Legacy Pollutants Research Articles

Throughfall and Litterfall Fluxes Reveal New Inputs and Foliar Cycling Maintain Pb, Cd, Cu, and Zn Pollution Legacy in Eastern U.S. Temperate Forests

Throughfall and Litterfall Fluxes Reveal New Inputs and Foliar Cycling Maintain Pb, Cd, Cu, and Zn Pollution Legacy in Eastern U.S. Temperate Forests

Effects of the organochlorine pesticide metabolite p,p’-DDE on the gastrointestinal lipidome in fish: A novel toxicity pathway for a legacy pollutant

Though phased out from use in the United States, environmental contamination by organochlorine pesticides (OCPs) remains a widespread issue, especially around intensive agricultural regions. OCPs, such as dichlorodiphenyltrichloroethane (DDT) and its primary metabolite, dichlorodiphenyldichloroethylene (DDE), have been detected in soils, sediments, surface waters, and biota decades after their discontinued use. As OCPs are persistent and can bioaccumulate in fats, these compounds can transfer and magnify across food webs. Freshwater predatory fish and birds can accumulate high OCP concentrations, leading to a myriad of deleterious impacts on organismal health. Studies have found evidence of reproductive disruption in predatory fish, such as the largemouth bass (LMB; Micropterus salmoides), associated with DDT and DDE exposure. DDE can act through estrogenic pathways and induce the expression of estrogenic signals in male animals; however, the molecular mechanism of disruption is unclear. Recently, metabolomics research has revealed corollary relationships between lipid signals and organic pollutant toxicity. Here, a two-month feeding experiment on LMB was conducted to assess the interactions of DDE (as p,p'-DDE) in food with gut and liver lipid signaling. Targeted lipidomic analysis revealed global alterations in the abundance of tissue lipids, especially cholesteryl esters and phospholipids, in LMB exposed to low levels of p,p'-DDE. Results from these studies indicate that p,p'-DDE may act through disruption of normal lipid homeostasis to cause toxicity in freshwater fish.

Co-analysis of total suspended particles and discharge reveals the dynamic of mercury input into glacier meltwater runoff in the northern Tibetan Plateau

Climate warming has accelerated glacier melting, releasing legacy pollutants such as mercury (Hg) into aquatic ecosystems. While the relationship between Hg in glacier meltwater runoff, total suspended particles (TSP), and runoff discharges has been established, the underlying inter-relationships and governing factors remain poorly understood. To address this knowledge gap, we conducted a continuous fixed-point sampling at Laohugou No. 12 Glacier in the northern Tibetan Plateau from June to September 2019 spanning the entire glacier ablation season. Our study analyzed the variations of Hg partition in the meltwater runoff and conducted a comprehensive co-analysis of Hg with TSP and discharge to uncover the dominant factors of Hg input into meltwater runoff. The concentration of total Hg (THg) in the meltwater runoff ranged from 0.7 to 112.6 ng/L, with an average concentration of 26.6 ± 25.1 ng/L. Particulate Hg (PHg) was found to be the predominant partition, while dissolved Hg (DHg) exhibited a notable increase in June and September. THg concentration significantly correlated with TSP concentration (r = 0.94, P < 0.01), exceeding the correlation with discharge (r = 0.76, P < 0.01) during the entire ablation period. However, further examination during varying hydrological periods revealed differing associations among Hg speciation concentrations, TSP concentration, and discharge. During the rising limb of the hydrograph, THg (r = 0.86, P < 0.01) and PHg concentrations (r = 0.87, P < 0.01) exhibited a significant correlation with TSP concentration, primarily driven by TSP, implying that Hg availability determines the Hg input into meltwater runoff. Conversely, during the recession limb of the hydrograph, THg concentration was primarily influenced by discharge (r = 0.85, P < 0.01). PHg (r = 0.84, P < 0.01) and TSP (r = 0.97, P < 0.01) concentrations were strongly influenced by discharge, indicating that hydraulic action is the dominant factor affecting Hg input. Our study elucidated the impact of glacier hydrological processes on Hg transport, revealing the dominant factors of Hg input during different hydrological periods. This contributes to a deeper understanding of Hg input into meltwater runoff and improves predictions of Hg export through glacier melt in high mountain regions.

