Source Of Mercury Research Articles

The Characteristics of Mercury Flux at the Interfaces between Two Typical Plants and the Air in Leymus chinensis Grasslands.

Mercury is a global pollutant. The mercury exchanges between vegetation and the atmosphere are important for the global mercury cycle. Grassland ecosystems occupy more than 25% of the global land area and have different succession processes and ecological functions. The current research regarding mercury exchanges between forests and the atmosphere have attracted much attention, but the research regarding grasslands tends to be rare. To reveal the characteristics of mercury exchanges in grasslands, this study conducted field in-situ monitoring experiments in a Leymus meadow grassland regions of the Songnen Plains in northeastern China. The exchange flux values of the GEM (gaseous element mercury) between the plants and the atmosphere were measured using a dynamic flux bag method (DFB). The experiments were conducted for the purpose of assessing the mercury flux levels between the vegetation and the atmosphere in a typical Leymus chinensis meadow. The goal was to further the understanding of the change characteristics and influential factors and to describe the source and sink actions and dynamics between the grassland vegetation and the atmosphere. The diurnal variation characteristics were as follows: High during the day and low at night, with peaks generally appearing at noon. The growing period was characterized by absorption peaks of atmospheric mercury by the plants. The breeding period was characterized by the peak release of atmospheric mercury by the plants. The change characteristics were as follows: During the growing period, the duration of the plants in a mercury absorption state exceeded 96.5%, which was represented as the net sink of the atmospheric mercury. During the breeding period, the time of mercury release ranged between 46.4% and 66.8%, making the breeding period the net source of atmospheric mercury. The results of this study’s analysis indicated that each environmental factor was correlated with the mercury flux, and the environmental factors had different effects on the mercury flux during the different stages of plant growth. The atmospheric mercury concentration levels were the main factor during the growing period. Atmospheric humidity was the main factor during the breeding period. Solar radiation was the decisive factor during the entire experimental period.

Author Correction: Rivers as the largest source of mercury to coastal oceans worldwide

Author Correction: Rivers as the largest source of mercury to coastal oceans worldwide

Integrated watershed process model for evaluating mercury sources, transport, and future remediation scenarios in an industrially contaminated site

We used the Soil Water Assessment Tool (SWAT) as a framework to develop an empirical Hg flux model for Upper East Fork Poplar Creek (UEFPC), a Hg-contaminated watershed in Oak Ridge, Tennessee. By integrating long-term Hg monitoring data with simulated flow and suspended solid loads in a site-specific empirical Hg transport model, we (1) quantified the spatial, temporal, and flow regime controls on daily Hg flux (adjusted R2 = 0.82) and (2) made predictions about Hg flux under future climate, land use, and management scenarios. We found that 62.79% of the average daily Hg flux in the watershed is currently driven by base flow, whereas variability in Hg flux is driven by storm and extreme flow. We estimate an average annual Hg flux of 28.82 g day-1 leaving the watershed under baseline precipitation, with an estimated 43.73% reduction in daily Hg flux under drought conditions and a 296% increase in daily Hg flux in extreme precipitation scenarios. We estimated that a new mercury treatment facility would result in a 24.7% reduction in Hg flux under baseline conditions and a 33.4% reduction under extreme precipitation scenarios. The study demonstrated the merit of this approach, which can be replicated for sites where information on flow, suspended solids, and Hg concentrations is available.

