옛 장항제련소 주변 중금속 오염토 세척공정 후 토양 특성 변화 연구

안경현(Keong-Hyeon An),김송희(Songhee Kim),정승우(Seung-Woo Jeong) 대한환경공학회 2020 대한환경공학회지 Vol.42 No.10

서론: (구)장항제련소 주변 비매입구역 중금속 오염토양에 대한 토양세척공정 적용 전, 후 토양특성 변화를 관찰하였다. 3개 다른 토양세척공정으로부터 토양세척공정 적용 전, 후 토양을 확보하여 토양 기본 특성을 분석하였고, 조사된 토양특성 결과는 농업진흥청에서 권장하고 있는 작물재배시비기준과 비교하여 토양 기능을 간접적으로 평가하였다. 또한 본 연구는 오염토양 공정 적용 후 발생하는 정화토 관리 필요에 대해 토의하였다. 방법: 3개 토양세척공정(1OU, 2OU, 3OU)은 공통적으로 입도 분급(파쇄, 마쇄, 분쇄 등)→물리적 선별(큰 돌, 미세토, 최소 미세토)→화학적 세척(미세토)→세척토 중화(소석회)→세척토 혼합 및 원위치 등의 순으로 진행된다. 1OU, 2OU, 3OU 세척공정의 최소 분류 입경은 각각 5 μm, 20 μm, 10 μm이었으며, 사용된 세척액은 각각 0.1 M H₂SO₄, 0.5 M H₂SO₄/0.5 M H₃PO₄, 0.1 N NaOH-Na₂CO₃(알칼리환원법)이었다. 본 연구는 세척 전, 후 토양을 채취하여 풍건 후 입경 2 mm 이하 토양에 대해 토성(texture), 용적밀도, 입단안정성, 보수력, pH, 전기전도도, 유기물함량, 총질소, 유효인산, 양이온교환능력, 치환성양이온(칼륨, 칼슘, 마그네슘, 나트륨) 등을 분석하였다. 결과 및 토의: 사질성 토양은 세척과정 중 토양 파쇄 및 분쇄과정으로 토성 변화가 크게 나타났지만 미사질성 토양은 세척 후에도 토성 변화가 없었다. 토성 변화가 크게 나타난 사질성 토양은 용적밀도 증가, 보수력 감소, 입단의 안정성 감소를 보였다. 세척 후 토양 pH는 사용된 세척액에 따라 영향을 받아 산성용액을 사용한 공정은 확연히 낮은 pH를 보였고 알칼리용액을 사용한 경우 높은 pH를 보였다. 세척 후 토양의 유기물함량, 전질소, 유효인산 및 CEC 등은 모두 감소하였다. 미사질 논토양의 경우 세척 후 유기물함량과 총질소 값이 확연하게 감소하였다. 세척 후 가장 두드러지게 변화된 토양특성은 전기전도도였다. 토양세척 후 토양 전기전도도는 1OU 0.51→6.21 ds/m, 2OU 1.09→3.73 ds/m, 3OU 0.99→9.30 ds/m로 모든 OU에서 급격히 증가하였다. 세척 전 오염토양의 전기전도도는 모두 적정수준인 2 ds/m 이하였지만 토양세척 후 크게 증가하여 강한 염류토양 수치를 보였다. 장항지역 작물별 시비처방기준으로 세척 전, 후 토양의 질을 평가한 결과 옛 장항제련소 주변 중금속 오염토는 세척(정화) 후 토양 질이 급격히 저하된 것으로 나타났다. 1OU, 2OU, 3OU를 모두 통틀어 집계하면 세척 전(오염토) “적정” 범위에 속한 토양 특성 값은 10개였지만 세척 후(정화토) 5개로 줄었다. 결론: 토양세척 공정 적용으로 인한 토양 질 변화는 심하게 나타났다. 가장 큰 변화는 토양 전기전도도의 급격한 증가로 나타나 토양 세척토를 재활용하기 위해서는 토양의 건강성 회복이 먼저 이루져야 한다. 중금속 세척공정으로 인한 급격한 토양 질 변화의 원인은 첫째, 중금속을 상대적으로 높게 함유한 미세토의 분리 및 폐기로 미세토가 빠져나간 것과 둘째, 화학세척액에 의한 토양교란이 이루어졌고, 셋째, 응집제 및 중화제 등 고농도 염을 사용하였기 때문이다. 따라서 정화토를 생태계의 일원으로 다시 되돌려 보내기 위해 앞으로 토양으로서 기능을 회복시킬 수 있도록 제도적 정비와 공학적 노력이 필요하다. Objectives : Changes in soil properties after washing of metal-contaminated soil near the former Janghang Smelter were investigated in this study. Contaminated input soils and remediated output soils were sampled from three different soil washing plants and analyzed for soil physical and chemical properties. Soil quality was evaluated by the soil fertilization guideline suggested by the Korea Rural Development Administration (KRDA). This study revealed the necessity of soil quality management for the remediated soil as an ecosystem member. Methods : Three soil washing plants (1OU, 2OU, 3OU) were commonly divided into the five steps: 1) the particle separation (crushing and grinding etc.)