Outlet Of Plant Research Articles

Rapid biodegradation of organophosphorus pesticides by Stenotrophomonas sp. G1

Organophosphorus insecticides have been widely used, which are highly poisonous and cause serious concerns over food safety and environmental pollution. A bacterial strain being capable of degrading O,O-dialkyl phosphorothioate and O,O-dialkyl phosphate insecticides, designated as G1, was isolated from sludge collected at the drain outlet of a chlorpyrifos manufacture plant. Physiological and biochemical characteristics and 16S rDNA gene sequence analysis suggested that strain G1 belongs to the genus Stenotrophomonas. At an initial concentration of 50mg/L, strain G1 degraded 100% of methyl parathion, methyl paraoxon, diazinon, and phoxim, 95% of parathion, 63% of chlorpyrifos, 38% of profenofos, and 34% of triazophos in 24h. Orthogonal experiments showed that the optimum conditions were an inoculum volume of 20% (v/v), a substrate concentration of 50mg/L, and an incubation temperature in 40°C. p-Nitrophenol was detected as the metabolite of methyl parathion, for which intracellular methyl parathion hydrolase was responsible. Strain G1 can efficiently degrade eight organophosphorus pesticides (OPs) and is a very excellent candidate for applications in OP pollution remediation.

Factors controlling nitrogen fixation in temperate seagrass beds

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 525:41-51 (2015) - DOI: https://doi.org/10.3354/meps11247 Factors controlling nitrogen fixation in temperate seagrass beds Perran L. M. Cook*, Victor Evrard, Ryan J. Woodland Water Studies Centre, School of Chemistry, Monash University, Clayton, 3800, Victoria, Australia *Corresponding author: perran.cook@monash.edu ABSTRACT: Nitrogen fixation is an ecologically significant process in marine systems because nitrogen is typically the key limiting nutrient controlling productivity. Seagrass beds are often hot spots for nitrogen fixation owing to the mutualistic relationship between seagrass and nitrogen-fixing sulphate-reducing bacteria. The objectives of this study were to: (1) investigate the factors that controlled nitrogen fixation within seagrass beds (Zostera muelleri and Z. nigricaulis) on a system scale in a temperate Australian embayment (Port Phillip Bay), and (2) investigate differences in nitrogen isotope ratios (15N/14N, δ15N) in seagrass and Ulva spp. tissue as a proxy for nitrogen fixation. Nitrogen fixation rates ranged between 3 and 90 µmol m-2 h-1 and were related to plant biomass during both summer and spring, except at a highly nitrogen-enriched site adjacent to a sewage treatment plant outlet. During spring, biomass-specific nitrogen fixation rates were strongly positively related to leaf C:N ratio, suggesting that nitrogen fixation rates increased with nitrogen limitation during the growing season. Leaves of Zostera spp. had δ15N values that were consistently depleted by 2.4 ± 1.5‰ relative to Ulva spp. collected from the same site. We postulate that this isotopic difference arises as a consequence of Zostera spp. mainly assimilating N from newly mineralized nitrogen within the sediment (vs. a negligible fraction from N fixation), which is isotopically depleted owing to fractionation during nitrogen mineralization. KEY WORDS: Seagrass · Nitrogen fixation · Nitrogen isotope · 15N · Nitrogen loading Full text in pdf format Erratum MEPS 535 PreviousNextCite this article as: Cook PLM, Evrard V, Woodland RJ (2015) Factors controlling nitrogen fixation in temperate seagrass beds. Mar Ecol Prog Ser 525:41-51. https://doi.org/10.3354/meps11247 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 525. Online publication date: April 09, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Occurrence of selected pharmaceuticals in water and sediment of Umgeni River, KwaZulu-Natal, South Africa.

