History Of Contamination Research Articles

Rapid Testing and Interventions to Control Legionella Proliferation following a Legionnaires' Disease Outbreak Associated with Cooling Towers.

Most literature to date on the use of rapid Legionella tests have compared different sampling and analytical techniques, with few studies on real-world experiences using such methods. Rapid tests offer a significantly shorter feedback loop on the effectiveness of the controls. This study involved a complex of five factories, three of which had a history of Legionella contamination in their cooling water distribution system. Multiple sampling locations were utilised to take monthly water samples over 39 months to analyse for Legionella by both culture and quantitative polymerase chain reaction (qPCR). Routine monitoring gave no positive Legionella results by culture (n = 330); however, samples were frequently (68%) positive by qPCR for Legionella spp. (n = 1564). Legionella spp. qPCR assay was thus found to be a good indicator of cooling tower system health and suitable as a routine monitoring tool. An in-house qPCR limit of 5000 genomic units (GU)/L Legionella spp. was established to trigger investigation and remedial action. This approach facilitated swift remedial action to prevent Legionella proliferation to levels that may represent a public health risk. Cooling tower operators may have to set their own action levels for their own systems; however, in this study, 5000 GU/L was deemed appropriate and pragmatic.

Multivariable 3D Geovisualization of Historic and Contemporary Lead Sediment Contamination in Lake Erie

Lead sediment contamination in Lake Erie stems from a long history of natural and synthetic resource production. Sediment samples with variable sampling densities were collected by the Canada Centre for Inland Waters in 1971, 1997/1998, and 2014. The kriging interpolation method was used to create continuous sediment contamination surfaces for time/space comparisons. Change detection analyses identified an overall decreasing trend in high lead pollution levels from 1971 to 2014, while sediments with the lowest concentrations increased in surface area. Lake-wide circulation patterns and bathymetric data were added to interpolated contamination surfaces to enhance the understanding of interrelated hydrodynamic processes and geophysical features in the movement of contaminated sediments. Utilizing visualization tools in Esri’s ArcScene, bathymetric data were employed to enhance the geographic context of contamination maps. The physical barriers to sediment transportation created by bathymetric features can be visualized in three-dimensions. Elevated features between lake basins are easily recognized as impedances to lake currents when circulation directions are draped over the bathymetric model. By using illumination tools and techniques, geovisualizations of lead sediment contamination throughout Lake Erie create a scientific communication tool for a wide audience to use in multiple-criteria decision making for environmental remediation of sediment contamination.

Long-term response of marine benthic fauna to thin-layer capping with powdered activated carbon in the Grenland fjords, Norway.

The Grenland fjords in Norway have a long history of contamination by large emissions of dioxins and mercury. As a possible sediment remediation method in situ, thin-layer capping with powdered activated carbon (AC) mixed with clay was applied at two test sites at 30m and 95m depth in the Grenland fjords. This study presents long-term effects of the AC treatment on the benthic community structure, i.e. nine years after capping. Capping with AC significantly reduced the number of species, their abundance and biomass at the two test sites, compared to uncapped reference sites. At the more shallow site, the dominant brittle star species Amphiura filiformis disappeared shortly after capping and did not re-establish nine years after capping. At the deeper site, the AC treatment also caused long-lasting negative effects on the benthic community, but some recovery was observed after nine years. Ecological indices used to assess environmental status did not capture the impaired benthic communities caused by the capping. The present study is the first documentation of negative effects of powdered AC on marine benthic communities on a decadal scale. Our results show that the benefits of reduced contaminant bioavailability from capping with AC should be carefully weighed against the cost of long-term detrimental effects on the benthic community. More research is needed to develop a thin-layer capping material that is efficient at sequestering contaminants without being harmful to benthic species.

