Microcystins and cyanobacteria trends in a 14 year monitoring of a temperate eutrophic reservoir (Aguieira, Portugal)

A monitoring program of cyanobacteria and cyanotoxins in the framework of the surveillance of the Water Treatment Plant efficiency of the municipality of Santa Comba D?o (Portugal) was conducted from 1994 until 2007. With these data we aimed to answer the question, are MCs produced evenly over the years in a single water body? Samples were taken by the local health authorities in the site of the Water treatment plant and analyzed for total phytoplankton, cyanobacteria and the hepatotoxic cyanotoxins microcystins (MCs). Apart from 1999 and 2000, cyanobacteria represented a high proportion of total phytoplankton, attaining during several months of the year more than 90% of total phytoplankton density. A total of 24 cyanobacteria species were identified and Microcystis aeruginosa, Anabaena flos-aquae and Aphanizomenon flos-aquae were the main potentially toxic cyanobacteria species present throughout the period. MC concentration varied between 0.3 μg MC-LR eq l?1 in October 98 and 87.0 μg MC-LR eq l?1 in September 2001. The evolution of the average cell quota does not reveal any especial trend, although in 2001 the quota was the highest but not significantly different from the other years. The threshold limit of 5000 cells per ml of Microcystis aeruginosa should be taken into consideration in monitoring programs because the 10,000 cells per ml proposed by several other national programs might not be enough to prevent human health risks. Due to high annual variation in MC cell quota, monitoring programs of cyanobacteria and MC should be extended in time, since short term studies do not provide us the data needed for a safe management of a water body used for human purposes.     

Cyanotoxin management and human health risk mitigation in recreational waters

The occurrence and severity of harmful cyanobacterial or blue-green algal blooms (HABs) have increased in recent decades, posing a serious threat of illness to humans. In some countries, water contaminated with cyanotoxins that is used for drinking or haemodialysis has posed a particularly serious risk. However, it is now recognized that recreational exposure to natural toxins by skin contact, accidental swallowing of water or inhalation can also cause a wide range of acute or chronic illnesses. In this review, we focus on the importance of cyanotoxin management in recreational waters. The symptoms related with HAB poisonings, the recommended safety concentrations limit for cyanobacteria and cyanotoxins in such waters, as well as early health hazard indicators of their presence and their monitoring are all discussed. We also present in this review an overview of the methods developed in recent decades for eliminating cyanobacteria and the toxic compounds that they produce.     

Pond bank access as an approach for managing toxic cyanobacteria in beef cattle pasture drinking water ponds

Forty-one livestock drinking water ponds in Alabama beef cattle pastures during were surveyed during the late summer to generally understand water quality patterns in these important water resources. Since livestock drinking water ponds are prone to excess nutrients that typically lead to eutrophication, which can promote blooms of toxigenic phytoplankton such as cyanobacteria, we also assessed the threat of exposure to the hepatotoxin, microcystin. Eighty percent of the ponds studied contained measurable microcystin, while three of these ponds had concentrations above human drinking water thresholds set by the US Environmental Protection Agency (i.e., 0.3 μg/L). Water quality patterns in the livestock drinking water ponds contrasted sharply with patterns typically observed for temperate freshwater lakes and reservoirs. Namely, we found several non-linear relationships between phytoplankton abundance (measured as chlorophyll) and nutrients or total suspended solids. Livestock had direct access to all the study ponds. Consequently, the proportion of inorganic suspended solids (e.g., sediment) increased with higher concentrations of total suspended solids, which underlies these patterns. Unimodal relationships were also observed between microcystin and phytoplankton abundance or nutrients. Euglenoids were abundant in the four ponds with chlorophyll concentrations >?250 μg/L (and dominated three of these ponds), which could explain why ponds with high chlorophyll concentrations would have low microcystin concentrations. Based on observations made during sampling events and available water quality data, livestock-mediated bioturbation is causing elevated total suspended solids that lead to reduced phytoplankton abundance and microcystin despite high concentrations of nutrients, such as phosphorus and nitrogen. Thus, livestock could be used to manage algal blooms, including toxic secondary metabolites, in their drinking water ponds by allowing them to walk in the ponds to increase turbidity.     