Relationships between atmospheric mercury and optical properties of spring outflow aerosols from Southeast Asia

Southeast Asia is a major biomass burning (BB) source area and BB has been identified as an important source of mercury (Hg) and aerosols to the atmosphere. Previous studies found correlations between atmospheric Hg and Delta-C (BC370–BC880) during the BB episodes in low-elevation BB source areas; however, whether this relationship persists during long-range transport remains unknown. Lulin Atmospheric Background Station (LABS), a high mountain background site in central Taiwan, has monitored the impact of BB long-range transports from Southeast Asia on atmospheric Hg and aerosols in downwind areas since 2006 and 2008, respectively. As such, these data provide an opportunity to investigate the relationship between atmospheric Hg (PBM and GOM) and aerosol optical properties, such as Delta-C and absorption Ångström exponent (AAE370-880). In this study, three long-range transport BB events were observed at LABS in the springtime during 2014–2016. Significant positive correlations with PBM/GOM were observed for Delta-C and (R2 = 0.34–0.51) and AAE370-880 (R2 = 0.41–0.54) during the BB events, while poor correlations were shown under non-BB episodes. Additionally, the positive correlation between PBM and AAE370-880 suggests that the Hg(II) may be preferably absorbed onto organic aerosols or originated from the same emission sources. This study demonstrated that AAE370-880 can be used to identify the source of Hg(II) from BB long-range transport. In addition, our results also indicated the influences of aerosol chemical compositions on the partitioning of Hg(II), which is important to further the understanding of atmospheric Hg cycling.

Climate-Associated Changes in Mercury Sources in the Arctic Fjord Sediments

Despite the large climatic fluctuations in the Arctic over the Holocene, the dominant mercury (Hg) sources and the potential changes in Hg sources associated with the climate remain unclear. Here, we use Hg isotopes to reconstruct changes in Hg sources and processes in two Svalbard fjord sediment cores spanning the Holocene. The Hg isotope ratios of the fjord sediment cores are similar to bedrock and Hg bound to terrestrial total organic carbon (TOC) but different from other sediment cores influenced by atmospheric Hg drawdowns via the sinking of marine particulate organic matter. The absence of significant Hg and TOC relationships indicates that bedrock erosion caused by glacier dynamics is the major Hg source to the fjord sediment rather than those bound to marine and terrestrial TOC. Measurable shifts in Hg sources are observed at regional cooling (4.3 ka) and during the Medieval Warm Period in the late Holocene. The negative shift in δ202Hg (by −0.5‰) at 4.3 ka from baseline (∼10 ka) is consistent with the rapid increase in glacier-mediated physical and chemical erosions of bedrock. The significant positive shifts in δ202Hg (by 0.5‰) in the late Holocene are explained by enhanced input of atmospheric Hg and its drawdown via the sinking of marine particulate organic matter and some anthropogenic influence, which suppressed the positive Δ199Hg and Δ200Hg shifts. This study suggests that Hg isotope ratios measured in sedimentary archives can be used to decipher climate and other local to global changes modifying Hg sources in the Arctic.

Mercury levels in a sample of the population in Southern Bolívar - Colombia at risk of environmental exposure

BACKGROUND AND AIM: Mercury contamination is a relevant problem today, due to the toxic effects it can have, ranging from cancer to nervous system disorders. Artisanal gold mining is an important source of mercury, due to the vapors from the process and the discharge into soils and bodies of water, reaching other trophic chains, biomagnifying and affecting humans METHODS: This research aimed to determine the serum levels of total mercury and methylmercury in a population under 18 years of age in the south of Bolivar in municipalities such as Barranco de Loba, Pueblo Mejia and Mina Azul in the Department of Bolivar - Colombia As a sampling technique, the protocol for collecting DBS (Dried Blood Spots in 19 inhabitants was implemented and static analysis was performed. RESULTS:The results showed methylmercury levels of 0.490–11.616 mcg/L, inorganic mercury of 0.302–7.120 mcg/L and total mercury of 1.844–13.772 mcg/L, values above the reference data (United States Environmental Protection Agency). In addition, a strong association was found between age, proximity to the river and total mercury concentrations. CONCLUSIONS:Note that these are preliminary studies, however, they alert future consequences that may be presented by the population vulnerable to this type of contamination. KEYWORDS: Heavy metals, Water quality, Exposures, Cancer and cancer precursors