→2) soil particle classification (big stone, fine soil, minimal fine soil) →3) chemical washing (fine soil)→4) neutralization of washed soil (lime)→5) return-back to the original position. The separating minimum particle diameters of the 1OU, 2OU, and 3OU washing processes were 5 μm, 20 μm, and 10 μm, respectively, and the chemical washing solutions used were respectively 0.1 M H₂SO₄, 0.5 M H₂SO₄/0.5 M H₃PO₄, and 0.1 N NaOH-Na₂CO₃ (alkali reduction). Soils were collected before and after washing, air-dried, sieved with < 2 mm and analyzed for soil texture, bulk density, aggregate stability (AS), water holding capacity (WHC), pH, electrical conductivity (EC), organic matter content (OM), total nitrogen (TN), available phosphate (AvP), cation exchange capacity (CEC), exchangeable cations (potassium, calcium, magnesium, sodium). Results and Discussion : Sandy soil showed a big change in soil texture before and after soil washing, while there was no change in soil texture for fine soil. Sandy soil showed an increase in bulk density, a decrease in WHC, and a decrease in AS. The pH of remediated soil was affected by the type of washing chemical. The acidic washing processes (1OU, 2OU) resulted in low pH soils, while an alkali reduction process (3OU) showed high pH soil. The soil OM, TN, AvP and CEC decreased after soil washing. In the case of silty paddy soil, OM and TN were significantly reduced by washing. The most important change in soil property after washing was EC. After soil washing, the soil electrical conductivity increased sharply in all OUs : 1OU 0.51→6.21 ds/m, 2OU 1.09→3.73 ds/m, 3OU 0.99→9.30 ds/m. The EC values of the contaminated soil before washing were all less than 2 ds/m, which is an appropriate agricultural level. However, EC was significantly increased after washing, implying a strong salty soil level. The soil quality evaluation results before and after washing showed that the soil quality of heavy-metal contaminated soil was apparently degraded by washing. The number of soil property in the optimal range before washing (contaminated soil) was 10, but the number decreased to 5 after washing (remediated soil). Conclusions : Soil quality may be significantly changed after soil washing. The most noticeable change was the significant increase in the EC of soil and the soil health should be restored first to recycle the remediated soil. The important causes of changes in the soil quality were the separation of fine soil particles containing relatively high heavy metals from the bulk soil, soil disturbance by chemical washing solution and addition of high salts such as coagulants and pH adjust. Soil management schemes considering soil health should be soon prepared to restore the remediated soil back as an ecosystem member.

