Mercury-contaminated Soil Research Articles

Mercury resistance and plant growth promoting traits of endophytic bacteria isolated from mercury-contaminated soil

Mercury (Hg) is a toxic trace element that can cause serious environmental problems. The main source of Hg contamination to soil across Indonesia is artisanal and small-scale gold mining (ASGM) and strategies to manage or remove Hg from soil are needed. This study isolated Hg-resistant endophytic bacteria from indigenous local grasses (Cynodon dactylon and Eleusine indica) growing in Hg-contaminated soils to identify potential inoculants that could increase plant growth and mercury uptake for phytoremediation. Grass samples were collected from an ASGM location on Lombok Island. The grass samples (both, root and shoot) were surface sterilized, aseptically mashed, and serially diluted with 0.9% sodium chloride (v/v) and an aliquot of the extracted bacteria was cultured on Nutrient Agar across a range of HgCl2 concentration from 0 to 1000 mg/L. Thirteen bacterial isolates were tested for their ability to detoxify Hg, Hg bioaccumulation, indole acetic acid (IAA) production, ammonium production, and siderophore production. Five of thirteen isolates were Hg-resistant and survived on a medium containing 250 mg/L HgCl2. One isolate from each of E. indica and C. dactylon showed complete Hg detoxification. The greatest Hg bioaccumulation was 85.04%. The highest expressed IAA and ammonium concentration was 13.17 mg/L and 2.58 mg/L respectively. Based on 16S rDNA sequence similarity, the two isolates with the greatest potential as inoculants (CD6 and EI6) were identified as Jeotgalicoccus huakuii (isolated from C. dactylon) and Bacillus amyloliquefaciens (isolated from E. indica) and could be used as inoculum for phytoremediation of Hg-contaminated soil in future studies.

Evaluation of the PGPR Capacity of Four Bacterial Strains and Their Mixtures, Tested on Lupinus albus var. Dorado Seedlings, for the Bioremediation of Mercury-Polluted Soils

Soil contamination by mercury, which is one of the most toxic heavy metals due to its bioaccumulative capacity, poses a risk to the environment as well as health. The Almadén mining district in Ciudad Real, Spain is one of the most heavily-polluted sites in the world, making the soils unusable. Bioremediation, and more specifically phyto-rhizoremediation, based on the synergistic interaction established between plant and Plant Growth Promoting Rhizobacteria (PGPR), improves the plant’s ability to grow, mobilize, accumulate, and extract contaminants from the soil. The objective of this study is to evaluate the plant growth-promoting ability of four PGPR strains (and mixtures), isolated from the bulk soil and rhizosphere of naturally grown plants in the Almadén mining district, when they are inoculated in emerged seeds of Lupinus albus, var. Dorado in the presence of high concentrations of mercury. After 20 days of incubation and subsequent harvesting of the seedlings, biometric measurements were carried out at the root and aerial levels. The results obtained show that the seeds treatment with PGPR strains improves plants biometry in the presence of mercury. Specifically, strain B2 (Pseudomonas baetica) and B1 (Pseudomonas moraviensis) were those that contributed the most to plant growth, both individually and as part of mixtures (CS5 and CS3). Thus, these are postulated to be good candidates for further in situ phyto-rhizoremediation tests of mercury-contaminated soils.

Self-cementation of the alkali-activated volcanic tuff coupling with thiol-functionalized expanded perlite that enhances the solidification and stabilization of the mercury-contaminated soil

