Assessments of natural and anthropogenic influences on water chemistry in the upper Nakdong River,South Korea

Abstract

The purpose of this study is to evaluate what sources principally affect the chemical compositions in the catchment of the upper Nakdong River, South Korea where bedrock mostly consists of silicates as a natural factor. From October 7^th to 9^th, 2015, thirty-three water samples were collected, including samples from tributaries which run alongside mines. We analyzed the major anions, cations, trace elements and water isotopes of the samples and the analyzed data are divided into four groups by principle component analysis (PCA). We determined that most of the water samples are influenced by water-rock interactions when we consider the PCA results and the chemical weathering equation line. However, six samples have excess concentrations of sulfate and plot below the equation line. These samples were mostly from streams beside a zinc-cadmium smelter, which was also consistent with the PCA results. Samples near populated area could also be separated into a group via domestic pollution. Based on the PCA and chemical results, the chemical compositions of the river can be affected by two anthropogenic inputs: mine wastes and domestic contaminants.     

Groundwater quality assessment and pollution source apportionment in an intensely exploited region of northern China

Deterioration in groundwater quality has attracted wide social interest in China. In this study, groundwater quality was monitored during December 2014 at 115 sites in the Hutuo River alluvial-pluvial fan region of northern China. Results showed that 21.7% of NO₃ ^? and 51.3% of total hardness samples exceeded grade III of the national quality standards for Chinese groundwater. In addition, results of gray relationship analysis (GRA) show that 64.3, 10.4, 21.7, and 3.6% of samples were within the I, II, IV, and V grades of groundwater in the Hutuo River region, respectively. The poor water quality in the study region is due to intense anthropogenic activities as well as aquifer vulnerability to contamination. Results of principal component analysis (PCA) revealed three major factors: (1) domestic wastewater and agricultural runoff pollution (anthropogenic activities), (2) water-rock interactions (natural processes), and (3) industrial wastewater pollution (anthropogenic activities). Using PCA and absolute principal component scores-multivariate linear regression (APCS-MLR), results show that domestic wastewater and agricultural runoff are the main sources of groundwater pollution in the Hutuo River alluvial-pluvial fan area. Thus, the most appropriate methods to prevent groundwater quality degradation are to improve capacities for wastewater treatment and to optimize fertilization strategies.     

Applicability of Fenton and H2O2/UV reactions in the treatment of tannery wastewaters

In this paper we evaluated the H2O2/UV and the Fenton's oxidation processes for the treatment of tannery wastewater under different experimental conditions. Efficiencies were judged by the amounts of organic substances degraded or eliminated under these treatment techniques. Daphnia magna and Vibrio fischeri were used to monitor toxicity. Organic compounds contained in the untreated and treated tannery wastewater were determined and identified using substance specific techniques. Gas chromatography-mass spectrometry (GC-MS) in positive electron impact (EI(+)) mode was applied to determine volatile organics. Atmospheric pressure ionization (API) mass (MS) and tandem mass spectrometry (MS-MS) coupled with flow injection analysis (FIA) or liquid chromatography (LC) were used to detect or identify polar organic pollutants. The experimental results indicated that both oxidation processes--H2O2/UV at pH 3 and Fenton at pH 3.5--are able to reduce TOC content by mineralisation of the organic compounds.     

Detailed PCB congener patterns in incinerator flue gas and commercial PCB formulations (Kanechlor)

In this study, we determined the detailed PCB congener patterns in flue gases from eight incinerators and four commercial PCB formulations (Kanechlors). About 160 PCB peaks were identified in samples using a DB-5 column and HRGC/HRMS. The concentration of incinerator stack emission gas ranged from 0.02 to 44 ngWHO-TEQ/Nm3. The ratios of dioxin-like PCBs in the total PCB concentration were from 3.4% to 25.7% and from 0.63% to 9.1% in stack emission gases and Kanechlor samples, respectively. The PCB congener profiles of Kanechlor samples were similar to those of previous studies. To determine characteristic congeners in flue gas and Kanechlor samples, principal component analysis (PCA) of the data was conducted using STATISTICA for Windows 5.0J (StatSoft, Inc.). As a result, we obtained four principal components (PCs) and accounted for 74% of the total variance. PC 1 was interpreted combustion, PC 2 and PC 3 were interpreted the difference in the number of substituted chlorines and, PC 4 could not be determined. Moreover, we obtained three groups according to the PCB congeners pattern among samples by PCA. These specific congeners that represent characteristics of each class were identified. These data will be useful for the source analysis of PCBs in the environment.     