Changes in soil toxicity by phosphate-aided soil washing: Effect of soil characteristics, chemical forms of arsenic, and cations in washing solutions

Jho, Eun Hea,Im, Jinwoo,Yang, Kyung,Kim, Young-Jin,Nam, Kyoungphile Elsevier 2015 CHEMOSPHERE - Vol.119 No.-

<P><B>Abstract</B></P> <P>This study was set to investigate the changes in the toxicity of arsenic (As)-contaminated soils after washing with phosphate solutions. The soil samples collected from two locations (A: rice paddy and B: forest land) of a former smelter site were contaminated with a similar level of As. Soil washing (0.5M phosphate solution for 2h) removed 24.5% As, on average, in soil from both locations. Regardless of soil washing, Location A soil toxicities, determined using Microtox, were greater than that of Location B and this could be largely attributed to different soil particle size distribution. With soils from both locations, the changes in As chemical forms resulted in either similar or greater toxicities after washing. This emphasizes the importance of considering ecotoxicological aspects, which are likely to differ depending on soil particle size distribution and changes in As chemical forms, in addition to the total concentration based remedial goals, in producing ecotoxicologically-sound soils for reuse. In addition, calcium phosphate used as the washing solution seemed to contribute more on the toxic effects of the washed soils than potassium phosphate and ammonium phosphate. Therefore, it would be more appropriate to use potassium or ammonium phosphate than calcium phosphate for phosphate-aided soil washing of the As-contaminated soils.</P> <P><B>Highlights</B></P> <P> <UL> <LI> As removal by soil washing may not reduce soil toxicity of As-contaminated soils. </LI> <LI> Negligible changes in soil toxicity could be due to changes in As chemical forms. </LI> <LI> Soil particle size distribution could affect soil toxicity following soil washing. </LI> <LI> Type of cations associated with phosphate affected toxicities of the washed soils. </LI> <LI> Ecotoxicological aspects need to be considered for reuse of soil after soil washing. </LI> </UL> </P>

A combination of ferric nitrate/EDDS-enhanced washing and sludge-derived biochar stabilization of metal-contaminated soils

Yoo, Jong-Chan,Beiyuan, Jingzi,Wang, Lei,Tsang, Daniel C.W.,Baek, Kitae,Bolan, Nanthi S.,Ok, Yong Sik,Li, Xiang-Dong Elsevier 2018 Science of the Total Environment Vol.616 No.-

<P><B>Abstract</B></P> <P>In this study, soil washing and stabilization as a two-step soil remediation strategy was performed to remediate Pb- and Cu-contaminated soils from shooting range and railway sites. Ferric nitrate (Fe(NO<SUB>3</SUB>)<SUB>3</SUB>) and [<I>S,S</I>]-ethylenediamine disuccinate (EDDS) were used as washing agents, whereas three types of sludge-derived biochars and phosphogypsum were employed as soil stabilizers. While Fe(NO<SUB>3</SUB>)<SUB>3</SUB> extracted larger amounts of metals compared to EDDS (84% Pb and 64% Cu from shooting range soil; 30% Pb and 40% Cu from railway site soil), it caused severe soil acidification. Both Fe(NO<SUB>3</SUB>)<SUB>3</SUB> and EDDS washing enhanced the mobility of residual metals in the two soils, which in most cases could be mitigated by subsequent 2-month stabilization by sludge-derived biochars or phosphogypsum. By contrast, the metal bioaccessibility could only be reduced by soil washing. Nutrient-rich sludge-derived biochar replenished available P and K in both soils, whereas Fe(NO<SUB>3</SUB>)<SUB>3</SUB> washing provided available nitrogen (N). Soil amendment enhanced acid phosphatase activity but marginally improved soil dehydrogenase and urease activity in the treated soils, possibly due to the influence of residual metals. This study supported the integration of soil washing (by Fe(NO<SUB>3</SUB>)<SUB>3</SUB> or EDDS) with soil stabilization (by sludge-derived biochars or phosphogypsum) for accomplishing the reduction of metal mobility and bioaccessibility, while restoring the environmental quality of the treated soils.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fe(NO<SUB>3</SUB>)<SUB>3</SUB> washing significantly removed Pb from shooting range and railway soils. </LI> <LI> Biochars neutralized acidic soil pH resulting from Fe(NO<SUB>3</SUB>)<SUB>3</SUB> washing. </LI> <LI> Phosphogypsum immobilized residual Pb by forming insoluble PbSO<SUB>4</SUB> precipitates. </LI> <LI> Sludge-derived biochars reduced metal mobility and enhanced soil quality. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

