River Contamination Research Articles

Environmental Sustainability in the Public Services Company of Sogamoso S.A. ESP. In the period 2013-2014

The contamination of rivers, lagoons, dams and other wastewater bodies has become a major concern due to its impact on the quality of life of the population and the development of economic activities that require the use of water of such bodies. This concern has led to the emergence of an administrative legal framework for regulating this problem, which, in turn, has stimulated the growth of investments in environmental sanitation projects. Considering that the use of these resources means a high opportunity cost, it is very important to raise the quality of such investments through the improvement of their social profitability

Seasonal variations, metal distribution and water quality in the Todos os Santos River, Southeastern Brazil: a multivariate analysis.

In aquatic habitats, metal contamination from natural and anthropogenic sources continues to pose a concern for human and environmental health. Thus, it is important to complete monitoring studies to assess patterns and the extent of metal contamination in these ecosystems. The purpose of this work was to determine the concentrations of 31 chemical elements and water quality parameters of the Todos os Santos River located in the Mucuri Valley, Minas Gerais, Brazil. A multivariate statistical analysis was used to determine any seasonal and spatial patterns from the data. Results demonstrated that metals including Al, Fe, and Ni exceeded Brazilian and international guidelines nutrients as P also exceed water quality standards. Principal components analysis indicated distinct geographical and seasonal patterns for multiple elements with hierarchical cluster analysis confirming the observed spatial patterns of contamination in the Todos os Santos River.

Efficacy of Dredging for Remediating Polychlorinated Biphenyl-Contaminated Sediments of the Lower Fox River

Abstract Dredging efficacy in reducing polychlorinated biphenyl (PCB) sediment contamination in the Lower Fox River, Wisconsin, was assessed by comparing predredging and postdredging concentration ...

Tracing the sources of suspended sediment and particle-bound trace metal elements in an urban catchment coupling elemental and isotopic geochemistry, and fallout radionuclides

The excessive supply of contaminants from urban areas to rivers during the last centuries has led to deleterious impacts on aquatic ecosystems. The sources, the behavior, and the dynamics of these contaminants must be better understood in order to reduce this excessive anthropogenic pollution. Accordingly, the current research investigated the particle-bound trace element (TE) contamination of the 900-km2 Orge River (Seine basin, France) and the potential sources of these particles (agricultural or forest soils, channel banks, road deposited sediments), through the analysis of multiple fallout radionuclides, elemental geochemistry, and lead isotopic composition on suspended particulate matter (SPM) collected during a hydrological year at four stations following an increasing urbanization gradient (300 to 5000 inhab.km−2). Fallout radionuclide measurements showed an increasing contribution of recently eroded particles from urban areas to the SPM in downstream direction. However, this contribution varied depending on hydrological conditions. A greater contribution of particles originating from urban areas was observed during low stage periods. On the contrary, the contribution of agricultural soils and channel banks that are less enriched in contaminants and fallout radionuclides was higher during seasonal floods, which explained the dilution of radionuclide contents in sediment transiting the river during those events. Trace element contamination of SPM in Cu, Zn, Pb, and Sb increased from moderate to significant levels with urban pressure in downstream direction (with corresponding enrichment factors raising from 2 to 6). In addition, Pb isotopic ratios indicated that the main source of Pb corresponded to the “urban” signature found in road deposited sediments. The low variations in lead isotope ratios found in the SPM for contrasting hydrological conditions demonstrated the occurrence of a single source of Pb contamination. These results demonstrate the need to better manage urban runoff during both flood and low precipitation events to prevent the supply of diffuse particle-bound contamination to rivers draining urban areas.

