Assessment of trace element pollution and ecological risks in a river basin impacted by mining in Colombia

Trace element pollution in rivers by anthropogenic activities is an increasing problem worldwide. In this study, the contamination and ecological risk by several trace elements were evaluated along a 100-km stretch of the San Jorge River in Colombia, impacted by different mining activities. The increase of average concentration levels and range of trace elements in sediments (in μg/g) was as follows: Cu 6656 (454–69,702) > Cd 1159 (0.061–16,227) > Zn 1064 (102–13,483) > Ni 105 (31–686) > Pb 7.2 (5.1–11.7) > As 1.8 (1.0–3.2) > Hg 0.31 (0.12–1.37). Results showed that surface sediments could be classified as very high ecological risk index (RI > 600), associated with high contamination of Hg, Cd, and Cu, in stations close mining activities. Values for pollution load index indicate an environmental deterioration (PLI > 1), and sediment quality guidelines (SQGs) suggested that Cu, Ni, Zn, and Hg caused adverse biological effects. We further used pollution indices such as contamination factor (CF), enrichment factor (EF), and geoaccumulation index (Igeo) to assess the extent of contamination. According to these indices, discharges of hazardous chemicals over many years have resulted in a high degree of pollution for Cu, Pb, and Cd, with critical values in stations receiving wastes from mining activities. Multivariate statistical analysis suggested that Hg, Cd, Cu, and Zn derived from gold and coal mining, Ni and As were related from the mining of ferronickel and coal, respectively, whereas the high Pb load was attributed to diffuse source of pollution. In sum, our study provided the first detailed database on metal concentration and ecological risks to organisms in sediments of the San Jorge River Basin, and the current results also suggested future research for public health action.

     

利用城市生态河道深度净化污水处理厂出水的工程技术研究

提出了城市生态河道工程构建的技术方法,并研究了示范工程对城市污水处理厂出水的深度净化规律。实验结果表明,在保证生态景观功能的前提下,将生态河道技术工艺用于污水处理厂出水的深度净化,能够高效、稳定地去除氮磷等营养物,河道出水可以满足城市景观水体补充水源的水质要求,出水TP、PO^3-₄、TN、NH₃-N和NO₃-N平均值分别达到0.263、0.116、2.570、0.752和2.438 mg/L,去除率分别达到85.4%、92.8%、60.8%、39.7%和77.2%。     

Boron pollution due to geothermal wastewater discharge into the Buyuk Menderes river, Turkey

Kizildere, which is the only commercial geothermal power plant in Turkey and located in Buyuk Menderes Graben in south-west Turkey, discharges annually 6 million tonnes of wastewater into the Buyuk Menderes river, creating environmental pollution. Currently, the wastewater, which includes up to 24 mg/l boron, is discharged into the river at a rate of 750–1500 tonnes per hour. The temperature of the wastewater is approximately 1401°C. The water quality of Buyuk Menderes river is very important for the environment and aquatic life. Reinjection seems to be the only possible solution to this environmental problem.     

The impact of an industrial effluent on the water quality,submersed macrophytes and benthic macroinvertebrates in a dammed river of Central Spain

This research was conducted in the middle Duratón River (Central Spain), in the vicinity of Burgomillodo Reservoir. An industrial effluent enters the river 300 m downstream from the dam. Fluoride and turbidity levels significantly increased downstream from the effluent, these levels being to some extent affected by differential water releases from the dam. The community of submersed macrophytes exhibited slighter responses and, accordingly, lower discriminatory power than the community of benthic macroinvertebrates, this indicating that metrics and indices based on macroinvertebrates may be more suitable for the biological monitoring of water pollution and habitat degradation in dammed rivers receiving industrial effluents. However, in relation to fluoride bioaccumulation at the organism level, macrophytes (Fontinalis antipyretica and Potamogeton pectinatus) were as suitable bioindicators of fluoride pollution as macroinvertebrates (Ancylus fluviatilis and Pacifastacus leniusculus). Fluoride bioaccumulation in both hard and soft tissues of these aquatic organisms could be used as suitable bioindicator of fluoride pollution (even lower than 1 mg F⁻ L⁻¹) in freshwater ecosystems. Echinogammarus calvus exhibited a great sensitivity to the toxicity of fluoride ions, with a 96 h LC₅₀ of 7.5 mg F⁻ L⁻¹ and an estimated safe concentration of 0.56 mg F⁻ L⁻¹. The great capacity of E. calvus to take up and retain fluoride during exposures to fluoride ions would be a major cause of its great sensitivity to fluoride toxicity. It is concluded that the observed fluoride pollution might be partly responsible for the absence of this native amphipod downstream from the industrial effluent.     