HgII contaminants tend to be soluble in the anoxic sediments, which would potentially deteriorate the traditional solidification/stabilization (S/S) process. The thiol-functionalized expanded perlite (thiol-Exp-p) was prepared and employed in the self-cementation of the alkali-activated volcanic tuff (VT) as both lightweight aggregate and adsorbent to enhance the S/S of the Hg-contaminated soil. The cementation experiments were comprehensively researched in a systematical design. The experiments of adsorption, self-cementation, coupling, and stability were subsequently configured and implemented to investigate the feasibility of the coupling system and to optimize the whole S/S process. Both the pseudo-first-order kinetic model and the intraparticle diffusion model were appropriate in fitting the dynamic adsorption of HgII to thiol-Exp-p. CaO among the three alkali components had the most significant influence on the self-cementation of VT. The factors including the curing temperatures, the grinding times of VT, and the mass ratios of fly ash (FA) to binder all affected the coupling S/S process of HgII-spiked soil. The compressive strengths gradually decreased over the dosage of soil samples ranging from 10% to 70% in the solidified blocks in the stability experiments with the leaching concentrations contrarily elevating in the range. The addition of thiol-Exp-p to the self-cementation of VT not only reinforced the stabilization of HgII species in the solidified sample but also positively influenced the solidification process.

Effect of inorganic carbonate and organic matter in thermal treatment of mercury-contaminated soil

Thermal treatment of mercury (Hg)-contaminated soil was studied to investigate the desorption behavior of Hg at different temperatures. The soil samples were collected from two locations with different land uses around the mine and industrial site. The effect of soil properties such as inorganic carbonate minerals and organic matter content on Hg desorption was investigated to understand the thermal desorption process. The effect of soil composition on Hg desorption showed that behavior at 100 °C was similar, but a different behavior could be found at 300 °C. The thermal desorption efficiency at 300 °C is affected by the thermal properties of soils and the Hg desorption capacity of the soils. The Hg from both soil types was removed above 300 °C, and Hg was effectively removed from mine soil due to the partial decomposition of carbonate in the soil composition, while industrial soil showed that desorption would be restrained by Hg organic matter complexes due to organic matter content. Despite a relatively higher concentration of Hg in the mine soil, Hg removal efficiency was greater than that in the industrial soil. Sequential extraction results showed that only the Hg fractions (residual fractions, step 6) in mine soil changed, while the industrial soil was affected by changes in Hg fractions (step 3 to step 6) at 300 °C. Changes in soil pH during thermal desorption are also influenced by heating time and temperature. Therefore, the mechanisms of Hg desorption during thermal treatment were observed by soil properties. The volatilization of Hg in the soil is induced by organic carbon, while soil Hg release is controlled by organic matter complexes.

Does mercury emission from small-scale gold mining cause widespread soil pollution in Ghana?

The use of mercury in small-scale gold mining is globally the largest anthropogenic source of mercury in the environment. In countries like Ghana, where small-scale gold mining is a highly important economic sector, the activity is also expected to cause local pollution. This study is based on a hypothesis that the mining activity in Ghana is causing more widespread soil pollution also outside active mining sites, and that the main part of regional differences in soil concentrations of mercury might come from pollution. Little systematic and dependable data has been collected to assess the extent of mercury contamination of soils in areas outside active mining areas. The regional aspect of mercury pollution from mining has not been studied in Ghana or other countries with a large small-scale gold mining sector. Systematic collection of soil samples on a 25×25km2 net covering the entire country was carried out to ensure the representativeness of data and to allow calculation of spatial trends. The soil concentrations found in one-third of the country, where most intensive mining takes place, are three times higher than concentrations in the rest of the country. This difference cannot be explained by sources of natural variation in mercury concentrations but can be explained by decades of atmospheric deposition. It is therefore likely that the mining activity has caused a more widespread increase in soil concentrations, also outside active mining sites. The mercury concentrations found are on average 0.024mgkg-1, which is low compared to published studies from other countries and regions and estimated world averages. All measured concentrations are well below soil quality criteria for human health. The build-up of soil concentrations in the mining area is still problematic because mercury is a hazardous substance in the environment.

