River Surface Water Research Articles

Ecotoxicological Assessment of the Doce River Surface Water After the Fundão Dam Collapse

On 5 November 2015, the Samarco Fe ore mining operations released approximately 50 million cubic meters of mining waste into the environment, due to a dam collapse. Aiming at understanding the potential effects on the Doce River, different regions of the course of tailings were monitored using acute and chronic ecotoxicological tests with 4 species: Ceriodaphnia dubia, Daphnia similis, Danio rerio, and Vibrio fischeri. The results showed no acute toxicity for water column organisms. However, chronic toxicity was observed with the tests with the microcrustacean C. dubia, mainly related to the physical effects of the passage of flood wave and increased suspended solids, given that toxicity was reduced after filtering the samples. The results showed different magnitudes of impact among the upper, middle, and lower Doce River, with greater impact close to the dam failure area. Integr Environ Assess Manag 2020;16:608-614. © 2020 SETAC.

Determination of main anthropogenic impacts and environmental risks for the Kryvyi Torets river basin (based on the EU Support Program for Ukrainian water policy)

The relevance of the study consists in the need for implementation of the calculation methods proposed by the EU Water Framework Directive. The methods are aimed at assessing the anthropogenic impacts аnd establishing the risks of not achieving the environmental objectives for different water bodies. The object of the study is the Kryvyi Torets River, one of the most polluted rivers in Ukraine. The study focuses on the indicators of anthropogenic impact affecting the quality of the river's surface waters and the identification of the risks of not ensuring a good ecological status of its basin.
 The work aims at determining the main anthropogenic impacts and their effects on the surface water status of the SWM of the Kryvyi Torets River in town of Druzhkivka and assessing the risk of failure to achieve the environmental objectives. For this purpose we used the data of hydrochemical observations up to 2018 inclusive which were compared with the established threshold values of the anthropogenic impacts. According to the Order of the Ministry of Ecology and Natural Resources of Ukraine No. 4 as of January 14, 2019, the monitoring point of the Kryvyi Torets River – town of Druzhkivka – belongs to a "heavily modified" surface water massif. In accordance with the hydromorphological monitoring effort for the Don RBD (river basin district) and the assessment of hydromorphological indicators within the framework of the project "Assistance in expanding the environmental monitoring system in the Donbas" implemented by the OSCE Project Co-ordinator in Ukraine the research allowed establishing the fact that the SWM of the Kryvyi Torets River is referred to as “a heavily modified” due to large-scale channelization activities. Based on the "Guidelines for determining the main anthropogenic impacts and their effects on the state of surface waters" the proposed study allowed evaluation of the anthropogenic impacts from the point sources (wastewater discharges) and diffuse sources (crop production and livestock farming). It was established that there is no environmental risk resulting from the volume of wastewater inflow to the annual runoff of the Kryvyi Torets River. However, a risk of failure to ensure a good environmental status was found in relation to the volume of wastewater inflow from point sources and the influence of crop production and livestock farming. According to chemical and physico-chemical indicators, a risk of not achieving environmental objectives was determined. According to chemical and physicochemical parameters, exceeding the limit values is set for ammonium. Identification of the environmental risk zones and percentiles was performed using the integrated curves of hydrochemical indicators distribution for the section of the Kryvyi Torets River at town of Druzhkivka.
 The largest values of anthropogenic impact correspond to wastewater discharge (Point Source Pollution) and livestock farming (Diffuse Source Pollution).

Relationship Between CO2 and CH4 Emissions in Urban Rivers and Sewage Discharging from a Municipal Drainage Network