The Negro River (Ancash-Peru): A unique case of water pollution, three environmental scenarios and an unresolved issue

This paper is focused on the hydrogeochemical characterization of the Negro River along its course, as well as in the proposal of a functioning model for the contamination processes in order to establish potential cause-effect relationships between water quality, geology (ARD), mining activities (AMD) and the tectonic framework as transmission vector of acidity, metals and sulphates. The scenario shows a heavily-contaminated river compared to the unaffected regional background. By graphical and statistical treatments of physico-chemical data of Negro River and the unaffected values of regional background and other AMD/ARD representative rivers' it is possible to conclude that Antamina Mine, is not the cause of the Negro River contamination, without the need of isotopic tracers, but just through the inexistent concentrations of Cu, Bi and Mo found in the waters. In the proposed contamination model, climatic factors (glacial retreat) activate geological (ARD) processes. The tectonic scenario (faults) intervenes as a transport medium of the contamination flux from the sulphide oxidation surface in upper altitudes until the spring in lower altitudes. At the end, it is concluded that this contamination comes from the recent glacial retreat in areas near the Cordillera Blanca that has left massive amounts of sulphide materials exposed to weathering conditions, oxidizing naturally (ARD processes) and finally contributing to the contamination of the Negro River through faults. In this case, we would face an ARD process in the strict sense, which is the direct oxidation of sulphides outcropping in the upper part of the mountain with the generation of sulphates, the release of hydrogen ions and the consequent generation of acid and the dissolution of the metals. This ARD process would come from the glacial retreat, which, through the faults, transports contaminated water until the spring.

Pharmaceuticals and personal care products in the urban river across the megacity Shanghai: Occurrence, source apportionment and a snapshot of influence of rainfall.

Occurrence of eleven pharmaceuticals and personal care products (PPCPs) along Huangpu River, a representative urban river of megacity Shanghai, was investigated in four sampling campaigns. The overall concentrations of PPCPs ranged from <LOQ to 1455 ng/L, and untreated domestic wastewater was proposed as an important source of PPCPs in Huangpu River. Higher contamination levels of target PPCPs were detected in the lower reach (urban area) and dry season, compared to those in the upper reach (rural area) and wet season, respectively. The influence of rainfall on the occurrence of PPCPs was also extensively discussed in different regions along Huangpu River. At sampling sites in the rural area, similar or even lower concentrations of PPCPs were detected after rainfall; while increased concentrations of PPCPs were observed at most sampling sites, especially in the urban area, suggesting that overflow of untreated wastewater exceeding the capacity of wastewater treatment plants and leachates generated at temporary storage and transfer station of solid wastes might be the additional sources of PPCPs in the urban area in rainy days. These findings indicated that management of wastewater or/and solid wastes was more important to solve the problem of PPCPs contamination in the urban river of megacity.

Arsenic and Trace Metals in Three West African rivers: Concentrations, Partitioning, and Distribution in Particle-Size Fractions.

Despite increasing mining activities, and fertilizer and pesticide use in agriculture, little information is available on the status of metal(loid) contamination in rivers in West Africa. Sixty water samples were collected from three significant rivers (the Bandama, Comoé, and Bia Rivers) in Côte d'Ivoire, the world's top cocoa producer, to examine As, Pb, Cu, Fe, Cd, and Zn concentrations, partitioning, and distribution in suspended particle-size fractions. The results showed higher total metal(loid) concentrations during the dry and flood seasons than during the rainy season. Significant As and Pb concentrations, moderate Cu and Fe concentrations, and low Zn concentrations were observed during the flood season. The metal(loid) concentrations decreased upstream to downstream primarily due to increased deposition through flocculation. Inverse or no obvious spatial trends often were observed, indicative of local contamination from anthropogenic activities. The suspended solid phase and the strength of metal affinity to the particles controlled the metal(loid) concentrations. Furthermore, total metal(loid) concentrations increased significantly with decreasing suspended particle-size fractions. The results underline that As and Pb contents in the Comoé and Bia Rivers threaten the health of at least 3million people in southeastern Côte d'Ivoire. Filtering river waters before use will significantly reduce human health risks.