Selected pharmaceuticals including antibiotics, antipyretics, a stimulant, an antiepileptic and an antipsychotic drug were determined in wastewater, surface water and sediment along the Umgeni River which is the main source of water to Durban City in KwaZulu-Natal, South Africa. Samples were analysed using high-performance liquid chromatography coupled to a mass spectrometer (HPLC-MS/MS) after clean up and pre-concentration by solid phase extraction (SPE). At the wastewater treatment plant outlet, the antipyretic ibuprofen was detected in concentrations up to 12.94μg/L and 15.96ng/g in wastewater and bio-solids, respectively. The antipsychotic clozapine was detected in concentrations up to 14.43μg/L and 18.75ng/g in wastewater and bio-solids, respectively. Other pharmaceuticals namely sulfamethazine, sulfamethoxazole, erythromycin, metronidazole, trimethoprim, acetaminophen, caffeine and carbamazepine were also detected but in lower concentration compared to clozapine and ibuprofen (<10μg/L or 10ng/g). Clozapine and ibuprofen were detected at high concentrations in the surface water and sediment of Umgeni River. The highest concentration of clozapine (78.33μg/L) was detected at the business park, while that for ibuprofen (62.0μg/L) was detected at the point where a tributary, Msunduzi, joins Umgeni. Metronidazole was only detected in sediment, and caffeine (2243.52ng/g) was detected at the highest concentration in the sediment at the blue lagoon sampling site. The antibiotic sulfamethoxazole was also detected in appreciable amounts up to 507.34ng/g in the sediment at the Msunduzi tributary sampling site. The data collected implies that while insufficiently treated wastewater contributes to surface water contamination, human activities also contribute appreciably to the pharmaceutical loading of River Umgeni.

Dynamics of bacterial communities before and after distribution in a full-scale drinking water network

Understanding the biological stability of drinking water distribution systems is imperative in the framework of process control and risk management. The objective of this research was to examine the dynamics of the bacterial community during drinking water distribution at high temporal resolution. Water samples (156 in total) were collected over short time-scales (minutes/hours/days) from the outlet of a treatment plant and a location in its corresponding distribution network. The drinking water is treated by biofiltration and disinfectant residuals are absent during distribution. The community was analyzed by 16S rRNA gene pyrosequencing and flow cytometry as well as conventional, culture-based methods. Despite a random dramatic event (detected with pyrosequencing and flow cytometry but not with plate counts), the bacterial community profile at the two locations did not vary significantly over time. A diverse core microbiome was shared between the two locations (58–65% of the taxa and 86–91% of the sequences) and found to be dependent on the treatment strategy. The bacterial community structure changed during distribution, with greater richness detected in the network and phyla such as Acidobacteria and Gemmatimonadetes becoming abundant. The rare taxa displayed the highest dynamicity, causing the major change during water distribution. This change did not have hygienic implications and is contingent on the sensitivity of the applied methods. The concept of biological stability therefore needs to be revised. Biostability is generally desired in drinking water guidelines but may be difficult to achieve in large-scale complex distribution systems that are inherently dynamic.

Experimental Research on Reduction Measures of Sediment Deposition of the Power Plant Port under the Long Period Wave

The maintenance cost of port project after its completion is very important, especially for work at outlet of power plant. Maintain regular dredging for channel and water intake is necessary, but severe deposition caused a large cost increase in the annual maintenance costs are also not in economy. Therefore, it is necessary to improve the current project scheme to reduce the deposition rate, so that long-term port maintenance costs would be greatly reduced. Because this power plant is located in the sea area under the long period waves, sediment is completely active, and deposition continually appears in the excavation process of harbour basin and channel, and the channel can’t be formed. In this paper, a physical modeling experiment of sediment under long period wave is carried out. Firstly, the sediment movement of the tale quale is validated and the reasons causing the severe deposition in the harbour basin are analyzed. Then, the deposition status and the effective controlling soil erosion in the harbour basin and the channel by using measures of lengthening the breakwater and building spur dikes are researched and their deposition intensity are analyzed. From the results, basic data and some useful measures can be provided for project optimization.

A Hierarchical Approach for Inland Lake Pollutant Load Allocation: A Case Study in Tangxun Lake Basin, Wuhan, China