基于主成分分析法的辽河水体中溶解性金属来源分析

在测定辽河水体中几种主要的溶解性金属(包括7种重金属)的含量和分析其空间分布特征的基础上,运用主成分分析(PCA)法分析了金属的可能来源。结果表明,辽河水体中溶解性金属的平均浓度为Al>Cu>Zn>Cr>Hg>As>Pb>Cd,与欧美发达国家的主要水体相比,辽河水体的金属污染状况总体较重;辽河水体中溶解性金属的污染来源主要分两类:农业面源和工业废水污染源,工业综合污染源;根据主成分得分系数可知,采样点2(通江口)、3(三合屯)、7(朱尔山)的金属污染主要来源于农业面源和工业废水污染源;采样点6(药王庙)的金属污染主要来源于工业综合污染源;基于PCA法的金属来源分析对辽河流域水体金属污染治理对策的制定有着重要的指导意义。     

Effects of wastewater disinfection on waterborne bacteria and viruses.

Wastewater disinfection is practiced with the goal of reducing risks of human exposure to pathogenic microorganisms. In most circumstances, the efficacy of a wastewater disinfection process is regulated and monitored based on measurements of the responses of indicator bacteria. However, inactivation of indicator bacteria does not guarantee an acceptable degree of inactivation among other waterborne microorganisms (e.g., microbial pathogens). Undisinfected effluent samples from several municipal wastewater treatment facilities were collected for analysis. Facilities were selected to provide a broad spectrum of effluent quality, particularly as related to nitrogenous compounds. Samples were subjected to bench-scale chlorination and dechlorination and UV irradiation under conditions that allowed compliance with relevant discharge regulations and such that disinfectant exposures could be accurately quantified. Disinfected samples were subjected to a battery of assays to assess the immediate and long-term effects of wastewater disinfection on waterborne bacteria and viruses. In general, (viable) bacterial populations showed an immediate decline as a result of disinfectant exposure; however, incubation of disinfected samples under conditions that were designed to mimic the conditions in a receiving stream resulted in substantial recovery of the total bacterial community. The bacterial groups that are commonly used as indicators do not provide an accurate representation of the response of the bacterial community to disinfectant exposure and subsequent recovery in the environment. UV irradiation and chlorination/dechlorination both accomplished measurable inactivation of indigenous phage; however, the extent of inactivation was fairly modest under the conditions of disinfection used in this study. UV irradiation was consistently more effective as a virucide than chlorination/dechlorination under the conditions of application, based on measurements of virus (phage) diversity and concentration. Taken together, and when considered in conjunction with previously published research, the results of these experiments illustrate several important limitations of common disinfection processes as applied in the treatment of municipal wastewaters. In general, it is not clear that conventional disinfection processes, as commonly implemented, are effective for control of the risks of disease transmission, particularly those associated with viral pathogens. Microbial quality in receiving streams may not be substantially improved by the application of these disinfection processes; under some circumstances, an argument can be made that disinfection may actually yield a decrease in effluent and receiving water quality. Decisions regarding the need for effluent disinfection must account for site-specific characteristics, but it is not clear that disinfection of municipal wastewater effluents is necessary or beneficial for all facilities. When direct human contact or ingestion of municipal wastewater effluents is likely, disinfection may be necessary. Under these circumstances, UV irradiation appears to be superior to chlorination in terms of microbial quality and chemistry and toxicology. This advantage is particularly evident in effluents that contain appreciable quantities of ammonia-nitrogen or organic nitrogen.     