Anthropogenic particles in the stomach contents and liver of the freshwater fish Squalius cephalus

Anthropogenic particles (APs) are a very broad category of particles produced directly or indirectly by human activities. Their ingestion by biota is well studied in the marine environment. In contrast, studies on AP ingestion in wild freshwater organisms are scarce despite high contamination levels in some rivers and lakes. In this study, we aimed to evaluate the ingestion of APs and the possible occurrence of APs in the liver and muscle of a freshwater fish, Squalius cephalus, from the Parisian conurbation. After isolation, the particles were analyzed using Raman spectroscopy. In sixty stomachs, eighteen APs were found, half of which were plastics and the other half were dyed particles. Twenty-five percent of sampled individuals had ingested at least one AP. The mean length of the APs was 2.41 mm. No significant difference was found between the sites upstream and downstream of Paris. Additionally, 5% of sampled livers contained one or more APs, which were characterized as microplastics (MPs). No APs were found in the muscle tissue. The majority of APs isolated from stomach contents were fibers, which is similar to the findings of a previous river contamination study. This highlights that fish could be more exposed to fibers than previously thought and that more studies on the impacts of fiber ingestion are required. Despite their low occurrence, MPs are reported, for the first time, in the liver of a wild freshwater fish species. While the pathways and impacts are still unknown, MPs also occur in liver of marine mollusks and fish. Physiological in vitro studies are needed to better evaluate the impacts of such phenomena.

Controls of Chloride Loading and Impairment at the River Network Scale in New England.

Chloride contamination of rivers due to nonpoint sources is increasing throughout developed temperate regions due to road salt application in winter. We developed a river-network model of chloride loading to watersheds to estimate road salt application rates and investigated the meteorological factors that control riverine impairment by chloride at concentrations above thresholds protective of aquatic organisms. Chloride loading from road salt was simulated in the Merrimack River watershed in New Hampshire, which has gradients in development density. After calibration to a regional network of stream chloride data, the model captured the distribution of regional discharge and chloride observations with efficiencies of 93 and 75%, respectively. The estimate of road salt application is within uncertainties of inventoried estimates of road salt loading and is 122 to 214% greater than recommended targets. Model predictions of chloride showed seasonal variation in chloride concentrations despite a large groundwater storage pool. Interannual variation of mean summer chloride concentration near the outlet varied up to 18%, and the total river length exceeding impairment thresholds varied 12%. Annual snowfall, which drives road salt loading, correlated with chloride impairment only in headwater streams, whereas concentration variability at the outlet was driven primarily by dilution from clean runoff-draining undeveloped forested areas of the watershed. The role of summer meteorology complicates the protection of freshwater systems from chloride contamination.

Potention of Active Charcoal from Musa Paradisiaca and Manihot Utilissima Shell in Degrading River Contamination

River water is one of type water surface which is a lot of finding in South Kalimantan. Generally, this water used by the citizen for cooking and bathing. But along with era growth, this river becomes as disposal of various industrial waste. The contamination of heavy metal like Fe, Mn, Pb, Cd, and turbidity enhance progressively and degrade the water quality. Some natural substance which can be used to improve river water quality is active charcoal from Musa paradisiaca and Manihot utilissima shell which is easy to get. Target research is determined to find optimum dose of active charcoal from Musa paradisiaca and Manihot utilissima shell that capable to degrade heavy metal contamination and turbidity in water river. It used experimentally with pretest and post-test with control group design. A result of research showed the optimum dose of active charcoal Musa paradisiaca shell was 15 gram , it could absorb Pb 28,8% and Mn 24,6%, but 10 gram can degrade turbidity until 83,8 %, while the optimum dose of Manihot utilissima shell to 25,4% Pb and degraded 77,5% of turbidity was 15 gram. Statistical test result with Kruskal Wallis got the p-value less than 0,05 it meant there was a difference between the treatment of active charcoal from Musa paradisiaca and Manihot utilissima shell in degrading the contamination. A conclusion is those active charcoal having a potential to enhance the water river quality. Suggested to use another activator to the potential like stirring, time of contact and the different mass.

Exposure to Arsenic Alters the Microbiome of Larval Zebrafish.

