The utilization of surrounding rocks is required in human living areas, and these development activities create large cut slopes and generate large amounts of cut rocks as construction materials. If these development areas are strata containing sulfide minerals (pyrite, etc.), contamination may occur, causing environmental pollution problems in the development site and surrounding areas. Several methods have been studied for the preliminary identification of potentially contaminated rocks, including Acid Base Accounting (ABA), Modified ABA procedures, Carbonate Neutralization Potential determinations, Humidity cell tests, Column tests, Batch reactor (Shake flask) tests, and Field tests (Orava, 1997; USEPA and Hardrock Mining, 2003). Studies on rock samples have resulted in most of the samples being classified as Non-Acid Forming (NAF), with some samples containing sulfide minerals (such as pyrite) being classified as Potentially Acid Forming (PAF). It can be expected that future development of these rocky areas may affect the surrounding environment or rock utilization. Therefore, these rock areas are considered to be in need of management. It would be desirable to investigate the occurrence of pollution sources caused by mineral sulfides in advance and take appropriate countermeasures. It is expected to reduce the economic losses that may occur in the future, and it is judged that the pollution problem of the surrounding environment can be further reduced.

A nationwide low-density geochemical map of arsenic was created using 723 composite stream sediment samples, and the geochemical distribution of arsenic was evaluated based on the map. The low-density composite samples, which were obtained from high-density stream sediment samples (23,696 samples) collected from the previous national geochemical mapping project, were used as a geological medium. To this end, each 1:50,000 topographic map of the entire country was divided into six sub-regions, and all individual stream sediment samples within each sub-region were mixed to create one composite sample (953 in total, approximately 1/100 km(2)). Chemical analysis was performed using a high resolution inductively coupled plasma-mass spectrometer (HR ICP-MS) after strong acid digestion (HF, HClO4, and HNO3), and strict quality control was applied. As a result, arsenic had an interquartile range (Q25 similar to Q75) of 4.53 similar to 7.99 mg/kg, a median of 5.78 mg/kg and a mean of 8.95 mg/kg. The geochemical threshold using the box plot of arsenic content was derived as 18.7 mg/kg, and approximately 3.5% of the samples exceeded this value. The nationwide spatial distribution of arsenic content shows a wide range of fluctuation patterns by geology, reflecting the underlying geological variations. The geochemical anomalies above the threshold indicate the influence of representative non-ferrous metal mineralization zones in Korea.

Nation-wide low-density geochemical maps are being constructed using composite samples of stream sediments for 10 elements (As, Be, Bi, Cd, Mo, Sb, Sn, Tl, U, W) that have not been previously mapped at the national level. To obtain high-quality geochemical data, rigorous quality control (QC) procedures were implemented, which included (1) the randomization of project samples, (2) the introduction of project standards, and (3) the insertion and analysis of analytical replicates. Threshold values were calculated and geochemical maps were created for five elements (Be, Bi, Sn, Tl, U). The remaining five elements that did not pass the QC are currently undergoing re-analysis. Low-density geochemical mapping can result in a loss of detailed geochemical information, but it is useful for identifying regional geochemical patterns and establishing threshold values.

As the industrial demand and use of vanadium increases, it is necessary to explore its new sources in Korea. In this study, using geospatial chemical data, we derived geochemical threshold values for the entire country and identified areas prospective for vanadium deposits. The regional (country-wide) threshold value was derived using logarithmic transformation of raw data (n = 23,548) of the first- and second-order stream sediments collected across the country in the late 1990s and the early 2000s. The median +2 median absolute deviation (MAD) and Tukey inner fence (TIF = Q75 +1.5 interquartile range) values were 116 mg/kg and 200 mg/kg, respectively. Of these, the TIF standard, which showed 0.6 % of data exceeding the threshold, was judged to be appropriate for distinguishing clear enrichment or contamination of vanadium. In the case of the Geumsan and Pocheon, areas with potential for vanadium development, the TIF and median +2 MAD values of 259 mg/kg and 218 mg/kg, respectively, can be used as the criteria for evaluating the impact of environmental pollution before and after deposit development.