Nitrate trend reversal in Dutch dual-permeability chalk springs, evaluated by tritium-based groundwater travel time distributions

Historical use of fertilizer and manure on farmlands is known to have a lasting impact on ecosystems and water resources, but few studies assess the legacy of nitrate pollution on groundwater and surface water after farming applications were reduced. We studied the response of nitrate in spring water to a reduction of nitrogen fertilizer applications in agriculture realized since the mid-1980s. We assessed the travel time distribution of groundwater based on a time series of tritium measurements for 90 springs and small brooks that drain a dual porosity chalk aquifer. The travel time distributions were constrained using the tritium data in combination with time series of nitrate concentrations, applying a shape-free travel time distribution model. A clear trend reversal of nitrate concentrations was observed and simulated for springs with a large fraction of young water (< 30 years old) whereas the nitrate response in springs with relatively older water was attenuated and delayed. We conclude that obtaining a time series of tritium data helps to constrain age distributions of water that is discharged from dual permeability aquifers. The fraction of water aged <30 years was a meaningful parameter to distinguish between different types of springs. Nitrate trends in springs that drain large fractions of young water (> 0.6) show higher peak concentrations, shorter lag-time between leaching and outflow peaks and steeper declines after trend reversal, relative to trends in springs which are dominantly fed by older groundwater. The study thus shows that the nitrate legacy of groundwater systems is strongly determined by the range of their travel time distributions, and trend reversal in receiving springs and surface waters may appear within 10 to 15 years after measures to reduce nitrate losses from farming.

Breathless in the Motor City: Unveiling the Legacy, Challenges, and Mitigation Strategies of Air Pollution in Detroit

This paper delves into the historical trajectory, current status, and consequential ramifications of air pollution in the city of Detroit. With a specific emphasis on the pollutants NO2, SO2, PM2.5, and O3, the study scrutinizes the health implications and societal burdens arising from the escalating air pollution levels against the backdrop of Detroit's historical evolution. Despite regulatory endeavors, Detroit's enduring role as an industrial and manufacturing hub substantiates the escalating health and economic toll of air pollution. These costs disproportionately impact vulnerable demographics, including the elderly, children, and individuals with chronic illnesses. The paper underscores racial disparities in the distribution of this burden. To address these challenges, the paper advocates for a mitigation strategy inspired by the European Union's NEC Directive. The proposed approach involves intensified monitoring of pollutants, implementation of targeted policies, and enhanced industrial regulations. Ultimately, this paper comprehensively examines the historical legacy, contemporary, and future dimensions of air pollution in Detroit, delineating the profound impact on the city and its residents, while offering strategic recommendations for mitigation.

A decade of data and hundreds of analytes: Legacy and emerging chemicals in North American herring gull plasma

Between 2010 and 2021, 199 herring gull serum samples were collected from Lake Michigan, Lake Huron, and Lake Erie, including two Areas of Concern: Saginaw Bay and the River Raisin. They were analyzed for 21 polybrominated diphenyl ether congeners, 10 non-PBDE flame retardants, 85 polychlorinated biphenyls, 17 legacy organochlorine pesticides, and 36 per- and polyfluoroalkyl substances. Σ36PFAS, Σ85PCB, Σ21PBDE, and Σ17Pesticide concentrations comprised 41–74%, 17–50%, 3–4%, and 5–9% of the total concentration, respectively. Median concentrations of the chemical groups ranged from 81.5 to 129 ng/g ww for PFAS, 26.3–158 ng/g ww for PCBs, 4.26–8.89 ng/g ww for PBDEs, and 8.08–23.0 ng/g ww for pesticides. The regional concentrations of all four classes of compounds are significantly decreasing when sites are combined with halving times of 11.3 ± 4.8, 8.2 ± 4.3, 5.9 ± 3.1, and 8.3 ± 4.2 years for the Penta-BDE mixture, ΣDDTs, Σ85PCBs and Σ36PFAS, respectively. These results suggest that, while PFAS has emerged as the dominant group of chemicals in the plasma, legacy pollutants continue to represent a threat to herring gulls and wildlife in the Great Lakes basin. PCBs were the largest contributors to the chemical load in plasma of birds whose colonies are located near the River Raisin, and continue to pose a threat to herring gulls within the two Areas of Concern.

