Effects of Small-Scale Gold Mining (SGM) to Mercury and Nutrient Contents in Soil in Kokap Subdistrict, Kulonprogo, Yogyakarta

Gold processing in Dusun Sangon, Kalirejo Village, Kokap Sub district, Kulonprogo Regency, SpecialRegion of Yogyakarta Province uses amalgamation method. Mercury use in gold processing has apotential impact on environmental damage and health of organism. Therefore, management onmercury-contaminated soil is needed to reduce environmental impacts. However, beforeperforming soil management, it is important to conduct research on initial condition of researchlocation, including research on the soil’s nutrient quality and mercury content. Testing wasconducted in the laboratory. Mercury (Hg) content testing used mercury analyzer testing method.pH testing used ISRIC 6th 2002 method. Organic carbon testing used SNI 13-4720-1998 testingmethod. Total nitrogen testing used SNI 2803-2010 testing method. C/N Ratio testing used SNI 13-4720-1998; SNI 2803-2010 testing methods. Results show that mercury contents in residualsamples of gold ore and soil samples were 4.81 mg/kg and 88.63 mg/kg respectively, which wereincluded in TC-B and TC-A in the aforementioned order. Meanwhile, mercury content in gold oreSamples 1 and 2 were 0.28 ppm and 0.14181 ppm respectively. Soil nutrient content parameters ofOrganic C, Total N, and C/N ratio were found to be very low. These results might be influenced byprocessing activities in gold ore mining.

Indigenous mercury-resistant bacteria isolated from contaminated soils around artisanal gold processing centers in Sukabumi, Indonesia

In Indonesia, the largest mercury pollution comes from artisanal and small-scale gold mining (ASGM), which may cause the distribution of mercury to agricultural land and can be absorbed by food crops. Sukabumi Regency in West Java, well-known as one hotspot of illegal artisanal gold mining and national rice producer, is potentially threatened by mercury pollution. Efforts to remediate mercury contaminated agricultural land can be done by using mercury-reducing bacteria. This research aims to select the most potential indigenous bacteria for mercury remediation. Soil and sludge samples were collected from 2 districts in Sukabumi, where gold processing using mercury is common. Bacteria were selectively isolated from cultured colonies grown in Luria Bertani broth supplemented with HgCl2 30 mg/L. We obtained 27 isolates that belong to 16 species, as identified by API® 20 E and 20 NE (BioMérieux, USA). The growth of each isolate was assessed by measuring the optical density of inoculated LB broth contained HgCl2 30 mg/L for 5 consecutive days. All isolates showed normal growth. The log phase reached its maximum value on the second or third day after inoculation and lag phase afterward. Twelve identified isolates were chosen for evaluation of their resistance to mercury by growing them in Mueller-Hinton agar supplemented with HgCl2 (30 mg/L, 50 mg/L, 100 mg/L, 150 mg/L, and 200 mg/L). Seven isolates were able to grow in media with HgCl2, but only Mer07 survived on HgCl2 150 mg/L.

Removal of Heavy Metal Mercury (Hg) Liquid Waste through Electrolysis Method in Paya Ateuk Village, Pasie Raja District, South Aceh

Electrolysis is one of the methods used to remove heavy metal mercury (Hg). The electrolysis process is carried out on residual liquid waste from gold processing by utilizing chemical reactions through electrodes immersed in an electrolyte solution. This research method is experimental. We conducted laboratory tests to see the electrolysis process on the residual liquid waste from gold processing in a 10-liter container. We took samples from 10 different containers, 1 liter each from each tub. Sampling time was carried out in the morning, afternoon, and evening. The results showed a significant decrease in mercury (Hg) levels up to 1.30% with 12 volts of electricity for 100 minutes. In contrast, the lowest decrease occurred in the electric current of 3.3 volts within 25 minutes. We use the electrolysis method. This heavy metal removal technique can be applied and managed properly by the community and local government to minimize heavy metal pollution such as mercury in the surrounding environment due to waste from the community's traditional gold processing.