납 오염 논토양의 원위치 세척을 위한 FeCl₃의 Bench-scale 적용성 평가: 세척전후 토양 특성변화

고일하,김지숙,장윤영,양재규,문덕현,최유림,고명수,지원현,Koh, Il-Ha,Kim, Gi Suk,Chang, Yoon-Young,Yang, Jae-Kyu,Moon, Deok Hyun,Choi, Yulim,Ko, Myoung-Soo,Ji, Won Hyun 한국지하수토양환경학회 2017 지하수토양환경 Vol.22 No.1

In a previous study, we assessed the feasibility of ferric chloride ($FeCl_3$) as a washing agent in bench-scale in-situ soil washing to remove Pb from agricultural paddy soil. Herein is a subsequent study to evaluate variations in soil properties after $FeCl_3$ soil washing in terms of fractionation and bioavailability of Pb and chemical properties of the soil. After soil washing, the soil pH decreased from 4.8 to 2.6 and the exchangeable fractions of Pb in the soil increased from 12 mg/kg to 15 mg/kg. Variations in the Pb fractionation of the soil increased Pb bioavailability by almost three-fold; however,the base saturation decreased by 75%. The concentrations of total nitrogen and available phosphate were similar before and after soil washing. The available silicate concentration significantly increased after soil washing but was two times lower than that of soil washed with HCl, which is widely used as a washing agent. This indicates that $FeCl_3$ can be an acceptable washing agent that protects the soil clay structure. The results suggest that soil amendment, such as liming, is needed to recover soil pH, reduce mobility of Pb, and provide exchangeable bases of Ca, Mg, and K as essential elements for the healthy growth of rice plants in reused soil that has been washed.

납 오염 논토양의 원위치 세척을 위한 FeCl3의 Bench-scale 적용성 평가: 세척전후 토양 특성변화

고일하,김지숙,장윤영,양재규,문덕현,최유림,고명수,지원현 한국지하수토양환경학회 2017 지하수토양환경 Vol.22 No.1

In a previous study, we assessed the feasibility of ferric chloride (FeCl3) as a washing agent in bench-scale in-situ soil washing to remove Pb from agricultural paddy soil. Herein is a subsequent study to evaluate variations in soil properties after FeCl3 soil washing in terms of fractionation and bioavailability of Pb and chemical properties of the soil. After soil washing, the soil pH decreased from 4.8 to 2.6 and the exchangeable fractions of Pb in the soil increased from 12 mg/kg to 15 mg/kg. Variations in the Pb fractionation of the soil increased Pb bioavailability by almost three-fold; however,the base saturation decreased by 75%. The concentrations of total nitrogen and available phosphate were similar before and after soil washing. The available silicate concentration significantly increased after soil washing but was two times lower than that of soil washed with HCl, which is widely used as a washing agent. This indicates that FeCl3 can be an acceptable washing agent that protects the soil clay structure. The results suggest that soil amendment, such as liming, is needed to recover soil pH, reduce mobility of Pb, and provide exchangeable bases of Ca, Mg, and K as essential elements for the healthy growth of rice plants in reused soil that has been washed.

토양 세척 시 초음파 적용에 따른 유기 오염물 제거 특성 평가

임찬수,김석구,김원재,고석오,Lim, Chan-Soo,Kim, Seog-Ku,Kim, Weon-Jae,Ko, Seok-Oh 한국지하수토양환경학회 2014 지하수토양환경 Vol.19 No.6

