Nitrate and ammonium ions removal from groundwater by a hybrid system of zero-valent iron combined with adsorbents

Nitrate (NO(3)(-)) is a commonly found contaminant in groundwater and surface water. It has created a major water quality problem worldwide. The laboratory batch experiments were conducted to investigate the feasibility of HCl-treated zero-valent iron (Fe(0)) combined with different adsorbents as hybrid systems for simultaneous removal of nitrate (NO(3)(-)) and ammonium (NH(4)(+)) ions from aqueous solution. The maximum NO(3)(-) removal in combined Fe(0)-granular activated carbon (GAC), Fe(0)-filtralite and Fe(0)-sepiolite systems was 86, 96 and 99%, respectively, at 45 °C for 24 h reaction time. The NO(3)(-) removal rate increased with the increase in initial NO(3)(-) concentration. The NO(3)(-) removal efficiency by hybrid systems was in the order of sepiolite > filtralite > GAC. The NH(4)(+) produced during the denitrification process by Fe(0) was successfully removed by the adsorbents, with the removal efficiency in the order of GAC > sepiolite > filtralite. Results of the present study suggest that the use of a hybrid system could be a promising technology for achieving simultaneous removal of NO(3)(-) and NH(4)(+) ions from aqueous solution.     

Radiation exposure to Marine biota around the Fukushima Daiichi NPP

The dose rates for six marine organisms, pelagic fish, benthic fish, mollusks, crustaceans, macroalgae, and polychaete worms, representative in marine ecosystems, have been predicted by the equilibrium model with the measured seawater activity concentrations at three locations around the Fukushima Daiich nuclear power plant after the accident on March 11, 2011. Model prediction showed that total dose rates for the biota in the costal sea reached 4.8E4 μGy/d for pelagic fish, 3.6E6 μGy/d for crustaceans, 3.8E6 μGy/d for benthic fish, 5.2E6 μGy/d for macroalgae, 6.6E6 μGy/d for mollusks, and 8.0E6 μGy/d for polychaete worms. The predicted total dose rates remained above the UNSCEAR’s (United Nations Scientific Committee on the Effect of Atomic Radiation) benchmark level (1.0E4 μGy/d for an individual aquatic organism), for only the initial short period, which seems to be insufficiently long to bring about any detrimental effect on the marine biota at the population level. Furthermore, the total dose rates for benthic fish and crustaceans approximated using the measured activity concentration of the biota and bottom sediment was well below the benchmark level. From these results, it may be concluded that the impact of the ionizing radiation on the marine biota around the Fukushima NPP as a consequence of the accident would be insignificant.     

Mussel watch program for organic contaminants along the Korean coast, 2001–2007

The level and extent of organic contaminants along the Korean coast were estimated through the mussel watch program, established in 2001. Mussels and oysters were collected at 20 sites along the Korean coast in 2001 and at 25 sites from 2002 to 2007. The mussel tissues were analyzed for PCBs, organochlorine presticides, PAHs, BTs, and PCDD/Fs. PCBs, PAHs, BTs, and PCDD/Fs were ubiquitous contaminants along the Korean coast, showing mean detection frequencies of more than 95% over 7 years. The concentrations of organic contaminants in mussels along the Korean coast were relatively low or moderate compared with foreign studies. Concentrations of DDTs, PCBs, and PCDD/Fs were below the action or maximum levels for humans established by USFDA and EU. Elevated concentrations above the 85th percentile were found for PCBs, PAHs, BTs, and PCDD/Fs at sites near industrial complexes or big harbors, for HCHs at sites near non-industrial complexes, and for DDTs at sites near both non-industrial and industrial complexes. Using two nonparametric tests to assess temporal trends, the Spearman test revealed that BTs and PCDD/Fs had significant decreasing trends at four sites (Gwangyang Bay, Cheonsu Bay, Garorym Bay, and the Incheon coast) and at six sites (Hupo coast, Guryongpo coast, eastern part of Geojedo, Gunsan coast, Garorym Bay, and Asan Bay), respectively.     