Chemical threats for the sentinel Pygoscelis adeliae from the Ross Sea (Antarctica): Occurrence and levels of persistent organic pollutants (POPs), perfluoroalkyl substances (PFAS) and mercury within the largest marine protected area worldwide

The Ross Sea Marine Protected Area (RS-MPA) hosts endemic species that have to cope with multiple threats, including chemical contamination. Adèlie penguin is considered a good sentinel species for monitoring pollutants. Here, 23 unhatched eggs, collected from three colonies along the Ross Sea coasts, were analysed to provide updated results on legacy pollutants and establish a baseline for newer ones. Average sum of polychlorinated biphenyls (∑PCBs) at the three colonies ranged 20.9–24.3 ng/g lipid weight (lw) and included PCBs IUPAC nos. 28, 118, 153, 138, 180. PCBs were dominated by hexachlorinated congeners as previously reported. Hexachlorobenzene (HCB) and p,p’-dichlorodiphenyldichloroethylene (p,p’-DDE) ranged between 134 and 166 and 181–228 ng/g lw, respectively. Overall, ∑PCBs was exceeded by pesticides, contrary to previous studies from the Ross Sea. Sum of polybrominated diphenyl ethers (∑PBDEs) ranged between 0.90 and 1.18 ng/g lw and consisted of BDE-47 (that prevailed as expected, representing 60–80 % of the ∑PBDEs) and BDE-85. Sum of perfluoroalkyl substances (∑PFAS) ranged from 1.04 to 1.53 ng/g wet weight and comprised five long-chain perfluorinated carboxylic acids (PFCAs), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS) and perfluorooctanoic acid (PFOA); perfluorooctane sulfonamide (PFOSA) was also detected. The PFAS profile was dominated by PFCAs as already observed in Arctic seabirds. Mercury ranged from 0.07 to 0.15 mg/kg dry weight similarly to previous studies. Legacy pollutants confirmed their ongoing presence in Antarctic biota and their levels seemed mostly in line with the past, but with minor variations in some cases, likely due to continued input or release from past reservoirs. PFAS were reported for the first time in penguins from the Ross Sea, highlighting their ubiquity. Although further studies would be useful to increase the sample size and accordingly improve our knowledge on spatial and temporal trends, this study provides interesting data for future monitoring programs within the RS-MPA that will be crucial to test its effectiveness against human impacts.

Enhanced Hydrologic Connectivity and Solute Dynamics Following Wildfire and Drought in a Contaminated Temperate Peatland Catchment

AbstractIntact peatlands provide hydrological ecosystem services, such as regulating water regimes and immobilizing pollutants within catchments. Climate change impacts including drought and wildfire may impair their functioning, potentially impacting ecosystem service delivery. Here we investigate stream water quality changes following the combined impacts of a summer drought and wildfire in a peat‐dominated catchment in the UK during 2018. The study catchment stores legacy pollutants (i.e., metals) due to past industrial activity, thus making it particularly susceptible to pollutant release during wildfires. We quantified changes in water chemistry during five storm events over a 9‐month period following the wildfire. Concentration‐discharge (C‐Q) relationships for nine solutes were analyzed to explore changes in activation and connectivity of solute source zones. Hysteresis and flushing indices of C‐Q responses further described solute dynamics during storm events. We found that most nutrient and base cation concentrations in the stream discharge were highest in the immediate post‐fire storm events and decreased during subsequent autumn and spring storms. Metal concentrations increased during autumn and spring storms, indicating delayed mobilization from within‐peat or distal headwater sources. Our findings suggest that seasonal re‐wetting and hydrologic connectivity following disturbance influenced solute source zone activation and transport in the study catchment. Water quality responses associated with wildfire and drought were primarily observed in the months following the wildfire, suggesting mobilization of pollutants peaks shortly after fire. Our results contribute to a critical understanding of the future of water quality risks in temperate peatland catchments subject to disturbances exacerbated by climate change.