Exposure of Mercury Species in Red Blood Cell and the Effects on Metabolites of Residents Living Near Coal-Fired Power Plants

BACKGROUND AND AIM: Coal-fired power plant is an important source of mercury for residents nearby. However, it’s still not clear for their exposure of different mercury species and the related health effects. Our study aims to assess the exposures of mercury species in residents near a coal-fired power plant and to clarify the effects of mercury species on metabolite profiles in human body. METHODS: Our study subjects were 152 adult residents living near a coal-fired power plant in central Taiwan, including 76 high-exposure group (HE) and 76 low-exposure group (LE), which were based on previous studies. We detected their inorganic mercury and methyl mercury levels in red blood cells by HPLC-ICPMS and analyzed the differences on levels and ratios between groups by SAS 9.4. The urinary and serum metabolites database of study subjects were established by previous study. MetaboAnalyst 4.0 was used to analyze and visualize the differences in metabolites profiles between the groups with high and low mercury species levels. RESULTS:The levels of inorganic mercury in red blood cells of HE group was significantly higher than those in LE group( 2.48 ± 0.48 µg / L and 1.13 ± 0.60 µg / L respectively) and there was no significant difference between two groups for methylmercury. The ratio of inorganic/total mercury levels were significantly higher in HE group when compared to LE group (12±13% and 7± 6% respectively). There was nine urinary and five serum metabolite profiles were significantly regulated by higher inorganic mercury levels of study subjects. There was no urinary and serum metabolite profiles significantly regulated by different methyl mercury levels. CONCLUSIONS:The levels of inorganic mercury in red blood cells were significantly higher among the residents living closer to the coal-fired power plant, and the higher inorganic mercury exposure might influence the expression of metabolites. KEYWORDS: Coal-fired power plant, Inorganic mercury, Methyl mercury, Metabolomics

Blood total mercury levels of Brazilian preschool children and associated risk factors: preliminary results

BACKGROUND AND AIM: Environmental exposure to mercury in preschool children can impact their health by increasing its blood levels, which can cause negative health outcomes. This study aimed to set the reference value for blood mercury in preschool children from a megacity in Brazil, and investigating associated risk factors. METHODS: Blood samples were collected of 2,463 children and the present study reports preliminary results from 1,020 1-4-year-old children attending 29 daycare centers (DCC) located in São Paulo, Brazil, 2013. Guardians answered sociodemographic and potential risk factors questionnaires. DCC and metal contaminated-sites (MCS) were georeferenced (QGIS™). Blood total mercury levels (BTM) were determined by Cold Vapor Atomic Absorption Spectrophotometry (CV-AAS). BTM was dichotomized (low/high levels) in a cut-off point of 1.06 μg.L⁻¹, which represents the 95th percentile reference value for total mercury established by the U.S. Centers for Disease Control and Prevention (CDC). Summary data and multiple logistic regression were performed (p0.05). RESULTS:The geometric mean for BTM was 1.71 μg.L⁻¹ (95%CI: 1.64-1.78 μg.L⁻¹) and the 95th percentile was 5.43 μg.L⁻¹ (95%CI: 4.89-6.26 μg.L⁻¹). DCCs located in the Northwest geographic zone were associated with high BTM when the model was adjusted for fish intake, age, sex, geographic zone, mother schooling, and amalgam (p=0.018). No associations were found between high BTM and fish consumption, amalgam teeth fillings, and georeferenced vicinity of the DCC to MCS. CONCLUSIONS:BTM in Brazilian preschoolers (95th percentile) was more than five times higher than U.S. children’s levels. Even the Brazilian geometric mean was higher than the U.S. BTM 95th percentile. More studies are necessary to identify potential mercury exposure sources for preschool children. Nevertheless, these results showed the need to formulate public health policies, intending to better understand and eliminate mercury sources. Funded by Fapesp (2011/13076-0, 2011/23272-0, 2012/21840-4) and Capes. KEYWORDS: Mercury, Preschool children, Environmental exposure, Public Health, Blood, Potentially Toxic Elements

Concentration and speciation of mercury in atmospheric particulates in the Wuda coal fire area, Inner Mongolia, China.