Historical pond systems as long-term composite archives of anthropogenic contamination in the Vrchlice River, Czechia

River damming has numerous benefits and adverse consequences. Unlike large dam reservoirs whose construction peaked in the twentieth century, historical ponds and their accumulated legacy sediments span much longer time periods. Small ponds in many areas worldwide are sinks for anthropogenic pollutants and affect sediment delivery to downstream river reaches. Thousands of ponds cover an area of >0.2 % of the territory of Czechia, equal to the area of its ten largest dam reservoirs. This paper reports a sequence of constructed and removed pond dams along the Vrchlice River, Czechia, and their use as sedimentary archives, in order to reconstruct the long-term (>200 yr) history of contamination. Historical maps, geophysical profiles, activities of caesium-137 isotope, grain size, and sediment geochemistry in 16 sediment cores enabled the reconstruction of contamination in the pond, dam reservoir, and floodplain sediments since ∼1780. Contamination by lead, copper, zinc, arsenic, and cadmium from atmospheric, geogenic and agricultural sources increased since ∼1850 peaked in the 1970s and 1980s, and then decreased slightly. Polycyclic aromatic hydrocarbons and pesticides polluted post-1970 sediments, reflecting their use in agriculture. The removal of dams resulted in the rapid incision of newly formed river channels into the old pond deposits. Following the reinstatement of dams, channels filled rapidly (up to 5.2 cm/yr) with new lacustrine sediment, whereas sediment accumulated slowly (<0.4 cm/yr) outside the channels. Upon dam removal, contaminated channel-fill sediment likely redistributed into the water course. As ponds are complex depositional systems with the heterogeneous distribution of sediment and associated contaminants, active and extinct ponds are promising long-term sedimentary archives that can extend understanding of human interactions with Earth systems.

Air Concentrations of Gaseous Elemental Mercury and Vegetation–Air Fluxes within Saltmarshes of the Tagus Estuary, Portugal

In situ air concentrations of gaseous elemental mercury (Hg(0)) and vegetation–atmosphere fluxes were quantified in both high (Cala Norte, CN) and low-to-moderate (Alcochete, ALC) Hg-contaminated saltmarsh areas of the Tagus estuary colonized by plant species Halimione portulacoides (Hp) and Sarcocornia fruticosa (Sf). Atmospheric Hg(0) ranged between 1.08–18.15 ng m−3 in CN and 1.18–3.53 ng m−3 in ALC. In CN, most of the high Hg(0) levels occurred during nighttime, while the opposite was observed at ALC, suggesting that photoreduction was not driving the air Hg(0) concentrations at the contaminated site. Vegetation–air Hg(0) fluxes were low in ALC and ranged from −0.76 to 1.52 ng m−2 (leaf area) h−1 for Hp and from −0.40 to 1.28 ng m−2 (leaf area) h−1 for Sf. In CN, higher Hg fluxes were observed for both plants, ranging from −9.90 to 15.45 ng m−2 (leaf area) h−1 for Hp and from −8.93 to 12.58 ng m−2 (leaf area) h−1 for Sf. Mercury flux results at CN were considered less reliable due to large and fast variations in the ambient air concentrations of Hg(0), which may have been influenced by emissions from the nearby chlor-alkali plant, or historical contamination. Improved experimental setup, the influence of high local Hg concentrations and the seasonal activity of the plants must be considered when assessing vegetation–air Hg(0) fluxes in Hg-contaminated areas.

Comparative history of Campylobacter contamination on chicken meat and campylobacteriosis cases in the United States: 1994–2018

In many countries campylobacteriosis ranks as one of the most frequently reported foodborne illnesses and poultry is the commodity that is most often associated with these illnesses. Nevertheless, efforts to reduce the occurrence of pathogen contamination on poultry are often more focused on Salmonella. While some control measures are pathogen specific, such as pre-harvest vaccination for Salmonella, improvements in sanitary dressing and interventions applied during the slaughter process can be effective against all forms of microbial contamination. To investigate the potential effectiveness of these non-specific pathogen reduction strategies in the United States, it is helpful to assess if, and by how much, Campylobacter contamination of chicken meat has changed across time. This study assesses change considering data collected in both slaughter and retail establishments and comparing observed trends in contamination with trends in human surveillance data. The results support the assertion that substantial reductions in Campylobacter contamination of chicken meat in the late 1990s and early 2000s contributed to a reduction in the human case rate of campylobacteriosis. Further reductions in chicken meat contamination between 2013 and 2018 are more difficult to associate with trends in human illnesses, with one contributing factor being the inclusion of culture independent diagnostic test results in the official case counts during that time. Other contributing factors are discussed.