The increasing carbon emission of polluted rivers in urban areas is an environmental problem commonly faced by many cities in China, especially the megacities with vast populations. In this study, two typical rivers located in the megacity of Shanghai, including the suburban river network R1 and urban river R2 (in the central city), were investigated for their emission characteristics of CO2 and CH4 in dry and wet weather. We also analyzed the relationship between the state and type of river pollution and CO2 and CH4 emissions, and further explained the mechanisms of CO2 and CH4 emissions in urban rivers impacted by sewage discharged from the municipal drainage network. The results show that:① In dry weather, the average fluxes of CO2 and CH4 emitted from the river in the central city (R2) were (2.48±1.02) mmol·(m2·h)-1 and (1.21×10-2±0.71×10-2) mmol·(m2·h)-1, respectively. The average fluxes of CO2 and CH4 from the suburban river (R1) network were (1.53±0.39) mmol·(m2·h)-1 and (9.26×10-3±9.18×10-3) mmol·(m2·h)-1, respectively. In wet weather, affected by sewage from the municipal drainage network, CH4 flux emitted from the surface water of the R2 river downstream of the pump station P increased by up to 119 times that in dry weather. ② Global carbon emission statistics, involving the data from our study and from other rivers around the world, seemed to imply a relationship between the carbon emission flux and the pollution state of an urban river, i.e., the rivers with high pollution showed significant carbon emission intensity. ③ According to the results of PCA, organic matter can be an essential factor in driving the variation of carbon emissions, and this trend is evident in all the rivers in urban and suburban areas. The relationship between carbon emissions and nitrogen pollution in a river varies with different types of underlying riparian surface. In the less polluted urban rivers, the aquatic physical factor can also be an essential factor. ④ In the short term, with massive quantities of sewage discharged into urban rivers, a large amount of CH4 flux can be emitted. In contrast, in the long run, the carbon cycle can be strengthened when the carbon storage is increased, and thus the emission potential of CO2 and CH4 is improved.

Major and trace elements in the surface water of Tonle Sap Lake, Mekong River, and other tributary rivers in Cambodia.

To evaluate the seasonal water circulation of Tonle Sap Lake and its tributary rivers in Cambodia, the spatial distribution patterns of major and trace elements in surface water were investigated. Based on the similarity of the dissolved elemental concentrations, the water samples were mainly divided into the three groups: samples with relatively high percentages of Ca, Mo, and Sb (Subcluster B1); samples with high Si, Al, and Fe (B2); and samples with high Na, K, and Mg (B3). During the rainy season, the elemental composition of lake water (B1) appeared to be greatly influenced by the intrusion of water from the Mekong River (B1) through the Tonle Sap River (B1). During the dry season, the type of lake water shifted to B3, suggesting that the lake water stored during the rainy season was replaced by inflow from other tributaries and groundwater in its vicinity. Thus, the seasonal changes in the elemental composition of the lake water were largely controlled by surface water and groundwater circulation. The dissolved As concentration was higher in the lake water and during the dry season than that in the river water and during the rainy season, indicating the discharge of As from the lake's bottom sediment during the dry season. Although the redox cycling of Fe and Mn appeared to be less important due to the shallow water depth in the lake, there are potential risks of As poisoning induced by the formation of an anoxic water mass and increment in the concentration of phosphorus if eutrophication continues to progress.

Microbial community composition across a coastal hydrological system affected by submarine groundwater discharge (SGD).

Mobile Bay, the fourth largest estuary in the USA located in the northern Gulf of Mexico, is known for extreme hypoxia in the water column during dry season caused by NH4+-rich and anoxic submarine groundwater discharge (SGD). Nutrient dynamics in the coastal ecosystem point to potentially elevated microbial activities; however, little is known about microbial community composition and their functional roles in this area. In this study, we investigated microbial community composition, distribution, and metabolic prediction along the coastal hydrological compartment of Mobile Bay using 16S rRNA gene sequencing. We collected microbial samples from surface (river and bay water) and subsurface water (groundwater and coastal pore water from two SGD sites with peat and sandy lithology, respectively). Salinity was identified as the primary factor affecting the distribution of microbial communities across surface water samples, while DON and PO43- were the major predictor of community shift within subsurface water samples. Higher microbial diversity was found in coastal pore water in comparison to surface water samples. Gammaproteobacteria, Bacteroidia, and Oxyphotobacteria dominated the bacterial community. Among the archaea, methanogens were prevalent in the peat-dominated SGD site, while the sandy SGD site was characterized by a higher proportion of ammonia-oxidizing archaea. Cyanobium PCC-6307 and unclassified Thermodesulfovibrionia were identified as dominant taxa strongly associated with trends in environmental parameters in surface and subsurface samples, respectively. Microbial communities found in the groundwater and peat layer consisted of taxa known for denitrification and dissimilatory nitrate reduction to ammonium (DNRA). This finding suggested that microbial communities might also play a significant role in mediating nitrogen transformation in the SGD flow path and in affecting the chemical composition of SGD discharging to the water column. Given the ecological importance of microorganisms, further studies at higher taxonomic and functional resolution are needed to accurately predict chemical biotransformation processes along the coastal hydrological continuum, which influence water quality and environmental condition in Mobile Bay.

