Sediment Concentration In Rivers Research Articles

Comparison between Hyperspectral and Multispectral Retrievals of Suspended Sediment Concentration in Rivers

Remote sensing (RS) is often employed to estimate suspended sediment concentration (SSC) in rivers, and the availability of hyperspectral imagery enhances the effectiveness of RS-based water quality monitoring due to its high spectral resolution. Yet, the necessity of hyperspectral imagery for SSC estimation in rivers has not been fully validated. This study thus compares the performance of hyperspectral RS with that of multispectral RS by conducting field-scale experiments in shallow rivers. In the field experiments, we measured radiance from a water body mixed with suspended sediments using a drone-mounted hyperspectral sensor, with the sediment and riverbed types considered as controlling factors. We retrieved the SSC from UAV imagery using an optimal band ratio analysis, which successfully estimated SSC distributions in the sand bed conditions with both multispectral and hyperspectral data. In the vegetated bed conditions, meanwhile, the prediction accuracy decreased significantly due to the temporally varying bottom reflectance associated with the random movement of vegetation caused by near-bed turbulence. This is because temporally inhomogeneous bottom reflectance distorts the relationship between the SSC and total reflectance. Nevertheless, the hyperspectral imaging exhibited better prediction accuracy than the multispectral imaging, effectively extracting optimal spectral bands sensitive to back-scattered reflectance from sediments while constraining the bottom reflectance caused by the vegetation-covered bed.

Magnetic Susceptibility and Hydrogen Cyanide Levels as Proxy Indicator for Gold Mining Pollution in River Sediment

Sumbawa’s Kuris River is one of the rivers contaminated by the island’s traditional gold mine. In order to detect contaminant levels, we examine the magnetic susceptibility, HCN levels, and the heavy metal contents on the river’s surface sediment. Environmental pollution has been widely assessed using a combination of magnetic properties and geochemical analysis. The goals of this research are to discover how magnetic susceptibility (χ) can be used as a first-order proxy for pollution. The relation between susceptibility and HCN is of particular interest, as this is a major contaminant associated with gold mining. The surface sediment samples were collected at ten different locations along the rivers. The magnetic susceptibility was determined using the Bartington MS2B, and the hydrogen cyanide (HCN) concentration was determined using Argentometric titration. The element content was determined by an Atomic Absorption Spectrometer (AAS). The low-frequency magnetic susceptibility (χlf) ranges from 71 to 115×10-8 m3/kg, with an average of 97×10-8 m3/kg, and the χfd(%) analysis ranges from 2% to 4%. The presence of spherical iron oxides, which are indicative of combustion byproducts, was also confirmed by SEM. The samples have low magnetic susceptibility but high levels of Hg and HCN. AAS results showed high Fe, Zn, and Cu concentrations in river sediments, with more variable concentrations of Hg, Mn, As, Cr, and Au. Because Fe, Cu, As, Hg, and HCN have a significant Pearson’s correlation with χfd(%), this parameter can be a useful indicator for contamination caused by gold mining waste.

Plastic pollution in riverbeds fundamentally affects natural sand transport processes

Over the past 50 years, rivers have become increasingly important vectors for plastic pollution. Lowland riverbeds exhibit coherent morphological features including ripple and dune bedforms, which transport sediment downstream via well-understood processes, yet the impact of plastic on sediment transport mechanics is largely unknown. Here we use flume tank experiments to show that when plastic particles are introduced to sandy riverbeds, even at relatively low concentrations, novel bedform morphologies and altered processes emerge, including irregular bedform stoss erosion and dune “washout”, causing topographic bedform amplitudes to decline. We detail (i) new mechanisms of plastic incorporation and transport in riverbed dunes, and (ii) how sedimentary processes are fundamentally influenced. Our laboratory flume tank experiments suggest that plastic is not a passive component of river systems but directly affects bed topography and locally increases the proportion of sand suspended in the water column, which at larger scales, has the potential to impact river ecosystems and wider landscapes. The resulting plastic distribution in the sediment is heterogeneous, highlighting the challenge of representatively sampling plastic concentrations in river sediments. Our insights are part of an ongoing suite of efforts contributing to the establishment of a new branch of process sedimentology: plastic – riverbed sand interactions.

Spatiotemporal distribution and pollution assessment of trace metals in the Buriganga River, Bangladesh.

