Jae E. Yang

Effects of pyrolysis temperature on soybean stover- and peanut shell-derived biochar properties and TCE adsorption in water

Conversion of crop residues into biochars (BCs) via pyrolysis is beneficial to environment compared to their direct combustion in agricultural field. Biochars developed from soybean stover at 300 and 700 °C (S-BC300 and S-BC700, respectively) and peanut shells at 300 and 700 °C (P-BC300 and P-BC700, respectively) were used for the removal of trichloroethylene (TCE) from water. Batch adsorption experiments showed that the TCE adsorption was strongly dependent on the BCs properties. Linear relationships were obtained between sorption parameters (K(M) and S(M)) and molar elemental ratios as well as surface area of the BCs. The high adsorption capacity of BCs produced at 700 °C was attributed to their high aromaticity and low polarity. The efficacy of S-BC700 and P-BC700 for removing TCE from water was comparable to that of activated carbon (AC). Pyrolysis temperature influencing the BC properties was a critical factor to assess the removal efficiency of TCE from water.

Effects of soil dilution and amendments (mussel shell, cow bone, and biochar) on Pb availability and phytotoxicity in military shooting range soil.

Bioavailability and bioaccessibility determine the level of metal toxicity in the soils. Inorganic soil amendments may decrease metal bioavailability and enhance soil quality. This study used mussel shell, cow bone, and biochar to reduce lead (Pb) toxicity in the highly contaminated military shooting range soil in Korea. Water-soluble and 1-M ammonium nitrate extractions, and a modified physiologically based extraction test (PBET) were performed to determine Pb bioavailability and bioaccessibility in the soil, respectively. Active C in the soil was also measured to evaluate the effects of the amendments on biological soil quality. The Pb contaminated soil was diluted in serial with uncontaminated soil for the bioassays. Seed germination and root elongation tests using lettuce (Lactuca sativa) showed increases in germination percentage and root length in soil treated with the amendments. Biochar was most effective and increased seed germination by 360% and root length by 189% compared to the unamended soil. Up to 20% soil dilution resulted in more than 50% seed germination. Bioavailability and bioaccessibility of Pb in the soils were decreased by 92.5% and 48.5% with mussel shell, by 84.8% and 34.5% with cow bone, and by 75.8% and 12.5% with biochar, respectively, compared to the unamended soil. We found that the Pb availability in the military shooting range soil can be reduced effectively by the tested amendments or soil dilution alternately, thereby decreasing the risk of ecotoxicity. Furthermore, the increasing active C from the amendments revitalized the soil contaminated with Pb.

Effects of rapeseed residue on lead and cadmium availability and uptake by rice plants in heavy metal contaminated paddy soil.

Rapeseed (Brassica napus L.) has been cultivated for biodiesel production worldwide. Winter rapeseed is commonly grown in the southern part of Korea under a rice-rapeseed double cropping system. In this study, a greenhouse pot experiment was conducted to assess the effects of rapeseed residue applied as a green manure alone or in combinations with mineral N fertilizer on Cd and Pb speciation in the contaminated paddy soil and their availability to rice plant (Oryza sativa L.). The changes in soil chemical and biological properties in response to the addition of rapeseed residue were also evaluated. Specifically, the following four treatments were evaluated: 100% mineral N fertilizer (N100) as a control, 70% mineral N fertilizer+rapeseed residue (N70+R), 30% mineral N fertilizer+rapeseed residue (N30+R) and rapeseed residue alone (R). The electrical conductivity and exchangeable cations of the rice paddy soil subjected to the R treatment or in combinations with mineral N fertilizer treatment, N70+R and N30+R, were higher than those in soils subjected to the N100 treatment. However, the soil pH value with the R treatment (pH 6.3) was lower than that with N100 treatment (pH 6.9). Use of rapeseed residue as a green manure led to an increase in soil organic matter (SOM) and enhanced the microbial populations in the soil. Sequential extraction also revealed that the addition of rapeseed residue decreased the easily accessible fraction of Cd by 5-14% and Pb by 30-39% through the transformation into less accessible fractions, thereby reducing metal availability to the rice plant. Overall, the incorporation of rapeseed residue into the metal contaminated rice paddy soils may sustain SOM, improve the soil chemical and biological properties, and decrease the heavy metal phytoavailability.

The phytoavailability soil test - PST.