Изучение токсикологического состояния поверхностных вод реки Ашкадар с использованием методов биотестирования

Изучение токсикологического состояния поверхностных вод реки Ашкадар с использованием методов биотестирования

Anthropogenic Release and Distribution of Titanium Dioxide Particles in a River Downstream of a Nanomaterial Manufacturer Industrial Site

Several industries manufacture and process large quantities of engineered nanomaterials, thus increasing the potential for their environmental release during waste management and disposal. Herein, we quantified the release and spatial distribution of titanium dioxide nanomaterials (TiO2 NMs) emitted from an industrial waste stream that flows into a nearby river. Two sampling campaigns were carried out on the river in fall 2017 and spring 2018 at selected sites upstream and downstream of the Industrial Effluent and an urban wastewater treatment plant (WWTP). Significant Ti accumulation was detected in the sediments at the Industrial Effluent and WWTP sites for both fall and spring samples, with measured Ti concentrations of 75–193 mg Ti/kg reaching 21–55× that of the local background upstream. X-ray diffraction analysis confirmed the anatase and rutile mineralogy of the inputs. River surface waters were filtered on-site to distinguish between particulate (>0.20 μm), colloidal (0.02–0.20 μm), and dissolved and/or small nanoparticulate (NP) ( 0.20 μm), and that the particles sediment rapidly near the emission source and accumulate in the sediment.

Impacts of the Sanmenxia Dam on the Interaction between Surface Water and Groundwater in the Lower Weihe River of Yellow River Watershed

Sanmenxia Dam, one of the most controversial water conservancy projects in China, has seriously impacted the lower Weihe River of the Yellow River Watershed since its operation. At the Huaxian Station, the dam operation controls the surface water level and leads to the variation of the surface water–groundwater interaction relationship. The river channel switched from a losing reach during the early stage (1959) to a gaining reach in 2010 eventually. The comparison of tracer (Cl−, δ18O and δ2H) characteristics of surface water in successive reaches with that of ambient groundwater shows that the general interaction condition is obviously affected by the dam operation and the impact area can be tracked back to Weinan City, around 65 km upstream of the estuary of the Weihe River. The anthropogenic inputs (i.e., agricultural fertilizer application, wastewater discharge, and rural industrial sewage) could be responsible for the deterioration of hydro-environment during the investigation periods of 2015 and 2016, as the population and fertilizer consumption escalated in the last 60 years. The use of contaminated river water for irrigation, along with the dissolved fertilizer inputs, can affect the groundwater quality, in particular resulting in the NO3− concentrations ranging from 139.4 to 374.1 mg/L. The unregulated industrial inputs in some rural areas may increase the Cl− contents in groundwater ranging from 298.4 to 472.9 mg/L. The findings are helpful for the improved comprehensive understanding of impacts of the Sanmenxia Dam on the interaction between surface water and groundwater, and for improving local water resources management.

Cyanide Contamination of the Puyango-Tumbes River Caused by Artisanal Gold Mining in Portovelo-Zaruma, Ecuador.