Partitioning and availability of sediment-bound metals following final sewage effluent release to a lowland river

A simple partitioning scheme was used to assess the partitioning and behaviour of copper, cadmium, iron, lead and manganese within the surface waters and sediments of the River Yare, Norfolk, UK, following the discharge of final effluent to the water course from municipal sewage treatment works (STW). Sewage effluent discharges were shown to increase metal concentrations and complexation capacities in receiving waters, but the tidal nature of the river meant that surface water monitoring could not accurately pinpoint the contamination source or the main metal partitioning trends. Sediments formed a more stable base on which to perform contaminant studies: these revealed that metals discharged from the STW rapidly accumulated in bottom deposits in relative stable chemical forms.     

Ecotoxicological risk assessment linked to the discharge by hospitals of bio-accumulative pharmaceuticals into aquatic media: The case of mitotane

The release of hospital wastewater into the urban sewer networks contributes to the general contamination of aquatic media by pharmaceutical residues. These residues include bio-accumulative pharmaceuticals that lead to increased risk for ecosystems because they can concentrate in organisms and food chains, and therefore reach toxic levels. In order to assess the ecotoxicological risks linked to this particular category of residues, we have developed a specific method, by combining a theoretical calculation of pollutant concentrations in organisms to estimate Body Residue (BR), and ecotoxicity biomarkers in fish cell lines, enabling the calculation of a Critical Body Residue (CBR). This method finally results in the calculation of a specific risk quotient (Qb = BR/CBR), characterizing the risk linked to this type of pollutant. This method was applied to mitotane, a bio-accumulative pharmaceutical typically found in hospital wastewater, in the framework of an exposure scenario corresponding to the discharge of all the hospital wastewaters into the Rhone River which flows through the city of Lyon, France. This approach leads to risk quotients (Qb and Qbg) much higher than those found with the classical approach, i.e. Q = PEC/PNEC (Predictive Environmental Concentration/Predictive Non Effect Concentration) = 0.0006. This difference in the appreciation of risk is important when using cytotoxicity as the criterion for measuring the toxicity of mitotane (Qb = 0.056) and it is even greater when the criterion used is genotoxicity (Qbg = 6.8). This study must be now consolidated by taking the biomagnification of the pharmaceuticals into consideration.     

Evaluation of effluent toxicity and ambient toxicity in a polluted lowland river

The impact of an industrial effluent containing high loads of calcium, cadmium, lead chloride and sulphate, on a river ecosystem was assessed using a combination of an effluent toxicity test, an ambient toxicity test and an ecological survey. Only this combination of techniques made it possible to discriminate between the effects of the discharge and those of the background pollution. Each of the individual techniques detected essential effects which the other failed to reveal. With the physical and chemical measurements, important increases of several components were measured at all sampling sites downstream of the discharge. With the ecological survey, however, no large changes in water quality could be determined at the sampling sites, due to the high degree of pollution present upstream of the discharge. Reproduction of Daphnia magna, exposed to sublethal effluent dilutions, was followed over two generations. The offspring of the first generation were shown to have an increased sensitivity to the effluent, compared to the first generation that was born from previously unexposed mothers. Besides the toxicity of the effluent, the acute and chronic toxicity of its main component, CaCl(2), was also determined. The results of the CaCl(2)-tests and toxicity data from literature for the suspected toxicants were transformed to Toxic Units (TU). Using the sum of the TUs we investigated the possibility of predicting effluent toxicity to Daphnia magna. Effluent toxicity was under-estimated by calculating the sum of the TUs of the individual components. Dilution of the effluent to a level at which the measured toxicant concentrations comply with European regulations still showed significant effects on Daphnia reproduction.     