Geochemical maps can be used for a variety of purposes, one of which is to establish regional or local geochemical thresholds for the analyzed elements. In the case of vanadium, as industrial demand and use increase, it is necessary to expand the development of vanadium in Korea. However, the environmental management standards are insufficient. Therefore, in this study, using geochemical data, we derived geochemical threshold values for the entire country and areas with potential for the development of vanadium deposits. The regional (country-wide) threshold value was derived using logarithmic transformation of raw data (N = 23,548) of the first- and second-order stream sediments collected across the country in the late 1990s and the early 2000s. The median + 2 median absolute deviation (MAD) and Tukey inner fence (TIF) values were 116 mg/kg and 200 mg/kg, respectively. Of these, the TIF standard, which showed 0.6% of data exceeding the threshold, was judged to be appropriate for distinguishing clear enrichment or contamination of vanadium. In the case of the Geumsan and Pocheon, areas with potential for vanadium development, the TIF and median + 2 MAD values of 259 mg/kg and 218 mg/kg, respectively, can be used as the criteria for evaluating the impact of environmental pollution before and after deposit development. Likewise, by deriving threshold values of the target elements using geochemical map data, it is possible to provide basic environmental information for geochemical evaluation and follow-up management in advance during large-scale site development.

As environmental criteria items are increased or strengthened, cases of heavy metal contamination by geogenic origin are increasing,and the need to distinguish between natural and anthropogenic origins in soil or groundwater exceeding the standard is increasing. Inthis study, geochemical occurrences of geogenic heavy metals were identified through statistical processing of the nationalgeochemical map data and evaluation of geochemical characteristics of regions with high geoaccumulation indices. Cobalt, Cr, Cu, Ni,Pb, V, and Zn were targeted for which the national geochemical maps were prepared, and Co, Cr, Ni, and V derived from ultrabasic orultramafic rocks were classified as factor 1. Copper, Pb and Zn of non-ferrous sulfide origin were classified as factor 2. In particular,enrichment of heavy metals by factor 1 occurs mainly in the serpentine distribution areas of the Chungcheong region, and there is arisk of contamination in neighboring areas. In the case of factor 2, geogenic occurrence is concerned not only in non-ferrous metalmineralization areas such as Taebacksan and Gyeongnam mineralization zones, but also in Au-Ag mineralization areas distributed nationwide.

Aggregate is an essential construction material, and the demand is increasing every year. Aggregate has different properties in each region, and it is difficult to supply it over long distances due to its quantity and weight. For the stabilization of aggregate supply and demand, regional aggregate resource surveys have been conducted since 1993 in Korea. In this study, an aggregate resource survey was conducted in Goyang City to understand the characteristics of aggregate distribution as part of the annual regional aggregate resource survey in 2020. Goyang City has a high mountainous area to the east, and the southwestern part shows a topography where a wide flatland develops. It has 18 small streams originated from the eastern mountainuos area and 1 large stream Han River. The drilling data shows that thickness of the Quaternary deposits tend to deepen toward the south. The aggregate reserves are relatively abundant, the depth of the aggregates are relatively deep. Changes in the depth of the Quaternary deposits and the amount of aggregate in Goyang are seems to be closely related to the activities of the Han River rather than the sedimentation characteristics from the upstream to the downstream of the small streams. This characteristics show a similar tendency to the distribution of aggregates in adjacent regions to the west coast in Korea. Therefore, the regions that close to west coast have a high probability of aggregate reserves around relatively large-scale streams flowing into the west coast.

To explore for new ore bodies, a geochemical survey was conducted at one existing carbonatite REE deposit in the Hongcheon area of Korea. Proper sampling strategies and baseline data for the interpretation of the results were determined through a pilot study conducted in the area. Enrichment in the concentration of LREE over that of HREE, which is typical in carbonatite-type deposits, was observed in stream sediments and heavy mineral samples collected during the geochemical survey. Maximum concentrations of LREE were 2,299 ppm and 27,798 ppm for stream sediments and heavy minerals, respectively. Lanthanum and Ce are the dominant components of all REEs, comprising approximately 68 % of mean concentrations. Considering the distribution pattern of La+Ce contents and the associations with the existing outcropping ore bodies, the zone of prospective REE mineralization was determined to be in the south-western part of the area. A detailed follow-up soil survey of the zone found even higher concentrations of La and Ce (2,450 and 3,100 ppm, respectively), and suggested the possible extension of the existing ore bodies.