To examine cyanide (CN-) contamination of a large river in southeastern Ecuador that has been severely impacted by the indiscriminate discharge of untreated gold processing effluents. Poor environmental stewardship of cyanide (CN-) use by 87 gold processing centers in Portovelo-Zaruma in southern Ecuador to leach residual gold from Hg-contaminated tailings has resulted in high CN- contamination of the Puyango-Tumbes River downstream from the centers. Free CN- concentrations were high in river surface waters for 50km below the processing plants, with the highest concentration 9088 times above the CCME standard of 5μg/L and 1136 times above the 24-h LC50 concentration of 40μg/L free CN- for some fish species. Due to cyanidation of mercury-contaminated tailings, the formation of Hg-CN complexes is a grave concern, as these complexes have been shown to be highly bioavailable. Preliminary tests conducted in a laboratory using bioassays with Danio rerio sp. and varying concentrations of synthetic Hg(CN)2 salt have shown significant THg bioaccumulation in muscle and kidney fish tissues exposed to concentrations >0.12mg/L. Furthermore, low MeHg results in fish tissues demonstrated little occurrence of methylation and that the bulk of the total mercury content was in the form of inorganic mercury. Although construction of a communal tailings facility (CTF) in Portovelo is a positive development to reduce riverine pollution, the requirement to truck tailings up to the CTF likely results in inadequate compliance of environmental regulations that are poorly enforced.

Distribution and sources of polycyclic aromatic hydrocarbons in the water column of Kongsfjorden, Arctic

Kongsfjorden is known for its characteristic multi-layer water mass formed by the convergence of freshwaters from nearby glaciers and rivers and saline water from the Atlantic and Arctic. The distribution of polycyclic aromatic hydrocarbons (PAHs) in the water column of Kongsfjorden was investigated and their potential sources were analyzed. The total concentrations of 16 PAHs in the surface seawater and river water were in the range of 33.4−79.8 ng/L (mean 48.5 ng/L) and 2.3−201.4 ng/L (mean 126.1 ng/L), respectively. Horizontally, PAHs were mainly concentrated around river estuaries and the glacier front in the dissolved phase. Vertically, the PAHs in the particulate phase followed surface-enrichment and depth-depletion patterns in most stations, with the maximum concentration found at 50 m depth in the central area of Kongsfjorden. The compositions of PAHs in seawater and rivers were similar, with two-ring and tricyclic PAHs comprising the majority of the dissolved and particulate phases. PAHs found in Kongsfjorden waters appeared to be derived from multiple sources such as petroleum and coal combustion. PAHs in the bay mouth of Kongsfjorden were mainly introduced by the West Spitsbergen Current and the Arctic waters, while in the inner bay, atmospheric deposition and local sources were the major contributors. The distribution of PAHs was mainly attributed to the suspended particulate distribution.

Pilot studies on the river water treatment using coagulation-UF membrane filtration and direct UF membrane filtration

The pilot tests of UF membrane filtration for river surface water were carried out with coagulation as a pre-treatment (test 1) and without coagulation (test 2). Both UF membrane filtrate water of the test 1 and the test 2 met drinking water quality standard in Vietnam. Additionally, the TMP and the filtration flow rate were kept stably during test periods without changes in operation conditions although the river water turbidity was varied due to heavy rain. It was indicated that the water treatment system can be simple by skipping coagulation and/or sedimentation as pre-treatments. The filtration flux of the test 1 and the test 2 were 138 L/m2 h and 93 L/m2 h, respectively. The flux was higher than the reported reference value indicating that the module number of modules required for the water treatment plant can be reduced by using the FG module. The test data of the test 2 was theoretically analysed by the equations based on Darcy’s low. The estimated TMP correlated highly with measured value (R2=0.71). The optimized parameters were used for the simulation of the operation. The simulation results indicated that the TMP before backwashing is increased around 35 kPa when the river water turbidity increased up to 500 NTU. It was indicated that the CIP interval should take into account the TMP increasing by turbidity variation.

A rapid, simple screening toxicity test using desiccated bdelloid rotifers: Rotifer Activity Inhibition Test (RAIT).

A protocol for an ultra-rapid screening toxicity test is described using the rotifer Philodina acuticornis/roseola. The test can be executed in 30 min starting from the rehydration of desiccated life stages called tuns. Philodina tuns remain viable for years when maintained dry and at low temperature. They are very useful for conducting toxicity tests because the test animals do not require cultivation and are available to initiate tests anytime and anywhere. The swimming/crawling activity of rehydrated Philodina tuns is used as an endpoint to compare activity in control dilution water with inhibition of activity in an environmental sample. The Rotifer Activity Inhibition Test (RAIT) estimates toxicity semi-quantitatively using four toxicity categories: non-toxic, slightly toxic, very toxic, and 100% toxic. As proof of principle, RAIT has been tested on environmental samples from a variety of habitats and RAIT results have been compared with those obtained from traditional toxicity tests with bacteria, algae, Daphnia, and fish. Broad congruence between the effect signals of the rapid RAIT screening test and traditional assays has been found for river surface waters, industrial wastewaters, and sludge leachates from waste water treatment plants. Rotifers are an important group of animals in aquatic and soil food webs, and RAIT is a welcome new method for simple, ultra-rapid, and low-cost toxicity screening with a representative of this ecologically important group.