Predisposing Factors, Clinical Presentations, and Outcomes of Contact Lens-Related Pythium Keratitis.

To describe predisposing factors, clinical presentations, and treatment outcomes of contact lens (CL)-related Pythium keratitis. This was an 11-year retrospective study of CL-related Pythium keratitis conducted from 2009 to 2019. Six eyes of 6 patients were identified. Demographics, predisposing factors, CL history, clinical presentation, diagnostic tests, treatments, and outcomes were reviewed. Mean age of the patients was 34 years (SD 16.3 years) with equal proportion between male and female patients. Five of 6 patients (83.3%) used soft CL, whereas 1 patient used rigid gas permeable lens. All patients had a history of water contamination (tap water and water from river and sea). Mean duration from the onset was 7.8 days (range 4-14 days). Mean size of the corneal lesion was 3.33 mm (SD 1.31 mm) in width. The typical feature of tentacle-like lesions radiating in a reticular pattern was observed in all patients. Feathery edge (1 eye), satellite lesions (2 eyes), and radial keratoneuritis (2 eyes) were also found. Every patient received therapeutic penetrating keratoplasty because of failed medical treatments. One patient subsequently underwent enucleation. Globe salvage was achieved in 5 patients (83.33%). Awareness of the history of water contamination, recognition of specific clinical features of Pythium keratitis, and performing surgical treatment are key for achieving globe salvage in patients with CL-related Pythium keratitis.

Analysis of the Transport Number of Cadmium and Lead from an Extract of Soils Contaminated with Mining Seals through a Commercial Membrane

The historical contamination of soils by heavy metals shows little degradation and therefore they are considered as persistent bioaccumulative toxins, which represent a marked risk to human health ecosystems. In recent years, technologies have been developed to help alleviate the problem of contaminated soils. The methods developed have mainly focused on in situ remediation, among which electro remediation stands out for both organic and inorganic pollutants. The present work aims to analyze variables for the treatment of soils with heavy metals using electrochemical strategies with the application of commercial membranes. The analysis made it possible to determine the transition zone where the depletion of the counterion occurs in the diffusion layer of the cadmium and lead ion. The results of the limit current analysis in the membrane reflect the presence of a mixture of ions where the diffusion layer is altered by the mixture of ions present. The results suggest that the membrane presents fouling of complexing organic compounds in the diffusion layer and therefore behaves like a reactive membrane where the permeation channels and the fixed charge change their original function.

Modeling degradation kinetics of profenofos using Acinetobacter sp.33F

Profenofos has been known for history of contamination to aquatic systems. The fate of profenofos in liquid medium is unknown due to limited number of studies performed. Very less information is available about the degradation behavior of profenofos in the liquid medium. This study is an attempt to analyze the growth and degradation kinetics of profenofos in the minimal salt medium and Hoagland’s solution using an efficient bacterial strain Acinetobacter sp.33F. Acinetobacter sp.33F has been proven to degrade profenofos in soil earlier, but its profenofos degradation kinetics has not been evaluated. Hoagland’s medium is considered for degradation studies because it is used in the hydroponics cultivation in soil-less environments. Hoagland’s solution will act as a mimic for the soil, and its effect on profenofos biodegradation will be evaluated. The study evaluated the growth and degradation kinetics of commercial and analytical grade profenofos using an efficient bacterium Acinetobacter sp.33F. The kinetics studies were performed in minimal salt medium and Hoagland’s medium. Growth kinetics parameters including μ max (h −1 ), K s (mg/L), K i (mg/L), and μ max /K s . were calculated. Degradation kinetics parameters including q max (mg h − 1 ) and K S (mg/L) were calculated. • Profenofos degradation kinetics modeling was performed in soil less aqueous solutions. • Profenofos degradation and kinetics modeling were performed at 25–200 mg/L. • The bacterium degrades profenofos in minimal medium as well as in hydroponic condition. • This is the first report of profenofos degradation kinetics in Hoagland’s solution.