Coal-seam fire is a source of atmospheric mercury that is difficult to control. The Wuda Coalfield in Inner Mongolia, China, is one of the most severe coal fire disaster areas worldwide and has been burning for more than 50 years. To investigate atmospheric mercury pollution from the Wuda coal fire, gaseous elemental mercury (GEM) concentrations and atmospheric particulate mercury (PHg) speciation were measured using a RA-915+ mercury analyzer and the temperature-programmed desorption method. Near-surface GEM concentrations in the Wuda Coalfield and adjacent urban area were 80 ng m-3 (65-90 ng m-3) and 52 ng m-3 (25-95 ng m-3), respectively, which are far higher than the local background value (22 ng m-3). PHg concentrations in the coalfield and urban area also reached significantly high levels, 33 ng m-3 (25-45 ng m-3) and 22 ng m-3 (14-29 ng m-3), respectively (p < 0.05). There is no clear evidence that PHg combines with organic carbon or elemental carbon, but PHg concentration appears to be controlled by air acidity. PHg mainly exists in inorganic forms, such as HgCl2, HgS, HgO, and Hg(NO3)2·H2O. This work can provide references for the speciation analysis of atmospheric PHg and the safety assessment of environmental mercury.

Содержание ртути и свинца в кормовой базе ценных видов рыб Каспийского моря

Mercury and lead are not essential elements and have a high degree of toxicity to all groups of living organisms, including hydrobionts. In turn, the accumulation of dangerous chemical elements in the primary trophic units of marine ecosystems is also reflected in the high level of accumulation and toxication of fish-valuable objects of fishing. As part of the study of the ecological state of the biota of the Volga-Caspian basin, there is a need to study the concentrations of heavy metals such as mercury and lead. The aim of the work is to study the content of mercury and lead in some invertebrate species of the Caspian Sea. The main source of mercury and lead in the body of the studied species is the water of the north-western part of the Caspian Sea. Among the studied taxonomic groups of organisms, mercury accumulators were all species of mollusks, as well as Balanus improvises and Rhithropanopeus harrisii. The lead concentrating organisms were Cerastoderma lamarcki and Mytilaster lineatus, Rhithropanopeus harrisii, and Balanus improvises.

Rivers as the largest source of mercury to coastal oceans worldwide

Rivers as the largest source of mercury to coastal oceans worldwide

Geochemical modeling of mercury in coastal groundwater

The systematic analysis of groundwater in the Greek island of Skiathos revealed a seasonal increase of total mercury concentrations after the extensive groundwater abstraction during the busy and heavily touristic summer months. This contamination was accompanied by a corresponding increase of the chloride content of groundwater, attributed to seawater intrusion into the freshwater-depleted aquifer within mercury-rich bedrock. The effects of elevated concentrations of chloride anions in the mobilization of mercury and its speciation were addressed by geochemical equilibrium modeling, considering cinnabar (HgS) as the mineral source of mercury. Adsorption onto hydrous ferric oxide (Fe2O3·H2O) was a necessary ingredient of the geochemical model for bringing the calculated concentrations in agreement with field measurements, after optimization of the cinnabar/adsorbent mass ratio to a value of 4.9 × 10−8. The speciation of mercury was found to depend on the acidity and redox status as well as on the chloride content of groundwater. Mercury concentrations in the groundwater of Skiathos rise above the World Health Organization limit of 1 μg L−1 for a seawater intrusion higher than 3 %, with HgCl2 being the dominant species followed by HgClOH, HgCl3− and HgCl42−. The assumed concentration of dissolved organic matter in groundwater had a negligible impact on the mercury speciation and its mobilization by chloride.