In assessing the adverse effects of acid mine drainage (AMD), the chemistry of AMD and stream water (i.e., pH and toxic metal concentrations) has been accounted as important monitoring parameters and its characteristics are regulated in many countries. Yet for the precise evaluation of eco-toxicological effect on AMD receiving streams, a more comprehensive evaluation parameter has to be recognized as a mandatory parameter. In this study, eco-toxicological correlations between chemical properties of water and sediments collected from an AMD receiving stream were investigated at an abandoned mine site in Korea. The stream water in the AMD watercourse near the mine adit that is highly acidic and contains high concentrations of heavy metals, has been neutralized as the AMD became diluted with nearby natural stream water. The toxicity of stream water showed a relatively strong correlation with the pH and dissolved metal concentrations of water implying the toxic effects of stream water on its stream biota. In contrast, the toxicity results obtained from stream sediments hardly showed close correlation with the composition of toxic elements, particularly with enriched arsenic.

During large constructions of roads or structures, unexpected acid rock drainage (ARD) can be caused by local mineralization containing sulfides in the geology. The potential of ARD occurrence of a certain area sometimes must be assessed before initiation of any engineering earth works. However, it is difficult to assess the entire area through collecting rock samples and predicting the potential by laboratory tests, such as the acid–base accounting method. In this study, a new prediction protocol using a geochemical exploration survey technique of stream sediment is proposed. Sediment samples were collected at the case study area where a large development is expected in the future, and the contents of some major and heavy metal elements were compared according to the major geologies of the sampling points. The modified geoaccumulation indices ( I geo ) of Fe, Pb and As could indicate a possible zone of pyrophyllite mineralization, which may cause the occurrence of ARD at the study area. Using the enrichment index of the three elements relative to the median values of the area, a high potential zone of ARD could be designated, which was in agreement with the laboratory ARD prediction tests of the rock samples. In the other areas with different mineralization processes, other metallic elements can be selected as indicators of the ARD potential. Likewise, the potential of the occurrence of ARD at an area can be assessed by evaluating the geochemical distributions and drawing the indicator elements for ARD through a stream sediment survey.

This paper discusses geochemical (GC) mapping techniques based on selected representative cases of GC maps since 1980s, e.g., GC maps surveyed by sheet-units of 1:50,000 scale covering the Taebaeksan Mineralized Belt and its neighboring areas, wide-spaced GC maps by sheet-units of 1:250,000 scale, nation-scale GC atlases for eight provinces, and regional GC maps for rare elements. Detailed discussions are given to understanding of data structures, class selection (e.g., arbitrary, percentile, boxplot), data processing and map production, definition and establishment of statistical estimates (e.g., outlier/threshold/anomaly; mean/background/baseline), and outlier detection. Advantages and problems in technical viewpoints are diagnosed from various types of GC maps, e.g., black-and-white growing dot maps, color contour/surface/block/symbol maps and Exploratory Data Analysis (EDA) symbol maps. The paper closes with some suggestions for current problems and practical responses related to GC mapping including a national GC database.

Because of the risk of diminishing supplies of rare earth elements (REEs) worldwide due to China's dominance over REE supply, the necessity of developing domestic resources of REE has been realized in other countries. To explore new ore bodies, a geochemical survey was conducted at one existing carbonatite REE deposit in the Hongcheon area of Korea. Proper sampling strategies and baseline data for the interpretation of the results were determined through a pilot study conducted in the area. Enrichment in the concentration of light REE (LREE) over that of heavy REE, which is typical in carbonatite-type deposits, was observed in stream sediments and heavy mineral samples collected during the geochemical survey. Maximum concentrations of LREE were 2,299 and 27,798 mg/kg for stream sediments and heavy minerals, respectively. Among LREEs, La and Ce are the dominant components of all REEs, comprising approximately 68 % of mean concentrations. Considering the distribution pattern of La + Ce contents and the associations with the existing outcropping ore bodies, the zone of prospective REE mineralization was determined to be in the south-western part of the area. A detailed follow-up soil survey of the zone found even higher concentrations of La and Ce (2,450 and 3,100 mg/kg, respectively), and suggested the possible extension of the existing ore bodies. Likewise, a systematic geochemical survey for REE is feasible for locating concealed ore bodies in the area, where the mineralization is mostly covered with soil, and rock outcrops are scarce.