Potential bacteria capable of remediating mercury contaminated soils

Mercury content in ex-artisanal and small-scale gold mining areas in Cianjur District, Province of West Java, Indonesia was 7 to 36 mg L−1. It has exceeded the threshold value for industrial land. Bioremediation of mercury using mercury-resistant bacteria is attractive to remove mercury from the environment because it is more effective and less expensive. The objective of this study was to obtain potential bacteria capable of accumulating mercury to be used to remediate mercury contaminated soils in ex-gold mining areas. Potential bacteria isolates were characterized for their phenotypic and biochemical properties using the Biolog system. Thirty-two mercury-resistant bacteria were successfully isolated from the rhizosphere of Pityrogramma tartarea growing predominantly around tailings of ex-artisanal gold mining. After screening the presence of mercury, the three best isolates showing high resistances are Pseudomonas putida R2.13 and P. maculicola R4.27 that are capable to tolerate 180 mg L−1 mercury, and Enterobacter aerogenes R3.24 that is capable to survive at 170 mg L−1. Furthermore, the three bacteria also can fix atmospheric nitrogen and solubilize phosphate, but they cannot solubilize potassium. These indicate that P. maculicola R4.27, P. putida R2.13, and E. aerogenes R3.24 are potential as bioaccumulation agents on mercury-contaminated soils.

Spread of liquid waste in un-licited gold mining by geoelectrical method in Krueng Sabee sub-district Aceh

Illegal gold mining has increased significantly in Keude village of Krueng Sabee Aceh Jaya subdistrict. This causes environmental damage in the form of waste mercury pollution in the area. Environmental pollution caused by waste needs to be addressed. However, it needs to determine the appropriate method to overcome it by knowing the depth and the spread of mercury waste. This study aims to visualize subsurface conditions in the area of Krueng Sabee to provide information and data on the spread of mercury wastes. By using the method of geoelectric resistivity Schlumberger array, the contamination can be seen below the surface by the resistivity value of the sites. Results from these measurements after inverted using Earth Imager software of Res2Dinv can get a picture and visualize the location of subsurface conditions of the study. The results show that the resistivity value of waste mercury-contaminated soil at the study site ranged from 2–5 Ωm, and waste mercury contamination occurs vertically to a depth of 3 meters.

Changes in clover rhizosphere microbial community and diazotrophs in mercury-contaminated soils

Little is known about the response of the soil microbiome (including bacteria in the rhizosphere of legumes such as clover) to mercury (Hg) despite the toxicity of Hg to soil microorganisms. Here, Hg-contaminated soils collected from Guizhou province, southwest China, were divided into three groups according to their Hg contents and were planted with clover. High-throughput sequencing of bacterial 16S rRNA and nitrogenase (nifH) genes and quantitative polymerase chain reaction (qPCR) were used to study the response of bacteria and diazotrophs to soil Hg stress and the effects of Hg on the abundance of functional genes in rhizosphere soils. High concentrations of soil Hg decreased bacterial community abundance and diversity and increased the abundance and diversity of nitrogen-fixing bacteria. LEfSe analysis indicates that Rhizobium was a biomarker at sites with high soil Hg contents and the co-occurrence network results indicate a positive relationship between the abundance of the dominant module (from the co-occurrence network analysis) of Rhizobiaceae and soil Hg concentration. Structural equation modeling (SEM) indicates that the Hg content in the clover shoots (ShootHg) was negatively correlated with the abundance of the mercury reductase (merA) gene (r = −0.26, P < 0.05) and the organomercury lyase (merB) gene (r = −0.23, P < 0.05) in rhizosphere soils. Moreover, correlation analysis and SEM indicate that soil total nitrogen (TN), nitrate‑nitrogen (NO3−N), soil organic matter (SOM), and available molybdenum (Mo) contents were also important factors affecting the structure of the microbial community and the abundance of functional genes. The results provide a basis for further study of the mechanism(s) by which microorganisms may impart tolerance of clover to Hg in contaminated soils.

