With the growth and development of chemical plants, the amount of mercury released in wastewater has increased. Mercury in wastewater contains harmful compounds which are hazardous to the human health and living organisms. Therefore, its removal from wastewater is significant. There are various techniques or methods available for removing mercury from aqueous solutions. This study focused upon the removal of mercury from aqueous solution with commercial activated carbon and activated carbon from sugarcane bagasse.  Activated carbon produced from sugarcane bagasse was used as adsorbent. This adsorbent was used to remove mercury from aqueous solution. For this purpose, first, the optimal mercury solution pH for mercury removal was obtained. Effective parameters such as contact time, initial concentration of mercury, adsorbent dose and agitation speed were investigated. The mercury adsorption was increased when the mass of activated carbon was increased. Increasing the initial mercury concentration leads to decrease in mercury adsorption efficiency. The results of experiments indicated that the speed of the stirrer was not considered to be an effective factor in the mercury adsorption. Experiments were also carried out on a commercial activated carbon. Adsorption results obtained for sugarcane bagasse activated carbon were compared with commercial activated carbon.  The adsorption efficiency was increased as the contact time was increased.  Finally, the experiment was carried out on water samples released from South Pars platforms. In addition to the mercury removal, other heavy metals removal such as lead and cadmium were also carried out.

Mercury (Hg) and methylmercury (CH3Hg) bind strongly to micro and nano (NP) particles and this partitioning impacts their fate and bioaccumulation into food webs, and, as a result, potential human exposure. This partitioning has been shown to influence the bioavailability of inorganic Hg to methylating bacteria, with NP-bound Hg being more bioavailable than particulate HgS, or organic particulate-bound Hg. In this study we set out to investigate whether the potential interactions between dissolved ionic Hg (HgII) and CH3Hg and NPs was due to incorporation of Hg into the core of the cadmium selenide and sulfide (CdSe; CdS) nanoparticles (metal exchange or surface precipitation), or due purely to surface interactions. The interaction was assessed based on the quenching of the fluorescence intensity and lifetime observed during HgII or CH3Hg titration experiments of these NP solutions. Additional analysis using inductively coupled plasma mass spectrometry of CdSe NPs and the separated solution, obtained after HgII additions, showed that there was no metal exchange, and X-ray photoelectron spectroscopy confirmed this and further indicated that the Hg was bound to cysteine, the NP capping agent. Our study suggests that Hg and CH3Hg adsorbed to the surfaces of NPs would have different bioavailability for release into water or to (de)methylating organisms or for bioaccumulation, and provides insights into the behavior of Hg in the environment in the presence of natural or manufactured NPs.

Forest ecosystem has long been suggested as a vital component in the global mercury (Hg) biogeochemical cycling. However, there remains large uncertainties in understanding total Hg (THg) and methylmercury (MeHg) variations and their controlling factors during the whole hydrological processes in forest ecosystems. Here, we quantified Hg mass flow along hydrological processes of wet deposition, throughfall, stemflow, litter leachate, soil leachate, surface runoff, and stream, and litterfall Hg deposition, and air-forest floor elemental Hg (Hg⁰) exchange flux to set up a Hg mass balance in a subtropical forest of China. Results showed that THg concentration in stream was lower than that in wet deposition, while an opposite characteristic for MeHg concentration, and both THg and MeHg fluxes of stream were lower than those of wet deposition. Variations of THg and MeHg in throughfall and litter leachate had strong direct and indirect effects on controlling variations of THg and MeHg in surface runoff, soil leachate and stream, respectively. Especially, the net Hg methylation was suggested in the forest canopy and forest floor layers, and significant particulate bound Hg (PBM) filtration was observed in soil layers. The Hg mass balance showed that the litterfall Hg deposition was the main Hg input for forest floor Hg, and the elemental Hg vapor (Hg⁰) re-emission from forest floor was the dominant Hg output. Overall, we estimated the net THg input flux of 13.8 μg m⁻² yr⁻¹ and net MeHg input flux of 0.6 μg m⁻² yr⁻¹ within the forest ecosystem. Our results highlighted the important roles of forest canopy and forest floor to shape Hg in output flow, and the forest floor is a distinct sink of MeHg.