Hospital wastewaters: A reservoir and source of clinically relevant bacteria and antibiotic resistant genes dissemination in urban river under tropical conditions.

The occurrence and dissemination of antibiotic resistant genes (ARGs) that are associated with clinical pathogens and the evaluation of associated risks are still under-investigated in developing countries under tropical conditions. In this context, cultivable and molecular approaches were performed to assess the dissemination of bacteria and the antibiotic resistance genes in aquatic environment in Kinshasa, Democratic Republic of the Congo. Cultivable approach quantified β-lactam, carbapenem resistant, and total Escherichia coli and Enterobacteriaceae in river sediments and surface waters that receive raw hospital effluents. The molecular approach utilized Quantitative Polymerase Chain Reaction (qPCR) to quantify the total bacteria and the richness of relevant bacteria (Escherichia coli, Enterococcus, and Pseudomonas), and antibiotic resistance genes (ARGs: blaOXA-48, blaCTX-M, blaIMP, blaTEM) in sediment samples. Statistical analysis were employed to highlight the significance of hospital contribution and seasonal variation of bacteria and ARGs into aquatic ecosystems in suburban municipalities of Kinshasa, Democratic Republic of the Congo. The contribution of hospitals to antibiotic resistance proliferation is higher in the dry season than during the wet season (p<0.05). Hospital similarly contributed Escherichia coli, Enterococcus, and Pseudomonas and ARGs significantly to the sediments in both seasons (p<0.05). The organic matter content correlated positively with E. coli (r=0.50, p<0.05). The total bacterial load correlated with Enterococcus, and Pseudomonas (0.49<r<0.69, p<0.05). Each ARG correlated with the total bacterial load or at least one relevant bacteria (0.41<r<0.81, p<0.05). Our findings confirm that hospital wastewaters contributed significantly to antibiotic resistance profile and the significance of this contribution increased in the dry season. Moreover, our analysis highlights this risk from untreated hospital wastewaters in developing countries, which presents a great threat to public health.

Patterns of nitrogen concentrations and their controls in two southern China urban river ecosystems

Urbanization influences both inorganic and organic nitrogen (N) forms in aquatic ecosystems, but most urban studies focus on these forms in isolation. This can have significant effects on N biogeochemical cycle, N budgets and N pollution abatement measures. In this regard, we conducted a comprehensive seasonal study to compare the patterns and controls of surface water inorganic and organic N forms between two contrasting Fuzhou river ecosystems in southern China. Surface waters of the urban Bailongjiang River (BJR) had significantly higher dissolved inorganic N (DIN; p < 0.001) and dissolved organic N (DON; p = 0.006) as well as total dissolved N (TDN; p < 0.001) than those of the suburban Wulongjiang River (WJR). This suggests that the BJR surface waters are currently experiencing elevated levels of anthropogenically driven N pollution, which can adversely affect the aquatic and human health. Surface waters during the summer were generally characterized by much lower N concentrations resulting from increased precipitation-driven dilution effects and temperature-induced biological activities than those across the other seasons (p < 0.05 in most cases). The ammonium-N (NH4+-N)/nitrate-N (NO3−-N) ratios were <1 whereas the DIN/DON ratios were >1, indicating the dominance of NO3−-N over NH4+-N in surface water DIN and DIN over DON in surface water TDN across rivers and seasons. In addition, the contributions of NH4+-N, NO3−-N and DON to the TDN followed the NO3−-N > DON > NH4+-N pattern in the BJR and WJR surface waters. During the entire course of the study, the concentrations of different surface water N forms were strongly positively correlated with each other (p < 0.05 in all cases), indicating that these investigated N forms were both influenced by urbanization-driven anthropogenic activities. Surface water N concentrations increased significantly with increasing precipitation and soil N concentrations (all p < 0.05). This suggests that increasing atmospheric N deposition and soil N pollution due to rapid urbanization will have dramatic consequences on surface water eutrophication. This study emphasizes that inorganic and organic N should be collectively examined for sustainable eutrophication abatement as their patterns in urban aquatic ecosystems are not only controlled by complex processes but also interdependent.