Occurrence and removal of polycyclic aromatic hydrocarbons and their derivatives in an ecological wastewater treatment plant in South China and effluent impact to the receiving river

Ecological wastewater treatment plant (EWWTP), a kind of emerging wastewater treatment plant (WWTP) in recent years, combined microbiology with botany which is efficient for the removal of nitrogen and organic matter, as well as deodorization. The occurrence and removal of micro-organic pollutants in EWWTPs were still not well known. Polycyclic aromatic hydrocarbons (PAHs) and their typical derivatives (SPAHs) including the oxygenated PAHs (OPAHs), chlorinated PAHs (ClPAHs), and methyl PAHs (MPAHs) were investigated in an EWWTP in Guangdong Province, China. The concentrations of the Σ6 OPAHs (114–384 ng/L) were higher than the Σ16 PAHs (92–250 ng/L), and much higher than the Σ4 MPAHs (13–64 ng/L) and Σ9 ClPAHs (2–3 ng/L) in the EWWTP and the effluent receiving river. The total removal efficiencies of the PAHs, OPAHs, MPAHs, and ClPAHs in the EWWTP (43?±?14%, 41?±?7%, 55?±?16%, and 18?±?4%) were lower than the traditional WWTPs, probably due to the lower concentration of the sludge in the ecological treatment. The advanced treatment process (microfiltration and UV disinfection treatment) contributed much less (0–20%) to the whole removal efficiency than the ecological treatment (80–100%). The effluent from the EWWTP slightly reduced the PAHs and SPAHs concentrations in the receiving river. The high concentrations of the PAHs and SPAHs in the receiving river were similar to the influent of the EWWTP, indicating that some untreated wastewater was directly discharged to the river, especially in the upstream.

     

Assessment of the effluent quality from a gold mining industry in Ghana

The physical and chemical qualities of the process effluent and the tailings dam wastewater of AngloGold-Ashanti Limited, a gold mining company in Ghana, were studied from June to September, 2010. The process effluent from the gold extraction plant contains high amounts of suspended solids and is therefore highly turbid. Arsenic, copper and cyanide were identified as the major pollutants in the process effluent with average concentrations of 10.0, 3.1 and 21.6 mg?L^?1, respectively. Arsenic, copper, iron and free cyanide (CN^?) concentrations in the process effluent exceeded the Ghana EPA discharge limits; therefore, it is necessary to treat the process effluent before it can be discharged into the environment. Principal component analysis of the data indicated that the process effluent characteristics were influenced by the gold extraction process as well as the nature of the gold-bearing ore processed. No significant correlation was observed between the wastewater characteristics themselves, except for the dissolved oxygen and the biochemical oxygen demand. The process effluent is fed to the Sansu tailings dam, which removes 99.9 % of the total suspended solids and 99.7 % of the turbidity; but copper, arsenic and cyanide concentrations were still high. The effluent produced can be classified as inorganic with a high load of non-biodegradable compounds. It was noted that, though the Sansu tailings dam stores the polluted effluent from the gold extraction plant, there will still be serious environmental problems in the event of failure of the dam.     

Biological denitrification of a highly nitrogenous industrial effluent: a case study in Zimbabwe

This paper describes the establishment and design of a scheme to denitrify industrial effluent with concentrations of N greater than 2000 mg litre(-1) to levels within the regulatory limits of the Zimbabwe Natural Resources Act which stipulates an upper limit of 10 mg litre(-1) of nitrate in effluent dumped in important catchment areas. The scheme was set up in 1978 and the data used in the discussion are for the year 1983, five years after the establishment of the scheme. The scheme consists of three impounding reservoirs in which effluent is held for at least 24 h in each case so that it undergoes biological denitrification at each stage. In some cases, the effluent is diverted after the second reservoir and is used to irrigate pastures on which dairy cattle are being grazed. In general, under this scheme, the N content of the effluent is within the regulatory limit by the time it enters the main river system, about 8 km away.     

