The major frequent contaminants in soil are heavy metals which may be responsible for detrimental health effects. The remediation of heavy metals in contaminated soils is considered as one of the ...most complicated tasks. Among different technologies, in situ immobilization of metals has received a great deal of attention and turned out to be a promising solution for soil remediation. In this review, remediation methods for removal of heavy metals in soil are explored with an emphasis on the in situ immobilization technique of metal(loid)s. Besides, the immobilization technique in contaminated soils is evaluated through the manipulation of the bioavailability of heavy metals using a range of soil amendment conditions. This technique is expected to efficiently alleviate the risk of groundwater contamination, plant uptake, and exposure to other living organisms. The efficacy of several amendments (e.g., red mud, biochar, phosphate rock) has been examined to emphasize the need for the simultaneous measurement of leaching and the phytoavailability of heavy metals. In addition, some amendments that are used in this technique are inexpensive and readily available in large quantities because they have been derived from bio-products or industrial by-products (e.g., biochar, red mud, and steel slag). Among different amendments, iron-rich compounds and biochars show high efficiency to remediate multi-metal contaminated soils. Thereupon, immobilization technique can be considered a preferable option as it is inexpensive and easily applicable to large quantities of contaminants derived from various sources.
Graphical Abstract
Rice plays an essential role in Asian sustenance. Moreover, it can take up toxic elements through its roots from contaminated soils, and even its leaves and grain can absorb the elements deposited on ...the soil surface. Hence in 2010, forty soil and polished rice samples were collected from four representative abandoned metal mining areas in Korea and analyzed for As and heavy metals, including Cd, Cu, Pb and Zn, by atomic absorption spectrometry (AAS). Average levels of As, Cd, Cu, Pb and Zn in agricultural soil samples were 64.4, 2.31, 63.5, 146 and 393mgkg−1, respectively. In addition, the average content of As, Cd, Cu, Pb and Zn in rice grain grown on the contaminated soils evaluated was 0.247, 0.174, 4.69, 0.804 and 16.8mgkg−1 (dry weight, DW), respectively. These levels are relatively higher than worldwide averages reported by various researchers. Assuming the average rice consumption of 199gday−1 by overall households in Korea, the amount of daily intake of As and the heavy metals was estimated. The appraised daily intake of As and Cd from the rice grown in the study areas is up to 50% and 80% of ADI (acceptable daily intake) suggested by the FAO/WHO Joint Food Additive and Contaminants Committee, respectively. Consequently, regular rice consumption grown in soils especially in the mining areas can cause health problems for local residents.
•Environmental impact on As and heavy metals in soils from mining sites•Analyzing As and heavy metals in paddy soils and polished rice•Compiling As and heavy metals in soils and rice grain from various countries•Calculating daily intake of As and metals by rice consumption
Heavy metal concentrations were measured in soils and plants in and around a copper-tungsten mine in southeast Korea to investigate the influence of past base metal mining on the surface environment. ...The results of chemical analysis indicate that the heavy metals in soils decreased with distance from the source, controlled mainly by water movement and topography. The metal concentrations measured in plant species generally decreased in the order; spring onions > soybean leaves > perilla leaves » red pepper > corn grains » jujube grains, although this pattern varied moderately between different elements. The results agree with other reports that metal concentrations in leaves are usually much higher than those in grain. Factors influencing the bioavailability of metals and their occurrences in crops were found as soil pH, cation exchange capacity, organic matter content, soil texture, and interaction among the target elements. It is concluded that total metal concentrations in soils are the main controls on their contents in plants. Soil pH was also an important factor. A stepwise linear multiple regression analysis was also conducted to identify the dominant factors influencing metal uptake by plants. Metal concentrations in plants were also estimated by computer-aided statistical methods.