Soil Bioavailability and Native Plant Uptake of Mercury in the Contaminated Sites at Kodaikanal, India

This paper presents the evaluation of soil contamination with bioaccumulation and bioavailability of mercury in the surroundings of a former thermometer factory at Kodaikanal in connection with several other soil chemical characteristics. Mercury (Hg), a rare earth element, evolves to be the global concern because of its solubility and its persistence in nature. It is also widely known as a potential neurotoxin since it has the ability to bind with the thiol functional groups in the living system because of the accumulation in food chain and its biomagnifications. The Study was carried out at Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore, India during 2018-2020. Geo-coded soil and plant samples were collected in and around the former thermometer factory in different possible direction. The total mercury content in the soil ranged from 0.19 to 4.7 mg kg-1 and the water soluble mercury fraction ranged from 0.01 to 0.07 mg kg-1 in various sampling sites. The total mercury of the samples ranged from 0.24 to 3.80, 0.84 to 1.55, 0.45 to 1.67 and 0.19 to 4.97 mg kg-1 in east, north, south and west directions, respectively whereas the water soluble mercury fraction ranged from 0.01 to 0.07 and 0.01 to 0.04 mg kg-1 in east and west direction, respectively corresponding to 0.5 to 5.36 % of the total. Despite this analysis, other chemical parameters were also studied to determine their extent of influence on mercury accumulation and availability. Among those parameters, pH was found to be having significant correlation with total mercury and water soluble mercury. The concentration of total mercury and water soluble mercury recorded were less than the permissible limit set by International standards (Canadian Soil Quality Guidelines). Among different plant species, Roots of Sterculia sp. was found to accumulate 1.19 mg kg-1 whereas mercury content was found to be below detectable limits in other plants. Based on the results obtained from Potential Ecological Risk Index, it was concluded that risk associated with soil mercury contamination is low in the study area at Kodaikanal.

Arsenic and mercury uptake and accumulation in oilseed sunflower accessions selected to mitigate co-contaminated soil coupled with oil and bioenergy production

Thirty-seven accessions of oilseed sunflower were evaluated under natural field conditions for growth performance, ligno-cellulosic mass production of bioenergy, and metal uptake potential during the remediation of arsenic and mercury-contaminated soil. Significant variations were observed in the ligno-cellulosic components of plant stems at maturity, decreasing the following order: total sugars > cellulose > hemicellulose > lignin > ash. A significant difference was also noted in metal uptake among the different accessions. The highest concentrations in the above-ground parts were 14.08 and 0.40 mg/kg, respectively for As and Hg. In rhizosphere soil concentrations of inorganic As species (arsenate: 69.73 mg/kg, arsenite: 4.41 mg/kg) were higher, as compared organic As (dimethyl arsenic: 0.22 mg/kg); mono-methyl arsenic: 0.02 mg/kg). Arsenate concentration (3.72 mg/kg) was higher in root, whereas arsenite concentration (0.47 mg/kg) was higher in the shoots. Many accessions showed good oil production (26–45.6%), with the highest percentage of oleic (75%) and linoleic acids (37.6%). These results suggest that some oilseed sunflower cultivars could be adopted as crop plants for effective remediation of lightly to moderately As-/Hg-contaminated soils, coupled with agro-production.

Solidification/stabilization treatment with MgO-based material for mercury-contaminated soil

水銀汚染土壌（模擬汚染土壌および実際の汚染土壌）に対して，酸化マグネシウム系材料（マグネシウム系固化材）および高炉セメントB種により不溶化処理を検討した室内試験の結果および不溶化処理土の長期溶出挙動の観察結果について報告する。水銀溶出量によっては助剤の併用が必要であるが，マグネシウム系固化材は水銀に対して安定して高い不溶化効果が長期間持続することが最長10年の観察により確認された。高炉セメントB種についても，水銀に対して一定の不溶化効果を発揮すること，材齢の進行により不溶化効果が増加すること，中性化（pH低下）により不溶化効果が低下する可能性があることを示した。

A gas reporting whole-cell microbial biosensor system for rapid on-site detection of mercury contamination in soils

As optical reporting elements, fluorescent proteins are extensively used in whole-cell microbial biosensors. However, the use of these optical reporters is limited in opaque media such as soil. This study described a method utilizing gas as a reporting signal that could be used for the rapid on-site detection of mercury in soil. In this biosensor, the MerR protein could capture mercury ions and then bind the promoter of the efe gene to initiate the synthesis of the ethylene (C2H4)-forming enzyme that produced the gas. The research showed that the mercury ion concentrations could be converted into C2H4 gas signals, which were quantified using a handheld C2H4 sensor. By optimizing the biosensor to improve its anti-interference ability in the system, it could detect mercury ion concentrations in the soil ranging from 0.2 to 20 mg/kg within 45 min, effectively reflecting whether the mercury pollution in the soil exceeded the limit standard. This study provides a simple, inexpensive, and portable method for the on-site detection of soil pollutants.