Abstract Current soil tests are based on single and multiple nutrient extractions with a wide range of chemical solutions. For most nutrients this approach provides an “index”; of plant availability, but it may not be accurate on specific soils or in certain regions. Major problems with chemical extraction soil testing cannot be solved because they are inherent in the approach. The Phytoavailability Soil Test (PST) is a simplified soil‐extraction methodology based on ion‐exchange‐resin extraction of nutrients from saturated paste soil samples. The need for drying and grinding soil samples is thus eliminated. PST provides a “universal”; extraction for all nutrients. It mimics nutrient accumulation in plants, thus providing a more theoretically accurate basis for soil testing. PST also provides a system which can be “standardized”; for use in all regions. Factors which influence the rate and amount of resin‐extracted nutrients, including type of resin, shape of resin bag, soil water content, microbial activ...

Monitoring of selected veterinary antibiotics in environmental compartments near a composting facility in Gangwon Province, Korea.

Many studies have been recently reported that veterinary antibiotics released into the environment have a detrimental effect on humans such as the occurrence of antibiotic-resistant bacteria. However, only limited information is available regarding to the release of antibiotics in environmental compartments in Korea. Objectives of this study were to evaluate the concentrations of antibiotics in water, sediment, and soil adjacent to a composting facility in Korea and to determine the dilution effects of antibiotics when released into the environment. Seven antibiotics of chlortetracycline, oxytetracycline, tetracycline, sulfamethazine, sulfamethoxazole, sulfathiazole, and tylosin were evaluated by high-performance liquid chromatography–tandem mass spectrometry following pretreatment using solid-phase extraction to clean the samples. Results showed that the highest concentration of each antibiotic in both aqueous and solid samples was detected from a site adjacent to the composting facility. We also found that the studied water, sediment, and soil samples are contaminated by veterinary antibiotics throughout comparison with studies from other countries. However, relatively lower concentrations of each antibiotic were observed from the rice paddy soil located at the bottom of the water stream. Further research is necessary to continuously monitor the antibiotics release into ecosystems, thereby developing an environmental risk assessment.

Screening of hexavalent chromium biosorbent from marine algae

Abstract A highly chromate-selective biosorbent with high adsorption capacity was found by examining the chromate adsorption capacities of 48 species of red, brown, or green marine algae sampled from the east coast of Korea. As a result of screening, a red marine alga showed excellent adsorption characteristics. It was identified as Pachymeniopsis sp. The timing of the sampling of Pachymeniopsis sp. did not affect the adsorption capacity of the alga but the optimum period for mass collection was April–May. The alga also showed high selectivity for chromate and its adsorption capacity for other heavy metal ions such as cadmium and manganese was relatively low. An investigation of the adsorption isotherm of Pachymeniopsis sp. as a dried powder for chromate adsorption at 25 °C showed Langmuir-type dependence. The maximum chromate adsorption capacity of the selected alga was about 225 mg/g. The desorption of adsorbed chromate from Pachymeniopsis sp. was done by treating samples with 1 N NaOH. It was confirmed that ion exchange type adsorption was observed with anion exchangers but not with cation exchangers. Therefore it is believed that the chromate adsorption is based on the anionic exchange of Pachymeniopsis sp.

Surface complexation modeling and spectroscopic evidence of antimony adsorption on iron-oxide-rich red earth soils.

Few studies have investigated surface complexation of antimony (Sb) on natural sorbents. In addition, intrinsic acidic constants, speciation, and spectroscopic data are scarce for Sb sorption in soil. Only simple sorption models have been proposed to describe the sorption of Sb(V) on specific mineral surfaces. This study therefore assessed the mechanisms of Sb(III) and Sb(V) adsorption on natural red earth (NRE), a naturally occurring iron coated sand, at various pHs and Sb loadings. The Sb(V) adsorption followed typical anion adsorption curve with adsorption reaching maximum around pH 4-5, while no pH dependence was observed for Sb(III) sorption. The FT-IR spectra revealed that shifts in absorbance of the hydroxyl groups in iron-oxide were related to the Fe-O-Sb bonds and provided evidence for inner sphere bond formation. Direct evidence on the strong interaction of Sb(III) and Sb(V) with ≡Fe-O and ≡Al-O was observed from the decrease in Fe-2p, Al-2p, and Si-2p peaks of the X-ray photoelectron spectroscopy (XPS) data before and after Sb(V) and Sb(III) adsorption on NRE. Successful data modeling using the 2-pK diffuse double layer model (DDLM) with the FITEQL revealed that sorption occurs through the formation of bidentate mononuclear and binuclear complexes. Model simulations showed a high affinity to the ≡FeOH sites at high Sb loadings, whereas at low loadings, both≡ FeOH and ≡AlOH sites showed similar affinities to Sb. In the case of Sb(V), multilayer formation was also revealed in addition to surface complexation by the isotherm data fitted with the Freundlich model and two sites Langmuir equations, which indicated heterogeneous multilayer adsorption of Sb(V) on NRE.

