life-forms, ecological guilds, or cell size offer other advantages. For instance, the relationships between trends in these metrics and environmental gradients are more robust, and make it easier to establish ecological hypotheses. We have therefore opted for this approach. To develop such a tool, outdoor, lotic mesocosm experiments lasting about 2 months were conducted from 2006 to 2008. Herbicides (diuron) and fungicides (azoxystrobin, tebuconazole) were tested at environmental concentrations (sum of pesticides concentrations from 1.11 to 3.01 μg L −1 for chronic pollutions and from 20.25 to 29.50 μg L −1 for short-term acute pollutions). Diatom communities in artificial channels were analyzed by light microscopy using standard European methods. The various parameters structuring diatom communities were assessed, and colonization time appeared to be the most important. However, pesticide contamination was the second most important, and had a more significant impact on the composition of ecological guilds than on species composition. Some metrics did not display any significant trends (benthic/planktonic, colonial, pedunculate, pioneer), but others looked promising for use in pesticide contamination assessment: the abundances of motile guild, low-profile guild and mucous tubule diatoms all increased in contaminated channels, whereas high-profile diatoms showed the opposite trend. Some possible explanations, such as a protective effect of the exopolysaccharide matrix, can be advanced: diatoms living inside a mucous tubule may be shielded from dissolved pesticides, as are motile diatoms, which have a micro-habitat preference for thick matrices which also allows them to withstand higher levels of water contamination. In the same way, high-profile guild diatoms are exposed to dissolved pesticides to a greater extent, and this could explain their lower abundance in contaminated channels.

Geochemistry of waters associated with the old mine workings at Fonte Santa (NE of Portugal)

The quartz veins containing scheelite from Fonte Santa mine cut the Lower Ordovician quartzites. A muscovite–biotite granite (G1) and a muscovite granite (G2), both S-type, crop out close to the Fonte Santa mine and are related to the Moncorvo–Bemposta shear zone. The most altered samples of G2 show intense muscovitization and microclinization and contain chlorite, columbite–tantalite, wolframite, W-ixiolite and Fe-oxides. The tin-bearing granites contain 18 ppm (G1) and 73 ppm (G2) Sn. The most altered samples of G2 correspond to a tungsten granite. The quartz veins contain muscovite, chlorite, tourmaline, scheelite, pyrrhotite, pyrite, sphalerite, chalcopyrite, galena, arsenopyrite, iron oxides, Fe sulfates, phosphates of Pb, Fe and Al. The Fonte Santa mine area was exploited for W between 1942 and 1982. At the end of November 2006, a flood event damaged the tailings dam of Fonte Santa mine, releasing contaminated material and increasing contaminant levels in water within the area of influence of the mine. The waters related to the Fonte Santa mine are poorly mineralized, with electrical conductivity of < 965 µS/cm, and of a mixed type or HCO 3 − and SO 4 2− types. Most pH values (5.0−8.5) indicate that there is no significant acidic drainage in the region, as found in other areas. More acidic values (pH = 3.4) were found in the mine's lagoon. Waters associated with mineralized veins and old mine activities have Fe and Mn concentrations that forbid their use for human consumption and agriculture. Natural Na, Mg and K water contents are associated with the alteration of albite, chlorite and muscovite of country rock, while Ca with the W-bearing quartz veins. Weathering agents are carbonic and sulphuric acids and the latter has a strong influence in areas draining fine-grained mine tailings.

Contamination of the Conchos River in Mexico: does it pose a health risk to local residents?

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.