Transgenic merA and merB expression reduces mercury contamination in vegetables and grains grown in mercury-contaminated soil.

Arabidopsis, tobacco, tomato and rice with merA/merB expressed reduced mercury concentration of leaves, fruits or grains. These mercury-breathing plants produce agricultural products with acceptable levels of mercury from contaminated soil. Mercury contamination in plant food products can cause serious health risks to consumers. Transgenic approaches to enhance mercury phytoremediation have been accomplished with expression of bacterial merA and merB genes to convert toxic organic mercury to less toxic elemental mercury. However, little is known whether these genes can be used to produce safe foods from plants grown on mercury-contaminated land. We have used Arabidopsis and tobacco as model plants for leafy vegetables, and tomato and rice as representative fruit and grain crops to investigate whether merA and merB expression allows for production of safe foods from mercury-contaminated soils. Our results show that grown on heavily contaminated land with mercury, merA and merB expressing transgenic plants can produce vegetables, fruits and grains safe for human and animal consumption, while the wild-type plants cannot. The merA and merB transgenic plants can also efficiently remove mercury from soil. With increasing mercury contamination problems for the agricultural land worldwide, the use of the merA and merB genes can help produce safe food from mercury-polluted land and also remediate contaminated soils.

Associations between microorganism and maize plant to remedy mercury-contaminated soil

Mercury (Hg) is one of the most toxic metals and is not essential for any organism. In this study, the potential of maize plants in association with bacteria to treat oxisol contaminated with Hg (II) was evaluated. The experiment was conducted in a controlled environment, and pots with 2 kg of oxisol were contaminated with HgCl2 solution at a dose of 36 mg kg-1 of Hg in a 7x4 factorial scheme: control (soil without Hg(II) and microorganisms), T2= (soil with Hg(II) and without microorganisms), and T3= soil with Hg(II) + Enterobacter cloacae, T4= Hg(II) + Bacillus subtilis, T5= Hg(II) + Enterobacter sp., T6= Hg(II) + Staphylococcus epidermidis, and T7= Hg(II) + Bacillus sp. Total Hg quantification was performed by atomic absorption spectrophotometry. At the end of the experiment, the soil pH was significantly lower (0.3 to 0.4 pH unit) in the T2 (no inoculation), Enterobacter cloacae, Enterobacter sp. and Bacillus sp. treatments. Neither contamination of soil with Hg nor plant associations with bacteria led to differences in the root dry mass of maize plants. Maize plants associated with Staphylococcus epidermidis and Bacillus sp. bacteria had lower shoot biomass (71 and 50%) compared to the treatment 2. The best remedial effect was observed with the association of maize plants with Bacillus sp., which recovered 19.67% of Hg(II) in the soil when compared to control and treatment 2 and treatment with B. subtilis. The recommendation is the use of B. subtilis to decrease the toxicity caused by Hg(II).

Endophytic bacteria stimulate mercury phytoremediation by modulating its bioaccumulation and volatilization