Bioaccumulated Mercury by Several Types of Plants in Ex-Traditional Gold Processing Area, Gogorea Village, Buru Island

This study examines the accumulation of metallic mercury by several types of plants in the traditional gold processing area in the village of Gogore, Buru district. The plants that were sampled in this study were guava, lempuyang gajah, and harendong bulu. These three plant species were chosen because they dominate the vegetation in the gold processing area. The analysis results showed that the lempuyang gajah was the plant that accumulated the highest mercury metal, namely in the roots of 16.79 ppm and the leaves of 15.03 ppm. Guava plants accumulated metal mercury in the roots and leaves of 11.73 ppm and 9.90 ppm, respectively. Meanwhile, harendong plants accumulated mercury in the roots and leaves of 2.59 ppm and 10.39 ppm, respectively. The BCF values ​​of guava, lempuyang gajah, and harendong bulu plants were 1.58, 0.41, and 0.39, respectively. Meanwhile, the TF values ​​of the three plants were 0.84, 0.89, and 4.01, respectively. From these results, it can be concluded that the three plants can accumulate mercury in high enough concentrations, so these three types of plants are categorized as hyper tolerant plants and accumulators.

Photocatalytic Advanced Oxidation Processes for Neutralizing Free Cyanide in Gold Processing Effluents in Arequipa, Southern Peru

Cyanide (CN−) from gold processing effluents must be removed to protect human health and the environment. Reducing the use of chemical reagents is desirable for small centralized and decentralized facilities. In this work, we aimed to optimize the use of ultraviolet (UV) radiation coupled with hydrogen peroxide (H2O2) to enhance the rate and extent of CN− removal in synthetic and actual gold processing effluents, from one centralized and one decentralized facility in southern Peru. Bench-scale studies conducted using H2O2 and ambient UV showed no significant effects on CN− destruction; however, experiments with higher UV intensity and H2O2 accelerated free CN− degradation. When a 1:1 stoichiometric ratio of CN−:H2O2 was tested, the highly concentrated effluent (1 g CN−/L) had a slower pseudo first-order rate constant (k = 0.0066 min−1) and took ~5 h longer to reach 99% destruction, compared with the low concentration effluent (100 mg CN−/L; k = 0.0306 min−1). Lastly, a TiO2 photocatalyst with low stoichiometric CN−:H2O2 ratios (1:0.1 and 1:0.2), in a compound parabolic solar concentrator, was tested to investigate the degradation of a high concentration effluent (1.28 g CN−/L). These results show a significant improvement to degradation rate within a 20 min period, advancing treatment options for mineral processing facilities.

Water Footprint Assessment of Carbon in Pulp Gold Processing in Turkey

This paper presents water the footprint assessment (WFA) of carbon in pulp (CIP) gold processing. The main objectives of the study are determining grey and blue water footprints and identifying the hotspots of the process. Results revealed that the total blue water footprint, including the extraction and processing of the gold, was found to be 452.40 m3/kg Au, and the grey WF to be 2300.69 m3/kg Au. According to the results, the lost return flow on the direct blue WF side has the largest contribution, with a value of 260.61 m3/kg Au, and the only source of the lost return flow is the tailing pond. On the indirect side, it is seen that the oxygen consumption used for the leaching process has the highest value, with 37.38 m3/kg. Among the nine contaminants in the mine tailings, the critical component responsible for the grey water footprint is by far arsenic, with a value of 1777 m3/kg Au. The results will be used to make recommendations for reducing water consumption in mining operations, for a better design for the environment. The study is a pioneering study, being the first implementation of water footprint assessment in a gold mine in Turkey.

Molecular Identification of Hg-Resistant Bacteria and Their Potential in Reducing Mercury Contamination

The aim of this research was to obtain and determine the identity of Hg-resistant bacteria in soil contaminatedwith gold processing waste and test its ability to reduce mercury contamination. Soil samples as a source of Hgresistant bacterial isolates were obtained from the gold processing location in Ilangata Village, Anggrek District,North Gorontalo Regency. The research was conducted at the Microbiology Laboratory, Department of Biology,Faculty of Mathematics and Natural Sciences. Mercury analysis was carried out at the Laboratory of FisheriesProduct Quality Development and Testing (LPPMHP), Gorontalo Province, and bacterial identification wascarried out at the Hasanuddin University Medical Research Center Research Unit. The parameters observed werethe types of Hg resistant bacteria and the ability of the bacteria to reduce mercury contamination. The resultsshowed that there were four bacterial isolates on the soil contaminated with 4.5 ppm mercury, which were namedILb01, ILB02, ILb03, and ILb04. Molecular identification showed that ILb01 was closely related toStenotrophomonas sp. SB67 and ILb02 close to Enterobacter cloacae strain CM 1, these strains were not resistantto mercury contamination; while ILb03 which is similar to strain BS0591 and ILb04 which is similar to BacteriumBacillus albus strain SQ30 16S could be resistant and was able to reduce mercury contamination by 99% at 10ppm levels. Key words: heavy metals, Hg-resistant bacteria, molecular identification, mercury