Water pollution control is a challenging task in water resources management. It is widely believed that integrating efficiency and fairness of socio-economic factors is an effective solution for water problems of inland Lake Basin. In this paper, a hierarchical approach of Tri-level Pollutant Loading Allocation (TPLA) was developed for the optimal allocation of pollutant load reduction. In TPLA, pollutant load reduction amount were allocated top-down, from basin scale to outlet scale, in three levels based on minimum marginal cost, Environmental Gini Coefficient (EGC) and water quality modeling to meet the set water quality goal. Tangxun Lake Basin, Wuhan, Central China, was selected as a case study. Results showed that the total CODMn loads reduction of point sources and non-point sources was allocated to 201.1 t/a and 24.1 t/a, respectively at the first level. Secondly, the districts within the lake basin are to cut off emission amount to different extent by minimizing EGC population to 0.22 and EGCIAV to 0.50. Minimum EGC method seems more adaptable to solve the inequality between pollution and population than that of industrial added value. At the third level, the largest reduction amount of 142.21 t/a was at Bee Jiaotou Plant outlet at Miaoshan District, followed by two outlets of 10.41 t/a in Zhifang District. Other outlets cut their emission by less than 10 t/a. The TPLA model can give an optimal pollutant loads allocation for the various pollutant sources, and is easy to understand for stakeholders and flexible to apply in practice.

Modeling of biological wastewater treatment plant efficiency

The research explores the efficiency of wastewater treatment at a biological treatment plant with respect to the biochemical oxygen demand indicators within five days at the inlet and outlet of the treatment plant. Different seasons have been provided with the mathematical models of the plant’s operational efficiency depending on the weather conditions that affect the load on the activated sludge and its treatability (taking into account the reliance on the air temperature, precipitation amount, and the presence of melting snow). The quality of the obtained models is evaluated with the determination coefficient d. The best determination coefficients are: for winter d=0.92, for spring d=0.98, for summer d=0.80, and for autumn d=0.82. Accounting for the forecast and the obtained dependencies will contribute to the implementation of operational actions, which provide the wastewater treatment quality.

Improving water and energy metabolism efficiency in urban water supply system through pressure stabilization by optimal operation on water tanks

Water supply consumes 2–3% of the worldwide energy. Water distribution system, which accounts for 70% electricity consumption of water supply, is a key link of urban water and energy metabolism. The operation of the secondary water supply system (SWSS) has great influence on the pressure stability and associated energy consumption as well as water loss of urban water distribution. This research developed an approach based on the hydraulic solver EPANET and genetic algorithm (GA) to investigate the impacts of two different operation strategies, user demand regulation (UDR) and tank level regulation (TLR) of SWSS, on pressure stability and energy efficiency. The results showed that the strategy of TLR could reduce the pressure fluctuations and increase the minimal pressure of the distribution network under the same supply–demand condition. Reduction of the pressure fluctuations is beneficial to the reliability and leakage control of pipe networks. Increase of the minimal pressure indicates that less energy is lost during the distribution. Therefore, the TLR strategy of SWSS can support to initiatively lower the water pressure of the pumps at the water plant outlet, thus improves the water and energy metabolism efficiency in urban water supply system.

Design and Analysis of Cross Flow Turbine for Micro Hydro Power Application using Sewerage Water

The objective of this study endeavor is to describe the design of an environment friendly captive micro hydel power plant at the sewerage treatment plant outlet fall at Lai Nallah located in I-9 Islamabad. It will use sewerage water of CDA as discharge water to run the turbine of the micro hydel power plant to generate electricity. The important phases of the project are to carry out survey for collection of data about hydrology, quantity of flow of water, fall head, geology and design of an efficient turbine. Complete design calculations of turbine have been performed along with static and model analysis of the turbine. Key parameters to increase efficiency of cross-flow turbine are discussed.

SOLMED: solar energy and polymers for seawater desalination

Combining thermal solar energy and polymer materials allows seawater desalination while fossil fuels are saved and use of chemicals against fouling and corrosion is reduced. SOLar Multi-Effect Desalination (SOLMED) meets recommendations of the US National Research Council and Middle East Desalination Research Center of Oman regarding the future of water desalination. Water cost reduction and development of technologies with low environmental impact are the main guidelines of SOLMED. Thermal efficiency is at the heart of SOLMED. Process is based on low-temperature multi-effect distillation (LT-MED) powered by a thermal solar collector field, or better, by heat recovery at the outlet of a solar power plant. Heat transfer surfaces are made of thin wall polymer tubes to ensure a high thermal duty in spite of low thermal conductivity of polymers. Targeted capacities lie within 500–1,000 m3/d. The objective is to develop a LT-MED prototype made of polymers and to operate the system plugged to a solar heat source. To reach these objectives, SOLMED gathers a consortium of six partners, merging experts of thermal systems and components, experts in polymers and transformation, and engineering partners in the field of solar energy and processes. Social aspects are also taken into account through acceptability, sustainability, design, management of innovation, market, and life cycle assessment. SOLMED is a three years project funded by the French National Research Agency. The first step is to build a 10 m3/d prototype to bring a proof of concept. The prototype will be operated with a 100 kW peak solar heat source. Developments are related to the modeling of the process itself and its integration in a solar system including heat storage, thin-wall tubes fabrication, optimization of tubes fixing, investigations related to heat transfer, and hydraulic. Regarding polymer materials, the challenge is to combine high thermal rate with long lifetime. Commercial step has to consider new optimization approach, taking into consideration the whole process, including heat source.