The role of moisture and salt distribution in the weathering of the medieval cave town of Uplistsikhe, Georgia

Knowledge of salt and moisture distribution is a key factor for understanding rock decay at cultural heritage sites. The cave town of Uplistsikhe in Georgia, carved from sandstone in late bronze age to medieval times, suffers from progressive scaling and flaking processes. Multi-method investigations of rock moisture and salt distribution were carried out in order to better understand the patterns of decay. Salt distribution was investigated using drill dust samples and paper pulp poultices; moisture was determined by 2D-resistivity and handheld microwave sensors, supplemented by infrared thermography. The combined results from the different methods revealed a complex pattern of salt and moisture distribution. At most sites, K2SO4 (arcanite) and its hydrates dominate, sometimes in combination with CaSO4 (gypsum). At one site (Grandhall), halite (NaCl) and niter (KNO3) prevail. Sulphates are assumed to be a legacy of air pollution; origin of halite and niter remains unsolved but might be due to concrete reinforcements. Two main sources of moisture were evidenced depending on season and spatial situation: (1) Condensation of air humidity at cool cave backwalls in spring (combined with and aided by salt hygroscopicity), evidenced by 2D-resistivity and infrared thermography; (2) seepage along joints particularly at the cave backwalls and roofs, evidenced by handheld microwave sensors. Further investigations should focus on identifying seepage pathways and on clarifying the origin of destructive halite and nitrates.

Mercury Dynamics in the Sea of Azov: Insights from a Mass Balance Model.

The Sea of Azov, an inland shelf sea bounding Ukraine and Russia, experiences the effects of ongoing and legacy pollution. One of the main contaminants of concern is the heavy metal mercury (Hg), which is emitted from the regional coal industry, former Hg refineries, and the historic use of mercury-containing pesticides. The aquatic biome acts both as a major sink and source in this cycle, thus meriting an examination of its environmental fate. This study collated existing Hg data for the SoA and the adjacent region to estimate current Hg influxes and cycling in the ecosystem. The mercury-specific model "Hg Environmental Ratios Multimedia Ecosystem Sources" (HERMES), originally developed for Canadian freshwater lakes, was used to estimate anthropogenic emissions to the sea and regional atmospheric Hg concentrations. The computed water and sediment concentrations (6.8 ng/L and 55.7 ng/g dw, respectively) approximate the reported literature values. The ongoing military conflict will increase environmental pollution in the region, thus further intensifying the existing (legacy) anthropogenic pressures. The results of this study provide a first insight into the environmental Hg cycle of the Sea of Azov ecosystem and underline the need for further emission control and remediation efforts to safeguard environmental quality.

Recent environmental and morphosedimentary evolution of the mining-impacted Nalón Estuary (Asturias, N Spain): Disentangling natural and anthropogenic processes

Distinguishing between natural and anthropogenic processes in sedimentary records from estuaries with legacy pollutants is an essential task, as it provides baselines to predict future environmental trajectories of coastal areas. Here, we have addressed the recent transformation history of the mining-impacted Nalón Estuary (Asturias, N Spain). Surface and core sediment records from marshes and tidal flats were examined through a broad multidisciplinary approach, involving micropaleontological (benthic foraminifera), sedimentological (grain-size), geochemical (trace metals, major element Al and total organic carbon), physical (magnetic susceptibility, frequency-dependent magnetic susceptibility and large microplastics) and radioisotopic (210Pb, 137Cs and 239+240Pu) proxies. Results suggest that the interplay between natural (high fluvial influence and extreme hydrological events) and anthropogenic (coal and mercury mining disposals) factors induced strong sedimentation-erosion processes, further shaping the recent evolution of the estuary. Short-time scale and intense sedimentation processes were revealed by overall high sediment accumulation rates, the dilution of some geological signatures and the rapid formation of a marsh in the lower estuary bay. The increasing mining fingerprints during the 20th century were shortly interrupted by the catastrophic riverine flooding of 1938. Conversely, current erosional processes by fluvial influence led to the remobilization of contaminated sedimentary materials and exposure of mining-legacy Hg levels in tidal flats from the middle sector. Fluvial activity, floodings and taphonomic biases exerted a major control on benthic foraminifera since the 19th century, although Hg ecotoxicological effects on modern assemblages at certain areas within the estuary cannot be discarded. These findings, along with the documented enhanced erosion of marshes with ‘trapped’ pollutants (Hg, coal microparticles and microplastics), highlight the importance of monitoring the environmental and geomorphic processes taking place in historically-contaminated estuaries.