Assessment of cylindrospermopsin toxin in an arid Saudi lake containing dense cyanobacterial bloom

This study reports the presence of the cyanobacterial toxin cylindrospermopisn (CYN) and its producer Cylindrospermopsis raciborskii for the first time in Saudi freshwater sources. C. raciborskii was found in Gazan Dam Lake water with two morphotypes (coiled and straight). The appearance and cell density of this species was significantly positively related to high temperature and high ammonium concentrations, and negatively with nitrate and phosphate concentrations in the lake. Intracellular concentrations of CYN (4–173 μg L^?1) were associated with C. raciborskii rather than other cyanobacteria with a maximal value obtained in June 2011, coinciding with the highest bloom of this species (19?×?10⁷ trichome L^?1). CYN cell quotas (0.6–14.6 pg cell^?1) varied significantly along the study period and correlated with most environmental factors. The results of ELISA and liquid chromatography-mass spectrometry proved that the CYN production by strains of this species was isolated from this lake during the present study, with an amount reaching 568 μg g^?1. Extracellular CYN was also detected in cell-free lake water at concentrations 0.03–23.3 μg L^?1, exceeding the drinking water guideline value of 1 μg L^?1 during the Apr–Jul period. As this lake is an important source for drinking and irrigation waters, CYN monitoring should be included in the environmental and health risk assessment plans of these water bodies.     

Temporal variation in density and diversity of cyanobacteria and cyanotoxins in lakes at Nagpur (Maharashtra State), India

Toxic cyanobacteria (TCB) are known worldwide for the adverse impacts on humans and animals. Species composition and the seasonal variation of TCB in water bodies depend on interactions between physical and chemical factors. The present investigation delineates temporal variations in physico-chemical water quality parameters, viz. nutrients and density, diversity, and distribution of toxic cyanobacteria and cyanotoxins in Lake Ambazari (21°7′52″N, 79°2′22″E) and Lake Phutala (21°9′18″N, 79°2′37″E) at Nagpur (Maharashtra State), India. These lakes are important sources of recreational activities and fisheries. Toxic cyanobacterial diversity comprised Anabaena, Oscillatoria, Lyngbya, Phormidium, and Microcystis, a well-known toxic cyanobacterial genus, as dominant. Chlorophyll-a concentrations in the lakes ranged from 1.44 to 71.74 mg/m³. A positive correlation of Microcystis biomass existed with orthophosphate-P (p?<?0.05) and nitrate-N (p?>?0.05). Identification and quantification of microcystin variants were carried out by high performance liquid chromatography equipped with photodiode array detector. Among all the tested toxin variants, microcystin-RR (arginine–arginine) was consistently recorded and exhibited a positive correlation (p?<?0.05) with Microcystis in both the water bodies. Microcystis bloom formation was remarkable between post-monsoon and summer. Besides nutrient concentrations governing bloom formation, the allelopathic role of microcystins needs to be established.     

Monitoring toxic cyanobacteria and cyanotoxins (microcystins and cylindrospermopsins) in four recreational reservoirs (Khon Kaen, Thailand)

