Monitoring of non-point source pollutants load from a mixed forest land use

The aim of this study was to determine the unit load of NPS (non-point source) pollutants including organic variables such as BOD (biochemical oxygen demand),COD (chemical oxygen demand) and DOC (dissolved organic carbon),nitrogen and phosphorus constituents,and suspended solids (SS) and their event mean concentration (EMC) of runoff flows from a water-shed of mixed forest land use by intensive field experiments.Field monitoring for continuous measurements of rainfall,flow,and water quality was conducted over 12 storm events during 2008–2009 using automated and manual sampling methods.The EMCs of individual runoff event were estimated for each water quality constituent based on the flow rate and concentration data of runoff discharge.The average EMCs of BOD,COD,DOC,SS,TN (total nitrogen),NH 4+ -N,NO 3- -N,TP (total phosphorus),PO 43- -P from the mixed forest land were 1.794,3.498,1.462,10.269,0.862,0.044,0.634,0.034,and 0.005 mg/L,respectively.The annual unit loads of BOD,COD,DOC,SS,TN,NH 4+ -N,NO 3- -N,TP and PO 43--P were estimated as 66.9,133.2,55.5,429.8,36.5,1.6,26.9,1.3 and 0.1 kg/(ha·yr),respectively.In addition,affecting parameters on the EMCs were investigated by statistic analysis of the field data.As a result,significant correlations with precipitation,rainfall intensity,and total runoff flows were found in most constituents.     

Investigation and risk assessment modeling of As and other heavy metals contamination around five abandoned metal mines in Korea

Tailings, agricultural soils, vegetables and groundwater samples were collected from abandoned metal mines (Duckum, Dongil, Dongjung, Myoungbong and Songchun mines) in Korea. Total concentrations of arsenic (As) and heavy metals (Cd, Cu, Pb and Zn) were analyzed to investigate the contamination level. Several digestion methods (Toxicity characteristics leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP), 0.1 N/1 N HCl) and sequential extraction analysis for mine tailings were conducted to examine the potential leachability of As and heavy metals from the tailings. The order of urgent remediation for the studied mines based on the risk assessment and remedial goals was suggested. The Songchun mine tailings were most severely contaminated by As and heavy metals. Total concentrations of As and Pb in the tailings were 38,600–58,700 mg/kg (av. 47,400 mg/kg) and 11,800–16,800 mg/kg (av. 14,600 mg/kg), respectively. Agricultural soils having high As concentrations were found at the all mines. Average concentrations of Cd in the vegetables exceeded the normal value at all mines areas, while As only at the Dongjung, Myoungbong, and Songchun mine area. One groundwater sample each from the Dongil and Myoungbong mines, and 4 groundwater samples from the Songchun mine had values above 10 μg/L of As concentration. The TCLP method revealed that only Pb in the Songchun tailings, 6.49 mg/L, exceeded the regulatory level (5 mg/L). Employing the 1-N HCl digestion method, the concentration of As in the Songchun mine tailings, 4,250 mg/kg, was up to 3,000 times higher than its Korean countermeasure standard. Results from the sequential extraction of As in the tailings showed that the easily releasable fraction in the Myoungbong and Songchun mine tailings was more than 30% and the residual fraction was less than 40%. Based on results showing the exposure health risk employing the hazard quotient and cancer risk of As, Cd and Zn, the Dongil mine needs the most urgent remedial action. The concentration reduction factor (CRF) of As in both soil and groundwater follows the order: Songchun>Dongjung>Dongil>Myoungbong>Duckum mine.     

Effects of NO2 and SO2 on selective catalytic reduction of nitrogen oxides by ammonia

The selective catalytic reduction (SCR) characteristics of NO and NO(2) over V(2)O(5)-WO(3)-MnO(2)/TiO(2) catalyst using ammonia as a reducing agent have been determined in a fixed-bed reactor at 200-400 degrees C. The presence of NO(2) enhances the SCR activity at lower temperatures and the optimum ratio of NO(2)/NO(x) is found to be 0.5. During the SCR reactions, there are some side reactions occurred such as ammonia oxidation and N(2)O formation. At higher temperatures, the selective catalytic oxidation of ammonia and the nitrous oxide formation compete with the SCR reactions. The denitrification (DeNO(x)) conversion decreases at lower temperatures but it increases at higher temperatures with increasing SO(2) concentration. The presence of SO(2) in the feeds inhibits N(2)O formation.     

