Removal rate and releases of polybrominated diphenyl ethers in two wastewater treatment plants,Korea

Wastewater treatment plants (WWTPs) play an important role in minimizing the release of many pollutants into the environment. Nineteen congeners in two WWTPs in Korea were determined to investigate the occurrence and fate of polybrominated diphenyl ethers (PBDEs) during wastewater treatment processes. The concentration of total PBDEs was 69.6 and 183 ng/L in influent, which declined to 1.59 and 2.34 ng/L in the final effluent, respectively (Tongyeong and Jinhae WWTPs). PBDEs were found to exist mostly in the particulate phase of wastewater, which rendered sedimentation efficient for the removal of PBDEs. BDE-209 was the predominant congener in the influent and sludge. Most of the PBDEs entering the WWTPs presumably ended up in the sludge, with < 2% being discharged with the final effluent. According to the mass loading estimation, every day 2.55–9.29 g PBDEs entered the two WWTPs, 2.8–10.4 g were disposed to landfill sites in sludge form and 0.06–0.12 g were discharged to the surrounding water through final effluent, respectively. Preliminary results indicated that the ecological risk to organisms in soil exposed to PBDEs through the usage of sludge application to agricultural land was relatively low. To our knowledge, this study is the first to report on the removal efficiency of PBDEs in a WWTP in Korea.     

Recent increase in surface fCO<Subscript>2</Subscript> in the western subtropical North Pacific

We observed unusually high levels (> 440 μatm) of carbon dioxide fugacity (fCO₂) in surface seawater in the western subtropical North Pacific, the area where Subtropical Mode Water is formed, during summer 2015. The NOAA Kuroshio Extension Observatory moored buoy located in this region also measured high CO₂ values, up to 500 μatm during this period. These high sea surface fCO₂ (fCO_2SW) values are explained by much higher normalized total dissolved inorganic carbon and slightly higher normalized total alkalinity concentrations in this region compared to the equatorial Pacific. Moreover, these values are much higher than the climatological CO₂ values, even considering increasing atmospheric CO₂, indicating a recent large increase in sea surface CO₂ concentrations. A large seasonal change in sea surface temperature contributed to higher surface fCO_2SW in the summer of 2015.     

Large temporal changes in contributions of groundwater-borne nutrients to coastal waters off a volcanic island

We examined the contribution of submarine groundwater discharge (SGD) to nutrient budgets in Hwasun Bay, Jeju Island, Korea in August 2009, October 2014, and May 2015. The concentrations of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) in fresh groundwater were in the range of 285?716 μM and 2.3?3.2 μM, respectively, which were each 1?2 orders of magnitude higher than those in the bay seawater. The outer-bay seawater flowing into the bay was oligotrophic (2.9 ± 1.9 μM for DIN and 0.2 ± 0.3 μM for DIP). Nutrient budget calculations were performed for each season by accounting for submarine fresh groundwater discharge (SFGD) and water residence times. In August 2009 (DIN = 1.8 μM and DIN:DIP ratio = 4.6 for the outerbay water), DIN inputs from SFGD accounted for approximately 40% of the DIN inventory in the bay seawater. In October 2014 (DIN = 1.1 μM and DIP < 0.05 μM for the outer-bay water), DIP from SFGD accounted for approximately 100% of the DIP inventory in the bay seawater. In May 2015, mean concentrations of DIN and DIP in the bay seawater were 8.6 ± 12 μM and 0.11 ± 0.04 μM, respectively, with conservative behaviors in the bay seawater in association with excessive groundwater inputs. These results imply that SGD plays a critical but different role in nutrient budgets and stoichiometry in coastal waters off a volcanic island depending on open-ocean nutrient conditions.     