Investigating the fate of iodinated X-ray contrast media iohexol and diatrizoate during microbial degradation in an MBBR system treating urban wastewater

The capability of a moving bed biofilm reactor (MBBR) to remove the iodinated contrast media (ICM) iohexol (IOX) and diatrizoate (DTZ) from municipal wastewater was studied. A selected number of clones of microorganisms present in the biofilm were identified. Biotransformation products were tentatively identified and the toxicity of the treated effluent was assessed. Microbial samples were DNA-sequenced and subjected to phylogenetic analysis in order to confirm the identity of the microorganisms present and determine the microbial diversity. The analysis demonstrated that the wastewater was populated by a bacterial consortium related to different members of Proteobacteria, Firmicutes, and Nitrisporae. The optimum removal values of the ICM achieved were 79 % for IOX and 73 % for DTZ, whereas 13 biotransformation products for IOX and 14 for DTZ were identified. Their determination was performed using ultra-performance liquid chromatography–tandem mass spectrometry. The toxicity of the treated effluent tested to Daphnia magna showed no statistical difference compared to that without the addition of the two ICM. The MBBR was proven to be a technology able to remove a significant percentage of the two ICM from urban wastewater without the formation of toxic biodegradation products. A large number of biotransformation products was found to be formed. Even though the amount of clones sequenced in this study does not reveal the entire bacterial diversity present, it provides an indication of the predominating phylotypes inhabiting the study site.     

Chlorinated solvents in a petrochemical wastewater treatment plant: an assessment of their removal using self-organising maps

The self-organising map approach was used to assess the efficiency of chlorinated solvent removal from petrochemical wastewater in a refinery wastewater treatment plant. Chlorinated solvents and inorganic anions (11 variables) were determined in 72 wastewater samples, collected from three different purification streams. The classification of variables identified technical solvents, brine from oil desalting and runoff sulphates as pollution sources in the refinery, affecting the quality of wastewater treatment plant influent. The classification of samples revealed the formation of five clusters: the first three clusters contained samples collected from the drainage water, process water and oiled rainwater treatment streams. The fourth cluster consisted mainly of samples collected after biological treatment, and the fifth one of samples collected after an unusual event. SOM analysis showed that the biological treatment step significantly reduced concentrations of chlorinated solvents in wastewater.     

Identifying natural and anthropogenic sources of metals in urban and rural soils using GIS-based data,PCA, and spatial interpolation

Determining sources of neurotoxic metals in rural and urban soils is important for mitigating human exposure. Surface soil from four areas with significant clusters of mental retardation and developmental delay (MR/DD) in children, and one control site were analyzed for nine metals and characterized by soil type, climate, ecological region, land use and industrial facilities using readily available GIS-based data. Kriging, principal component analysis (PCA) and cluster analysis (CA) were used to identify commonalities of metal distribution. Three MR/DD areas (one rural and two urban) had similar soil types and significantly higher soil metal concentrations. PCA and CA results suggested that Ba, Be and Mn were consistently from natural sources; Pb and Hg from anthropogenic sources; and As, Cr, Cu, and Ni from both sources. Arsenic had low commonality estimates, was highly associated with a third PCA factor, and had a complex distribution, complicating mitigation strategies to minimize concentrations and exposures.     

Reduction of photoreactivation with the combined UV/peracetic acid process or by delayed exposure to visible light.

Photoreactivation of microorganisms following UV inactivation is a well-known, but complex, phenomenon. It is affected by several factors, including UV fluence, wavelength, light intensity, and exposure time to photoreactivating light. The effect on photoreactivation of a combined peracetic acid (PAA)/UV process has not been investigated. Accordingly, this study compared the degree of photoreactivation, under both sunlight and artificial lights, following UV and combined PAA/UV inactivation of fecal coliforms. Effluent samples from the Montreal Wastewater Treatment Plant (MWTP) (Quebec, Canada) were exposed, for 3 hours, to both low- and high-intensity artificial lights and sunlight. All resulted in similar photoreactivation levels. However, average photoreactivation for UV-treated wastewater samples was 1.2 logs, compared with 0.1 log for the combined PAA/UV treatment. Hence, the use of PAA in combination with UV can significantly reduce the potential for photoreactivation. To simulate the photoreactivation conditions of the MWTP effluent (which passes through a 4-km outfall tunnel with approximately 3 hours detention time), UV-treated samples were kept in the dark for 3 hours before photoreactivating light exposure. After this period, photoreactivation levels were close to zero. Hence, the effects of photoreactivation may be diminished by use of a combined disinfection scheme and/or by delaying exposure of the disinfected wastewater to light.     