Understanding how mercury (Hg) accumulates in the aquatic food web requires information on the factors driving methylmercury (MeHg) contamination. This paper employs data on MeHg in muscle tissue of three black bass species (Largemouth Bass, Spotted Bass, and Smallmouth Bass) sampled from 21 reservoirs in California. During a two-year period, reservoirs were sampled for total Hg in sediment, total Hg and MeHg in water, chlorophyll a, organic carbon, sulfate, dissolved oxygen, pH, conductivity, and temperature. These data, combined with land-use statistics and reservoir morphometry, were used to investigate relationships to size-normalized black bass MeHg concentrations. Significant correlations to black bass MeHg were observed for total Hg in sediment, total Hg and MeHg in surface water, and forested area. A multivariate statistical model predicted Largemouth Bass MeHg as a function of total Hg in sediment, MeHg in surface water, specific conductivity, total Hg in soils, and forested area. Comparison to historical reservoir sediment data suggested there has been no significant decline in sediment total Hg at five northern California reservoirs during the past 20 years. Overall, total Hg in sediment was indicated as the most influential factor associated with black bass MeHg contamination. The results of this study improve understanding of how MeHg varies in California reservoirs and the factors that correlate with fish MeHg contamination.

Whereas early life stages are usually considered as particularly sensitive to both organic and inorganic contaminants, field studies assessing contaminant bioaccumulation in these stages are scarce. Selenium (Se) is thought to counteract Hg toxic effects when it is found at Se:Hg molar ratios above 1. However, the variation of this ratio in key fish tissues of different early life stages is mostly unknown. The present study therefore aimed to assess Hg and Se content in gravid female tissues (gonads, muscle, liver, gut, and brain) and different life stages (egg masses, newly hatched larvae (NHL), larvae and juvenile) of Yellow Perch (YP) in a large fluvial lake (Lake Saint-Pierre, Québec, Canada). Se:Hg molar ratios were measured for each compartment in order to fill associated knowledge gaps. Total Hg (THg) and methylmercury (MeHg) concentration varied between tissue according to the following trend: Muscle > Liver > Gut > Brain > Gonads. During YP early life stages, MeHg values increased according to an ontogenetic pattern (mg/kg dw) (mean ± SEM): Egg masses (0.01 ± 0.002) < NHL (0.015 ± 0.001) < Larvae (0.14 ± 0.01) < Juveniles (0.18 ± 0.01). Se concentrations in different YP tissues showed the following trend (mg/kg dw) (mean ± SEM): Gut (3.6 ± 0.1) > Liver (2.5 ± 0.1) > Gonads (1.92 ± 0.06) > Brain (1.26 ± 0.03) > Muscle (1.23 ± 0.06). In YP early life stages, Se concentrations were highest in NHL (3.0 ± 0.2), and then decreased as follows: Egg masses (2.8 ± 0.1) > Larvae (1.37 ± 0.04) > Juveniles (0.93 ± 0.05). Se:Hg molar ratios varied considerably and were systematically above 1. This is the first study to simultaneously report Hg and Se bioaccumulation through fish life cycle.

Fish-associated antibiotic resistance genes (ARGs) have attracted increasing attention due to their potential risks to human beings via the food chain. However, data are scarce regarding the antibiotic resistance in fish themselves. Herein, the antibiotic resistance genes (ARGs) were assessed in the gut of four major Chinese freshwater carp (i.e., silver carp, grass carp, bighead carp, and crucian carp) from food retail markets. Results show that the abundances of target ARGs (e.g., tetA, tetO, tetQ, tetW, sulI, sulII, and blaTEM₋₁) and class 1 integrase (intI1) were in the range 9.4 × 10⁻⁶ - 1.6 × 10⁻¹ and 6.7 × 10⁻⁵ - 5.2 × 10⁻² gene copies per 16S rRNA gene, respectively. The sulI, sulII, and tetQ strongly correlated with silver and mercury resistance genes (e.g., silE and merR). The microbial taxa of fish gut could be partly separated among retail markets based on the PCA analysis. About 15.0% of the OTUs in fish gut were shared and 74.5% of the shared OTUs were identified as Acidobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Firmicutes, and Proteobacteria. These phyla may constitute the core microbiota in the guts of the four Chinese freshwater carp. The possible ARG hosts were revealed based on the network analysis, and the presence of pathogen-associated resistant genera in fish gut highlights the need to fully understand their potential human health risks.

This study aimed to determine if there is a co-elevation of human blood arsenic and mercury levels in the Midwestern population of the United States (U.S.) and to determine any geographical patterns and variation of arsenic and mercury that may exist in Michigan. 58,800 blood specimens along with associated demographic/geographic data from the contiguous United States were reviewed. Univariate and multivariable logistic regression were used to analyze demographic/geographic variables associated with elevated arsenic concentrations. Furthermore, blood data from patients in Michigan were aggregated to the ZIP code tabulation area (ZCTA) in order to assess geographic variation using spatial regression models. SaTScan software was also used to analyze potential clustering of arsenic and mercury across Michigan ZCTAs. Within the contiguous United States, elevated mercury blood concentrations, older age, female sex, and coastal status were all associated with elevated arsenic blood concentrations (elevated mercury odds ratio (OR) 3.18 (3.04–3.33); female sex OR 1.06 (1.02–1.11); +10 yr age OR 1.12 (1.11–1.14); coastal state OR 1.33 (1.27–1.40). Within the state of Michigan, as with the continuous U.S., elevated mercury blood concentrations and older age were associated with elevated arsenic blood concentrations (elevated mercury OR 2.75 (2.38–3.18); female sex OR 1.06 (0.95–1.19); +10 yr age OR 1.10 (1.06–1.13). Using spatial regression, it was determined that within Michigan, economic inequality (measured via the Gini coefficient) was also associated with elevated concentrations of mercury in the blood. Clinical reference laboratory data, in conjunction with spatial analysis methods, may enhance our understanding of how elemental exposure affects human health and should be considered for studying how environmental contaminants, socioeconomics and geography affect the health of populations.