The toxic cyanobacterial communities of four recreational reservoirs (Bueng Kaen Nakhon, Bueng Thung Sang, Bueng Nong Khot, and Bueng See Than) in Amphur Muang, Khon Kaen Province, Thailand, were investigated. Water samples were collected via monthly sampling from June to October 2011 for the study on the diversity and density of toxic cyanobacteria and toxin quantification. The main toxic cyanobacteria present in these reservoirs were Aphanocapsa sp., Cylindrospermopsis sp., Leptolyngbya sp., Limnothrix sp., Microcystis sp., Oscillatoria sp., Planktolyngbya sp., Planktotrix sp., and Pseudanabaena sp. The dominant bloom-forming genera in the water samples from Bueng Nong Khot and Bueng See Than were Microcystis sp. and Cylindrospermopsis sp., respectively. Enzyme-linked immunosorbent assays specific for cyanotoxins were performed to detect and quantify microcystins and cylindrospermopsins, with the highest average microcystins content (0.913 μgL^?1) being found in the sample collected from Bueng Nong Khot and the highest average cylindrospermopsins content (0.463 μgL^?1) being found in the sample collected from Bueng See Than. The application of 16S rRNA analyses to cyanobacterial isolates BKN2, BNK1, BNK2, and BST1 indicated that these isolates are most closely related to Limnothrix planctonica (JQ004026) (98 % similarity), Leptolyngbya sp. (FM177494) (99 % similarity), Microcystis aeruginosa (DQ887510) (99 % similarity), and Limnothrix redekei (FM177493) (99 % similarity), respectively.     

Exposure assessment of endocrine disruptors in bottled drinking water of Lebanon

Bisphenol A (BPA) is a commonly used monomer in various products including bottled water. Numerous studies have reported endocrine adverse effects and neoplasia associated with BPA exposure in animals. However, considerable discrepancies exist among these studies with respect to both the nature of the toxic effects and the threshold dose. In Lebanon, 19-L polycarbonate (PC) bottles of drinking water are widely used in urban areas. The present study aims at assessing BPA human exposure and associated health risks from drinking water in Lebanese. A total of 22 bottled water sources, packaged in PC, were identified from licensed and non-licensed sources. Water samples were analyzed following exposure to sunlight for 72 h. BPA in water was quantified by HPLC, and other potential organic pollutants were screened by GC/MS. Fifty-nine percent of samples showed BPA levels above detection limits (>0.05 ng/mL). The median BPA level was 0.1 ng/mL (range 0.05 to 1.37 ng/mL). The mean BPA level for the total number of samples was 0.169 ng/mL (±0.280). A higher mean BPA level was found in water from licensed companies compared to non-licensed sources, however, not statistically significant. Screening showed the presence of dibutyl-phthalate and dioctyl-phthalate in only two samples. Endocrine disruptors (EDR) are ubiquitous contaminants in bottled water in Lebanon with potential health risk implications. Although estimated exposure levels are below the reference dose (RfD), further studies are needed to quantitate exposure from various sources and to investigate EDR contribution to existing epidemics in the country.     

Investigations on boron levels in drinking water sources in China

To evaluate boron contamination of public drinking water in China, both dissolved and total boron contents in 98 public drinking water sources from 49 cities, 42 brands of bottled water samples from supermarkets in several cities, and 58 water samples from boron industrial area were measured by inductively coupled plasma-mass spectrometry (ICP-MS). Our experimental results showed that boron existed in public drinking water sources mainly in dissolved status with total concentrations ranging from 0.003 to 0.337 mg/L (mean = 0.046 mg/L). The mean boron concentrations in mineral and pure bottled water were 0.052 and 0.028 mg/L, respectively. The results obtained in this work showed that there was no health risk on view of boron in public drinking water sources and bottled water. In boron industrial area, boron concentrations in surface water and ground water were 1.28 mg/L (range = 0.007–3.8 mg/L) and 18.3 mg/L (range = 0.015–140 mg/L), respectively, which indicated that boron industry caused boron pollution in local water system.     