Influence of four different types of amendments raw rice husk (RRH), rice husk biochar (RHB), raw maple leaves (RML), and maple leaf biochar (MLB) at the low application dosages (0.5, 1, and 2% w/w) ...was investigated on (im)mobilization of Cd, Cu, Pb, and Zn in an agricultural soil. A greenhouse experiment using mustard green “
Brassica juncea
” was conducted to evaluate the efficiency of soil amendments on bioavailability of metals. Metal leaching was remarkably decreased at biochar-treated samples, which was primarily attributed to biochar-induced increase in soil pH. Application of RRH and RML (2%), however, slightly increased heavy metal mobilization because of their acidic nature. Both biochars incorporation induced a considerable decline (> 80%) in the phytoavailability of metals. Generally, maximum immobilization efficiency for Cd, Cu, Pb, and Zn was observed in the case of RHB and MLB (2%), MLB (2%), RHB (2%), and RHB (2%) treatments, by 61–62%, 71%, 76%, and 40%, respectively. A comparison between various application dosages of amendments showed a noticeable difference between 0.5% and 2% for metal immobilization. Overall, results demonstrated the efficacy of several amendments for metals (im)mobilization while stressing the need to measure simultaneously the leaching and phytoavailability of metals induced by amendments.
Industrialization advances have led to an increase soil contamination by heavy metals. Among different technologies, in situ stabilization of metals combined with revegetation attracted attention. ...Therefore, this study aimed at comparing effects of biochars rice husk biochar (RHB), maple leaves biochar (MLB) and common inorganic amendments red mud (RM), and steel slag (SS) at different rates (0.5, 1, and 2% w/w) on leaching, and phytoavailability of metals (assessed using mustard green
“Brassica juncea”
). Soil pH in treated soils significantly (
p
< 0.01) increased, with the optimal pH ranges for plant growth observed in biochar-treated soils. The leaching of Cd, Cu, Pb, and Zn through soil significantly (
p
< 0.05) decreased in treated soils. Plant uptake and accumulation of Cd, Cu, Pb, and Zn decreased by 79–66, 13–19, 87–86, and 37–36% in RHB- and MLB-treated soils, respectively. Sequential extraction analysis pointed out that the major stabilization mechanism for metals using biochars involved the formation of organic and carbonate bonds, while for RM and SS was believed to involve the formation of inner sphere complexes with Fe/Al (hydr)oxides. The plant available fractions for Cd were generally higher than those for others. Overall, high dosage addition (2%) of each amendment offered the best compromise as it successfully reduced both leaching and phytoavailability of metals. Using MLB for the first time, showed promising results to immobilize metals with an increase in plant biomass.
The presence of copper (Cu)-contaminated soil has increased recently due to agricultural and industrial activities. Immobilization techniques using soil amendments have attracted significant research ...because of their cost-effectiveness, eco-friendliness, and community acceptance. This study used various commercial amendments, including magnetite (M), talc (T), activated carbon (AC), and cornstarch (CS), to immobilize Cu in soil contaminated by acidic waste materials with Cu in Korea (9546 ± 5 mg/kg). To evaluate the immobilizing effect of these amendments, this study applied a sequential process of column leaching and plant uptake tests to observe the ability of Cu to remain in soil with and without amendments through the Cu removal rate. The amendments were characterized by SEM, XRD, and specific surface area and applied to the soil at a rate of 2% (w/w). The first stage of evaluation, i.e., the column leaching test, was conducted by continuously pumping distilled water (DW) for 28 days, and the second stage of evaluation, i.e., the plant uptake test, was started immediately after by planting 10-day-old lettuce seedlings for 28 days. The experimental results showed that all of the amendments had a significant effect on Cu immobilization Cu in soil (p < 0.05), and the T treatment showed the highest efficiency in Cu immobilization, with only 47.0% Cu loss compared to 73.5% in the control soil when assessed by sequential column leaching and plant uptake tests. In conclusion, this study provides an effective assessment method to evaluate the effect of amendments on Cu immobilization in soil, as well as providing feasible options to immobilize Cu using commercial amendments.
This study aims to explore trends of NOx (NO + NO2) pollution over ten years (2004–2013) at an urban monitoring station at Yongsan in Seoul, Korea. The mean concentrations (in nmol/mol) of NO, NO2, ...and O3 measured over the entire study period were 25.3 ± 7.30, 36.9 ± 1.76, and 17.5 ± 1.31, respectively. The decadal trend of these pollutants exhibited statistically significant, but contrasting, results with downward NO and NOx trends and upward O3 trends throughout the study period. Correlation studies and principal component analysis (PCA) explained association of NO and NO2 with traffic related pollutants (CO, PM, and SO) at a statistically significant level while O3 exhibited patterns correlated with meteorological parameters. The overall results of this study indicate that the decadal trend of NO and NO2 was highly dependent on automotive related pollution, while O3 concentration was influenced by both the availability of NO and meteorological conditions.