The Buriganga River plays a key role in the socioeconomic structure of Dhaka, the capital of Bangladesh. However, this river is severely polluted and is considered one of the most polluted in the world. Therefore, this study aimed to assess the concentrations of various metals in the Buriganga River. A study was conducted from August 2019 to February 2020 to determine the concentrations of 16 metals in water samples (n = 210) collected from 10 distinct sites in the Buriganga River. The mean values for the concentrations of Cr, Mn, Ni, Zn, As, Se, Cd, Sb, and Pb in river water were above the guideline values prescribed by the WHO, Japan, and Bangladesh. Moreover, the fraction ratios of Be, Cr, Co, Ni, Cu, Zn, Se, Mo, Ag, Cd, Sb, and Pb were high (>0.85); consequently, these metals could accumulate at high concentrations in river sediments. Assessment using the single-factor pollution index allowed the classification of the pollution level as 'serious pollution' for Sb and 'heavy pollution' for Cd, Ni, and Pb. The trace metal concentrations in this river imply that crops cultivated along the river using river water may also be contaminated with trace metals.

Emergent Contaminants in Freshwater Ecosystem: A case study from Turkey

The current study evaluated certain emerging contaminants in the Susurluk sub-basin, which is under significant anthropogenic pollution pressure. Polychlorinated Biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organochlorine insecticides, and microplastics were investigated from both surface and sediment samples collected in dry and wet seasons. In the Kocaçay river reaching the Marmara Sea, γ-HCH and β-HCH were detected in the dry season. Dieldrin was also observed in very high concentrations in river sediments during the dry season. Nilüfer stream is a significant waterway close to industrial and urban areas resulting in pollution of high concentrations of PCBs, DDT, and its metabolites. Sediment samples contained higher contaminants: DDT and metabolites in the sediment from almost all stations. According to the Hazard quotient coefficient, all detected pollutants were found to be >1, indicating a high risk in the river system. Fiber was the dominant microplastic. The water quality of Nilüfer Stream was poor/bad in quality both in dry and wet seasons, while Kocaçay River was moderate and poor/bad quality in dry and wet seasons, respectively. The findings of bacterial growth augmented and worsened water quality in the river basin with coliforms dominating, as assessed at the genus/species level and were very abundant.

Ranking of Basin-Scale Factors Affecting Metal Concentrations in River Sediment

River sediments often contain potentially harmful pollutants such as metals. Much research has been conducted to identify factors involved in sediment concentrations of metals. While most metal pollution studies focus on smaller scales, it has been shown that basin-scale parameters are powerful predictors of river water quality. The present study focused on basin-scale factors of metal concentrations in river sediments. The study was performed on the contiguous USA using Random Forest (R.F.) to analyze the importance of different factors of the metal pollution potential of river sediments and evaluate the possibility of assessing this potential from basin characteristics. Results indicated that the most important factors belonged to the groups Geology, Dams, and Land cover. Rock characteristics (contents of K2O, CaO, and SiO2) and reservoir drainage area were strong factors. Vegetation indices were more important than land cover types. The response of different metals to basin-scale factors varied greatly. The R.F. models performed well with prediction errors of 16.5% to 28.1%, showing that basin-scale parameters hold sufficient information for predicting potential metal concentrations. The results contribute to research and policymaking dependent on understanding large-scale factors of metal pollution.

Quantification and thermo-desorption studies of mercury in sediments from Mokolo River, Limpopo Province, South Africa

ABSTRACT Mercury can travel over long distances, and bioaccumulate in the trophic chain thereby posing a threat to not only humans but also animals and plants. Mercury also causes neurological problems such as the Minamata diseases. Pollution and toxicity of mercury have become a global problem that requires immediate attention. In this study, a thermal-desorption technique using a Zeeman direct mercury (Hg) analyser (DMA) was employed for the quantification of Hg in river sediments as well as for Hg thermo-scanning to investigate the behaviour of Hg release from sediments. Thermal speciation was based on comparison of the temperatures at which Hg species in sediments were thermally released to the temperatures at which Hg in known standards were released. Moreover, total Hg concentrations in river sediments were measured using a DMA. The accuracy of the method for total Hg quantification was confirmed by the analysis of several standard reference materials of sediment (SRM2709a, NCS DC 73325, NCS DC 73374, NCS DC 73316 and NCS DC 73322) and quantitative percentage recoveries ranging from 84 to 99% were obtained. The total Hg concentrations in sediments ranged from 7.4 to 35.2 ng/g and 2.1 to 21.2 ng/g in the low and high flow seasons, respectively. Different forms of Hg associated with river sediments were successfully identified by thermo-desorption technique. The concentrations of Hg in the sediment samples were all below 200 ng/g which is the sediment quality guideline set by the United States Environmental Protection Agency (US EPA). Different species of Hg were present in the sediment samples, with humic acid and/or iron oxide being the most predominant forms of Hg associated with the sediments.