Combination of in vitro bioassays for the determination of cytotoxic and genotoxic potential of wastewater, surface water and drinking water samples

In this study we evaluated genotoxicity and cytotoxicity of native samples of wastewaters (15 samples), surface waters (28 samples) and potable waters (8 samples) with the SOS/umuC assay with Salmonella typhimurium TA1535/pSK1002 and MTT assay with human hepatoma HepG2 cells. The genotoxicity of selected samples was confirmed with the comet assay with HepG2 cells. In the SOS/umuC assay 13 out of the 51 samples were genotoxic: two effluent samples from chemical industry; one sample of wastewater treatment plant effluent; two hospital wastewater samples; three river water samples and four lake water samples. Six samples were cytotoxic for HepG2 cells: both effluent samples of chemical industry, two wastewater treatment plant effluent samples, and two river water samples, however, only the chemical industry effluent samples were genotoxic and cytotoxic, indicating that different contaminants are responsible for genotoxic and toxic effects. Comparing genotoxicity of river and lake water samples with the chemical analytical data of the presence of the residues of pharmaceutical and personal care products (non-steroidal anti-inflammatory drugs, UV filters and disinfectants) in these samples, indicated that the presence of UV filters might be linked to the genotoxicity of these samples. The results showed that the application of the bacterial SOS/umuC assay and mammalian cell assays (MTT and comet assay) with HepG2 cells was suitably sensitive combination of assays to monitor genotoxicity and cytotoxicity of native samples of wastewaters and surface waters. With this study we also confirmed that the toxicity/genotoxicity bioassays should be an integral tool in the evaluation of toxicity of complex wastewaters before the release into environment, as well as for the monitoring of surface water quality, providing data useful in risk assessment.     

Examination of dioxin fluxes recorded in dated aquatic-sediment cores in the Kanto region of Japan using multivariate data analysis

Past dioxin (coplanar polychlorinated biphenyl (Co-PCB), 2,3,7,8-substituted polychlorinated dibenzo-p-dioxin (PCDD) and 2,3,7,8-substituted polychlorinated dibenzofuran (PCDF)) fluxes recorded in dated aquatic-sediment cores were analyzed using principal component analysis (PCA). The data set consisted of samples from four cores collected from the Kanto region of Japan. Time trends and spatial differences in the dioxin flux were examined, and the potential relationship to emission sources was investigated. Twenty-five compounds and 58 core slices, corresponding to the later half of the 20th century, were subjected to the analysis. The PCA of both log-transformed and maximum-value-standardized data successfully divided the dioxin compounds into a small number of groups, and three similar clusters of Co-PCBs, PCDDs and penta- to hepta-CDFs were identified. PCB formulations used in the past are judged to have been responsible for the major part of the Co-PCB flux recorded in the sediment cores. However, the relationship to emission sources needs further investigation. It is suggested that most 2,3,7,8-substituted PCDDs and PCDFs are different from Co-PCBs in their emission sources or movements in the environment. The subcore clusters obtained from the PCA of log-transformed data show that the cores from different sampling areas exhibited distinct dioxin fluxes and compositions. Common time trends among the cores were more effectively summarized by the PCA of maximum-value-standardized data focusing on relative time trends. PC scores show that recently the flux of each dioxin compound in the four cores has been generally declining after having reached a peak.     