An epidemic model integrating direct and fomite transmission as well as household structure applied to COVID-19

This paper stresses its base contribution on a new SIR-type model including direct and fomite transmission as well as the effect of distinct household structures. The model derivation is modulated by several mechanistic processes inherent from typical airborne diseases. The notion of minimum contact radius is included in the direct transmission, facilitating the arguments on physical distancing. As fomite transmission heavily relates to former-trace of sneezes, the vector field of the system naturally contains an integral kernel with time delay indicating the contribution of undetected and non-quarantined asymptomatic cases in accumulating the historical contamination of surfaces. We then increase the complexity by including the different transmission routines within and between households. For airborne diseases, within-household interactions play a significant role in the propagation of the disease rendering countrywide effect. Two steps were taken to include the effect of household structure. The first step subdivides the entire compartments (susceptible, exposed, asymptomatic, symptomatic, recovered, death) into the household level and different infection rates for the direct transmission within and between households were distinguished. Under predefined conditions and assumptions, the governing system on household level can be raised to the community level. The second step then raises the governing system to the country level, where the final state variables estimate the total individuals from all compartments in the country. Two key attributes related to the household structure (number of local households and number of household members) effectively classify countries to be of low or high risk in terms of effective disease propagation. The basic reproductive number is calculated and its biological meaning is invoked properly. The numerical methods for solving the DIDE-system and the parameter estimation problem were mentioned. Our optimal model solutions are in quite good agreement with datasets of COVID-19 active cases and related deaths from Germany and Sri Lanka in early infection, allowing us to hypothesize several unobservable situations in the two countries. Focusing on extending minimum contact radius and reducing the intensity of individual activities, we were able to synthesize the key parameters telling what to practice.

Assessment of Pollution and Ecological Risk Index of Heavy Metals in the Surface Sediment of Estuary and the Coastal Environment of Bay of Bengal

The Mahanadi River, surrounding estuaries along the coastal water are important to understand the relationship between heavy metals, ecosystem and human health, as the region being used largely by fisher communities for the potential fishing ground and agriculture. The study evaluates the ecological risk index of heavy metals in the surface sediments along the coastal environment of the Bay of Bengal between 2011 and 2012. The metals concentrations were varied from a maximum in Manganese (4,137 mg/kg) to a minimum in Cadmium (17 mg/kg). The factor analysis result shows that higher concentration of cadmium (Cd), chromium (Cr), Nickel (Ni), lead (Pb), and Zinc (Zn) were significant environmental risk in the study region. The cluster analysis indicated that the creek sediment is heavily polluted than the estuary ecosystem of the coastal environment. Enrichment factor and Geo-accumulation Index of the surface sediment resulted that, the Cd was high enrichment and was moderate to severe in the study region. Pollution load index denoted that the sampling sites in the creek sediment were more polluted than coastal due to the influence of agricultural runoff, industrial and anthropogenic. The Cr, Cu, Ni, Pb, and Cd concentrations result in the potential toxicity to the aquatic organisms based on the comparison with the SQGs. Indicates the average magnitude of the metals in the study period in the decreasing order of Mn, Cr, Cu, Ni, Pb, and Cd which were alarming except iron (Fe) in the estuary and coastal ecosystem of the Bay of Bengal. The present investigation would be a first-hand informant to understand the impact of heavy metals in the ecosystem in the region. The result inputs need to be monitored further in the long term basis for isotopic sediment dating to reconstruct the contamination history for the ecosystem modeling, sustainable ecosystem, and coastal zone management.

Soil Lead Concentration and Speciation in Community Farms of Newark, New Jersey, USA