Monitoring metal ions present in the effluent discharged from a surface treatment plant: Analytical results

Precise data concerning the metals occurring in industrial discharge water from the surface treatment sector as well as their qualitative and quantitative fluctuations have to our knowledge never been reported. In the present study, we monitored 28 metals in the effluent from a surface treatment plant every week for about a year. The effluent studied was taken at the outlet of a depollution plant that removed a large proportion of the metals as insoluble forms. We report and discuss the analytical results obtained on a total of 49 samples. The results, expressed both as concentrations and as fluxes, showed high levels of polymetallic contamination of the effluent. Of the 28 metals tested for, 13 were detected and 6 (Co, Cr, Fe, Mn, Ni, and Zn) were systematically present at quantifiable levels. Our findings also indicated how Cr, Fe, Ni and Zn levels were strongly dependent on certain conditions prevailing at the inlet of the wastewater treatment unit. Even though the levels of each metal were under the regulatory limits when taken individually, overall pollution from metals was far from negligible, with a calculated total of 264 kg of metals being discharged each year.

Combining flow cytometry and 16S rRNA gene pyrosequencing: A promising approach for drinking water monitoring and characterization

The combination of flow cytometry (FCM) and 16S rRNA gene pyrosequencing data was investigated for the purpose of monitoring and characterizing microbial changes in drinking water distribution systems. High frequency sampling (5 min intervals for 1 h) was performed at the outlet of a treatment plant and at one location in the full-scale distribution network. In total, 52 bulk water samples were analysed with FCM, pyrosequencing and conventional methods (adenosine-triphosphate, ATP; heterotrophic plate count, HPC). FCM and pyrosequencing results individually showed that changes in the microbial community occurred in the water distribution system, which was not detected with conventional monitoring. FCM data showed an increase in the total bacterial cell concentrations (from 345 ± 15 × 103 to 425 ± 35 × 103 cells mL−1) and in the percentage of intact bacterial cells (from 39 ± 3.5% to 53 ± 4.4%) during water distribution. This shift was also observed in the FCM fluorescence fingerprints, which are characteristic of each water sample. A similar shift was detected in the microbial community composition as characterized with pyrosequencing, showing that FCM and genetic fingerprints are congruent. FCM and pyrosequencing data were subsequently combined for the calculation of cell concentration changes for each bacterial phylum. The results revealed an increase in cell concentrations of specific bacterial phyla (e.g., Proteobacteria), along with a decrease in other phyla (e.g., Actinobacteria), which could not be concluded from the two methods individually. The combination of FCM and pyrosequencing methods is a promising approach for future drinking water quality monitoring and for advanced studies on drinking water distribution pipeline ecology.

Into the abyss of Lake Geneva: the elemo interdisciplinary field investigation using the MIR submersibles

In summer 2011, the two Russian MIR submersibles were brought to Switzerland to perform deep water dives in Lake Geneva. Research teams from several environmental science institutes, both national and international, participated in this interdisciplinary effort to investigate the deeper parts of Lake Geneva. Using the MIRs allowed the scientists to see and precisely select the sites where they could extract specific sediment cores and carry out detailed in situ measurements at the sediment–water boundary. One focus site was the surrounding of the outlet of the wastewater treatment plant of the City of Lausanne, which discharges into the Vidy Bay. The investigations concentrated on the pollution of the local sediments, pollution-related ecotoxicological risks, microbial activity and spreading and removal of the effluents from the bay to the open waters of the lake. The other focus site was the Rhone River delta and its subaquatic canyons, which formed as a result of the long-term interplay of the deposition of river-borne sediments and flood-triggered canyon erosion events.