Exposure to environmental toxins such as heavy metals can perturb the development and stability of microbial communities associated with human or animal hosts. Widespread arsenic contamination in rivers and riparian habitats therefore presents environmental and health concerns for populations living near sources of contamination. To investigate how arsenic affects host microbiomes, we sequenced and characterized the microbiomes of twenty larval zebrafish exposed to three concentrations of arsenic that are found in contaminated water—low (10 ppb), medium (50 ppb), and high (100 ppb) for 20 days. We found that even a small concentration of arsenic changed the overall microbial composition, structure and diversity of microbial communities, causing dysbiosis in developing larval zebrafish microbiota. In addition, we found that a high concentration of arsenic also increased the abundance of a class 1 integron, an integrase-dependent system facilitating the horizontal transfer of genes conferring resistance to heavy metals and antibiotics.

Emerging contaminants in Brazilian rivers: Occurrence and effects on gene expression in zebrafish (Danio rerio) embryos

Emerging contaminants (ECs) are synthetic or naturally occurring chemicals that are not commonly monitored despite having the potential of entering the environment and causing adverse ecological and/or human health effects. This study aimed to determine whether ECs are present in the surface waters of two rivers in Mato Grosso do Sul State, Brazil, and evaluate the effects of ECs mixtures at environmentally relevant concentrations on zebrafish (Danio rerio) gene expression. ECs concentrations were determined using solid-phase extraction and liquid chromatography-mass spectrometry. The ECs most frequently detected were caffeine, imidacloprid, 2-hydroxy atrazine, tebuthiuron, atrazine, and bisphenol A. We used these data to reconstruct ECs mixtures reflecting environmental concentrations, codenamed T1, T2, and T3. No effects were observed, so the concentrations were increased. After a preliminary evaluation of the No Observed Effect Concentration for each mixture, we analyzed changes in the expression of zebrafish target genes (cyp1a, hsp70, cat, sod1, tsh, cyp19a1a, cyp19a1b, cyp26b1, casp8, sox2, cyb561d2, and thrb). cat was overrepresented in T1 and underrepresented in the other treatments. All of the mixtures induced the expression of cyp19a1b, which is a marker for (xeno-)estrogen exposure, and two of them increased the expression of cyp1a, which is used to indicate the presence of dioxin-like compounds. The rivers studied had low EC concentrations, and there was no indication of any harmful effects on the zebrafish. However, intensive agricultural activity may result in unsuspected peaks of EC pollution, and subsequent negative effects on living organisms.

STUDY OF FATE AND TRANSPORT OF EMERGENT CONTAMINANTS AT WASTE WATER TREATMENT PLANT

Contaminants of emerging concern such as pharmaceuticals, personal care products, bacteria, viruses, and pesticides are frequently found in waste water, groundwater, and surface waters. The search to find the sources of these compounds has routinely led to wastewater treatment plants (WWTPs) as an entry point of contaminants into the natural environment. The unknown effects of low concentrations of emerging contaminants in the aquatic ecosystem require scientists to study the occurrence, sources, fate, and transport of these compounds in wastewater treatment, to better understand and possibly identify mitigation opportunities. Reducing the contaminant levels in WWTP effluent helps minimize the contamination in lakes and rivers, which are both WWTP receiving waters as well as drinking water sources. Emerging contaminants end up in wastewater through several pathways including the disposal and use of consumer products, farm runoff, toxic spills, and excretion via the urine and feces of those consuming pharmaceuticals. The human body only metabolizes a percentage of each drug taken, expelling the rest into the municipal wastewater system. Another source is from consumer products such as soap, shampoo, disinfectant washes, and toothpaste which contain biologically active compounds that, when used, release these contaminants into the sewer system where they are then transported to a wastewater treatment plant (WWTP). Municipal wastewater treatment plants are not specifically designed to deal with the trace levels of emerging contaminates found in wastewater and many compounds pass through conventional treatment systems without removal. From the WWTP effluent, emerging contaminants are discharged into surface waters where they may have measurable effects on aquatic life at low concentrations. Once in surface waters, pharmaceuticals have been shown to interrupt the natural biochemistry of many aquatic organisms including fish and algae. Many of the problems associated with the removal of emerging contaminants from municipal wastewater stem from their low concentrations and chemical diversity, which make detection and analysis difficult. Low concentrations require extremely sensitive analytical equipment while the wide range of distinct chemical compounds necessitates techniques to identify many chemicals at once. Only recently have scientists become aware of the presence of some emerging contaminants in wastewater because analytical techniques able to detect them at the ng/l have only recently been developed. As laboratory procedures are developed and emerging contaminants can be accurately quantified, scientists are becoming increasingly able investigate the sources, removal pathways, and fate of pharmaceuticals in municipal wastewater. In addition to emerging contaminants, the potential entrance of prions into the wastewater system and their fate in wastewater treatment is an area of concern and a topic of interest in this study. A sampling program will implement to monitor the sources and fate of emerging contaminants in municipal wastewater treatment system. Laboratories will test for twelve different classes of emerging contaminants ranging from pharmaceuticals to flame-retardants. Hospitals, funeral homes, slaughterhouses and residential neighborhoods will monitor to determine possible point sources of contaminants into municipal sewer systems. Multiple locations within each wastewater treatment plant will monitor to trace the fate of each emerging contaminant class through the wastewater treatment process in an attempt to understand the fate removal pathways of each contaminant.