Compositions and spatio-temporal distributions of different nitrogen species and lability of dissolved organic nitrogen from the Dafengjiang River to the Sanniang Bay, China

Field investigations and incubation experiment were carried out in the Dafengjiang River (DFJR) and Sanniang Bay (SNB) surface water from September 2017 to July 2018 to study the composition and spatio-temporal distributions of different nitrogen (N) species, lability of dissolved organic N (DON), and contributions of different N species from the DFJR to the dissolved inorganic N (DIN) level in the SNB. The spatio-temporal distributions of different N species exhibited significant seasonal variation (p < 0.05). The average contribution of DIN, DON, and particulate nitrogen (PN) to TN was 31.91%, 46.57%, and 21.52%, respectively. Comparatively being the dominant form of N in the study area, the average lability of DON across the incubation sites D1, D5 and D7 ranged from 72%–79%. DIN, DON, and PN from the DFJR respectively contributed to 55.95%, 7.03%, and 5.63% of water quality in the SNB.

Prevalence and seasonal dynamics of blaCTX-M antibiotic resistance genes and fecal indicator organisms in the lower Lahn River, Germany.

Antibiotic-resistant bacteria represent an emerging global health problem and are frequently detected in riverine environments. Analyzing the occurrence of corresponding antibiotic-resistant genes in rivers is of public interest as it contributes towards understanding the origin and dissemination of these emerging microbial contaminants via surface water. This is critical for devising strategies to mitigate the spread of resistances in the environment. Concentrations of blaCTX-M antibiotic resistance genes were quantified weekly over a 12-month period in Lahn River surface water at two sampling sites using quantitative real-time PCR. Gene abundances were statistically assessed with regard to previously determined concentrations of fecal indicator organisms Escherichia coli, intestinal enterococci and somatic coliphages, as well as influential environmental factors. Similar seasonal patterns and strong positive correlations between fecal indicators and blaCTX-M genes indicated identical sources. Accordingly, linear regression analyses showed that blaCTX-M concentrations could largely be explained by fecal pollution. E. coli provided the best estimates (75% explained variance) at the upstream site, where proportions of blaCTX-M genes in relation to fecal indicator organisms were highest. At this site, rainfall proved to be more influential, hinting at surface runoff as an emission source. The level of agricultural impact increased from downstream to upstream, linking increasing blaCTX-M concentrations after rainfall events to the degree of agricultural land use. Exposure assessment revealed that even participants in non-swimming recreational activities were at risk of incidentally ingesting blaCTX-M genes and thus potentially antibiotic resistant bacteria. Considering that blaCTX-M genes are ubiquitous in Lahn River and participants in bathing and non-bathing water sports are at risk of exposure, results highlight the importance of microbial water quality monitoring with an emphasis on antibiotic resistance not only in designated bathing waters. Moreover, E. coli might serve as a suitable estimate for the presence of respective antibiotic resistant strains.

Impact of Microplastic Fibers from the Degradation of Nonwoven Synthetic Textiles to the Magdalena River Water Column and River Sediments by the City of Neiva, Huila (Colombia)