Spatiotemporal distribution of polycyclic aromatic hydrocarbons in sediments of a typical river located in the Loess Plateau, China: Influence of human activities and land-use changes

The Loess Plateau, as the key energy base of China, has sensitive responses to the global changes, and receives polycyclic aromatic hydrocarbons (PAHs) from anthropogenic activities. However, understanding how anthropogenic and climate factors affect synergistically the PAHs distribution in this vulnerable ecological environment is deficient. Here the spatiotemporal distribution of PAHs in sediments from a typical river of the Loess Plateau were investigated. The PAHs were mainly from coal combustion in the range of 194–514 ng g−1, and their concentrations were generally higher in normal season than wet season as the dilution effect of high river discharge and strong precipitation. The interactive effects of land-use and precipitation showed PAHs enriched in forest-grass land were transferred into rivers through surface and subsurface runoff during light rainfall, resulting in the increase of the PAHs concentrations in river sediments. In contrast, large precipitation in wet season would obscure any spatial variations. In addition, human activities, especially energy production, directly enhanced PAHs accumulation in river sediments due to the emission from the production processing of oil and coal, and indirectly influenced the PAHs by impacting the per capita GDP. These findings had important implications for the management and prediction of PAH accumulation.

Integration of ANFIS with PCA and DWT for daily suspended sediment concentration prediction

Quantifying sediment load is vital for aquatic and riverine biota and has been the subject of various environmental studies since sediment plays a key role in maintaining ecological integrity, river morphology and agricultural productivity. However, predicting sediment concentration in rivers is difficult because of the non-linear relationships of flow rates, geophysical characteristics and sediment loads. It is thus very important to propose suitable statistical methods which can provide fast, accurate and robust prediction of suspended sediment concentration (SSC) for management guidance. In this study, we developed coupled models of discrete wavelet transform (DWT) with adaptive neuro-fuzzy inference system (ANFIS), named DWT-ANFIS, and principal component analysis (PCA) with ANFIS, named PCA-ANFIS, for SSC time-series modeling. The coupled models and single ANFIS model were trained and tested using long-term daily SSC and river discharge which were measured on the Schuylkill and Iowa Rivers in the United States. The findings showed that the PCA-ANFIS performed better than the single ANFIS and the coupled DWT-ANFIS. Further applications of the PCA-ANFIS should be considered for simulation and prediction of other indicators relating to weather, water resources, and the environment.

Cascading Hazards in the Aftermath of Australia's 2019/2020 Black Summer Wildfires

AbstractFollowing an unprecedented drought, Australia's 2019/2020 “Black Summer” fire season caused severe damage, gravely impacting both humans and ecosystems, and increasing susceptibility to other hazards. Heavy precipitation in early 2020 led to flooding and runoff that entrained ash and soil in burned areas, increasing sediment concentration in rivers, and reducing water quality. We exemplify this hazard cascade in a catchment in New South Wales by mapping burn severity, flood, and rainfall recurrence; estimating changes in soil erosion; and comparing them with river turbidity data. We show that following the extreme drought and wildfires, even moderate rain and floods led to undue increases in soil erosion and reductions in water quality. While natural risk analysis and planning commonly focuses on a single hazard, we emphasize the need to consider the entire hazard cascade, and highlight the impacts of ongoing climate change beyond its direct effect on wildfires.