Acoustic monitoring using bamboo set net in the Southern Sea of Korea

High-temporal resolution profiles of acoustic backscatter were collected from a traditional bamboo set net along the coast of the Southern Sea, Korea, using sideward-looking multi-beam imaging sonar. These data were used to examine the impact of variations in tidal cycles and current speeds on the bamboo set net. The relatively high influx of fish during the nighttime compared to the low influx and high outflux of fish during the daytime suggests visual avoidance of the net by the fish during the daytime. The observed diel variation in the captured fish flux was significantly correlated with the current speed (day: r = 0.35, p = 0.002, night: r = 0.60, p < 0.001). The ratio of influx and outflux of fish, and current speed were correlated in a linear relationship (day: r = 0.45, p < 0.001; night: r = 0.56, p < 0.001). The fish activity of those inhabiting the bamboo set nets appears to be greatly influenced by day-night differences and current speed. The present study enhances understanding of fish behavior via utilization of a bamboo set net in the coastal zone.     

Sources and distribution of allochthonous organic matter in surface sediment from the Seomjin River to the southern inner shelf of Korea

The spatial distributions of δ¹³C, δ¹⁵N, and n-alkanes were investigated to determine the source and transportation of allochthonous organic matter from the mouth of the Seomjin River to the southern inner shelf break of Korea. Total organic carbon (%) ranged from 0.3% to 1.6% (average = 0.80%, n = 81), and the C/N ratio varied from 2.4 to 12.4 (average = 6.76, n = 81). The δ¹³C values ranged from ?25.86 to ?20.26‰ (average = ?21.47‰, n = 81), and δ¹⁵N values ranged from 4.37‰ to 8.57‰ (average = 6.72‰, n = 81). The contribution of the terrestrial fraction of organic matter to the total ranged from 4.4% to 97.7% (average = 24.4%, n = 81), suggesting higher amounts around the catchment area and lower amounts in the offshore area. The concentration of total n-alkanes (nC₂₅ ? nC₃₅) was higher at the boundary between the outer bay and inner shelf break (BOBIS). Average chain length and the carbon preference index both indicated that major leaf wax n-alkanes accounted for the observed distribution of terrestrial organic matter, and were dominant in the inner shelf break (around BOBIS) and outer shelf break. Based on the spatial distribution of the total n-alkanes and the sum of nC₂₇, nC₂₉, and nC₃₁, the terrestrial organic matter distribution was considered to be controlled by local oceanographic conditions, especially at the center of the BOBIS. In addition to enabling the distribution and source of terrestrial organic matter to be identified, the n-alkanes indicated that minor anthropogenic allochthonous organic materials were superimposed on the total organic materials in the central part of Yeosu Bay and the catchment area. The n-alkane indices revealed weathered petroleum contamination, with contamination levels being relatively low at the present time.     

Sulfate Reduction and Sulfur Cycles at Two Seagrass Beds Inhabited by Cold Affinity <Emphasis Type="Italic">Zostera marina</Emphasis> and Warm Affinity <Emphasis Type="Italic">Halophila nipponica</Emphasis> in Temperate Coastal Waters

To evaluate the impact of invading seagrass on biogeochemical processes associated with sulfur cycles, we investigated the geochemical properties and sulfate reduction rates (SRRs) in sediments inhabited by invasive warm affinity Halophila nipponica and indigenous cold affinity Zostera marina. A more positive relationship between SRR and below-ground biomass (BGB) was observed at the H. nipponica bed (SRR = 0.6809 × BGB ? 4.3162, r ² = 0.9878, p = 0.0006) than at the Z. marina bed (SRR = 0.3470 × BGB ? 4.0341, r ² = 0.7082, p = 0.0357). These results suggested that SR was more stimulated by the dissolved organic carbon (DOC) exuded from the roots of H. nipponica than by the DOC released from the roots of Z. marina. Despite the enhanced SR in spring-summer, the relatively lower proportion (average, 20%) of acid-volatile sulfur (AVS) in total reduced sulfur and the strong correlation between total oxalate-extractable Fe (Fe_(oxal)) and chromium-reducible sulfur (CRS = 0.2321 × total Fe_(oxal) + 1.8180, r ² = 0.3344, p = 0.0076) in the sediments suggested the rapid re-oxidation of sulfide and precipitation of sulfide with Fe. The turnover rate of the AVS at the H. nipponica bed (0.13 day^?1) was 2.5 times lower than that at the Z. marina bed (0.33 day^?1). Together with lower AVS turnover, the stronger correlation of SRR to BGB in the H. nipponica bed suggests that the extension of H. nipponica resulting from the warming of seawater might provoke more sulfide accumulation in coastal sediments.     