Sequential soil washing techniques using hydrochloric acid and sodium hydroxide for remediating arsenic-contaminated soils in abandoned iron-ore mines

Sequential washing techniques using single or dual agents [sodium hydroxide (NaOH) and hydrochloric acid (HCl) solutions] were applied to arsenic-contaminated soils in an abandoned iron-ore mine area. We investigated the best remediation strategies to maximize arsenic removal efficiency for both soils and arsenic-containing washing solution through conducting a series of batch experiments. Based on the results of a sequential extraction procedure, most arsenic prevails in Fe-As precipitates or coprecipitates, and iron exists mostly in the crystalline forms of iron oxide. Soil washing by use of a single agent was not effective in remediating arsenic-contaminated soils because arsenic extractions determined by the Korean standard test (KST) methods for washed soils were not lower than 6mg kg(-1) in all experimental conditions. The results of X-ray diffraction (XRD) indicated that iron-ore fines produced mobile colloids through coagulation and flocculation in water contacting the soils, containing dissolved arsenic and fine particles of ferric arsenate-coprecipitated silicate. The first washing step using 0.2M HCl was mostly effective in increasing the cationic hydrolysis of amorphous ferrihydrite, inducing high removal of arsenic. Thus, the removal step of arsenic-containing flocs can lower arsenic extractions (KST methods) of washed soils. Among several washing trials, alternative sequential washing using 0.2M HCl followed by 1M HCl (second step) and 1M NaOH solution (third step) showed reliable and lower values of arsenic extractions (KST methods) of washed soils. This washing method can satisfy the arsenic regulation of washed soil for reuse or safe disposal application. The kinetic data of washing tests revealed that dissolved arsenic was easily readsorbed into remaining soils at a low pH. This result might have occurred due to dominant species of positively charged crystalline iron oxides characterized through the sequential extraction procedure. However, alkaline extraction using NaOH was effective in removing arsenic readsorbed onto the surface of crystalline minerals. This is because of the ligand displacement reaction of hydroxyl ions with arsenic species and high pH conditions that can prevent readsorption of arsenic.     

Medical waste generation in selected clinical facilities in Taiwan

This study investigated the type and amount of medical waste generated from small clinical facilities in Taiwan. We sampled 200 small medical establishments, with few or no patient beds, to survey the wastes generated and disposed. The surveyed medical facilities consisted of four groups including private clinics, medical laboratories, blood centers and public clinics. Private clinics providing surgical, dental, obstetrical, and dialysis services were included in this survey because they may generate higher amounts of infectious waste than other specialties. The overall mean general waste production rate was 3.97 kg/bed/day (or 0.075 kg/patient/day) at all the surveyed facilities, higher than that obtained from larger hospitals in Taiwan, which ranged from 2.41 to 3.26 kg/bed/day. The highest amount of infectious wastes generated among the four groups of facilities were from blood centers (3.14 kg/bed/day), followed by private clinics, medical laboratories and public clinics (1.91, 1.07, and 0.053 kg/bed/day, respectively). The overall average was 2.08 kg/bed/day. This study suggests that the waste generated at small medical facilities ranged widely.     

Assessment of Young Dong tributary and Imgok Creek impacted by Young Dong coal mine,South Korea

An initial reclamation of the Young Dong coal mine site, located in northeastern South Korea, was completed in 1995. Despite the filling of the adit with limestone, acid rock drainage (ARD) enters Young Dong tributary and is then discharged to Imgok Creek. This ARD carries an average of 500 mg CaCO₃/l of mineral acidity, primarily as Fe(II) and Al. Before spring runoff, the flow of Imgok Creek is 3.3–4 times greater than that of the tributary and has an alkalinity of 100 mg CaCO₃/l, which is sufficient to eliminate the mineral acidity and raise the pH to about 6.5. From April through September 2008, there were at least two periods of high surface flow that affects the flow of ARD from the adit. Flow of ARD reaches 2.8 m³/min during spring runoff. This raised the concentrations of Fe and Al in the confluence with Imgok Creek. However, by 2 km downstream the pH of the Imgok Creek is 6.5 and only dissolved Fe is above the Korean drinking water criteria (0.30 mg/l). This suggests only a minor impact of Young Dong Creek water on Imgok Creek. Acid digestion of the sediments in Imgok Creek and Young Dong Tributary reveals considerable abundances of heavy metals, which could have a long-term impact on water quality. However, several water-based leaching tests, which better simulate the bioavailable metals pool, released only Al, Fe, Mn, and Zn at concentrations exceeding the criteria for drinking water or aquatic life.

     

Impact of aquaculture on distribution of dissolved organic matter in coastal Jeju Island,Korea, based on absorption and fluorescence spectroscopy

Environmental Science and Pollution Research - In Jeju Island, multiple land-based aquafarms were fully operational along most coastal region. However, the effect of effluent on distribution and...