Tectonic Controls on Surface Erosion Rates in the Longmen Shan, Eastern Tibet

AbstractThe Longmen Shan range, located on the eastern margin of the Tibetan Plateau, is characterized by steep topography and a shortening rate of <3 mm/yr. This peculiar configuration is a source of controversy and questions about the topographic evolution and dynamics of this orogenic plateau margin. Investigating the variations in surface denudation over different spatial and temporal scales is important for a better understanding of topographic evolution, but there is still a lack of erosion‐rate data averaged over millennial timescales along the frontal range of the Longmen Shan, especially in its southern part. We present 25 new catchment‐wide denudation rates derived from 10Be concentrations in river sediments across the southern Longmen Shan. Our results show that average denudation rates increase from <0.15 mm/yr near Ya'an, located in the Sichuan Basin, northwestward to >0.50 mm/yr inside the southern Longmen Shan. The denudation rates correlate with slope gradient, relief, channel steepness, and specific stream power but exhibit a fair degree of scattering at high values. In combination with previous 10Be and low‐temperature thermochronology analyses, we found the denudation rates over kyr‐ to Myr‐timescales to be roughly consistent across the southern Longmen Shan, suggesting this part of the range is close to an exhumational steady state. In terms of spatial distribution, high rates of exhumation and denudation are localized in the hanging walls of major thrust faults, highlighting the role of tectonic structures in regulating the pattern of denudation and topography across the Longmen Shan. Our results favor the “brittle crustal shortening” model in which rock uplift pattern across the Longmen Shan is largely controlled by upper crustal shortening. Along‐strike variations in the distribution of denudation rates and topography can probably be attributed to segmentation of subsurface fault structures.

Dissipation of organochlorine insecticide residues in the environment of Taiwan, 1973-1999

Organochlorine insecticides were used in Taiwan for agricultural and public health purposes mainly from 1950 to 1974. In this study, various survey and analysis studies on soil, water, sediment and animals from 1973 to 1999 were compared, temporal trends were analyzed, and the significance was discussed. In 1973, DDT, DDE, DDD, dieldrin, lindane and aldrin were the major organochlorine insecticides found at higher levels in rice paddy soil in Taiwan. In 1981, average total DDTs concentration of surface soil decreased to one-third of the 1973 level. Subsequently in 1994, total DDTs concentration in surface soil again decreased to one-third of the 1981 level. Dieldrin, lindane and aldrin concentrations decreased even faster and were much lower compared to DDT since 1981. Organochlorine insecticide mean concentrations in river water had reached ppt levels from 1973-1976, but were rarely detected in the 1990s. River sediment concentrations showed a rapid decrease from 1973 to 1976, but although there were variations among different rivers in Taiwan, sediment concentrations of lindane, DDT, DDE and aldrin reached a few ppb and were higher in 1981 compared to 1973-1976 on average. In recent years, total organochlorine insecticide concentration decreased to the ppb level, with most individual insecticide concentrations below 1 ppb. Shellfish organochlorine pesticide concentrations were slightly higher than sediment, and shellfish DDT, DDE, aldrin, dieldrin concentrations also showed an increase from 1973 to 1983 on average. The mean concentrations of DDT and aldrin were higher than 10 ppb in shellfish in 1983 and decreased to below the ppb level in the 1990s. Fish muscle contained ppb levels of organochlorine insecticides in 1973. In recent years, most of the organochlorine insecticide concentrations in shellfish and fish were less than 1 ppb except DDE. Duck eggs and human milk had been found to contain sub ppm levels of DDT and DDE in the 1970s and 1980s, but there was few recent data available. Although organochlorine insecticide levels in the environment of Taiwan have fallen fast over the last 26 years, DDTs and other organochlorine insecticide residue levels in higher animals should be determined for their bioaccumulation potential through the food chain.

Influence of microplastics on nutrients and metal concentrations in river sediments

Microplastics pose threats to aquatic environments because they serve as hard-substrate for microbial community colonization and biofilm formation due to their long-life span and hydrophobic surface which can impact on aquatic ecosystems. However, the association between microplastics and other pollutants, particularly nutrients and metals in river sediments are largely unknown. In this study, microplastics abundance and hazard scores which are the risks arising from chemical compounds used for plastics manufacture, and the correlations between microplastics and the concentrations of total carbon (TC), total nitrogen (TN), total phosphorus (TP) and metals commonly present in the urban environment such as Al, As, Cr, Co, Cu, Fe, Mg, Mn, Ni, Cd, Se, Sr, Zn, Pb, in Brisbane River sediments were investigated. The study confirmed that the risk associated with microplastics is based on their monomer composition rather than the quantities present. Sediments having relatively higher abundance of microplastics with a relatively lower hazard score result in higher nutrient concentrations. The concentrations of metals in river sediments are more dependent on their original sources rather than the concentration of microplastics. Nevertheless, leachate from plastics should be considered in risk assessment in relation to the association between metals and plastics in aquatic environments.