Farmed urban soils often bear legacies of historic contamination from anthropogenic and industrial sources. Soils from seven community farms in Newark, New Jersey (NJ), USA, were analyzed to determine the concentration and speciation of lead (Pb) depending on garden location and cultivation status. Samples were evaluated using single-step 1 M nitric acid (HNO3) and Tessier sequential extractions in combination with X-ray absorption fine structure spectroscopy (XAFS) analysis. Single-step extractable Pb concentration ranged from 22 to 830 mg kg−1, with 21% of samples reporting concentrations of Pb &gt; 400 mg kg−1, which is the NJ Department of Environmental Protection (NJDEP) limit for residential soils. Sequential extractions indicated lowest Pb concentrations in the exchangeable fraction (0–211 mg kg−1), with highest concentrations (0–3002 mg kg−1) in the oxidizable and reducible fractions. For samples with Pb &gt; 400 mg kg−1, Pb distribution was mostly uniform in particle size fractions of &lt;0.125–1 mm, with slightly higher Pb concentrations in the &lt;0.125 mm fraction. XAFS analysis confirmed that Pb was predominantly associated with pyromorphite, iron–manganese oxides and organic matter. Overall results showed that lowest concentrations of Pb are detected in raised beds, whereas uncultivated native soil and parking lot samples had highest values of Pb. As most of the Pb is associated with reducible and oxidizable soil fractions, there is a lower risk of mobility and bioavailability. However, Pb exposure through ingestion and inhalation pathways is still of concern when directly handling the soil. With increasing interest in urban farming in cities across the USA, this study highlights the need for awareness of soil contaminants and the utility of coupled macroscopic and molecular-scale geochemical techniques to understand the distribution and speciation of soil Pb.

Health risk assessment in urban parks soils contaminated by metals, Rio Grande city (Brazil) case study

Soils and artificial surfaces of urban parks can be contaminated by toxic substances and offer risk to the human health, especially to children. Rio Grande city, southern Brazil, is a peculiar site from the point of view of environmental contamination, since the current levels of contamination reflect an accumulation of different polluting sources started in the 18th century up to the urban and industrial sources of the present. The history of Hg contamination refers to the use of Hg salts in textile activities in the 18th century and the consequent use of contaminated sediments to land urban areas. The current contamination involves metals such as Cu, Ni, Pb and Zn is related to the high degree of urbanization in the city, as well as the petrochemical and fertilizer industry. The study aimed to achieve a human health risk assessment of urban parks soils, specifically for Cu, Hg, Ni, Pb and Zn. To carry out the risk assessment using the USEPA model, three urban parks with a history of contamination were studied, using different soil exposure pathways (oral, dermal and inhalation) in the carcinogenic (Ni and Pb) and non-carcinogenic (Cu, Hg, Ni, Pb and Zn) scenarios for children and adults. The non-carcinogenic risk of Pb was found in the three urban parks studied, for children and Hg in two urban parks. Pb and Ni showed no carcinogenic risk. Even so, the high non-carcinogenic risk of Hg and Pb showed that the contamination of the past and the present are found in the urban parks of Rio Grande city, putting the health of children who use these collective spaces at risk.

GROUNDWATER FLOW AND MULTI-COMPONENT REACTIVE TRANSPORT SIMULATION OF ACID MINE DRAINAGE AT A FORMER MINE SITE

Contamination of groundwater resources due to Acid Mine Drainage (AMD) is one of the severest environmental problems. Understanding complex geochemical processes responsible for the generation of AMD within the mine waste deposits is imperative for effective management and remediation of contaminated mine sites. A multi-component reactive transport simulation is developed based on PHT3D to simulate the geochemical evolution of AMD at the Rum Jungle Mine site that has undergone a long history of groundwater contamination. The reactive transport simulation utilized hydraulic head distribution obtained from MODFLOW based calibrated flow model. Geochemical processes considered for the reactive simulation were conceptualized based on previous geochemical characterization and the contaminant of concerns were limited to copper, iron, manganese, aluminum, zinc, and pyrite minerals considering their environmental significance. The simulation results showed that the simulated plume followed mobility pattern dominated by oxidation of sulfide minerals resulting in AMD and subsequent escalation in the concentration of dissolved metals. Simulated and observed concentration for different reactive species appeared to be in a similar range implying reasonable approximation of the physical system. The detailed calibration of reactive transport simulation is restrained by uncertainties associated with aquifer heterogeneity, sparsity in available information, and inaccurate understanding of the geochemical processes.