The aims of this study were to determine concentrations of selected metals (As, Cd, Cr, Co, Cu, Ni, Sb, Pb and Zn) in Asian and non-Asian dust collected in Daejeon, Korea between February 2007 and December 2007 and to estimate the pollution sources. The geoaccumulation index (Igeo) and the enrichment factor (EF) show that the pollution levels of Cd, Pb, Zn, Sb, Cu, and As are much higher than those of Cr, Co and Ni. As, Cd, Cu, Sb, Pb, and Zn are the ones most strongly affected by anthropogenic inputs such as airborne pollutants. The (206)Pb/(207)Pb ratios of Asian and non-Asian dust are similar to those of the airborne particles in some heavily industrialized Chinese cities and the soils of the Alashan desert. To address the highly elevated levels of heavy metals found in Asian and non-Asian dust, studies should be performed to assess the potential impacts of settled particles on surface ecosystems, water resources, and human health in Korea.

We evaluated the geochemical characteristics and their potential pollution of Asian Dusts in Daejeon, Korea during spring 2007. Compared with the chemical compositions of soils in source area of Asian Dust, those of aerosols in Daejeon were enriched with trace elements (ten to hundred fold), inferring that pollutants from China have affected on local environment in adjoining country such as Korea. Chemical analysis of aerosols during Asian dust showed that fine particles (PM2.5) contained high contents of trace elements such as Cr, Cu, Pb, Zn, V, S, As, Cd, Co, Ni, Mo, Sb, Cs, Rb, Th, Sc and Y. In the case of TSP (Total Suspended Particle), Zr, Sr, Ba, Li, Th and U were contained much more than other trace elements. The contents of some elements (i.e. Li, Cs, Co, U, Cr, Ni, Rb, V, Th, Y, Sr and Sc) in aerosols collected in Asian Dust period, which are not likely enriched by air pollutants, were higher (2 - 4.2 fold) than those in Non Asian Dust period, indicating that these elements could be used as indicator elements for determining the occurrence of Asian Dust phenomena (especially, Sr, V, Cr & Li). In the case of Asian Dust coming through the big cities and/or industrial areas of China, the domestic aerosols had higher contents of trace elements (such as S, Cd, Zn, Pb, Cu, Mo and As) than those from Northeastern China via North Korea, indicating that the transportation courses of air mass are very important to determine the pollution degrees. Using the enrichment factors of trace elements in aerosols during Asian Dust and Non Asian Dust, we identified that some elements (i.e. S, Zn, Cu, Pb, As, Mo and Cd) were most problematic in terms of environmental hazard aspects, and these elements could affect adverse effects on human health as well as ecosystem and surface environment (soil and water) through long-lived precipitation.

In this study, we investigated the chemical characteristics of soils collected from the several deserts and loess in China known as the typical source areas of Asian dust (the Taklamakan desert, the Alashan desert, the Ordos desert and the Loess Plateau). Based on our analysis, we examined the possibility of adverse effects on environments and human health. In each desert and loess, major elemental compositions of soils did not show large variations, implying that the long-periodic mixing of soils in each area made their chemical compositions homogeneous. Minor elements of soils in each desert and loess showed more complicated patterns with strong correlations each other (e.g., Cr, Cu, As, Co, Ni, V, Y, Sc, Sn, Pb, Zn, Cd, Cs, Li, Th, U). These results thus enable us to discriminate the soil of the Loess Plateau from those of the other deserts in China. The results of sequential extraction experiments for soils showed that the chemical speciation of Fe was dominant in residual fraction (>85%) in all deserts and loess, but the fractions of Mn and Ca chemical speciations were very different in each area. In the case of Mn, the fraction of amorphous Fe-Mn hydroxides (55.4%) in the Central Loess Plateau and the carbonate fraction (33.8%) in Taklamakan desert were higher as much as 2 to 5 times than other deserts. The chemical speciations of Ca are dominant in carbonate fraction in Taklamakan (75.9%) and Alashan (50.5%) deserts, but carbonate fractions of Ca in the Loess Plateau and Ordos deserts were low (6.6% and 2.1%, respectively). According to the mobility of trace elements inferred from the results of sequential extraction procedure, we could classify them into five groups, and the mobility of Cd, Pb and Cu are more than 87%, 33% and 30%, respectively. Therefore, Cd, Pb and Cu in soils of deserts and loess could be easily dissolved when interacted with surface water. As such, they could give adverse effects on surficial environments and human health.