The quantification, efficiency, and possible mechanisms of mercury phytoremediation by endophytic bacteria are poorly understood. Here we selected 8 out of 34 previously isolated endophytic bacterial strains with a broad resistance profile to metals and 11 antibiotics: Acinetobacter baumannii BacI43, Bacillus sp. BacI34, Enterobacter sp. BacI14, Klebsiella pneumoniae BacI20, Pantoea sp. BacI23, Pseudomonas sp. BacI7, Pseudomonas sp. BacI38, and Serratia marcescens BacI56. Except for Klebsiella pneumoniae BacI20, the other seven bacterial strains promoted maize growth on a mercury-contaminated substrate. Acinetobacter baumannii BacI43 and Bacillus sp. BacI34 increased total dry biomass by approximately 47%. The bacteria assisted mercury remediation by decreasing the metal amount in the substrate, possibly by promoting its volatilization. The plants inoculated with Serratia marcescens BacI56 and Pseudomonas sp. BacI38 increased mercury volatilization to 47.16% and 62.42%, respectively. Except for Bacillus sp. BacI34 and Pantoea sp. BacI23, the other six bacterial strains favored mercury bioaccumulation in plant tissues. Endophytic bacteria-assisted phytoremediation contributed to reduce the substrate toxicity assessed in different model organisms. The endophytic bacterial strains selected herein are potential candidates for assisted phytoremediation that shall help reduce environmental toxicity of mercury-contaminated soils.

Hyperspectral inversion of mercury in reed leaves under different levels of soil mercury contamination.

High mercury (Hg) affects biochemical-physiological characteristics of plant leaves such as leaf chlorophyll, causing refractive discontinuity and modifications in leaf spectra. Furthermore, the hyperspectroscopy provides a potential tool for fast non-destructive estimation of leaf Hg. However, there are few studies that have investigated Hg for wetland plants via hyperspectral inversion. In this study, reeds (Phragmites australis) leaf Hg concentration and hyperspectra were measured under different soil Hg treatment. Hg-sensitive parameters were identified by basic spectral transformations and continuous wavelet transformation (CWT). Inversion models were developed using stepwise multiple linear regressions (SMLR), partial least square regression (PLSR), and random forest (RF) to estimate leaf Hg. The results indicated that CWT improved the correlation of hyperspectra and leaf Hg by 0.020-0.227, and R2 of the CWT-related model increased by 0.0557-0.2441. In addition, Hg-sensitive bands were predominant at 600-750 (visible region) and 1500-2300nm (mid-infrared), and Hg might modify leaves spectra primarily by affecting chlorophyll and water contents. Of the studied models, SMLR using normalized transformation (NR) and CWT (NR-CWT-SMLR) model (R2 = 0.8594, RMSE = 0.0961) and RF using NR and CWT (NR-CWT-RF) model (R2 = 0.8560, RMSE = 0.1062) suited for leaf Hg inversion. For Hg content < 1.0mgkg-1, the former model was more reliable and accurate. This study provided a method for the estimation of Hg contamination in wetland plant and indicated that model-based hyperspectral inversion was feasible for fast and non-destructive monitoring.

Transfer and bioaccumulation of mercury from soil in cowpea in gold mining sites

In this study, we evaluated the phytoremediation ability of three different genotypes of cowpea (Vigna unguiculata L. Walp) grown on mercury-contaminated soils from gold mining areas. In particular we compared a native genotype with two commercial lines L-019 and L-042. The plants were cultivated in soils amended at different concentrations of Hg (i.e. 0.2, 1, 2, 5 and 8 mg kg−1). After three months exposure, we determined plant growth, seed production, and Hg accumulation in different plant tissues (root, leaf, seed and stem). Indices of soil-plant metal transfer such as translocation, bioconcentration and bioaccumulation factors were calculated. Results showed that the native variety presented the highest seed production (3.8 g), however the highest plant biomass (7.9 g) was observed in line L-019, both on Hg-contaminated soil of 1 mg kg−1. The different plant tissues differed in terms of Hg concentration (root > leaf > stem). In the highest treated soil, the line L-042 accumulates higher Hg in both roots and leaves, while line L-019 accumulates more metal in stems. In line L-019, Hg concentrations in the fruit showed significant differences being higher in the valves than in the seeds. The transfer factors were generally lower than 1 and indicates the low accumulation of Hg by cowpeas. The estimated daily Hg intake through cowpea consumption showed values far below the threshold of 0.57 μg kg−1 dw day−1 recommended by the World Health Organization. Our results show cowpea V. unguiculata as a good protein-rich food substitute of Hg-contaminated fish for populations living near gold mining sites.