Cavitation generated by ultrasonic irradiation can enhance the diffusional transport of organic contaminants from soil surfaces or pores. Therefore, ultrasound soil washing can be an alternative of traditional soil washing process. In this study, soil was artificially contaminated with n-tetradecane, n-hexadecane and phenanthrene. A plate type ultrasonic reactor at 25 kHz frequency and 1000W power was used for laboratory soil washing experiments. Ultrasonic soil washing efficiency was compared with those of traditional soil washing using mechanical mixing. Various operational parameter such as soil/liquid ratio, irradiation time, particle size, and soil organic matter content was tested to find out the optimum condition. It was found that ultrasonic soil washing demonstrates better performance than mechanical soil washing. Optimum soil:liquid ratio for ultrasonic soil washing was 1 : 5. Desorption of organic contaminants from soils by ultrasonic irradiation was relatively fast and reached equilibrium within 10 minute. However, decrease in the soil particle sizes by ultrasonic irradiation results in re-adsorption of contaminants to soil phase. It was also observed that soil particle size distribution and soil organic matter content have significant effects on the efficiency of ultrasonic soil washing.

Humic substances as a washing agent for Cd-contaminated soils

Meng, Fande,Yuan, Guodong,Wei, Jing,Bi, Dongxue,Ok, Yong Sik,Wang, Hailong Elsevier 2017 CHEMOSPHERE - Vol.181 No.-

<P><B>Abstract</B></P> <P>Cost-effective and eco-friendly washing agents are in demand for Cd contaminated soils. Here, we used leonardite-derived humic substances to wash different types of Cd-contaminated soils, namely, a silty loam (Soil 1), a silty clay loam (Soil 2), and a sandy loam (Soil 3). Washing conditions were investigated for their effects on Cd removal efficiency. Cadmium removal was enhanced by a high humic substance concentration, long washing time, near neutral pH, and large solution/soil ratio. Based on the tradeoff between efficiency and cost, an optimum working condition was established as follows: humic substance concentration (3150 mg C/L), solution pH (6.0), washing time (2 h) and a washing solution/soil ratio (5). A single washing removed 0.55 mg Cd/kg from Soil 1 (1.33 mg Cd/kg), 2.32 mg Cd/kg from Soil 2 (6.57 mg Cd/kg), and 1.97 mg Cd/kg from Soil 3 (2.63 mg Cd/kg). Cd in effluents was effectively treated by adding a small dose of calcium hydroxide, reducing its concentration below the discharge limit of 0.1 mg/L in China. Being cost-effective and safe, humic substances have a great potential to replace common washing agents for the remediation of Cd-contaminated soils. Besides being environmentally benign, humic substances can improve soil physical, chemical, and biological properties.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Leonardite is an excellent source of humic substances. </LI> <LI> Humic substances as a washing agent effectively removed Cd from contaminated soils. </LI> <LI> Cd in effluent was easily removed by Ca(OH)<SUB>2</SUB>. </LI> </UL> </P>

A Study on the Decontamination Performance of Cesium by Soil Washing Process With Flocculating Agent

Jong Soon Song,Sun Il Kim 한국방사성폐기물학회 2018 방사성폐기물학회지 Vol.16 No.1

원전사고 및 시설보수 과정에서 방출되는 방사성물질 중 137Cs은 토양의 주 오염원 중 하나이다. 세슘으로 인한 토양오염은 주민의 거주 및 공업용지로의 재사용을 위해 제염이 불가피하다. 본 연구에서는 다양한 토양복원 기술 중 국내·외에서 실 제 방사성물질로 오염된 토양에 적용한 사례가 있는 토양세척 기술을 선정하였다. 토양세척 공정은 세척제를 사용하여 토양 과 세슘의 표면장력을 약화시켜 토양과 세슘을 분리하는 원리이다. 이러한 토양세척 공정의 세척수 재사용을 통해 공정효율 을 높이고자 세척수에 응집제를 적용하여 미세토양 및 세슘의 제거 성능 실험을 수행하였다. ICP-OES를 통해 세슘 수용액 에 토양을 첨가하여 세슘을 흡착시킨 후 응집제를 첨가하여 세슘의 농도를 측정하였으며 응집제 적용시 최대 세슘 제거율은 약 88%, 최소는 67%였다. Visual MINTEQ Code를 통한 세슘과 토양과의 종결합을 예측하였으며 탁도 측정을 통해 응집제 투여 후 탁도를 측정하여 세척수의 재사용 여부 및 미세토양 제거율을 분석하였다. Radioactive substances, especially 137Cs discharged in the course of Nuclear Power Plant Accident or maintenance of power plants, cause contamination of the soil. For habitation of residents and reuse of industrial land, it is inevitably necessary to decontaminate the soil. This study examines a soil washing process that has actually been used for washing of radioactivecontaminated soil. The soil washing process uses a washing agent to weaken surface tension of the soil and cesium, separating cesium from the soil. In this study, in order to raise the efficiency of the process, a flocculating agent was added to the washing water to remove fine soil and cesium. The cesium concentrations before and after applying the flocculating agent to cesium solution were measured through ICP-OES. When using 0.1 g of J-AF flocculating agent in the experiment, the maximum Cs removal performance was approximately 88%; the minimum value was 67%. Species combinations between cesium and soil were predicted using Visual MINTEQ Code; the ability to reuse the washing water or not, and the removal rate of the fine soil, determined via measurement of the turbidity after applying the flocculating agent, were determined.