Historic contamination alters mercury sources and cycling in temperate estuaries relative to uncontaminated sites

Mercury (Hg) is a global and persistent pollutant which can be methylated to more toxic forms (methylmercury; MeHg) in natural systems. Both forms pose a health risk to humans and wildlife, and exposure often begins in aquatic environments. Therefore, quantifying aquatic concentrations and identifying source pathways is important for understanding biotic exposure. In this study, data from estuaries in the Northeast United States were combined to evaluate how point source contamination impacts the concentration and source dynamics of water column total and MeHg with an emphasis on sediment versus non-sediment sources. Partial least squares regression models were implemented to identify a set of variables most related to water column MeHg and total Hg (HgT) across the estuaries. The main findings suggest that contaminated sites have strong internal recycling of HgT that dominates over external inputs, and this leads to elevated concentrations of HgT and MeHg in the local water columns. However, HgT sources in uncontaminated estuarine systems have a strong connection to the local watershed with dissolved HgT linked to dissolved organic carbon, and particulate HgT linked to watershed land use and estuarine mixing. There was little correlative evidence that water column MeHg concentrations were linked to sediment in such systems, but unlike HgT, the concentrations were also not clearly linked to the watershed. Instead, in situ methylation of dissolved water column HgT appeared to dominate the MeHg source pathway. The results suggest that Hg point-source contaminated sites should be considered independently from non-contaminated sites in terms of management, and that land use plays an important indirect role in coastal MeHg dynamics.

Investigation into Adaptation in Genes Associated with Response to Estrogenic Pollution in Populations of Roach (Rutilus rutilus) Living in English Rivers.

Exposure of male fish to estrogenic substances from wastewater treatment works (WwTWs) results in feminization and reduced reproductive fitness. Nevertheless, self-sustaining populations of roach (Rutilus rutilus) inhabit river stretches polluted with estrogenic WwTW effluents. In this study, we examine whether such roach populations have evolved adaptations to tolerate estrogenic pollution by comparing frequency differences in single-nucleotide polymorphisms (SNPs) between populations sampled from rivers receiving either high- or low-level WwTW discharges. SNPs within 36 "candidate" genes, selected for their involvement in estrogenic responses, and 120 SNPs in reference genes were genotyped in 465 roaches. There was no evidence for selection in highly estrogen-dependent candidate genes, including those for the estrogen receptors, aromatases, and vitellogenins. The androgen receptor (ar) and cytochrome P450 1A genes were associated with large shifts in allele frequencies between catchments and in individual populations, but there is no clear link to estrogen pollution. Selection at ar in the effluent-dominated River Lee may have resulted from historical contamination with endocrine-disrupting pesticides. Critically, although our results suggest population-specific selection including at genes related to endocrine disruption, there was no strong evidence that the selection resulted from exposure to estrogen pollution.

Identifying redox transition zones in the subsurface of a site with historical contamination

Reactive iron mineral coatings found throughout reduction-oxidation (redox) transition zones play an important role in contaminant transformation processes. This research focuses on demonstrating a process for effectively delineating redox transition zones at a site with historical contamination. An 18.3 meter core was collected, subsampled, and preserved under anoxic conditions to maintain its original redox status. To ensure a high vertical resolution, sampling increments of 5.08 cm in length were analyzed for elemental concentrations with X-ray fluorescence (XRF), sediment pH, sediment oxidation-reduction potential (ORP), total volatile organic carbon (TVOC) concentration in the sample headspace, and abundant bacteria (16S rRNA sequencing). Over the core's length, gradients observed ranged from 3.74 to 8.03 for sediment pH, −141.4 mV to +651.0 mV for sediment ORP, and from below detection to a maximum of 9.6 ppm TVOC concentration (as chlorobenzene) in the headspace. The Fe and S gradients correlated with the presence of Fe and S reducing bacteria. S concentrations peaked in the Upper Zone and Zone 1 where Desulfosporosinus was abundant, suggesting precipitation of iron sulfide minerals. In Zone 2, Fe concentrations decreased where Geobacter was abundant, potentially resulting in Fe reduction, dissolution, and precipitation of minerals with increased solubility compared to the Fe(III) minerals. Using complementary geochemical and microbial data, five redox transition zones were delineated in the core collected. This research demonstrates a systematic approach to characterizing redox transition zones in a contaminated environment.