The effects of a basic effluent on macroinvertebrate community structure in a temporary Mediterranean river

Macroinvertebrate communities and environmental variables were assessed seasonally for 1 year in a temporary river in South Portugal receiving an effluent with high conductivity, pH, sulphates, nitrates and low oxygen content. The usefulness of the ordination method canonical correspondence analysis (CCA) and the classification method cluster analysis (UPGMA) were examined to evaluate the perturbation. Macroinvertebrate samples were segregated along the first ordination axis by CCA, which in turn correlated with sulphates and nitrates. CCA produced a two-dimensional distribution of sites similar to the grouping formed by cluster analysis. In general, three or four groups were distinguished. Immediately downstream of the effluent discharge point, only taxa tolerant to low oxygen, high pH and high sulphate and nitrate concentrations were present. Further downstream, sites had a community similar to the reference sampling locations. During flowing conditions the CCA ordination axis 1 was also correlated with several classic measures of water quality (i.e. taxon richness, diversity and biotic indices). In other periods, only the percentage of Ephemeroptera, Plecoptera and Trichoptera (%EPT) and the ratio EPT/(Chironomidae + EPT) were significantly correlated with CCA axis one. This suggests that ordination methods outperform benthic indices in detecting pollution during low flows and segregated polluted from clean/recovered sites in all periods.     

Evaluation of membrane bioreactor process capabilities to meet stringent effluent nutrient discharge requirements.

A six-stage membrane bioreactor (MBR) pilot plant was operated to determine and demonstrate the capability of this process to produce a low-nutrient effluent, consistent with the nutrient reduction goals for the Chesapeake Bay. Biological nitrogen removal was accomplished using a multistage configuration with an initial anoxic zone (using the carbon in the influent wastewater), an aerobic zone (where nitrification occurred), a downstream anoxic zone (where methanol was added as a carbon source), and the aerated submerged membrane zone. The capability to reliably reduce effluent total nitrogen to less than 3 mg/L as nitrogen (N) was demonstrated. A combination of biological (using an initial anaerobic zone) and chemical (using alum) phosphorus removal was used to achieve effluent total phosphate concentrations reliably less than 0.1 mg/L as phosphorus (P) and as low as 0.03 mg/L as P. Alum addition also appeared to enhance the filtration characteristics of the MBR sludge and to reduce membrane fouling. Aeration of the submerged membranes results in thickened sludge with a high dissolved oxygen concentration (approaching saturation), which can be recycled to the main aeration zone rather than to an anoxic or anaerobic zone to optimize biological nutrient removal. Biological nutrient removal was characterized using the International Water Association Activated Sludge Model No. 2d. The stoichiometry of chemical phosphorus removal was also consistent with conventional theory and experience. The characteristics of the solids produced in the MBR were compared with those of a parallel full-scale conventional biological nitrogen removal process and were generally found to be similar. These results provide valuable insight to the design and operating characteristics of MBRs intended to produce effluents with very low nutrient concentrations.     

Enhanced removal of arsenic from a highly laden industrial effluent using a combined coprecipitation/nano-adsorption process

Effective arsenic removal from highly laden industrial wastewater is an important but challenging task. Here, a combined coprecipitation/nano-adsorption process, with ferric chloride and calcium chloride as coprecipitation agents and polymer-based nanocomposite as selective adsorbent, has been validated for arsenic removal from tungsten-smelting wastewater. On the basis of operating optimization, a binary FeCl₃ (520 mg/L)–CaCl₂ (300 mg/L) coprecipitation agent could remove more than 93 % arsenic from the wastewater. The resulting precipitate has proved environmental safety based on leaching toxicity test. Fixed-bed column packed with zirconium or ferric-oxide-loaded nanocomposite was employed for further elimination of arsenic in coprecipitated effluent, resulting in a significant decrease of arsenic (from 0.96 to less than 0.5 mg/L). The working capacity of zirconium-loaded nanocomposite was 220 bed volumes per run, much higher than that of ferric-loaded nanocomposite (40 bed volumes per run). The exhausted zirconium-loaded nanocomposite could be efficiently in situ regenerated with a binary NaOH–NaCl solution for reuse without any significant capacity loss. The results validated the combinational coprecipitation/nano-adsorption process to be a potential alternative for effective arsenic removal from highly laden industrial effluent.     