Soil pollution assessment and identification of hyperaccumulating plants in chromated copper arsenate (CCA) contaminated sites, Korea.

In recent decades, heavy metal contamination in soil adjacent to chromated copper arsenate (CCA) treated wood has received increasing attention. This study was conducted to determine the pollution level (PL) based on the concentrations of Cr, Cu and As in soils and to evaluate the remediative capacity of native plant species grown in the CCA contaminated site, Gangwon Province, Korea. The pollution index (PI), integrated pollution index (IPI), bioaccumulation factors (BAF(shoots) and BAF(roots)) and translocation factor (TF) were determined to ensure soil contamination and phytoremediation availability. The 19 soil samples from 10 locations possibly contaminated with Cr, Cu and As were collected. The concentrations of Cr, Cu and As in the soil samples ranged from 50.56-94.13 mg kg(-1), 27.78-120.83 mg kg(-1), and 0.13-9.43 mg kg(-1), respectively. Generally, the metal concentrations decreased as the distance between the CCA-treated wood structure and sampling point increased. For investigating phytoremediative capacity, the 19 native plant species were also collected in the same area with soil samples. Our results showed that only one plant species of Iris ensata, which presented the highest accumulations of Cr (1120 mg kg(-1)) in its shoot, was identified as a hyperaccumulator. Moreover, the relatively higher values of BAF(shoot) (3.23-22.10) were observed for Typha orientalis, Iris ensata and Scirpus radicans Schk, suggesting that these plant species might be applicable for selective metal extraction from the soils. For phytostabilization, the 15 plant species with BAF(root) values>1 and TF values<1 were suitable; however, Typha orientalis was the best for Cr.

An assessment of the utilization of waste resources for the immobilization of Pb and Cu in the soil from a Korean military shooting range

Military shooting range soils contaminated by heavy metals have been subjected to remediation efforts to alleviate the detrimental effects of exposure on humans and the surrounding environment. Waste materials can be used as cost-effective soil amendments to immobilize heavy metals in contaminated soils. In this study, naturally occurring lime-based waste materials including egg shells, oyster shells, and mussel shells were assessed for their effectiveness toward heavy metal immobilization in military shooting range soil in Korea. Soil was treated in batch leaching experiments with 0, 2.5, 5, 10, and 15% of each lime-based waste material. The results showed that the lime-based waste materials effectively reduced water-soluble Pb at an application rate of 2.5% by weight of the soil. Increase in soil pH from 6.6 to 8.0 was considered to be the main chemistry of Pb immobilization, which was supported by the formation of insoluble Pb species at high pH values as confirmed by the visual MINTEQ thermodynamic model. In contrary, water-soluble Cu was increased in the lime-based waste material-treated soils when compared to the untreated soil. This was likely attributed to the formation of soluble Cu–DOC (dissolved organic carbon) complexes as all lime-based waste materials applied increased DOC contents in the soil. Therefore, care must be taken in selecting the appropriate amendment for immobilizing metals in shooting range soils.

Global rainfall erosivity assessment based on high-temporal resolution rainfall records

The exposure of the Earth’s surface to the energetic input of rainfall is one of the key factors controlling water erosion. While water erosion is identified as the most serious cause of soil degradation globally, global patterns of rainfall erosivity remain poorly quantified and estimates have large uncertainties. This hampers the implementation of effective soil degradation mitigation and restoration strategies. Quantifying rainfall erosivity is challenging as it requires high temporal resolution(<30 min) and high fidelity rainfall recordings. We present the results of an extensive global data collection effort whereby we estimated rainfall erosivity for 3,625 stations covering 63 countries. This first ever Global Rainfall Erosivity Database was used to develop a global erosivity map at 30 arc-seconds(~1 km) based on a Gaussian Process Regression(GPR). Globally, the mean rainfall erosivity was estimated to be 2,190 MJ mm ha−1 h−1 yr−1, with the highest values in South America and the Caribbean countries, Central east Africa and South east Asia. The lowest values are mainly found in Canada, the Russian Federation, Northern Europe, Northern Africa and the Middle East. The tropical climate zone has the highest mean rainfall erosivity followed by the temperate whereas the lowest mean was estimated in the cold climate zone.