Sensitivity of macroinvertebrate indicator taxa to metal gradients in mining areas in Northern Spain

The study of macroinvertebrate communities using a Reference Condition Approach (RCA) is a powerful tool for detecting the impacts of mining activities due to heavy metal contamination in rivers. However, studies on this topic based on an RCA fully satisfying the Water Framework Directive (WFD) criteria for reference site selection are still scarce. Following a WFD-compliant RCA design, a total of 14 reference and 15 test sites were intensively sampled during July 2015 in the Nalón River basin (Asturias, Northern Spain). Macroinvertebrate samples, water physicochemistry, metal concentrations in sediments and habitat quality were evaluated at each selected site. To determine whether increasing heavy metal levels in sediments have significant ecological impacts in the structure of macroinvertebrate communities in the study area, we applied a combination of non-parametric multivariate and univariate procedures, as well as gradient analysis and Threshold Indicator Taxa ANalysis (TITAN) over the biotic and environmental datasets. We found significant alterations in the macroinvertebrate community structure with respect to the reference condition (REF group) for those test sites within mercury (HG group) and gold (AU group) mining areas, with Ephemeroptera, Plecoptera and Trichoptera (EPT) richness and abundance being the community descriptors showing the strongest alterations in relation to mining pressures in the studied area. Metal concentrations in sediments were significantly correlated to the metrics of community structure related to abundance, richness and biodiversity, with As and Hg being the two metals showing higher biological effects on macroinvertebrate assemblages. TITAN also allowed us to establish a set of macroinvertebrate families specifically sensitive to metal concentrations in sediments, most of which corresponded to EPT families. Our results prove that determined sensitive taxa could be considered as reliable indicators of metal pollution in the mining areas of Northern Spain. From a WFD perspective, our study clearly indicates that the responsive community descriptors found in this study are actually key parameters in the evaluation of the ecological status in the rivers of Northern Spain. These data are highly relevant for the future development of environmental quality standards for river sediments in Spain.

Occurrence and ecological risk of pharmaceuticals in river surface water of Bangladesh

Pharmaceutical contamination in the aquatic environment is a global issue that affects aquatic animals, micro-organisms and human health. The occurrence and preliminary ecological risk of 12 (11 antibiotics and 1 antiepileptic drug) pharmaceuticals were investigated for the first time in the surface water of the old Brahmaputra River, where open-water-fed aquaculture activities are being practiced in Bangladesh. The pharmaceuticals were quantified by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS), operated with positive electrospray ionization (ESI+) and a multiple reaction monitoring (MRM) mode. Nine pharmaceuticals were detected in the river surface water, whereas three were below the limit of detection (LOD). Metronidazole was detected in all the samples with concentrations ranging from 0.05 to 13.51 ng L−1. Trimethoprim had the second highest frequency of detection (95%) with the highest concentration (17.20 ng L−1). The ranges of concentration and detection frequency of sulfonamides and macrolides were <LOD-11.35 and <LOD-16.68 ng L−1; 35–70 and 60–85%, respectively, whereas carbamazepine was in the range of <LOD-8.80 ng L−1 and had a detection frequency of 65%. The concentrations of sulfamethoxazole, trimethoprim, erythromycin-H2O and tylosin were distinctly higher in the fed aquaculture areas. The principal component analysis confirmed that fed aquaculture activities contributed most of the pharmaceutical contamination in the river surface water. Hospitals, nursing homes, sewage wastewater or surface runoff from the surrounding areas might all contribute to the presence of metronidazole and carbamazepine. The preliminary ecological risk assessment revealed that sulfamethoxazole, erythromycin-H2O and tylosin showed medium risk, and carbamazepine displayed low risk to sensitive aquatic organisms for maximum measured concentrations. Thus, this study suggests that pharmaceutical contamination in different rivers and seasons needs to be quantified, and ecological as well as human health risks need to be assessed in Bangladesh.