Environmental and industrial factors relating to flavor tainting of fish in the upper Wisconsin river

Extracts from Large Toothed Aspen (Populous grandidenta Michx.) and Jack Pine (Pinus banksiana Lamb.) contained many odor compounds found in flavor-tainted walleye from the Wisconsin River, including alkylphenols. Aspen wood contained 8 ppb of 2-isopropylphenol, and river sediments also contained low ppb levels of many alkylphenols, including 2-isopropylphenol. Thiophenol and thiocresol which sporadically cause offensive sulfury taints in Wisconsin River fish were also found in river sediment. Quantitative analysis of fish for alkylphenols supported a hypothesis involving a food chain-mediated seasonal fluctuation of alkylphenol levels in fish. Thiophenols are postulated to be derived from pulp mill activities on the river.     

潮汐式生态滤床在平原河网地区污染河流治理中的应用

以梁塘河治理措施中的主体工程潮汐式生态滤床为研究对象,考察其对平原河网地区污染河流中的N、P及有机污染物等的去除效果,并通过高通量测序技术分析潮汐式生态滤床混合层的微生物群落组成。结果表明,以潮汐式生态滤床为主体的治理工程运行稳定,河流水质趋好,且在受到污染冲击后,水质能迅速恢复。潮汐式生态滤床对[NH₄⁺-N]有很好的去除效果,[NH₄⁺-N]去除率最高为99.42%,平均去除率为80.94%。潮汐式生态滤床对TP和I_Mn也有一定的去除效果,平均去除率为34.37%和35.65%。潮汐式生态滤床内部硝化作用明显,微生物群落分析结果表明,滤床内主要的优势菌属是norank_f_norank_o_Chloroplast (1.72%~12.61%) 和硝化螺旋菌属 (Nitrospiria,1.75%~8.75%) 。norank_f_norank_o_Chloroplast作为第一优势菌属,其相对丰度远超其他菌属,且随着滤床的持续运行,具有硝化作用的硝化螺旋菌属相对丰度增长显著。微生物群落相似性和差异性分析结果表明,滤床微生物群落结构稳定,不受季节、温度的影响,尽管运行时长对滤床内部群落组成造成一定差异,但并不存在显著性。本研究以梁塘河水系为例开展水环境生态治理,一方面旨在提升梁塘河水环境质量,另一方面也为平原河网地区,尤其是位于城区的平原河网地区河流生态治理提供示范参考。     

Assessment of nematode community structure as a bioindicator in river monitoring

Nematode communities from river water and sediments were assessed for the abundance, feeding types, maturity indices and nematode channel ratio (NCR). The sampling sites studied included different levels of pollution and contamination from agricultural, industrial and sewage sources. The nematode abundance found in the sediment samples was more than that in the water samples. The lowest nematode abundance in sediment samples and the lowest NCR in water samples were both found at the industrial pollution site. Water samples showed positive correlation between the NCR and river pollution index (RPI). Mean maturity indices in sediment samples were inversely correlated with RPI. The pollutant source determined the relationship between NCR and pollution level, while maturity index always showed negative correlation with pollutant level regardless of the pollutant sources. The nematode abundance and its community structure were both reliable bioindicators for monitoring long-term river pollution in both qualitative and quantitative aspects.     

应用大型底栖无脊椎动物评价常州市“清水工程生态修复”示范河道的研究

通过连续两年对常州市19条"清水工程生态修复"示范河道大型底栖无脊椎动物(以下简称底栖动物)的调查,了解市区河道底栖动物群落现状及发展趋势,同时从底栖动物群落多样性的角度评价各河道生态修复的效果,并利用污染生物效应指数(BPI)评估河道水质及生态变化发展趋势。结果发现,各调查河道底栖动物群落结构和多样性的指标与污染生物效应评价结果相互印证,保持高度一致性。2011年各河道的底栖动物群落结构完整性、种群多样性均较2010年有所提升,BPI则较2010年有所下降。说明在这些河道实施的生态修复工程具有一定成效,有望实现城市河道水体生态循环系统的全面恢复。     

Evaluating the distribution and potential ecological risks of heavy metal in coal gangue

Environmental Science and Pollution Research - The heavy metals, which derived from accumulated coal gangue, are important source of environmental pollution. In this study, coal gangue dumps,...