Living in a post‐industrial landscape: repeated patterns of genetic divergence in brown trout (Salmo trutta L.) across the British Isles

AbstractAimThe British Isles have been worked for millennia to extract metal ores to feed industrial development, leaving a legacy of mine water pollution that continues to impact freshwater communities in many regions. Brown trout (Salmo trutta L.) have long been observed to persist in these metal‐impacted systems as apex predators, with previous studies showing a small number of impacted populations to be highly genetically divergent. We sought to understand the scale of genetic diversity across regions and the repeatability of genetic divergence in trout populations affected by metal pollution.LocationWe examined four mine water‐impacted regions across the British Isles: west Wales, northeast England, southwest England and southeast Ireland.MethodsWe employed a panel of 95 SNP loci to screen 1236 individuals from 71 sites representing paired metal‐impacted and clean sites from across the four regions. From these, we obtained diversity statistics, assessed genetic structuring of populations and modelled historical demographic scenarios to understand which factors most credibly explain genetic variation in divergent populations.ResultsWe evidenced hierarchical population structure in the regions studied, in line with expectations from phylogeographic history. However, in a hierarchical analysis of genetic structuring the first level of differentiation was driven by the divergence of the metal‐impacted trout of Cornwall in southwest England. Within regions we observed reduced genetic diversity and repeated patterns of local genetic sub‐structuring between paired samples from metal‐impacted and relatively clean sites. Demographic history analyses suggested the timing of these splits to be relatively recent and to be associated with periods of peak mining activity.Main conclusionsOur findings demonstrate distinct patterns of genetic isolation and reduced diversity arising from legacy pollution in freshwater ecosystems, with impacts being most apparent where both chemical pollution and physical barriers are present. Management should focus on the amelioration of mine water wash‐out and the removal of barriers to fish movement to safeguard genetic diversity in impacted populations.

Spatial Investigation of Legacy Pollutants within a Confirmed Cancer Cluster in Three Houston, TX Neighborhoods

Spatial Investigation of Legacy Pollutants within a Confirmed Cancer Cluster in Three Houston, TX Neighborhoods

Multi-isotopic composition of brown crab (Cancer pagurus) and seafloor sediment from a mine tailing sea disposal impacted fjord ecosystem

Sea disposal of mine tailings in fjord ecosystems is an important coastal management issue in Norway and occurs at the land-sea interface. Here we studied accumulation of heavy metals in brown crab (Cancer pagurus) and seafloor sediment from Jøssingfjord, Norway during 2018 to evaluate long-term, legacy pollution effects of coastal mine tailing sea disposal activities. Nickel and copper sediment pollution in the mine tailing sea disposal area was classified as moderate and severe, respectively, under Norwegian environmental quality standards, and highlights the persistent hazard and legacy impacts of heavy metals in these impacted fjord ecosystems. Mercury, zinc, and arsenic had stronger affinities to brown crab muscle likely due to the presence of thiols, and availability of metal binding sites. Our multi-isotopic composition data showed that lead isotopes were the most useful source apportionment tool for this fjord. Overall, our study highlights the importance and value of measuring several different heavy metals and multiple isotopic signatures in different crab organs and seafloor sediment to comprehensively evaluate fjord pollution and kinetic uptake dynamics. Brown crabs were suitable eco-indicators of benthic ecosystem heavy metal pollution in a fjord ecosystem still experiencing short- and long-term physical and chemical impacts from coastal mining sea disposal activities.

Antagonistic effects of a COX1/2 inhibitor drug in human HepG2 cells exposed to an environmental carcinogen