Remote Sensing Monitoring on Spatial Differentiation of Suspended Sediment Concentration in a River-Lake System Based on Sentinel-2 MSI Imaging:A Case for Shengjin Lake and Connected Yangtze River Section in Anhui Province

Carrying out monitoring of suspended sediment concentration in river and lake systems is of great significance for understanding the laws of sediment transport in water and formulating policies on water environmental control. Taking Shengjin Lake and the connected Yangtze river section in Anhui province as the study area, band reflectance of a Sentinel-2 MSI sensor is simulated according to field spectral datasets, and the retrieval model is established by statistical regression from the synchronized suspended sediment concentration measurements. Then, the retrieved results from 28 scene MSI images during 2017-2019 are used to analyze the spatiotemporal variation of suspended sediment concentration in rivers and lakes, and the influence of water level variation on their spatial differentiation is also discussed. The results show that:① The retrieval model established by the ratio of the sixth band to the third band of the MSI sensor is suitable for high-turbidity water type, with high accuracy (R2=0.863, RMSE=22.211 mg·L-1). ② Spatially, the suspended sediment concentration near the lake entrances, northwestern parts of the upper and middle lake areas, and the lower lake is relatively higher, and that of Shengjin Lake is lower than that of the Yangtze River overall except for in summer. Temporally, the suspended sediment concentration in Shengjin Lake is relatively lower in summer and higher in other seasons, while the connected Yangtze River section exhibits the opposite intra-annual variation. ③ The water level, which is caused by the connectivity of rivers and lakes under the influence of the sluice, is the key factor affecting the spatial differentiation of suspended sediment concentration in the river and lake system. The suspended sediment concentration in Shengjin Lake contributes to the Yangtze River in dry and normal water periods, and that in the normal water period is more significant. In contrast, during the flood period, the correlation between suspended sediment concentration in the Yangtze River and that in Shengjin Lake is not obvious.

Globally applicable water quality simulation model for river basin chemical risk assessment

Abstract Many companies around the world need to assess water environmental risks in accordance with sustainable development goals (SDGs) set by the United Nations, environmental, social, and governance (ESG) investment, the Carbon Disclosure Project (CDP) water program, and also their corporate social responsibility (CSR) activities. Although companies have been requested to voluntarily evaluate their water risks and provide information thereon, the water quality risk in river basins is difficult to assess owing to insufficient monitoring information. This paper proposes the National Institute of Advanced Industrial Science and Technology - Standardized Hydrology-based AssessmeNt tool for chemical Exposure Load (AIST-SHANEL) model as a river water quality simulation model that can be employed for chemical risk assessment and evaluation of the effects of use of a company's consumer products on river basins. AIST-SHANEL is the only unsteady analysis model that estimates spatial and temporal chemical concentrations and assesses water quality within river basins by point/non-point emission of chemical substances. To evaluate the efficacy of AIST-SHANEL, a case study focused on the surfactant linear alkylbenzene sulfonate (LAS), found in the detergents of widely used health care products, was conducted. The water risk assessment was performed in three Japanese river basins with different watershed characteristics: Tama River in urban Tokyo with high sewerage penetration rate, Nikko River in urban Nagoya with a low sewerage penetration rate, and the nonurban None River with no sewerage. In Tama River, the LAS river water concentrations were found to be strongly influenced by seasonal variations as well as the flow rate associated with dilution and temperature-induced biodegradation. Their concentrations in Nikko River were strongly affected by flooding, indicating that the influence on their transport through the drainage channel was due more to low sewage levels than temperature-induced biodegradation. In None River, the LAS river water concentrations were only slightly affected by dilution. The river sediment concentrations of LAS in the three river basins showed mild seasonal variations. The 95th percentile of river water concentrations, predicted environmental concentration (PEC), at the most downstream and maximum concentration grids in the three river basins were 4.5 and 51.2 mg/m3 for Tama River, 30 and 58.6 mg/m3 for Nikko River, and 0.15 mg/m3 for None River. Neither of the PECs nor maximum values at these grids exceeded the predicted no-effect concentration (PNEC) of LAS (270 mg/m3), suggesting minimal ecological risk in these river basins over the year for all target river basins due to LAS. Furthermore, we analyzed a scenario in which LAS was substituted with the highly biodegradable alcohol ethoxylates (AE) for corporate self-management measures in Nikko River with only a few sewers, and therefore only a low risk. The AIST-SHANEL model has useful and widespread application with no need for monitoring by companies; as long as the relevant watershed characteristics can be obtained, water risk assessments of chemical substances can be performed for any river basin in the world.