Optimal conditions for three brood chronic toxicity test method using a freshwater macroinvertebrate <Emphasis Type="Italic">Moina macrocopa</Emphasis>

Freshwater cladocera such as Daphnia magna and Ceriodaphnia dubia have been used extensively for freshwater toxicity test worldwide. However, these species may not be indigenous in certain geographical regions, which restrict the utility of these organisms as test species. In the present study, we investigated optimal culture and test conditions for an indigenous freshwater macroinvertebrate of Korea, Moina macrocopa. The culture conditions that were evaluated included water temperature (20°C and 25°C), rearing media (moderately hard water or MHW, with or without selenium supplementation, or Elendt M4), and food density (2.5 × 10⁷ and 5 × 10⁷ cells/mL of Selenastrum capricornutum), and their effects on the life history characteristics of M. macrocopa were determined. Population growth rate of M. macrocopa was maximized at 25°C with 5 × 10⁷ cells/mL of algal food density in MHW. A series of chronic three brood reference toxicant tests were conducted under the ideal culture conditions that were identified here, and the results of the tests indicated reliable reproducibility of the test protocol. Optimal culture and test conditions that were identified for M. macrocopa in the present study are suggested for evaluation of chronic toxicity of chemicals and industrial or municipal discharge.     

Hydrochemistry of urban groundwater, Seoul, Korea: the impact of subway tunnels on groundwater quality

Hydrogeologic and hydrochemical data for subway tunnel seepage waters in Seoul (Republic of Korea) were examined to understand the effect of underground tunnels on the degradation of urban groundwater. A very large quantity of groundwater (up to 63 million m³ year^− 1) is discharged into subway tunnels with a total length of 287 km, resulting in a significant drop of the local groundwater table and the abandonment of groundwater wells. For the tunnel seepage water samples (n = 72) collected from 43 subway stations, at least one parameter among pathogenic microbes (total coliform, heterotrophic bacteria), dissolved Mn and Fe, NH₄⁺, NO₃⁻, turbidity, and color exceeded the Korean Drinking Water Standards. Locally, tunnel seepage water was enriched in dissolved Mn (avg. 0.70 mg L^− 1, max. 5.58 mg L^− 1), in addition to dissolved Fe, NH₄⁺, and pathogenic microbes, likely due to significant inflow of sewage water from broken or leaking sewer pipes.Geochemical modeling of redox reactions was conducted to simulate the characteristic hydrochemistry of subway tunnel seepage. The results show that variations in the reducing conditions occur in urban groundwater, dependent upon the amount of organic matter-rich municipal sewage contaminating the aquifer. The organic matter facilitates the reduction and dissolution of Mn- and Fe-bearing solids in aquifers and/or tunnel construction materials, resulting in the successive increase of dissolved Mn and Fe. The present study clearly demonstrates that locally significant deterioration of urban groundwater is caused by a series of interlinked hydrogeologic and hydrochemical changes induced by underground tunnels.     

Removal of arsenate and arsenite from aqueous solution by waste cast iron

The removal of As(III) and As(V) from aqueous solution was investigated using waste cast iron, which is a byproduct of the iron casting process in foundries. Two types of waste cast iron were used in the experiment: grind precipitate dust (GPD) and cast iron shot (CIS). The X-ray diffraction analysis indicated the presence of Fe0 on GPD and CIS. Batch experiments were performed under different concentrations of As(III) and As(V) and at various initial pH levels. Results showed that waste cast iron was effective in the removal of arsenic. The adsorption isotherm study indicated that the Langmuir isotherm was better than the Freundlich isotherm at describing the experimental result. In the adsorption of both As(III) and As(V), the adsorption capacity of GPD was greater than CIS, mainly due to the fact that GPD had higher surface area and weight percent of Fe than CIS. Results also indicated the removal of As(III) and As(V) by GPD and CIS was influenced by the initial solution pH, generally decreasing with increasing pH from 3.0 to 10.5. In addition, both GPD and CIS were more effective at the removal of As(III) than As(V) under given experimental conditions. This study demonstrates that waste cast iron has potential as a reactive material to treat wastewater and groundwater containing arsenic.     