•From the view point of air quality, NO2 is more important than NO due to its greater human health effects.•Further, O3 is an important greenhouse gas making significant contributions to the climate change.•A study has been undertaken to explain the long-term changes in NOx/O3 levels in urban air.•Korea has been actively pursuing policies to reduce pollutant emissions from traffic-related sources.•The decadal trend of NOx was dependent on traffic pollution, while that of O3 on NO and meteorology.
The objectives of this study are to examine the feasibility of the releasable asbestos sampler (RAS) equipment for laboratory tests as an alternative to activity-based sampling (ABS), and to apply ...the equipment controlled by wind velocity and water contents in the field to asbestos-contaminated soils. Two asbestos-contaminated mines (the Jecheon mine and the Jongmin-ri mine) were selected. At each mine, 21 surface soils (0~15 cm) were sampled, the asbestos concentrations were analyzed, and then three representative sites, containing 0.25%, 0.50%, and 0.75% of asbestos in soils, were chosen to evaluate the amount of releasable asbestos by the modified RAS with wind velocity and water contents. The results showed that the levels of releasable asbestos from soil to air increased with higher wind velocities and lower water content. In addition, the application of risk assessment of releasable asbestos in the soils as an alternative to the activity-based sampling (ABS) method was established at each site, and an estimation of the excess lifetime cancer risk (ELCR) was also calculated. According to the calculation, the estimated ELCR values did not exceed the threshold value (1 × 10
) in the Jecheon mine for all the soils, while some samples from the Jongmin-ri mine exceeded the threshold value. Therefore, proper remediation work is needed to control friable asbestos from soils to air in the vicinity of the mines.
Resistance to antimicrobials was measured in 73 isolates of Campylobacter jejuni (C. jejuni) and 121 isolates of Campylobacter coli (C. coli) from chicken and swine feces and carcasses in Korea. Both ...bacterial species showed the highest resistance to (fluoro) quinolones (ciprofloxacin and nalidixic acid) out of the nine antimicrobials tested. Erythromycin resistance was much higher in C. coli (19.0%, 23/121) than in C. jejuni (6.8%, 5/73). The mutation in the 23S rRNA gene was primarily responsible for macrolide resistance in Campylobacter isolates. Several amino acid substitutions in the L4 and L22 ribosomal proteins may play a role in the mechanism of resistance, but the role requires further evaluation. A total of eight virulence genes were detected in 28 erythromycin-resistant Campylobacter isolates. All C. jejuni isolates carried more than four such genes, while C. coli isolates carried fewer than three such genes. The high rate of resistance highlights the need to employ more prudent use of critically important antimicrobials, such as fluoroquinolones and macrolides, in swine and poultry production, and to more carefully monitor antimicrobial resistance in Campylobacter isolates in food animals.
Identifying the proper chemical and biological materials as soil amendments is a great concern because they replace soil properties and subsequently change the soil quality. Hence, this study was ...conducted to evaluate the effects of a diverse range of soil amendments including bentonite (B), talc (T), activated carbon (AC), and cornstarch (CS) in form of sole and composite on the immobilization and bioavailability of As, Cu, and Zn. The amendments were characterized by SEM, FT-IR, and XRF, and applied at 2% (w/w) in the experimental pots with an Asteraceae (i.e., lettuce) for 45 days to monitor plant growth parameters and soil microbial community. Soil pH from 6.1 ± 0.02 significantly increased in the amended soils with the maximum value found for TAC (7.4 ± 0.04). The results showed that soil amendments reduced easily in an exchangeable fractionation of As, Cu, and Zn with the maximum values found for BAC by 66.4%, AC by 84.2%, and T by 89.7% respectively. Adding B, T, AC, and their composites induced dry biomass of lettuce >40 wt.%, while CS and its composites did not affect the dry biomass of the plant. The average content of Cu and Zn in plant tissues decreased >45 wt.% in B, AC, and their composites amended soils; meanwhile, AC and its composites mitigated As uptake by >30 wt.% in lettuce. The results of Biolog Ecoplate showed that the amending soils improved the microbial community, especially for composites (e.g., TCS). The results demonstrated that adding composites amendments provided an efficient method for the immobilization of metals and metalloids, and also induced plant growth parameters and microbial community.
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