Probability-based nitrate contamination map of groundwater in Kinmen

Groundwater supplies over 50 % of drinking water in Kinmen. Approximately 16.8 % of groundwater samples in Kinmen exceed the drinking water quality standard (DWQS) of NO₃ ^?-N (10 mg/L). The residents drinking high nitrate-polluted groundwater pose a potential risk to health. To formulate effective water quality management plan and assure a safe drinking water in Kinmen, the detailed spatial distribution of nitrate–N in groundwater is a prerequisite. The aim of this study is to develop an efficient scheme for evaluating spatial distribution of nitrate–N in residential well water using logistic regression (LR) model. A probability-based nitrate–N contamination map in Kinmen is constructed. The LR model predicted the binary occurrence probability of groundwater nitrate–N concentrations exceeding DWQS by simple measurement variables as independent variables, including sampling season, soil type, water table depth, pH, EC, DO, and Eh. The analyzed results reveal that three statistically significant explanatory variables, soil type, pH, and EC, are selected for the forward stepwise LR analysis. The total ratio of correct classification reaches 92.7 %. The highest probability of nitrate–N contamination map presents in the central zone, indicating that groundwater in the central zone should not be used for drinking purposes. Furthermore, a handy EC–pH-probability curve of nitrate–N exceeding the threshold of DWQS was developed. This curve can be used for preliminary screening of nitrate–N contamination in Kinmen groundwater. This study recommended that the local agency should implement the best management practice strategies to control nonpoint nitrogen sources and carry out a systematic monitoring of groundwater quality in residential wells of the high nitrate–N contamination zones.     

Health risk assessment of fluoride in drinking water from Anhui Province in China

This study analyzes the concentrations and health risks of fluoride in 249 drinking water samples collected from different regions of Anhui Province in China. Results indicated that fluoride content in drinking water ranged from 0.12 to 1.94 mg L^?1 (mean?=?0.57 mg L^?1) in the following order: Huaibei plain region > Jianghuai hill region ≈ Dabieshan mountainous region > plain along the Yangtze River region > southern Anhui mountainous region. The fluoride contents were less than 0.50 mg L^?1 in 66.66 % of the drinking water samples, 0.51–1.0 mg L^?1 in 23.29 %, and higher than 1.0 mg L^?1 in 12.04 %. The fluoride levels in some samples were lower than the recommended values for controlling dental caries (0.50–1.0 mg L^?1). The total fluoride intake from drinking water was between 0.14 and 2.33 mg per day in different regions of the province, supposing an individual consumes 1.2 L of water per day. Therefore, measures should be taken to increase fluoride intake in the Jianghuai hill region, Dabieshan mountainous region, plain along the Yangtze River, and southern Anhui mountainous region to control dental caries. On the other hand, the fluoride levels must be reduced in the Huaibei plain region to decrease endemic fluorosis. The results serve as crucial guidelines for managing fluoride safety in drinking water and controlling endemic fluorosis in different regions of Anhui Province.     

Feasibility of the hydrogen sulfide test for the assessment of drinking water quality in post-earthquake Haiti

In 2010, a magnitude 7.0 earthquake struck Haiti, severely damaging the drinking and wastewater infrastructure and leaving millions homeless. Compounding this problem, the introduction of Vibrio cholerae resulted in a massive cholera outbreak that infected over 700,000 people and threatened the safety of Haiti’s drinking water. To mitigate this public health crisis, non-government organizations installed thousands of wells to provide communities with safe drinking water. However, despite increased access, Haiti currently lacks the monitoring capacity to assure the microbial safety of any of its water resources. For these reasons, this study was designed to assess the feasibility of using a simple, low-cost method to detect indicators of fecal contamination of drinking water that could be implemented at the community level. Water samples from 358 sources of drinking water in the Léogâne flood basin were screened with a commercially available hydrogen sulfide test and a standard membrane method for the enumeration of thermotolerant coliforms. When compared with the gold standard method, the hydrogen sulfide test had a sensitivity of 65 % and a specificity of 93 %. While the sensitivity of the assay increased at higher fecal coliform concentrations, it never exceeded 88 %, even with fecal coliform concentrations greater than 100 colony-forming units per 100 ml. While its simplicity makes the hydrogen sulfide test attractive for assessing water quality in low-resource settings, the low sensitivity raises concerns about its use as the sole indicator of the presence or absence of fecal coliforms in individual or community water sources.     