Exposure radius of a local coal mine in an Arctic coastal system; correlation between PAHs and mercury as a marker for a local mercury source

Mercury in the Arctic originates from emissions and releases at lower latitudes and, to a lesser extent, from local and regional sources. The relationship between mercury (Hg) and polycyclic aromatic hydrocarbons (PAHs) in sediment can be applied as an indicator of the mercury source. This research examines the Hg contamination gradient from a land-based coal mine to the surrounding coastal environment to quantify the impact of local sources. Total mercury and PAH (Σ14PAH) were measured in terrestrial and marine sediments as well as in marine biota. Samples were collected at the mine and two reference sites. Mercury and Σ14PAH concentrations in samples collected at the mine site were significantly higher than those at the reference sites. This was also found in the biota samples, although less pronounced. This work addresses the complexities of interpreting data concerning very low contaminant levels in a relatively pristine environment. A clear correlation between PAH and Hg concentration in sediment was found, although a large number of samples had levels below detection limits. PAH profiles, hierarchical clustering, and molecular diagnostic ratios provided further insight into the origin of PAHs and Hg, showing that signatures in sediments from the nearest reference site were more similar to the mine, which was not the case for the other reference site. The observed exposure radius from the mine was small and diluted from land to water to marine biota. Due to low contamination levels and variable PAH profiles, marine biota was less suitable for tracing the exposure radius for this local land-based Hg source. With an expected increase in mobility and availability of contaminants in the warming Arctic, changes in input of PAHs and Hg from land-based sources to the marine system need close monitoring.Graphical abstract

Toxic Meals for Seabirds and Seals: Monitoring Mercury in the San Francisco Bay

Mercury is a metal pollutant that travels thousands of miles through air and water. It flows along rivers to lakes, estuaries, and the sea, cycling between animals and their environments. Extensive mercury mining during the Gold Rush left lasting impacts on the San Francisco Bay Delta, one of California’s largest wetland habitats and home to thousands of species. Burning fossil fuels in cities like San Francisco also releases mercury, leading to its buildup in local food chains. Mercury accumulates from plankton to fish to top predators like sharks and seals, where it reaches potentially harmful levels. Mercury never fully breaks down and continues cycling in ecosystems, even reaching migratory animals living offshore in the Pacific Ocean. Scientists collect samples from wildlife to uncover clues about mercury sources and threats to human health. This article explains the mercury problem and why we track this invisible pollutant in the San Francisco Bay.

Mercury Anomaly in Oligocene–Miocene Maykop Group Sediments (Caucasus Continental Collision Zone): Mercury Hosts, Distribution, and Sources

The Oligocene–Miocene Maykop Group sediments, mainly composed of illite–smectite, store mercury in strongly variable concentrations from 10 to 920 μg/kg. Extremely high Hg levels (98–920 μg/kg) coupled with abnormal mercury-to-total organic carbon (TOC) ratios (Hg/TOC = 109 to 3000 μg/kg/wt%; TOC = 0.2 wt% to 1.2 wt%) were measured in the Middle Maykop marine shales that were deposited in the deepwater Indol–Kuban Basin under anoxic conditions. The Middle Maykop shales contain up to 70% of total mercury in sulfide form. In heavy mineral fractions, abundant Hg-bearing pyrite (with up to 4810 µg/kg Hg in hand-picked concentrates) is accompanied by sporadic cinnabar. Relative to the Middle Maykop sediments, the Upper Maykop shales have much lower Hg concentrations and Hg/TOC ratios: 10 to 63 μg/kg (34 μg/kg on average) and 7.7 to 137 μg/kg/wt% (39 μg/kg/wt% on average), respectively. Mercury sequestration is inferred to occur mostly by binding in sulfide hosts in the Middle Maykop anoxic deep-sea sediments and in organic matter, Fe3+-(oxy)hydroxides, and clay particles in the Upper Maykop shales which were deposited in a more oxygenated environment. Mercury inputs to the marine shales during Maykopian sedimentation were possibly associated with local Oligocene–Lower Miocene volcanic activity in the Caucasus Continental Collision Zone. At the same time, the mode of Hg binding in sediments was controlled by redox conditions which changed from anoxic to disoxic and suboxic at the Middle-to-Upper Maykop transition.