Monitoring of effluent DOM biodegradation using fluorescence, UV and DOC measurements

The potential of effluent DOM to undergo microbial degradation was assessed in batch experiments. Effluent samples from Haifa wastewater treatment plant and Qishon reservoir (Greater Haifa wastewater reclamation complex, Israel) were incubated either with effluent or soil microorganisms for a period of 2-4 months and were characterized by dissolved organic carbon contents (DOC), UV(254) absorbance and by fluorescence excitation-emission matrices. Three main fluorescence peaks were identified that can be attributed to humic/fulvic components and "protein-like" structures. During biodegradation, specific fluorescences (F/DOC) of the three peaks were increased at various extents, suggesting selective degradation of non-fluorescing constituents. In some cases increase in the effluent fluorescence (F) was observed thus proposing (i) the formation of new fluorescing material associated with DOM biodegradation and/or (ii) degradation of certain organic components capable of quenching DOM fluorescence. Based on the ratio between fluorescence intensity and UV(254), different biodegradation dynamics for fluorescent DOM constituents as compared with other UV-absorbing molecules was delineated. Overall, about 50% of the total DOM was found to be readily degradable such that residual resistant DOC levels were between 8 and 10 mg l(-1). Enhanced levels of residual DOM in effluent-irrigated soils may contribute to the DOM pool capable of carrying pollutants to groundwater.     

Ecological risk assessment using RAPD and distribution pattern of a rare and endangered species

Environmental and ecological risk assessment always provide useful evidence for characterisation and conservation of the rare and endangered species, e.g. seven-son flower (Heptacodium miconioides Rehd.). Seven-son flower is a deciduous arbor species, but endangered, with a restricted distribution in the subtropical forests of China. Genetic risk assessment of 56 samples of the flower from nine main populations in Zhejiang (China) was carried out by using the RAPD analysis. This was to study the ecological characteristics, spatial distribution and genetic features of the seven-son flower communities and establish a feasible conservation plan. Twenty-one primers screened from 50 yielded 119 RAPD bands with 72 polymorphic products and 60.50% of total bands. The genetic variation was found to be partitioned mainly among rather than within populations. Percentages of genetic diversity among populations were quantified by Shannon index and the Nei's gene diversity coefficient. AMOVA also demonstrated that these relict populations were highly differentiated. The high level of population variation observed is in contrast to that expected for a primarily outcrossed woody perennial plant, and suggests that there may be a degree of inbreeding. The dendrogram constructed from genetic distances through UPGMA method based on Nei's coefficients shows two groups among nine population clusters, which is further supported by a principle components analysis (PCA) of RAPD phenotypic data. The analysis showed that the biologic characteristics and habitat fragmentation were the reasons of the great genetic variation among populations. Some strategies of its genetic diversity conservation were proposed in the fragmented habitats based on its genetic structure and its biological characteristics in this study.     

Treatment of Arctic wastewater by chemical coagulation,UV and peracetic acid disinfection

Conventional wastewater treatment is challenging in the Arctic region due to the cold climate and scattered population. Thus, no wastewater treatment plant exists in Greenland, and raw wastewater is discharged directly to nearby waterbodies without treatment. We investigated the efficiency of physicochemical wastewater treatment, in Kangerlussuaq, Greenland. Raw wastewater from Kangerlussuaq was treated by chemical coagulation and UV disinfection. By applying 7.5 mg Al/L polyaluminium chloride (PAX XL100), 73% of turbidity and 28% phosphate was removed from raw wastewater. E. coli and Enterococcus were removed by 4 and 2.5 log, respectively, when UV irradiation of 0.70 kWh/m³ was applied to coagulated wastewater. Furthermore, coagulated raw wastewater in Denmark, which has a chemical quality similar to Greenlandic wastewater, was disinfected by peracetic acid or UV irradiation. Removal of heterotrophic bacteria by applying 6 and 12 mg/L peracetic acid was 2.8 and 3.1 log, respectively. Similarly, removal of heterotrophic bacteria by applying 0.21 and 2.10 kWh/m³ for UV irradiation was 2.1 and greater than 4 log, respectively. Physicochemical treatment of raw wastewater followed by UV irradiation and/or peracetic acid disinfection showed the potential for treatment of arctic wastewater.     