Magdalena River surface water and shoreline sediments were sampled for microplastic particles at three locations in the city of Neiva, Colombia: upstream, city center, and downstream of the raw wastewater outflow. The absence of an industrial and manufacturing sector in Neiva provided an opportunity to assess the impact of upstream agricultural practices, as well as municipal activities such as wastewater outflow and laundry washing, on the quantity, polymer composition, and morphology of microplastic particles produced per capita and entering a river system. Microplastic particle concentrations increased with downstream distance, with microfiber concentrations ranging from 0.097 to 0.135 fibers/L in the river water and 25.5 to 102.4 fibers/kg in shoreline sediment. Microplastic fragment concentrations were 0.013–0.028 fragments/L in surface water and 10.4–12.7 fragments/kg of sediment. Raman microscope and scanning electron microscopy identified the relative composition of the polymers comprising the microplastic particles was similar regardless of sampling site or whether the sample was collected from the surface water or shoreline sediments, with polypropylene and polyethylene comprising at least 75% of the total polymers in all samples. Average fiber widths of &lt; 20 µm in all but one sample, along with the lack of acrylic and polyester fibers used predominantly in woven synthetic textiles, indicated that the degradation of nonwoven synthetic textiles is the predominant origin of these microplastic fibers in the Magdalena River.

Chemometrics characterization of The Llobregat river dissolved organic matter

The potential use of multivariate chemometric methods for the investigation of the dissolved organic matter (DOM) sources in surface river waters monitored by UV absorbance and excitation-emission fluorescence spectroscopy is shown. The Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) method is applied to the analysis of the excitation-emission multidimensional data matrices acquired at ten different river sampling sites along the basin of the Llobregat river (located at the north-west of the Iberian Peninsula), from its origin to its mouth, during three different monitoring campaigns. The results obtained by MCR-ALS provided information about the compositional changes of the different DOM sources (i.e. humic-, fulvic- or protein-like sources) present in the investigated river samples, about their site distribution along the river basin and about their changes in three different monitoring campaigns. Eight different MCR-ALS components were resolved describing several types of DOM, with different excitation and emission spectra and with distinct distribution profiles along the river sampling sites. A comparative study of each single sampling site describing the changes in their DOM composition during the three monitoring campaigns was also performed.

Ecological state of surface waters of rivers in industrial cities

The paper analyzes the chemical composition of the surface waters of a river flowing through an industrial city. Samples were taken in the Ussuri River, flowing through the city of Lesozavodsk. Four factors were derived that describe 78% of the variance of the variables. The first factor is associated with elements such as oxygen, BOD5 (Biological Oxygen Demand in 5 days), NH4, Fe, as well as phenols. Oil products and SSAS (Synthetic Surface-Active Substance) stood out in the second factor. The third factor is related to COD (Chemical Oxygen Demand), and NO3. Suspension and copper stood out as the fourth factor.

Evolution and variation characteristics of the recorded runoff for the major rivers in China during 1956—2018

Surface water is a key natural resources and a restrictive element to maintain regional ecological balance and support development of social economy. River runoff is the main form of surface water resources. Variation of the both river runoff and surface water will directly influence water resources management of a basin. Based on the annual report series of water resources and the recorded runoff of 10 representative hydrometric stations on major rivers in China, the variations of the surface water resources of the ten water resources zones and recorded runoff of major rivers in China during 1956—2018 were investigated. The results show that:① The annual runoff gauged on major rivers during 1956—2018 shows a downward trend with exception of the Datong station on the Yangtze River. ② The recorded annual runoff of the Tangnaihai station on the upper Yellow River presented an insignificant decreasing trend while that gauged at the Huayuankou station on the Yellow River exhibited a significant decreasing trend. During 1980—2000 and 2001—2018, the recorded runoff at the Tangnaihai station changed by 1.8% and-5.9% as comparing to baseline in 1956—1979 while that of the Huayuankou station decreased by 26.7% and 41.0% respectively. ③ Geographically, the Yellow River could be treated as separation boundary of runoff variation trends from the north to the south of China in terms of significance level. Recorded annual runoff presented significant decreasing trends for rivers in the north to the Yellow River while that exhibited insignificant variation trends for rivers in its south. The recorded runoff in 2001—2018 decreased by more than 25% relative to the baseline of 1956—1979 for the northern China rivers, with the highest reduction of over-80% occurring in the Haihe River. ④ The average annual surface water resources of China during 1956—2018 was approximately 2 726.6 billion m3, which is 12.2 billion m3 less than that in the second water resources assessment conduced in 2004. Reduction of surface water in the Haihe River zone, Yellow River zone, and Liaohe River zone aggravated contradiction between water supply and water demand since the early 21st century.