Mercury alters the rhizobacterial community in Brazilian wetlands and it can be bioremediated by the plant-bacteria association.

This study examined how soil mercury contamination affected the structure and functionality of rhizobacteria communities from Aeschynomene fluminensis and Polygonum acuminatum and how rhizobacteria mediate metal bioremediation. The strains were isolated using culture-dependent methods, identified through 16S rDNA gene sequencing, and characterized with respect to their functional traits related to plant growth promotion and resistance to metals and antibiotics. The bioremediation capacity of the rhizobacteria was determined in greenhouse using corn plants. The isolated bacteria belonged to the phyla Actinobacteria, Deinococcus-Thermus, Firmicutes, and Proteobacteria, with great abundance of the species Microbacterium trichothecenolyticum. The rhizobacteria abundance, richness, and diversity were greater in mercury-contaminated soils. Bacteria isolated from contaminated environments had higher minimum inhibitory concentration values, presented plasmids and the merA gene, and were multi-resistant to metals and antibiotics. Enterobacter sp._C35 and M. trichothecenolyticum_C34 significantly improved (Dunnett's test, p < 0.05) corn plant growth in mercury-contaminated soil. These bacteria helped to reduce up to 87% of the mercury content in the soil, and increased the mercury bioaccumulation factor by up to 94%. Mercury bioremediation mitigated toxicity of the contaminated substrate. Enterobacter sp._C35, Bacillus megaterium_C28, and Bacillus mycoides_C1 stimulated corn plant growth and could be added to biofertilizers produced in research and related industries.

Studi Akumulasi Logam Berat Merkuri Menggunakan Tanaman Awar-Awar (Ficus Septica Burm F)

This research aims to to study the ability of awar-awar plants ((Ficus Septica Burm. F)) to accumulate heavy metals. Awar-awar are grown in glass reactors and treated with 10 ppm mercury solution wich one, two, and three weeks in time variations. The analysis using CV-AAS showed that the total absorption of mercury heavy metals by awar-awar plants in reactors I, II and III was 81.7%, 34.6% and 85.4% respectively. When the phytoremediation process takes place the plant shows no symptoms of damage or even death even though it has accumulated more than 50% of mercury from the growing media. The BCF value of awar-awar plants in reactor I was 2.79 reactor II was 0.53 and reactor III was 0.55. While the TF values ​​in reactors I, II and III were 0.04; 1.13 and 0.97. The calculation results of BCF and TF values ​​show that Awar-awar plants (Ficus Septica Burm. F) can accumulate heavy metals of mercury so it is recommended to be used as a phytoremediation agent in mercury-contaminated soils.

Effects of Brownfield Remediation on Total Gaseous Mercury Concentrations in an Urban Landscape.

In order to obtain a better perspective of the impacts of brownfields on the land–atmosphere exchange of mercury in urban areas, total gaseous mercury (TGM) was measured at two heights (1.8 m and 42.7 m) prior to 2011–2012 and after 2015–2016 for the remediation of a brownfield and installation of a parking lot adjacent to the Syracuse Center of Excellence in Syracuse, NY, USA. Prior to brownfield remediation, the annual average TGM concentrations were 1.6 ± 0.6 and 1.4 ± 0.4 at the ground and upper heights, respectively. After brownfield remediation, the annual average TGM concentrations decreased by 32% and 22% at the ground and the upper height, respectively. Mercury soil flux measurements during summer after remediation showed net TGM deposition of 1.7 suggesting that the site transitioned from a mercury source to a net mercury sink. Measurements from the Atmospheric Mercury Network (AMNet) indicate that there was no regional decrease in TGM concentrations during the study period. This study demonstrates that evasion from mercury-contaminated soil significantly increased local TGM concentrations, which was subsequently mitigated after soil restoration. Considering the large number of brownfields, they may be an important source of mercury emissions source to local urban ecosystems and warrant future study at additional locations.