Basinga: A cell‐by‐cell GIS toolbox for computing basin average scaling factors, cosmogenic production rates and denudation rates

AbstractThe calculation of denudation rates from the measured cosmogenic nuclide concentrations in river sediments requires assumptions and approximations. Several different approaches and numerical tools are available in the literature. A widely used analytical approach represents the muogenic production with one or two exponentials, assumes the attenuation length of muons to be constant and also neglects temporal variations in the Earth's magnetic field. The denudation rates are then calculated directly and analytically from the measured concentrations. A second numerical and iterative approach was more recently proposed and considers a more rigorous muogenic production law based on pre‐calculated variable attenuation length of muons and accounts for temporal changes of the magnetic field. It also assumes a specific distribution of denudation rates throughout the basin and uses an iterative approach to calculate the basin average denudation rates.We tested the two approaches across several natural basins and found that both approaches provide similar denudation results. Hence, assuming exponential muogenic production and constant attenuation length of muons in the rock has little impact on the derived denudation rates. Therefore, unless a priori known distributions of denudation rates are to be tested, there does not appear to be any particular gain from using the second iterative method which is computationally less effective.Based on these findings, we developed and describe here Basinga, a new ArcGIS® and QGIS toolbox which computes the basin average scaling factors, cosmogenic production rates and denudation rates for several tens of drainage basins together. Basinga follows either the Lal/Stone or the Lifton/Sato/Dunai scaling schemes and includes several optional tools for correcting for topographic shielding, ice cover and lithology. We have also developed an original method for correcting the cosmogenic production rates for past variations in the Earth's magnetic field. © 2019 John Wiley & Sons, Ltd.

Use of NDVI and Landscape Metrics to Assess Effects of Riverine Inputs on Wetland Productivity and Stability

Alterations to Louisiana’s river systems and local hydrology have resulted in reduced freshwater, sediment, and nutrient inputs to wetland landscapes, causing significant negative impacts on marsh productivity and stability. This study set out to assess regional- and basin-scale impacts of river connectivity and sediment availability on wetland productivity. Satellite data were used in conjunction with river discharge, river sediment concentration, and wetland accretion data to evaluate correlations between river connectivity and wetland productivity and stability. Significant correlations were observed between river connectivity and Normalized Difference Vegetation Index (NDVI) and Aggregation Index (AI) values across a 10 year period of analysis. Moderate correlations (r2 = 0.51) between mean NDVI and AI values were observed for all wetland vegetation in coastal Louisiana. Middle Coast wetlands had the highest river connectivity and significantly higher aboveground productivity, spatial integrity, and wetland area. The Chenier Plain, with moderate sediment and nutrient inputs, consisted primarily of moderate productivity and integrity. The majority of the inactive Deltaic Plain, which is largely sediment deprived, consists of landscapes with the lowest wetland productivity and spatial integrity. This study linked wetland area, configuration, and productivity with river connectivity to provide an enhanced understanding of river and sediment importance for wetland stability and restoration.

Evidence for plunging river plume deposits in the Pahrump Hills member of the Murray formation, Gale crater, Mars