Sediment characteristics,phosphorus types and phosphorus release rates between river and lake sediments

The Han river is 469.7 km long with 26219-km2 area watershed, and is the primary drinking water source for the 20 million people that live in Seoul, Kangwon-Do and Kyunggi-Do, Korea. Phosphorus release from sediments impacts water quality, and is endangering the beneficial use of the river. This research measures phosphorus release and predicts future releases from bottom sediments of two tributary areas (Chungpyung Lake (CPL) and Jamsil submerged dam (JSD) area in the Han river). Sediment samples were taken over a 4-year period from four points in the Jamsil dam area and from 92 points in CPL. The sediments were analyzed for total phosphorus, the form of the phosphorus and release rates under different conditions to the water column. Sediment phosphorus distribution from CPL was 3-5% adsorbed-P (Ads-P), 15-20% non-apatite-P (NAI-P), 25-30% apatite-P (A-P) and 45-57% residual-P (R-P). In the JSD area, the phosphorus distribution ranges were 1-3% Ads-P, 22-39% NAI-P, 26-40% A-P and 30-39% R-P. Laboratory experiments showed that phosphorus release rates from 60 to 80 mg/m2 week in JSD area and ranged from 25 to 40 mg/m2 week in CPL sediments.     

Effects of activated carbon types and service life on removal of endocrine disrupting chemicals: amitrol, nonylphenol, and bisphenol-A

Removal performances of endocrine disrupting chemicals (EDC) such as amitrol, nonylphenol, and bisphenol-A were evaluated in this study using granular activated carbon (GAC) adsorption. This study found that GAC adsorption was effective in removal of EDCs with high K_ow value. Nonylphenol and bisphenol-A were effectively adsorbed onto all carbons (including the used carbons) tested in this study. As indicated by K_ow value, nonylphenol was more effectively adsorbed than bisphenol-A. The coal-based carbon was found more effective than other carbons in the adsorption of nonylphenol and bisphenol-A due to its larger pore volume. The adsorption capacity reduced with the operation year, and the extent of the reduction was different depending upon the carbon type and the operation year. Amitrol was effectively removed by biological degradation, but was poorly adsorbed. Since the microbes residing at the used carbons already accustomed to amitrol, the used carbons removed amitrol better than the virgin carbons. Although the coal-based carbon showed the best removal performance of amitrol, GAC adsorption could not be recommended for amitrol removal because considerable portion of incoming amitrol (9–87%) passed through GAC adsorption column. According to this study, pore volume mainly influenced the adsorption capacity, but the surface charge was also important due to electrical interaction. The adsorption parameters for nonylphenol and bisphenol-A provided by this study could be valuable when GAC adsorption was considered to handle an accidental spill of nonylphenol and bisphenol-A.     

An experimental study to explore WTP for aviation carbon offsets: the impact of a carbon tax on the voluntary action

As Australia recently introduced a mandatory carbon price, this paper provides a rare perspective of how such institutional changes influence consumer preferences for voluntary climate action. When examined using three contingent valuation questions, the results show that the compliance mechanism induces a substantial reduction in the number of air travellers who are willing to pay extra for voluntary carbon offsets and in the payment amount, although the crowding-out effect is incomplete. A disproportionately larger welfare benefit is attached to the carbon offsets for a domestic flight than its international counterpart. Overall empirical findings advocate the continued role of voluntary programmes.     

Seasonal and spatial variation of solvent extractable organic compounds in fine suspended particulate matter in Hong Kong

The results of a 12-month study of more than 100 solvent extractable organic compounds (SEOC) in particulate matter (PM) less than or equal to 2.5 microm (PM2.5) collected at three air monitoring stations located at roadside, urban, and rural sites in Hong Kong are reported. The total yield of SEOC that accounts for approximately 8-18% of organic carbon (OC) determined by a thermal optical transmittance method was 125-2060 ng/m3, which included 14.6-128 ng/m3 resolved aliphatic hydrocarbons, 39.4-1380 ng/m3 unresolved complex mixtures, 0.6-17.2 ng/m3 polycyclic aromatic hydrocarbons, 41.6-520 ng/m3 fatty acids, and < 0.1-12.1 ng/m3 alkanols. Distinct seasonal variations (summer/winter differences) were observed with higher concentrations of the total and each class of SEOC in the winter and lower concentrations in the summer. Spatial variations are also obvious, with the roadside samples having the highest concentrations of SEOC and the rural samples having the lowest concentrations in all seasons. Characteristic ratios of petroleum hydrocarbons, such as carbon preference index, unresolved to resolved components, and carbon number with maximum concentration, suggest that PM2.5 carbon in Hong Kong originates from both biogenic and anthropogenic sources. The proportion of SEOC in PM2.5 from anthropogenic sources is estimated.