The cobalt ferrite-reduced oxidized graphene (CoFe2O4/rGO) catalyst was synthesized by hydrothermal method and characterized by Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), Brunauere Emmette Teller (BET) and Hysteresis loop. For developing a new method of removing elemental mercury (Hg0) from flue gas, the effects of catalyst dosage, PMS concentration, solution pH and reaction temperature on the removal efficiency were investigated experimentally by using peroxymonosulfate (PMS) catalyzed by CoFe2O4/rGO at a self-made bubbling reactor. The average removal efficiency of Hg0 in a 30-min period reached 95.56%, when CoFe2O4/rGO dosage was 0.288 g/L, PMS concentration was 3.5 mmol/L, solution pH was 5.5 and reaction temperature was 55 °C. Meanwhile, based on the free radical quenching experiments, in which, ethyl alcohol and tert butyl alcohol were used as quenchers to prove indirectly the presence of •OH and SO4•−, the characterizations of catalysts and reaction products, and the existing results from other scholars. The reaction mechanism was proposed.

This study developed a novel Hg(II) immobilization strategy by firstly incubating algal cells in high-phosphate cultures for surface modification, followed by obtaining the P-rich biomass as adsorbents for enhanced Hg(II) removal and then charring the Hg-loaded biomass to prevent leaching of phosphate and to immobilize Hg(II). For algal surface modification, Scenedesmus obtusus XJ-15 were cultivated under different P concentrations and obtained the highest sites concentration of surface phosphoryl functional groups in 80 mg L⁻¹ P cultures. For Hg(II) adsorption, biomass from 80 mg L⁻¹ P cultures (B-80) achieved the highest saturated sorption capacity of 95 mg g⁻¹ fitting to Langmuir isotherm model under the optimum pH of 5.0. For charring stabilization, the Hg-loaded B-80 was calcinated under different temperatures, and the product obtained from 300 °C charring showed the lowest Hg(II) leaching rate without P release. Moreover, FT-IR and XPS analysis indicate that the surge of surface phosphoryl functional groups dominated the enhancement of Hg(II) sorption and also Hg(II) charring immobilization. The above results suggested that the developed strategy is promising for both phosphate and mercury removal from water and for co-immobilization of P and Hg(II) to prevent leaching.

Mercury-antimony (HgSb) mining activities are important anthropogenic sources of Hg and Sb to the local environment. The Xunyang HgSb mine situated in Shaanxi Province is an active Hg mine in China. To understand the emission, transportation, and deposition of Sb through HgSb mining activities, current study systematically monitored the Sb concentration in precipitation in the Xunyang HgSb mining district. Five groups of experimental pots were carefully designed to further investigate the influence of HgSb mining activities on the Sb contamination in the local surface soil. Based on the overtime increasing of the Sb concentrations in soil from experimental pots, for the first trial, we estimated the atmospheric deposition flux/mass of Sb in the Xunyang HgSb mining district. Our results showed that the concentrations of Sb in precipitation in the Xunyang HgSb mining district ranged from 0.71 μg L−1 to 19 μg L−1 (mean = 4.2 ± 4.5 μg L−1), which was orders of magnitude higher than that at the control site. As expected, the concentration of Sb in precipitation was highly elevated near of the HgSb smelter and gradually decreased with distance from the smelter. After 12 months exposure, Sb concentrations in soil of experimental pots were increased by 1.2–8.5 times. The average atmospheric wet and dry deposition flux of Sb in the Xunyang HgSb mining district were 7.2 ± 6.9 μg m−2 day−1 and 2.1 ± 4.7 mg m−2 day−1, respectively; the annual wet and dry deposition mass of Sb through HgSb mining activities were estimated to be 1.6 t y−1 and 158 t y−1, respectively, indicating that dry deposition was the dominant pathway (98 ± 1.2%) for the removal of Sb from the atmosphere. Our results confirmed that the ongoing HgSb mining activities resulted to serious Sb contamination to terrestrial ecosystems, posing a potential threat to local residents in the Xunyang HgSb mining district.