Freshwater environmental quality parameters of man-made lakes of Serbia

In this study, 28 lakes were selected from the freshwater resources of the network of man-made lakes throughout the Vojvodina Province and the central part of Serbia. Samples were analyzed for the physicochemicals indicators of the water and nutrients. Most of the values of the chemicals indicators and nutrients of the samples from the Vojvodina Province exceeded the Water Act and Regulations on the Monitoring of Water Quality introduced by the Government of the Republic of Serbia (MWQ) and/or the World Health Organization (WHO) drinking water standards. These samples may not be suitable for human consumption. The sample from Lake Me?uvr?je, where the NH₄ ⁺ concentration was 0.28 mg/L, and the sample from Ovcar Banja, where the total phosphorus (TP) content was 0.15 mg/L with a high total nitrogen (TN) content of 1.21 mg/L, are particularly noteworthy. These high concentrations exceeded the proposed guidelines for safe drinking water; therefore, water from these lakes should be used with care as harmful health effects may occur. The majority of the Serbian lakes are characterized by phosphorus-limited photosynthesis.     

Health risk assessment of heavy metal variability in sachet water sold in Ado-Odo Ota,South-Western Nigeria

The sales of sachet water (SW), also known as “pure water” (PW), in Nigeria is a lucrative business. It serves many people, especially low-income earners, by providing a more affordable access to safe drinking water when compared with table water. However, some of the producers of SW do not effectively treat raw water before packaging them for sale. This study investigates the presence and concentrations of heavy metals, such as chromium (Cr), iron (Fe), manganese (Mn), copper (Cu), aluminum (Al), and zinc (Zn) in some samples of SW sold within Ota, Ogun State, Nigeria. Samples of SW from nine different producers were purchased for four consecutive weeks and analyzed to determine the concentrations of these heavy metals in them. Furthermore, health risk indicators, such as chronic daily intake (CDI) and health risk indices (HRI) for children and adults, were calculated separately. The metal concentrations were compared with allowable limits set by the World Health Organization (WHO), Nigerian Industrial Standard (NIS), and the United States Environmental Protection Agency (US EPA). High concentrations of Cr, Fe, and Al were found in all the nine samples and exceeded the maximum allowable limits (MAL) of all the standards considered. However, the concentrations of Zn, Mn, and Cu were within permissible limits. The HRIs of heavy metals were in the order of Cu > Fe > Zn > Mn > Al > Cr, but since the standard limits set for some metals were exceeded, proper and effective treatment is required to safeguard the health of consumers.     

Molybdenum distributions and variability in drinking water from England and Wales

An investigation has been carried out of molybdenum in drinking water from a selection of public supply sources and domestic taps across England and Wales. This was to assess concentrations in relation to the World Health Organization (WHO) health-based value for Mo in drinking water of 70 μg/l and the decision to remove the element from the list of formal guideline values. Samples of treated drinking water from 12 water supply works were monitored up to four times over an 18-month period, and 24 domestic taps were sampled from three of their supply areas. Significant (p?p?>?0.05) were detected. Tap water samples collected from three towns (North Wales, the English Midlands, and South East England) supplied uniquely by upland reservoir water, river water, and Chalk groundwater, respectively, also showed a remarkable uniformity in Mo concentrations at each location. Within each, the variability was very small between houses (old and new), between pre-flush and post-flush samples, and between the tap water and respective source water samples. The results indicate that water distribution pipework has a negligible effect on supplied tap water Mo concentrations. The findings contrast with those for Cu, Zn, Ni, Pb, and Cd, which showed significant differences (p?England and Wales.     

The variability of PCDD/F concentrations in the effluent of wastewater treatment plants with regard to their hydrological environment