Can resistant coral-Symbiodinium associations enable coral communities to survive climate change? A study of a site exposed to long-term hot water input.

Climate change has led to a decline in the health of corals and coral reefs around the world. Studies have shown that, while some corals can cope with natural and anthropogenic stressors either through resistance mechanisms of coral hosts or through sustainable relationships with Symbiodinium clades or types, many coral species cannot. Here, we show that the corals present in a reef in southern Taiwan, and exposed to long-term elevated seawater temperatures due to the presence of a nuclear power plant outlet (NPP OL), are unique in terms of species and associated Symbiodinium types. At shallow depths (<3 m), eleven coral genera elsewhere in Kenting predominantly found with Symbiodinium types C1 and C3 (stress sensitive) were instead hosting Symbiodinium type D1a (stress tolerant) or a mixture of Symbiodinium type C1/C3/C21a/C15 and Symbiodinium type D1a. Of the 16 coral genera that dominate the local reefs, two that are apparently unable to associate with Symbiodinium type D1a are not present at NPP OL at depths of <3 m. Two other genera present at NPP OL and other locations host a specific type of Symbiodinium type C15. These data imply that coral assemblages may have the capacity to maintain their presence at the generic level against long-term disturbances such as elevated seawater temperatures by acclimatization through successful association with a stress-tolerant Symbiodinium over time. However, at the community level it comes at the cost of some coral genera being lost, suggesting that species unable to associate with a stress-tolerant Symbiodinium are likely to become extinct locally and unfavorable shifts in coral communities are likely to occur under the impact of climate change.

A computational tool for the characterisation of rapid fluctuations in flow and stage in rivers caused by hydropeaking

Power production by hydro-electric plants in response to short-term variations in the energy demand and market (hydropeaking) may lead to frequent and rapid fluctuations in flow and stage in rivers downstream of power plant outlets. We have developed a time series analysis tool designed to quantify these rapid fluctuations. They were identified by establishing river- and data-specific thresholds both for the rates of change in flow or stage, and for other peaking event parameters. In contrast to previous similar analyses, we separated peaking events into rapid increases and rapid decreases. We also analysed other parameters such as daylight conditions during peaking events, and calculated both mean and maximum rates of change in flow and stage. The results of such analysis in a Norwegian river were used to demonstrate outputs from the tool. Our tool may be useful with respect to environmental impact assessment and mitigation related to stream hydropeaking.

Anthropogenic and natural metal contents of coastal sediments with potential transfer to associated waters: the case of El Melah lagoon near Slimane, Tunisia

Cu, Zn, Ni, Cr and Co pollution of El Melah lagoon waters near the city of Slimane in northwestern Tunisia was evaluated relative to identified human activity and waste repositories in the neighborhood. These metals were measured in lagoon waters and sediments, and in the potential pollutants, during two consecutive years for evaluation of their impact on the lagoon waters. A sequential extraction of the metals from sediments was designed to distinguish those potentially anthropogenic from those naturally scavenged by the sediments. This procedure allowed identification and quantification of the metals that are temporarily trapped, therefore contributing directly to the ecotoxicity of the lagoon waters, from those incorporated in the sediments. The highest supplies of Cr and Co to the lagoon waters come from El-Bey creek waters, while the wastewater treatment plant contributes for most of the Zn, and the urban garbage deposit for most of the Ni. Alternatively, the impact of the cultivated soils is minimal for the studied metals. In fact, Zn and Ni contents of the sediments amount 100 to 20 times less than in the present water, which is negligible. Cr is potentially the most polluting with contents up to ten times more in the sediments of the eastern lagoon pool and next to the outlet of the wastewater plant than in the waters. Potentially, contents of the anthropogenic Cu of the sediments amount 3–15 times less than in the lagoon waters.