A successful transformation of conventional SBR to MBR at Indian casino and facility: a case study of Chumash Casino and Resort Water Reclamation Facility (WRF), water reuse perspectives

A conventional sequencing batch reactor (SBR) was successfully transformed to a membrane bioreactor (MBR) at an Indian casino resort and hotel, Santa Ynez, California. The technical difficulties from the existing process at the site including a 3-mm screening unit, SBR biological tanks, and sand filtration were relieved of by new biological membrane technology. As the hotel and its vicinity expanded, the existing SBR was not able to treat an increased flow, which was major driving force for such membrane-upgraded project. In addition, as the area was in a high drought zone, without meeting the purpose of water reuse, new hotel expansion was not permitted. New membrane process was designed and built with new 2-mm screening unit, pre-anoxic, oxic (or aerobic), post-anoxic, and MBR tanks along with UV disinfection. The retrofitting work was conducted, minimizing a major revision on the existing SBR structure and its civil work. Therefore, the new packaged system has brought a number of benefits to the customer, thereby utilizing reclaimed water highly meeting the California Code of Regulations (CCR) Title 22 requirements. The reclaimed water goes to toilet water, cooling tower, and irrigation. This study details how such process transformation was technically finished and would help other similar cases in terms of retrofitting exiting biological process to a membrane application without a major civil construction. The cost analysis including capital, operation and maintenance (O&M) costs was included so that it will be practical to ones who will conduct future similar projects.     

Interrelationship between geochemical elements of sediment and groundwater at Samrak Park Delta of Nakdong River Basin in Korea: multivariate statistical analyses and artificial neural network approaches

This research was conducted at Samrak Park Delta of Nakdong River Basin in Busan Metropolitan City, Korea. The main objective of this study was to evaluate the interrelationship of geochemical elements in sediments and groundwater through multivariate statistical analyses and a multilayer perceptron artificial neural network model. The mean concentrations of chemical elements were Si (46%), Fe (16.9%), Al (15.7%), K (7.5%) and Ca (4.5%) in sediments, and Na (8650 mg/L), Mg (999 mg/L), Ca (432 mg/L), K (293 mg/L) and Cl (17,640 mg/L) in groundwater, respectively. The principal component analysis produced 3 kinds of factors with the variances of 63.37, 27.02 and 9.62%, respectively. It is suggested that the chemical components of sediments and groundwater were mainly originated from source rocks and seawater intrusion, with the minor impacts of irrigation and industry. Cluster analysis also showed that chemical elements were mainly controlled by the natural geogenic sources and seawater intrusion. Multilayer perceptron of artificial neural network (ANN) presented the good interrelationship between sediment and groundwater. The determination coefficients (R ²) between ANN predicted values and observed values in groundwater showed the high values of 0.61–0.97 except Mg, Mn and Sr. It is revealed that the chemical components of sediment and groundwater were derived from local geological origin and from the minor impact of anthropogenic sources. Multivariate analyses and ANN contributed to the identification of the mutual relationship between the geochemical elements of sediment and those of groundwater.     

Solar-activity cycle from observations of magnetic characteristics of prominences

According to measurements of the magnetic fields in quiescent prominences carried out by different teams in 1964–1989, the maximum values of the field correspond to the minimum values of the Wolf numbers averaged through the corresponding periods of observations. It has been shown that the synoptic noneclipse 2D linear polarimetry of quiescent Hα-prominences can be actually implemented; this method is based on the use of a coronagraph with a primary-optics diameter equal to or larger than 100 mm, a narrow-band filter with FWHM ≤ 0.4 nm, a standard linear polariod, and a high-precision linear polarimetric technique.