Understanding interactions between legacy and emerging environmental contaminants has important implications for risk assessment, especially when mutagens and carcinogens are involved, whose critical effects are chronic and therefore difficult to predict. The current work aimed to investigate potential interactions between benzo[a]pyrene (B[a]P), a carcinogenic polycyclic aromatic hydrocarbon and legacy pollutant, and diclofenac (DFC), a non-steroidal anti-inflammatory drug and pollutant of emerging concern, and how DFC affects B[a]P toxicity. Exposure to binary mixtures of these chemicals resulted in substantially reduced cytotoxicity in human HepG2 cells compared to single-chemical exposures. Significant antagonistic effects were observed in response to high concentrations of B[a]P in combination with DFC at IC50 and ⅕ IC50. While additive effects were found for levels of intracellular reactive oxygen species, antagonistic mixture effects were observed for genotoxicity. B[a]P induced DNA strand breaks, γH2AX activation, and micronuclei formation at ½ IC50 concentrations or lower, whereas DFC induced only low levels of DNA strand breaks. Their mixture caused significantly lower levels of genotoxicity by all three endpoints compared to those expected based on concentration additivity. In addition, antagonistic mixture effects on CYP1 enzyme activity suggested that the observed reduced genotoxicity of B[a]P was due to its reduced metabolic activation as a result of enzymatic inhibition by DFC. Overall, the findings further support the growing concern that co-exposure to environmental toxicants and their non-additive interactions may be a confounding factor that should not be neglected in environmental and human health risk assessment.

Is current generation of polychlorinated biphenyls exceeding peak production of the 1970s?

Polychlorinated biphenyls (PCBs) are man-made chemicals that were once widely produced as commercial mixtures for various industrial applications. PCBs were later recognized as environmental pollutants and health hazards, leading to their global phase-out and strict regulations on their production, use, and disposal. Most investigations on PCBs focus on measuring the specific PCBs present in commercial mixtures or marker compounds representing those mixtures. However, there are new sources of PCBs that are gaining more attention. These ‘by-product PCBs’ are inadvertently produced in certain chemical and product formulations. Our estimates show that U.S. legislation currently permits the generation of more by-product PCBs (~100 million lb. (~45,000 Tonnes) per year) than during peak commercial production of the 1970s (85 million lb. (~39,000 Tonnes) per year). These PCBs are currently going un-detected in most investigations. Therefore, they may be a posing a growing, unmonitored environmental and human health risk. Most people assume PCBs to be legacy pollutants from historically formulated commercial mixtures. However, our research suggests that due to the emergence of by-product PCBs they may need to be reconsidered as an emerging pollutant of concern.

A perceptual approach to address complex water management issues in lowland permeable catchments

Water quality management is a pressing global concern, and an increasingly complex issue due to climate and land-use change, legacy pollution, and the persistent release of well-known and emerging contaminants from diffuse and point sources. The increasing availability of high-frequency monitoring data is leading existing, often heuristic approaches, to be judged inadequate. Water managers frequently rely on simple qualitative and/or quantitative approaches for decision-making, but a lack of tangible improvement in freshwater quality outcomes is demanding new and innovative approaches that rely more on physical process understanding, rather than precedent. In this study, we drew upon local geological, hydrogeological, and hydrological data to infer a high-level perceptual model of surface/groundwater interactions in a chalk stream in Dorset, UK. We used the perceptual model to interrogate spatial and temporal trends in historical water quality data and to construct reach-scale nutrient mass balances. Through novel representation with Sankey diagrams, the perceptual model highlighted the relative importance of different hydrological features. Surface/groundwater interactions were found to occur predominantly by spring flow. We demonstrate that river flow accretion was dominated by the Chalk aquifer despite only occupying ca. 15 % of the surface bedrock area, and that spring sources, whilst vital to dilute treated sewage inputs in baseflow conditions, were also major sources of legacy nitrate. Nutrient mass balances showed that sewage treatment works contributed ca. 13 % to soluble reactive phosphorus load, with groundwater accounting for ca. 48 %. Thus, a determinand often associated with point-source pollution was shown to be diffuse dominated in this river. The study demonstrated how a multi-disciplinary approach to water management, based on a comprehensive perceptual modelling approach, could identify hitherto unknown sources and relative contributors to freshwater pollution and allow flow and load apportionment studies to provide useful decision-support to manage nutrient pollution. The novel application of perceptual modelling tools, such as the Sankey diagram, allows different source attributions to be presented in an accessible manner, and can be readily transferred to other study areas.