Total gaseous mercury (TGM) concentration over Lake Superior and Lake Michigan

Mercury-contaminated fish are a serious problem in the Great Lakes basin, because mercury is a potent neurotoxin that poses a danger to both humans and wildlife. Lake Superior lake trout and walleye have the highest mercury concentrations of the five Great Lakes. Because the atmosphere is the major source of mercury to the Great Lakes, information on the over-water mercury concentration is essential to model the mercury biogeochemical cycle. For the first time in the peer-reviewed literature, this paper presents total gaseous mercury (TGM) measurements made over Lake Superior and Lake Michigan. The Lake Superior aircraft measurements were made at an altitude of 300 m, and the Lake Michigan aircraft measurements at a variable altitude of 30–300 m. The over-water Lake Superior TGM of 1.02 ± 0.34 ng/m3 is much lower than the TGM from nine stations in the Canadian Atmospheric Mercury Measurement Network (CAMNet) and six stations in the Atmospheric Mercury Network (AMNet). The land-based TGM concentrations average range from 1.25 to 1.75 ng/m3 which are in good agreement with current global average values of 1.3–1.6 ng/m3. The over-water Lake Michigan TGM is 1.65 ± 0.61 ng/m3. We also present Lake Superior over-water measurements of volatile organic compounds (VOC), ozone (O3), nitrogen oxide (NOy), and particulate matter. Elemental carbon (EC) is a tracer for mercury because mercury is released during the combustion of coal. EC is significantly correlated with TGM over both Lake Superior and Lake Michigan. TGM over Lake Michigan is also significantly correlated with organic carbon, sulfate, nitrate and ammonium.

Mercury concentration and isotopic composition on different atmospheric particles (PM10 and PM2.5) in the subtropical coastal suburb of Xiamen Bay, Southern China

The concentration and isotopic composition of particulate-bound mercury (PBM) on both PM2.5 and PM10 were simultaneously measured (24 months) in a typical subtropical coastal suburb of Xiamen bay (SCXB), southern China. The results showed that most mercury was concentrated in PM2.5 and small particulates enriched heavier isotopes of mercury more than lighter ones. Negative Δ199Hg values and slightly positive Δ200Hg values were observed in both PM2.5 and PM10. PBM input sources were identified with isotopic compositions and meteorological data using the NOAA HYSPLIT model. It revealed that biomass combustion is the main source of particulate mercury in SCXB, and the two other sources are urban anthropogenic emissions and potential marine sources. Seasonal variations in isotopic composition and correlation analysis suggested that PBM in SCXB mainly originate from inland after long-distance transportation in spring and under the influence of oceanic air masses in summer. The Δ199Hg/Δ201Hg ratios in all samples (1.01 ± 0.05, 2SE) indicated that the photoreduction of Hg(II) in the aerosol was the main reaction process of PBM transformation in the atmosphere. Seasonal variations in Δ200Hg values were also found, indicating the possibility of even mass independent fractionation in tracing the mercury sources.