The stone-dust is an unavoidable by-product of aggregate production, which is produced about 0.8~1.0 million annually. The stone-dust is currently regarded as a hazard material on environment because it is classified as an industrial waste in the Waste Management Law of Korea. At present, the stone-dust is considered as a environmentally hazardous material, and is classified as an industrial waste according to the Waste Management Law of Korea. In this study, we assessed the heavy-metal contamination of the stone-dust on surrounding environments by various leaching tests. Leaching experiments (such as Korea Standard Leaching Procedure (KSLP), Soil Environment Preservation Act of Korea (SEPAK), Toxicity Characteristic Leaching Procedure (TCLP), and Synthetic Precipitation Leaching Procedure (SPLP)) show that very low heavy metals (As, Cd, Cu, Pb, Zn, Hg) and CN are leached out, or much less than each regulatory thresholds. The resuts of the leaching test with time in acidic solution (initial pH 5 and 3) indicate that pH-buffering minerals are present in the stone-dust. These results suggest that the stone-dust can not potentially affect adverse impact on surrounding environments such as surface water, groundwater and soil etc..

To construct the standard methods for evaluation of physicochemical characteristics of tailings in Korea, specific gravity, paste pH, grain size, mineral compositions and heavy metal concentrations of total 26 tailings from 21 metallic mines were analyzed. Specific gravity of tailings ranged from 2.61 to 4.31 (avg. 3.04), and sand and silt grain were dominant in the tailings. Ranges of paste pH were 2.1-9.5 in tailings (7.1-9.2 at magmatic, skarn and hydrothermal replacement deposits and 2.1-9.5 at hydrothermal vein deposits). Additionally, hydrothermal vein deposits could be reclassified into three categories: (1) paste pH>7.0, (2) 4.0<paste pH<7.0, and (3) paste pH<4.0. Tailings above pH 7.0 have large amounts of carbonate minerals. However, tailings under pH 7.0 have small amount of carbonates, but have sulfide minerals commonly. Especially, tailings under pH 4.0 typically contain supergene minerals. The presence and amounts of carbonates were more important than those of sulfides in determining paste pH in tailings. From the comprehensive results of total concentrations, grain size and extraction experiments, it is revealed that types of deposits were not related with the total and leaching concentrations in tailings, but the ore minerals and their amounts in deposits determined the metal content in tailings. Most mines having tailings with pH<4.0, contained large amounts of heavy metals and strong acidic characteristics, indicating that the deposits of this type have possibility of contamination and/or have contaminated surrounding environments. In this study, problematic elements, inferred from extraction experiment by Korean standard method for soils, were As and Zn. Especially, arsenic appeared to exceed the regulatory level in tailings (pH<4.0) from hydrothermal vein deposits, and in a less degree, zinc often exceeded regulatory level in most type of deposits, except of magmatic deposit.

All of the water and stone-dust samples with or without flocculant, in and around quarry mines, were analyzed for total concentrations of heavy metals, cyanide(CN), toxic organic compounds and organic phosphorus. Extraction experiments on stone-dust by EDTA and various pH solutions were also carried out, in order to evaluate the contaminant leaching from the long-term heaped stone-dust within quarry mines. The concentrations of Cr6+, Hg, CN, TCE/PCE and total phosphorus in all samples (water and stone-dust) were under detection limits, confirming no environmental contamination from stone-dust in quarry mine areas. Lead and cadmium were not detected in all water samples. Copper and zinc were found in some water samples, and arsenic was detected in a few water samples. But they also showed levels much lower than the drinking water standard. Results of the extraction experiments by EDTA and pH solutions showed that Pb, Cr, Cd, Cu and Zn were leached out in less amounts or under detection limits. Arsenic was detected only at pH 3. From above results, we suggested that environmental contamination by quarry mine development is likely to be minor or negligible.