Remediation of heavy metal-contaminated soils using eco-friendly nano-scale chelators

Lim, Heejun,Park, Sungyoon,Yang, Jun Won,Cho, Wooyoun,Lim, Yejee,Park, Young Goo,Kwon, Dohyeong,Kim, Han S. Techno-Press 2018 Membrane water treatment Vol.9 No.3

Soil washing is one of the most frequently used remediation technologies for heavy metal-contaminated soils. Inorganic and organic acids and chelating agents that can enhance the removal of heavy metals from contaminated soils have been employed as soil washing agents. However, the toxicity, low removal efficiency and high cost of these chemicals limit their use. Given that humic substance (HS) can effectively chelate heavy metals, the development of an eco-friendly, performance-efficient and cost-effective soil washing agent using a nano-scale chelator composed of HS was examined in this study. Copper (Cu) and lead (Pb) were selected as target heavy metals. In soil washing experiments, HS concentration, pH, soil:washing solution ratio and extraction time were evaluated with regard to washing efficiency and the chelation effect. The highest removal rates by soil washing (69% for Cu and 56% for Pb) were achieved at an HS concentration of 1,000 mg/L and soil:washing solution ratio of 1:25. Washing with HS was found to be effective when the pH value was higher than 8, which can be attributed to the increased chelation effect between HS and heavy metals at the high pH range. In contrast, the washing efficiency decreased markedly in the low pH range due to HS precipitation. The chelation capacities for Cu and Pb in the aqueous phase were determined to be 0.547mmol-Cu/g-HS and 0.192mmol-Pb/g-HS, respectively.

Mechanical and physicochemical contribution in removal of different soil types on cotton fabric

Han, Hye Ree,Chung, Seung Eun,Kim, Jooyoun,Park, Chung Hee Sage Science Press 2015 Textile Research Journal Vol. No.

<P>The research was conducted to identify the optimal washing methods for three types of soils, in terms of washing efficiency and eco-efficiency. To this end, the mechanical action by the washer’s agitation and the physicochemical action by detergents were investigated for their respective contribution to the detergency of three kinds of artificial soils: oil, protein, and their mixture. In general, washing efficiency increased with the increased agitation speed and the amount of detergent use. Most of the washing conditions presented a positive synergistic effect when both the mechanical and physicochemical actions were applied simultaneously.</P><P>The contributing ratio of the physicochemical action was greater for oily soil than for other soil types, due to the effective rolling-up by the detergent for the oily soil. The contributing ratio attributable to the mechanical action was higher when the protein was present in the soil composition, and the mechanical contribution was compromised as detergent usage was increased. The washing condition with the largest synergy did not always correspond with the condition of the highest washing efficiency. Energy Efficiency for Detergency was increased in all soil types as the agitation speed increased. It is suggested that the washing method be determined considering (1) the level of soiling and the acceptable washing performance, (2) the synergistic effect of mechanical and physicochemical actions, and (3) the eco-efficiency of washing methods.</P>