Assessing how spatial variations of land use pattern affect water quality across a typical urbanized watershed in Beijing, China

Understanding the relationship between land use patterns and water quality in urbanized areas can provide insight into urban water quality management. In this study, a self-organizing map (SOM) and a linear mixed effects (LME) model were applied to explore the spatiotemporal patterns of nutrients and their relationship with land use characteristics in the highly urbanized Beiyun River watershed. The SOM classified 324 sampling data from 2014 to 2015 at 25 typical river sampling sites into nine clusters, with differences in land use patterns and seasonal (rainy and dry seasons) distributions. In the urbanized upstream reach of the river, concentrations of most pollutants were low, while in downstream sites the concentrations were higher for these pollution parameters. Nitrate-N (NO3−-N), however, exhibited the opposite pattern, probably due to the sources of pollutants and biochemical processes. The explanatory ability of the LME model in the established urbanized area and newly developed area in the upstream portion of the watershed was much better than in the downstream area, probably due to the influence of upstream nutrient contributions and the point source inputs in the downstream area. These statistical results indicated that sewage disposal and the main urbanized land use types were the most important drivers of river contamination. Forest land positively or negatively influenced river water quality depending on its spatial location as well as the water quality indicators. Therefore, sewage disposal as well as spatial non-stationarity of land-use impacts should be taken into consideration to reduce water pollution in the Beiyun River watershed.

Quantifying suspended solids in small rivers using satellite data

The management of suspended solids and associated contaminants in rivers requires knowledge of sediment sources. In-situ sampling can only describe the integrated impact of the upstream sources. Empirical models that use surface reflectance from satellite images to estimate total suspended solid (TSS) concentrations can be used to supplement measurements and provide spatially continuous maps. However, there are few examples, especially in narrow, shallow and hydrologically dynamic rivers found in mountainous areas. A case study of the Didipio catchment in Philippines was used to address these issues. Four 5-m resolution RapidEye images, from between the years 2014 and 2016, and near-simultaneous ground measurements of TSS concentrations were used to develop a power law model that approximates the relationship between TSS and reflectance for each of four spectral bands. A second dataset using two 2-m resolution Pleiades-1A and a third using a 6-m resolution SPOT-6 image along with ground-based measurements, were consistent with the model when using the red band data. Using that model, encompassing data from all three datasets, gave an R2 value of 65% and a root mean square error of 519mgL−1. A linear relationship between reflectance and TSS exists from 1mgL−1 to approximately 500mgL−1. In contrast, for TSS measurements between 500mgL−1 and 3580mgL−1 reflectance increases at a generally lower and more variable rate. The results were not sensitive to changing the pixel location within the vicinity of the ground sampling location. The model was used to generate a continuous map of TSS concentration within the catchment. Further ground-based measurements including TSS concentrations that are higher than 3580mgL−1 would allow the model to be developed and applied more confidently over the full relevant range of TSS.