КОЭФФИЦИЕНТЫ НАКОПЛЕНИЯ ХИМИЧЕСКИХ ЭЛЕМЕНТОВ В ОРГАНАХ И ТКАНЯХ РУССКОГО (ACIPENSER GUELDENSTAEDTII, BRANDT, 1833) И ПЕРСИДСКОГО (ACIPENSER PERSICUS, BORODIN, 1897) ОСЕТРОВ КАСПИЙСКОГО МОРЯ

The article is focused on the possible ways of accumulating chemical elements (zinc, copper, chromium, nickel, lead, mercury) in the organs of aquatic organisms. In the course of the study, the coefficients of accumulating the chemical elements in the organs and tissues were calculated for the Russian (Acipenser gueldenstaedtii, Brandt, 1833) and Persian sturgeons (Acipenser persicus, Borodin, 1897) relative to the water of the northwestern part of the Caspian Sea, bottom sediments and the main objects of their food (Khvalyn goby (Neogobius caspius), Sandpiper goby (Neogobius fluviatilis), Caspian goblin (Benthophilus microcephalus), roach (Rutilus rutilus caspicus)). The studies were carried out according to the standard method of atomic absorption spectrometry. It is shown that the main source of accumulating the studied chemical elements in the organs and tissues of the Russian and Persian sturgeons is the water of the northwestern part of the Caspian Sea. It was found that the bottom sediments of the Caspian Sea act as an additional source of zinc and mercury found in the liver and kidneys of sturgeon species. Based on the calculated accumulation coefficients of chemical elements, there was revealed a predominantly alimentary nature of accumulating copper, nickel and mercury in the organs of both sturgeon species.

Blast-furnace process as a source of anthropogenic mercury emissions

The metallurgical industry is a major source of anthropogenic emissions of mercury, whose compounds have an adverse impact on the environment and human health. In the year 2017 in the European Union, the industry was responsible for nearly 13 % of mercury emissions, being their third largest source. In Poland the industry is the fourth largest source of emissions, accounting for approximately 3.6 % the total. There are several component processes in the steel production process. The first consists of the preparation of ferrous additive, mainly in the sintering process. The second consists of smelting of pig iron in a blast furnace and the last entails processing in a converter or arc furnace. The main source of mercury in the blast furnace process is the fuel (coal and coke). The largest stream of mercury leaves the furnace with the blast furnace gas, which contains 2.4 &mu;g/m3 after cleaning. Mercury content in pig iron has always been below detection levels with respect to analysis methods used. Using balance investigation results and data available in literature, an emission index has been determined for the whole production cycle: 10.181 mg Hg/Mg of steel. This value consists of emissions generated in the following steps: preparation of sinter &ndash; 1.622 mg Hg/Mg of steel, coke production &ndash; 4.953 mg Hg/Mg of steel, combustion of blast furnace gas produced during the blast furnace process &ndash; 3.557 mg Hg/Mg of steel and pig iron processing &ndash; 0.050 mg Hg/Mg of steel. This research was financed from the AGH University of Science and Technology Research Subsidies no. 16.16.210.476 and 16.16.110.663.

Effect of different rice farming practices on the bioavailability of mercury: A mesocosm experiment with common goldfish (Carassius auratus)

Wetlands such as rice paddies are important ecosystems that provide habitat for a numerous range of species but are considered as a major source of mercury in the most toxic form of methylmercury. An in situ mesocosm experiment was conducted during the rice cultivation season of 2018 in rice paddies from the Ebro Delta (NE Spain) to investigate the bioaccumulation of mercury in fish. Common goldfish (Carassius auratus) were exposed to three types of rice-fields subject to different agricultural management (conventional or ecological agriculture) and different hydric practices (wet, dry) and were sampled monthly. Total mercury concentration in fish increased over time for almost all the fields under study, but the mercury increase was particularly higher for fish exposed to ecological fields. We conducted δ15N and δ13C measurements to follow up fish diet changes within or among fields. The results have shown there were no variations in the diet of the fish over time within fields, although differences among management practices were observed, which could explain to some extent the THg variation in fish exposed to each of the agricultural practices. Results indicate that wetting and drying rice fields might be a greater source of mercury for fish and a potential hotspot for MeHg production enhanced by physicochemical parameters. Thus, mercury bioaccumulation in fish inhabiting rice paddies depend on several factors what, in turn, could lead to biomagnification across the food webs.