Temporal mercury dynamics throughout the rice cultivation season in the Ebro Delta (NE Spain): An integrative approach

During the last few decades, inputs of mercury (Hg) to the environment from anthropogenic sources have increased. The Ebro Delta is an important area of rice production in the Iberian Peninsula. Given the industrial activity and its legacy pollution along the Ebro river, residues containing Hg have been transported throughout the Ebro Delta ecosystems. Rice paddies are regarded as propitious environments for Hg methylation and its subsequent incorporation to plants and rice paddies' food webs. We have analyzed how Hg dynamics change throughout the rice cultivation season in different compartments from the paddies' ecosystems: soil, water, rice plants and fauna. Furthermore, we assessed the effect of different agricultural practices (ecological vs. conventional) associated to various flooding patterns (wet vs. mild alternating wet and dry) to the Hg levels in rice fields. Finally, we have estimated the proportion of methylmercury (MeHg) to total mercury in a subset of samples, as MeHg is the most bioaccumulable toxic form for humans and wildlife. Overall, we observed varying degrees of mercury concentration over the rice cultivation season in the different compartments. We found that different agricultural practices and flooding patterns did not influence the THg levels observed in water, soil or plants. However, Hg concentrations in fauna samples seemed to be affected by hydroperiod and we also observed evidence of Hg biomagnification along the rice fields’ aquatic food webs.

Response of Chironomidae (Diptera) to DDT, Mercury, and Arsenic Legacy Pollution in Sediments of the Toce River (Northern Italy).

The Toce River (Northern Italy) is characterized by legacy contamination of dichloro-diphenyl-trichloroethane (DDT), mercury, and arsenic deriving from an industrial plant active between ca. 1915 and 1996. Chironomidae taxa assemblages and sediments were collected in 2014 and 2019 upstream and downstream of the industrial area to analyze species responses to toxic substances in a river stretch with relatively uniform natural (i.e., hydro-morphological) characteristics. A total of 32 chironomid taxa were identified. Sediment concentrations reached levels potentially toxic for benthic invertebrates: 15.7 µg kg-1 1% organic carbon for DDT, 197 µg kg-1 dry weight (d.w.) for Hg, and 55.7 mg kg-1 d.w. for As. Canonical Correspondence Analysis (CCA) revealed a predominant seasonal gradient, followed by an upstream-downstream gradient. Partial CCA indicated that 5.2% of the total variation was associated with sediment contamination. Self-Organizing Maps (SOMs) were used to represent species responses to toxicants. Most species appeared to be tolerant, e.g., Chironomus riparius, Micropsectra atrofasciata, Conchapelopia pallidula, and Polypedilum spp. Sensitivity to contaminants was observed in only a few species: Diamesa spp., Sympotthastia spinifera, and Prodiamesa olivacea to DDT; Potthastia longimanus to Hg; Odontomesa fulva and Microtendipes pedellus to As. The chironomid community was characterized in presence of contamination levels commonly observed in freshwater ecosystems.

Insights into polybrominated diphenyl ethers: occurrence, sources, and exposure health risk in selected solid waste impacted soils

&lt;p&gt;The Coordinated management of solid waste dumps from different anthropogenic environments is important for pollution management of immediate and adjacent ecosystems. This study took three soil profile samples from three functional zones: the rural, the suburban, and the urban solid waste dumps. The samples were analyzed for the concentration, origin, and associated risks of thirty-nine Polybrominated diphenyl ethers (Ʃ39PBDEs). Σ39PBDEs demonstrated high concentrations and ranged from 0.12 to 119 ng g−1 dw, in the order of rural &amp;gt; suburban &amp;gt; urban, and topsoil &amp;gt; subsoil &amp;gt; bottom soil. BDE-10, -11, -13, -15, -17, -99 and -119 showed relative abundance. Penta-BDE was moderately above standard and screening levels and demonstrated high and medium ecological risk in the rural and semi-urban zones. The non-carcinogenic and cancer risks highlight onsite exposure risks. PCA evaluation depicts an abundance of persistent and toxic flame retardant additives, and cluster analysis showed PBDEs were from a common source—cancer and hazard index exposure risk depicted rural &amp;gt; suburban &amp;gt; urban zone. The results suggested the continual use of banned flame retardant additives in commercial formulations. A comparison of PBDE implied that PBDEs in the suburban and urban zones could have undergone environmental processes, and the rural zone received fresh deposition. Migration and exposure to the detected -BDEs may increase the risk to humans in these zones. The results highlighted the need to establish a standard management protocol and monitor legacy pollutants in environmental and biological samples around solid waste dump sites and similar catchments.&lt;/p&gt;&#x0D;