Deciphering centurial anthropogenic pollution processes in large lakes dominated by socio-economic impacts

Human activities have greatly increased the influx of pollutants into global freshwater ecosystems. Understanding the pollution patterns at multi-decadal scales, and how the socio-economic development and public policy have shaped them, are crucial to assess the current status of environmental quality and develop sound strategies for watershed management. This study takes the test case of large Taihu Lake (∼2,338 km2) in rapidly developing regions of China, to examine the temporal-spatial patterns and driving factors of centurial trace metal and metalloid contamination. Using comparative sedimentary records, we applied multiple geochemical indices and positive matrix factorization modelling to identify the anthropogenic versus natural sources and their contributions. Results identified cadmium, antimony and lead as typical pollutants, with high anthropogenic contribution rates of 58–79 %, 54–62 % and 28–36 %, respectively. Contamination histories were asynchronous across the lake, starting from the 1940s (North) to mid-1990s (East), following the gradient of socio-economic stressors of the sub-basins. Specifically, industrial and agricultural inputs through runoff and river networks were main sources of metal in the northern and western lake parts, accounting for ≥ 70 % since the 1980s. In contrast, aquaculture and agriculture related sources (≥ 80 %) dominated in Eastern Taihu Lake over the last decade. Moreover, atmospheric metal deposition from nearby industrial cities significantly affected the northern parts of the lake. The stationary and/or slightly decreased contamination trends, especially after 2000 AD, shed light into the effectiveness of recent environmental regulation. Our findings suggest, however, that agricultural non-point sources and legacy effects probably delayed reductions in the input of pollutants. Sustainable management of similar large watersheds worldwide, therefore, would benefit by highlighting the role of multiple anthropogenic sources, legacy contamination and lake-specific response.

Depositional environments and historical contamination as a framework to reconstruct fluvial sedimentary evolution

In this study, we explore the variability of sedimentation conditions (e.g., grain-size, accumulation rate, contamination) according to fluvial depositional environments. Indeed, sediment cores are commonly used as archives of natural and anthropogenic activities in hydrosystems, but their interpretation is often complex, especially in a fluvial context where many factors may affect the quality, continuity, and resolution of the record. It is therefore critical to thoroughly understand the nature and dynamics of an environment in which a sediment core is sampled to be able to interpret it. To that end, four depositional environments from a bypassed reach of the Rhône River were comparatively investigated through geophysics in order to assess the range of sedimentation conditions: a floodplain, a semi-active secondary channel, an active secondary channel, and a dam reservoir. Sediment cores were retrieved from each environment and thoroughly characterised (e.g., grain-size, Total Organic Carbon, organic contaminants). Robust age-depth models were elaborated for each core based on 137Cs, 210Pbex, and Persistent Organic Pollutants (POPs) trends. The results show that each depositional environment recorded a different time-period, and therefore different contamination levels and trends. In particular, a shift from polychlorinated biphenyls (PCBs) to polybrominated diphenyl ethers (PBDEs) as the predominant POP in the sediments can be observed, the tipping point being set in the 1970s. Two types of infrastructure-induced legacy sediments related to two periods of river engineering in the reach were also identified using grain-size analysis. The combination of geophysical methods (Ground Penetrating Radar) and sediment cores is therefore confirmed as a relevant methodology that should be promoted in fluvial contexts in order to reconstruct the sedimentary evolution of fluvial corridors. The study also highlights the challenges of dating recent fluvial sediments and proposes a multi-proxy dating methodology using POPs contamination trends.

History of environmental contamination at Sunny Corner Ag-Pb-Zn mine, eastern Australia: A meta-analysis approach.

Environmental impacts associated with mining can be important even after cessation of ore extraction, particularly where sites are abandoned and unremediated. Acid Mine Drainage (AMD) is a common concern in such legacy mines where sulfide ores were extracted. AMD can introduce large concentrations of heavy metals to aquatic systems and contaminate the environment for many kilometres downstream of old mines. Understanding the pattern and history of contamination from legacy mines can help environmental managers make better management decisions. Meta-analysis is a statistical tool that can help determine the significance of changes in metal contamination over the years since cessation of mining. Here we use meta-analysis to examine metal contamination at and downstream of Sunny Corner silver (Ag)-lead (Pb)-zinc (Zn) mine in eastern Australia. Copper (Cu), Zn and Pb concentrations in water increased from 1978 to 2018 within 2km downstream of the main mine adit, whereas for stream sediment, only Zn concentrations increased significantly over the same period. In contrast, Pb concentrations in surface soil decreased over the years from 2000 to 2018.