Dimension reduction and source identification for multispecies groundwater contamination

Assessment of chemical contamination at large industrial complexes with long and sometimes unknown histories of operation represents a challenging environmental problem. The spatial and temporal complexity of the contaminant may be due to changes in production processes, differences in the chemical transport, and the physical heterogeneity of the soil and aquifer materials. Traditional mapping techniques are of limited value for sites where dozens of chemicals with diverse transport characteristics may be scattered over large spatial areas without documentation of disposal histories. In this context, a site with a long and largely undocumented disposal history of shallow groundwater contamination is examined using principal component analysis (PCA). The dominant chemical groups and chemical "modes" at the site were identified. PCA results indicate that five primary and three transition chemical groups can be identified in the space of the first three eigenvectors of the correlation matrix, which account for 61% of the total variance of the data. These groups represent a significant reduction in the dimension of the original data (116 chemicals). It is shown that each group represents a class of chemicals with similar chemo-dynamic properties and/or environmental response. Finally, the groups are mapped back onto the site map to infer delineation of contaminant source areas for each class of compounds. The approach serves as a preliminary step in subsurface characterization, and a data reduction strategy for source identification, subsurface modeling and remediation planning.     

Phototransformation of herbicide metsulfuron methyl

Phototransformation of the herbicide metsulfuron methyl was investigated on glass surface under sunlight and ultraviolet (UV) light and compared with dark condition. The half-lives of metsulfuron methyl under UV light and sunlight were found to be 0.5 and 7.8 days respectively. Rate of phototransformation followed first order kinetics with significant correlation coefficient. The major photoproducts were identified as methyl-2-sulfonyl-amino-benzoate, 2-amino-6-methoxy-4-methyltriazine and saccharin (O-sulfobenzoimide). Various metabolites from this study were identified by high performance liquid chromatography (HPLC). Authentic samples required for HPLC comparison were prepared in laboratory and characterized on the basis of nuclear magnetic resonance (NMR) and infra red (IR) spectral data. These metabolites were also identified from metsulfuron methyl treated wheat field soil.     

Point-of-use water disinfection using UV light-emitting diodes to reduce bacterial contamination

The treatment process described in this research explores the impact of exposing water samples containing fecal coliforms to the radiation produced by single ultraviolet (UV) light-emitting diodes (LEDs) operating at 265 nm. UV LEDs are long lasting, compact in size and produce more efficient light output than traditional mercury-vapour bulbs, making them ideal for application in point-of-use disinfection systems, such as in remote areas. In this study, contaminated water samples containing either a pure culture of Escherichia coli or tertiary effluent from the City of Regina Wastewater Treatment Plant were used to study the application and efficiency of using UV LEDs for water disinfection. The results indicate that bacterial inactivation was achieved in a time-dependent manner, with 1- and 2.5-log E. coli reductions in water following 20 and 50 min of UV LED exposure, respectively. Ultraviolet radiation was less effective in reducing coliform bacteria in wastewater samples due to the elevated turbidity levels. Further work remains to be completed to optimize the application of UV LEDs for point-of-use disinfection systems; however, the results from this study support that bacterial inactivation using UV LEDs is possible, meriting further future technological development of the LEDs.     

Phototransformation of herbicide metsulfuron methyl

Phototransformation of the herbicide metsulfuron methyl was investigated on glass surface under sunlight and ultraviolet (UV) light and compared with dark condition. The half-lives of metsulfuron methyl under UV light and sunlight were found to be 0.5 and 7.8 days respectively. Rate of phototransformation followed first order kinetics with significant correlation coefficient. The major photoproducts were identified as methyl-2-sulfonyl-amino-benzoate, 2-amino-6-methoxy-4-methyltriazine and saccharin (O-sulfobenzoimide). Various metabolites from this study were identified by high performance liquid chromatography (HPLC). Authentic samples required for HPLC comparison were prepared in laboratory and characterized on the basis of nuclear magnetic resonance (NMR) and infra red (IR) spectral data. These metabolites were also identified from metsulfuron methyl treated wheat field soil.