AbstractRecent robotic missions to Mars have offered new insights into the extent, diversity and habitability of the Martian sedimentary rock record. Since the Curiosity rover landed in Gale crater in August 2012, the Mars Science Laboratory Science Team has explored the origins and habitability of ancient fluvial, deltaic, lacustrine and aeolian deposits preserved within the crater. This study describes the sedimentology of a ca 13 m thick succession named the Pahrump Hills member of the Murray formation, the first thick fine‐grained deposit discovered in situ on Mars. This work evaluates the depositional processes responsible for its formation and reconstructs its palaeoenvironmental setting. The Pahrump Hills succession can be sub‐divided into four distinct sedimentary facies: (i) thinly laminated mudstone; (ii) low‐angle cross‐stratified mudstone; (iii) cross‐stratified sandstone; and (iv) thickly laminated mudstone–sandstone. The very fine grain size of the mudstone facies and abundant millimetre‐scale and sub‐millimetre‐scale laminations exhibiting quasi‐uniform thickness throughout the Pahrump Hills succession are most consistent with lacustrine deposition. Low‐angle geometric discordances in the mudstone facies are interpreted as ‘scour and drape’ structures and suggest the action of currents, such as those associated with hyperpycnal river‐generated plumes plunging into a lake. Observation of an overall upward coarsening in grain size and thickening of laminae throughout the Pahrump Hills succession is consistent with deposition from basinward progradation of a fluvial‐deltaic system derived from the northern crater rim into the Gale crater lake. Palaeohydraulic modelling constrains the salinity of the ancient lake in Gale crater: assuming river sediment concentrations typical of floods on Earth, plunging river plumes and sedimentary structures like those observed at Pahrump Hills would have required lake densities near freshwater to form. The depositional model for the Pahrump Hills member presented here implies the presence of an ancient sustained, habitable freshwater lake in Gale crater for at least ca 103 to 107 Earth years.

Untreated wastewater as a source of carbapenem-resistant bacteria to the riverine ecosystem

Bacteriological pollution, especially that including clinically important bacteria, of the aquatic environment caused by anthropogenic pressure attracts much attention with regard to public health. Reports to date have not addressed the concentration of emerging carbapenem-resistant bacteria (CRB) in riverine ecosystems, and the source of this pollution is hard to track. We examined the impact of discharge of untreated wastewaters on the bacterial population in the riverine ecosystem, with emphasis on clinically important CRB using a small river in Croatia as a model. River sediments were analysed mineralogically and geochemically. Cultivation of CRB was performed at 37 and 42°C to distinguish the presumably environmental intrinsically resistant (CRB37) from the presumably clinically important acquired resistance (CRB42) species. The significantly positive correlation of CRB42 with CRB37 and total heterotrophs, but not with intestinal enterococci, suggests that entry of CRB42 in riverine ecosystem is not necessarily connected to faecal pollution. The numbers and prevalence of CRB42 are rather dependent on the type of pollution, and is connected to the discharge of wastewaters from different human and animal healthcare centres. Emerging hospital pathogens Acinetobacter baumannii and Klebsiella pneumoniae were exclusively isolated among CRB42 from river water after the discharge of wastewater of a general hospital. The CRB42, once discharged into the riverine ecosystem, behaves as part of the indigenous bacterial population, and could be spread through the natural water bodies or accumulate in river sediments. This implies the need for disinfection of hospital wastewater prior to its discharge into the natural environment in order to avoid the consequent public-health threat. The anthropogenic impact evidenced as bacteriological changes is accompanied by an increase in heavy metal concentrations in river sediments.

Regional Comparison of Impacts from Seven Australian Coal Mine Wastewater Discharges on Downstream River Sediment Chemistry, Sydney Basin, New South Wales Australia

This study investigates the accumulation of licensed and regulated coal mine wastewater pollutants from seven coal mines on each mines respective receiving waterways river sediments. Results from this study shows that the coal mine wastewater pollutants are accumulating within river sediments downstream of the coal mine wastewater inflows at varying levels often greater than the ANZECC guidelines for sediment and often above reference condition sediment concentrations. This is of great concern as these pollutants will likely continue to persist in the river sediment and eventually become legacy pollutants. Coal mine wastewater discharges in New South Wales are regulated by the New South Wales Environmental Protection Authority [NSW EPA] and environmental protection of receiving waterways is implemented through Environmental Protection Licenses. Environmental Protection Licenses set discharge limits for water quality and chemical concentrations within the coal mine waste waters. Though they do not take into account river sediment concentrations. It appears water column pollution regulation at these coal mines is in fact failing to protect the environment whilst still regulated and will continue into the future post mining, licensing and regulation. Water column regulation may well be impractical in protecting the environment as it appears that water column concentrations do not portray the overall environmental impact. It is recommended that the New South Wales Environmental Protection Authority investigate these findings and continue to improve water column pollutant limits as to alleviate the continued accumulation and magnification of the contaminants.