The occurrence, concentrations, patterns, and loads of 17 2,3,7,8-substituted congeners of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were determined in treated wastewater collected at the outlets from 14 wastewater treatment plants (WTPs), divided into three size categories. The analysis also considered the effect of wastewater outflow on the final concentrations of PCDDs/Fs, as the samples were collected during flooding and stable hydrological conditions. None of the studied WTPs were found to completely remove toxic congeners of PCDDs/Fs from wastewater: the PCDD concentrations in the outgoing effluent during stable wastewater flow ranged from 2.99 to 177.19 pg/L, PCDFs from 6.05 to 51.30 pg/L, and the Toxic Equivalent (TEQ) was between 0.94 and 4.87 pg/L. The results from high wastewater flow were less diversified, ranging from 5.04 to 8.85 pg/L for PCDDs, from 11.47 to 32.33 pg/L for PCDFs and from 2.00 to 4.65 pg/L for TEQ. The smallest WTPs demonstrated the highest average total and TEQ concentrations due to limited volume, short retention time and outdated technology, and, hence, insufficient treatment efficiency. The largest WTPs have the potential to substantially affect the quality of river water, as despite being associated with the lowest concentrations, they released much greater volumes of treated wastewater and, hence, the greatest amounts of analyzed compounds. Elevated TEQ values were observed at high flow in all WTP size categories indicating the impact of high and stable wastewater flow on the concentrations of the observed PCDDs/Fs.     

The first detection of potentially toxic <Emphasis Type="Italic">Microcystis</Emphasis> strains in two Middle Atlas Mountains natural lakes (Morocco)

Aguelmam Azizgza (LAZ) and Dayet Afourgah (DAF) are two Moroccan natural lakes located in a humid hydrographic basin of the Middle Atlas Mountains. Both are considered important reservoirs of plant and animal biodiversity. In addition, they are extensively used for recreational and fishing activities and as a water source for irrigation of agricultural crops. Recurrent cyanobacteria scum episodes in the two water bodies have been reported, Microcystis being the main genus in the scums. Here, we report on the toxic potential of three Microcystis aeruginosa strains isolated from those lakes: Mic LAZ and Mic B7 from LAZ and Mic DAF isolated from DAF. The toxic potential was checked by their microcystin (MC) content and the presence of mcy genes involved in MC synthesis. The identification and quantification of MC variants were performed by high-performance liquid chromatography-photo-diode array. The detection of mcy genes was achieved by whole-cell multiplex PCR that allowed the simultaneous amplification of DNA sequences corresponding to specific mcy regions. MC content of cultured cells, as MC-LR equivalents per gram cell biomass, was slightly higher in Mic LAZ (ca. 860) than in Mic B7 (ca. 700) and Mic DAF (ca. 690). Four MC variants were identified in the three isolates: MC-WR, MC-RR, MC-DM-WR, and MC-YR. The presence of toxic Microcystis strains in the two studied lakes may be regarded as an environmental and health hazard, especially during periods of bloom proliferation. It would be recommended the use of two complementary techniques, as those utilized herein (HPLC and mcy detection) to alert on highly probable toxicity of such lakes.     

Removing arsenic from groundwater in Cambodia using high performance iron adsorbent

In Cambodia, groundwater has been contaminated with arsenic, and purification of the water is an urgent issue. From 2010 to 2012, an international collaborative project between Japan and Cambodia for developing arsenic-removing technology from well water was conducted and supported by the foundation of New Energy and Industrial Technology Development Organization, Japan. Quality of well water was surveyed in Kandal, Prey Veng, and Kampong Cham Provinces, and a monitoring trial of the arsenic removal equipment using our patented amorphous iron (hydr)oxide adsorbent was performed. Of the 37 wells surveyed, arsenic concentration of 24 exceeded the Cambodian guideline value (50 μg L^?1), and those of 27 exceeded the WHO guideline for drinking water (10 μg L^?1). Levels of arsenic were extremely high in some wells (>1,000–6,000 μg L^?1), suggesting that arsenic pollution of groundwater is serious in these areas. Based on the survey results, 16 arsenic removal equipments were installed in six schools, three temples, two health centers, four private houses, and one commune office. Over 10 months of monitoring, the average arsenic concentrations of the treated water were between 0 and 10 μg L^?1 at four locations, 10–50 μg L^?1 at eight locations, and >50 μg L^?1 at four locations. The arsenic removal rate ranged in 83.1–99.7 %, with an average of 93.8 %, indicating that the arsenic removal equipment greatly lower the risk of arsenic exposure to the residents. Results of the field trial showed that As concentration of the treated water could be reduced to <10 µg L^?1 by managing the As removal equipment properly, suggesting that the amorphous iron (hydr)oxide adsorbent has high adsorbing capacity for As not only in the laboratory environment but also in the field condition. This is one of the succeeding As removal techniques that could reduce As concentration of water below the WHO guideline value for As in situ.     