Environmental Impact of Wastewater Discharges from FERMENCAM

This study aims to assess the environmental impact of wastewater discharges from FERMENCAM. Effluent and wastewater samples were collected respectively at the plant outlet and in the receiving environment, and physico-chemical analyses carried out revealed an organic pollution with a high pollution load that can be observed by phosphate levels in water at the plant outlet. Biochemical oxygen demand (BOD5) is high at the plant outlet (20300 mg of O2 / L) and 16200 mg of O2 / L are found in the receiving environment. The BOD5/COD (chemical oxygen demand) ratio of effluents discharged by FERMENCAM and that of the receiving environment is 0.90. This value is higher than 0.5, meaning that the organic matter of both effluents is highly biodegradable. The results show that the increase in conductivity and decrease in total dissolved salts are due to an excessive mineralization of organic matters. The results show that the chlorophyll synthesis in Amaranthus viridis leaves is linked to the quality of the environment, and that is why such leaves can easily adapt to the polluted environment. In short, the wastewater impact on water quality of the receiving environment is evident, and these data will allow better environmental protection, thus promoting the development of various waterfront activities. In addition, the need for sustainable wastewater management (wastewater treatment plants, pre-treatment of industrial waters and sensitization) in the study area proves to be vital and urgent in order to improve wastewater quality and contribute to improving the state of the environment.

Monitoring of tritium, 60Co and 137Cs in the vicinity of the warm water outlet of The Paks Nuclear Power Plant, Hungary

Danube water, sediment and various aquatic organisms (snail, mussel, predatory and omnivorous fish) were collected upstream (at a background site) and downstream of the outlet of the warm water channel of Paks Nuclear Power Plant. Gamma emitters, tissue free-water tritium (TFWT) and total organically-bound tritium (T-OBT) measurements were performed. A slight contribution of the power plant to the natural tritium background concentration was measured in water samples from the Danube section downstream of the warm water channel. Sediment samples also contained elevated tritium concentrations, along with a detectable amount of 60Co. In the case of biota samples, TFWT exhibited only a very slight difference compared to the tritium concentration of the Danube water, however, the OBT was higher than the tritium concentration in the Danube, independent of the origin of the samples. The elevated OBT concentration in the mollusc samples downstream of the warm water channel may be attributed to the excess emission from the nuclear power plant. The whole data set obtained was used for dose rate calculations and will be contributed to the development of the ERICA database.

Study on the TOC concentration in raw water and HAAs in Tehran’s water treatment plant outlet

A sampling has been undertaken to investigate the variation of haloacetic acids formation and nature organic matter through 81 samples were collected from three water treatment plant and three major rivers of Tehran Iran. Changes in the total organic matter (TOC), ultraviolet absorbance (UV254), specific ultraviolet absorbance (SUVA) were measured in raw water samples. Haloacetic acids concentrations were monitored using a new static headspace GC-ECD method without a manual pre-concentration in three water treatment plants. The average concentration of TOC and HAAs in three rivers and three water treatment plants in spring, summer and fall, were 4, 2.41 and 4.03 mg/L and 48.75, 43.79 and 51.07 μg/L respectively. Seasonal variation indicated that HAAs levels were much higher in spring and fall.

Influence of a wastewater treatment plant on mercury contamination and sediment characteristics in Vidy Bay (Lake Geneva, Switzerland)

Previous direct observations of the sediment surface in Vidy Bay, Lake Geneva (Switzerland), revealed a range of sediment characteristics in terms of colour, texture and morphology. Dives with the MIR submersibles during the éLEMO project permitted the exploration of a large portion of Vidy Bay. It is the most contaminated part of Lake Geneva, due to inputs of treated and untreated waters from a large wastewater treatment plant (WWTP). To evaluate the influence of WWTP effluent on mercury contamination and sediment characteristics, 14 sediment cores were retrieved in the vicinity of the wastewater treatment plant effluent. Total mercury concentrations in sediments ranged between 0.32 and 10.1 mg/kg. Inorganic mercury and monomethylmercury concentrations in overlying and pore waters were also measured. The total partition coefficients of mercury (logK d) ranged from 3.6 to 5.8. The monomethylmercury concentration in pore waters of surface sediments was a large proportion of the total mercury concentration (44 ± 25 %). A Spearman test showed a negative correlation between the distance to the wastewater treatment plant outlet and the concentrations of total mercury in sediments and pore waters. Visual observations from the submersible allowed recognizing six different types of sediment. The areal distribution of these different sediment types clearly showed the influence of the wastewater treatment plant outlet on the sediment surface patterns. However, no relationship with mercury concentrations could be established.