Bentonite-decorated calix [4] arene: A new, promising hybrid material for heavy-metal removal

There is global concern about the contamination of ground, river, and tap waters as well as soil contamination with heavy metal ions; these chemical species are known to not degrade and to cause severe health problems if ingested by humans and animals. Such environmental and health concerns necessitate the development of ultrasensitive sensors and high-capacity adsorbents. This study demonstrates for the first time the potential of organophilic bentonite combined with tetra(2-pyridylmethyl)amide calix [4] arene as a high-performance hybrid material for the removal of toxic heavy metals. After consecutive synthesis steps, the modified bentonites were thoroughly characterized by FT-IR, XRD, UV spectroscopy, and TEM. In particular, the XRD analysis showed strong supporting evidence for intercalation in the clay following each modification step. The salient feature of the newly prepared hybrid material is its high extraction capacity for Cd(II) and Zn(II) metals, as determined by atomic absorption spectrometry and UV spectrometry. Different preparation methods, with respect to the quantity of the added cationic surfactant, were investigated to determine the optimal conditions for synthesis. The extraction percentage for the as-prepared hybrid material was measured to be as high as 97.4% and 94.2% for Cd(II) and Zn(II), respectively.

Benthic diatom community response to metal contamination from an abandoned Cu mine: Case study of the Gromolo Torrent (Italy)

Environmental contamination has become a global problem of increasing intensity due to the exponential growth of industrialization. One main debated issue is the metal contamination of rivers receiving Acid Mine Drainage (AMD) from active/abandoned mines. In order to assess the quality of lotic systems, diatoms are commonly used, as their assemblage modifies on the basis of changes in environmental parameters. Benthic diatom changes were analyzed along the metal-impacted Gromolo Torrent (Liguria, NW Italy) with the aim of understanding the effects of input from the abandoned Libiola Cu mine. The results support the hypothesis that metals from AMD lead to massive changes in diatoms, resulting in low biological diversity and in a shift of dominance, passing from the genera Cymbella and Cocconeis to more tolerant and opportunistic species, such as Achnanthidium minutissimum and Fragilaria rumpens. The high concentrations of labile metals, measured through Diffusion Gradients in Thin-films (DGT) immediately downstream of the two AMD inputs in the torrent, corresponded to a sudden decrease in the presence of diatoms, indicating the possible reaching of acute toxic levels. In particular, A. minutissimum dominated the mining area and was positively correlated with Cu and Zn; whereas F. rumpens bloomed downstream of this area, where the metal content was diluted, and was positively correlated with As and Pb. Finally, an important abundance of Nitzschia palea and teratological forms of A. minutissimum and F. rumpens were observed downstream from the mine, indicating that metals may have an important impact on diatoms up to the torrent mouth.

Transport of sediment borne contaminants in a Mediterranean river during a high flow event

Pollutants' dynamics in rivers flowing through industrial areas is linked to the entrainment and transport of contaminants attached to solid particles. The transport of sediment is mainly associated to high discharges and flood episodes, and these events constitute one of the main factors causing fluxes of buried pollutants in rivers. We performed a field study in the lower River Cinca (Ebro basin, Northeast Spain) to quantify the mobilization and transfer of several contaminants present in the river bed sediments. We focused on contaminants previously identified (PCBs, DDXs, PBDEs, HBCDs and PFRs) to occur in the river. River bed sediment samples were collected during low flows and a subsequent sampling campaign was used to capture sediment borne contaminants during a flood event. Water samples were taken at the same locations as the static sediment samples and used to determine the suspended sediment concentrations and the contaminants content (i.e. mass of contaminant per sediment mass unit) during the event. We estimated mass fluxes for both sediment and pollutants, and determined that sediment transport followed a clockwise hysteresis. This is typically observed in high flow events after dry summer periods. With sediments there was a large mobilization of PFRs (36 kg in 48 h in one of the main tributaries) and PCBs not previously observed in the static sediment. Observed contaminant load ranges during the two-day sampling campaign were: PCB (34–152 g), DDT (12–213 g), PBDE (50–1740 g), HBCD (0–2.2 g) and PFR (2410–35,895 g). An environmental risk assessment was carried out by comparing the pollutant concentrations found in the sediments with the Canadian quality guidelines (ISQC), showing a significant noncompliance for PCBs in dynamic sediments. Our results point out to the need of a regular assessment of the downstream transfer of the sediment-borne pollutants in drainage basins historically affected by intense industrial activities and associated contamination.