Assessments of some metals contamination in lipsticks and their associated health risks to lipstick consumers in Iran

In this study, the concentrations of lead, cadmium, and chromium in lipstick samples were evaluated. The samples were from different brands and produced in different countries. The average lead, cadmium, and chromium concentrations in all lipstick samples were 1.851, 0.017, and 4.300 mg kg^?1 ww, respectively. There was a significant difference in the concentrations of lead, cadmium, and chromium among the brands (p?<?0.05). The concentrations of the measured elements in the brands did not exceed the values of the international standards provided for lipstick. The values of hazard quotient (HQ), health risk index (HI), relative intake index (RII), and estimated daily intake (EDI) indices were calculated. The results of the HQ and HI indices showed that in more than 50% of the lipstick brands, there is a potential threat to consumer health due to the presence of these elements in lipstick. Therefore, it can be concluded that, due to the simultaneous use of lipstick with other types of cosmetics and hence the potential exposure of consumers to toxic elements through all cosmetics, continuous monitoring of the concentrations of these elements in these types of products is necessary to avoid potential health risks.     

Arsenic concentration variability, health risk assessment, and source identification using multivariate analysis in selected villages of public water system, Lahore, Pakistan

This paper reports high levels and variability in arsenic (As) levels at locations identified as one of the highest As-contaminated locations in Pakistan. Groundwater pollution related to arsenic has been reported since many years in the areas lying in outskirts of District Lahore, Pakistan. A comparative study is done to determine temporal variations of As from three villages, i.e., Kalalanwala (KLW), Manga Mandi (MM), and Shamki Bhattian (SKB). Seventy-three percent of the 30 investigated samples ranging in depth from 20 to 200 m, show an increasing trend in variations of As concentration over a time span of 4 years and 87 % of samples exceeded the WHO standard of 10 μg/L for As while 77 % of samples have As concentration >50 μg/L (national standard). Further results indicate that high levels of As is accompanied with increase pH (r?=?0.8) favoring desorption of As from minerals at higher pH under oxidizing conditions. For health risk assessment of arsenic, the average daily dose, hazard quotient (HQ), and cancer risk were calculated. The residents of the studied areas had toxic risk index in the order of SKB>KLW>MM, with 87 % of samples exceeding the typical toxic risk index 1.00 (ranging from 2.3–48.6) which was 83 % (ranging from 0.3–41) 4 years before. The results of the present study therefore indicate that arsenic concentrations are increasing in the area, which needs an immediate attention to provide alternate sources of water to save people at risk.     

Identification of microcystins contamination in surface water samples from the Three Gorges Reservoir, China

Physicochemical and biological parameters related to water quality and microcystins (MCs) contamination in aquatic environment of the Three Gorges Reservoir were investigated in August 2004 and January 2005. A solid-phase extraction method and an HPLC equipped with photodiode array were used for MC-LR detection. A quantitative analysis showed the total MC-LR concentrations of water samples ranged from non-detectable to 0.57 μg L?1 among the seven sampling sites. The highest MC-LR concentration was found at sampling site G (Wushan), which was followed by F (Kaixian), E (Wanzhou), D (Fuling), C (Cuntan), and A (Daxigou). The correlation analysis showed the MC-LR concentration was positively correlated with chlorophyll-a concentration. This result suggests that MC concentration in water can be indirectly estimated by analyzing the chlorophyll-a concentration. Overall, the results of this study suggest that more importance should be placed on monitoring of MC contamination and water quality in the Three Gorges Reservoir to ensure drinking water safety and reduce the potential exposure of people to these health hazards.