Analysis of polychlorinated dibenzo-p-dioxins and furans in various aqueous samples in Taiwan

Twenty-one fresh water samples were taken from reservoirs, wells and drinking water treatment plants in Taiwan for measurement of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) concentrations. Due to low concentration of PCDD/Fs, water samples (400-1000 L) were collected by using the on-site large volume pre-concentration system and analyzed by high resolution gas chromatography (HRGC)/high resolution mass spectrometer (HRMS). Different characteristics of dioxin profiles in surface water and groundwater are observed. The PCDD/F concentrations in fresh water samples varied from 0.001 to 0.265 pg WHO₉₈-TEQ/L which are lower than the standard (12 pg WHO₉₈-TEQ/L) set by the Taiwan Environmental Protection Administration (TEPA) for drinking water. Only a small fraction (<5%) of the total PCDD/F concentration in fresh water samples was water-soluble. As a result of their hydrophobicity, PCDD/Fs are effectively removed along with suspended solid via the water treatment process (average 98% removal efficiency).     

Aquaculture farmers’ perceptions of climate-related risks in the Mekong Region

Natural protected areas (NPA) are portions of the Mexican territory where the original environment has not been modified and which are protected in order t     

Potential for the desalination of a brackish groundwater aquifer under a background of rising sea level via salt intrusion prevention river gates in the coastal area of the Red River Delta,Vietnam

Additional freshwater sources are required in many parts of the world, including the coastal areas of the Red River Delta (RRD), where the groundwater (GW) is generally brackish. Determining a feasible method for desalinating brackish aquifers would help provide additional freshwater sources. However, substantial desalination of brackish aquifers cannot be achieved under the natural conditions of GW flow and precipitation recharge. Although rainfall recharge to the shallow Holocene aquifer has occurred for hundreds of years, the aquifer still remains brackish since the natural hydraulic conditions do not allow a complete mixing between the fresh recharged water and aquifer salinized water or the discharging of the aquifer salinized water. The planned salt intrusion prevention gates in the Red River, Tra Ly River and Hoa River in the RRD coastal area, combined with increased GW abstraction and associated aquifer recharge with fresh river water, could result in the gradual desalination of the shallow Holocene aquifer. These effects would help improve the area’s resilience to freshwater shortages and sea level rises and would allow for the creation of a long-term sustainable water resource development plan to manage the salinization of water resources caused by sea level rises. Finite element (FE) modeling of GW flow, solute transport via GW flow and dynamic programming (DP) have been used to study the potential desalination of brackish aquifers, the magnitude of GW abstraction quantities and the spatial and temporal aspects of desalination. FE modeling of GW flow coupled with DP was utilized to identify the magnitude of sustainable abstraction quantities and the GW flow field, which is required in salt transport models. Multiple sizes of elements and time steps were used to adapt to the unsteady state of GW flow and hydraulic head variables between the elements in the FE meshes in order to ensure reasonable accuracy of numerical modeling. The GW flow and salt transport modeling and DP allowed determining quasi-steady-state GW abstraction rates and aquifer salinity levels for conditions that did and did not include the shallow Holocene unconfined aquifer recharge from rainfall. The aquifer modeled domain which is supposed to serve the pumping well field is 1.5 km². The results showed that the Holocene aquifer may provide a stable abstraction rate of 100 m³/day starting in the 6th year (for the worst-case scenario with zero aquifer recharge from rainfall) to 130 m³/day starting in the 3rd year (for the scenario with aquifer recharge equal to 3% of the rainfall levels). During the first years of GW abstraction, the desalination of the brackish upper Holocene aquifer will mainly occur in the area close to the river, and at the 18th year of abstraction, almost the entire area between the river and line of pumping wells would be desalinized. From the 10th year of abstraction, the abstracted water has a total dissolved solids content lower than 0.5 g/l for the worst-case scenario with zero aquifer recharge from rainfall and lower than 0.42 g/l for the scenario with aquifer recharge equal to 3% of the rainfall. The modeling results indicate the simulated process by which abstraction of groundwater adjacent to the Tra Ly River could desalinize the brackish aquifer via freshwater recharge from the river.     

Assessment of some trace heavy metals and radioactivity concentration in water of Bendimahi River Basin (Van, Turkey)

The levels of heavy metals were determined in the water of Bendimahi River Basin, statistically analysed and compared to natural gross radioactivity concentration. Fifteen samples of water were collected from Bendimahi River and Van Lake for two seasons in 2005. Water samples were analyzed for eight trace elements and concluded together with gross-alpha and gross-beta radioactivity concentrations. Atomic absorption spectrometry (AAS) was used to determine the concentrations of heavy metals in water samples collected from Bendimahi River basin. Correlation analysis was made for radioactivity and heavy metal concentrations and the Pearson correlation coefficients between gross-alpha and gross-beta radioactivity and heavy metal were determined. The concentrations of all metals were found to be higher than WHO, EC, EPA and TSE-266 guidelines for drinking water, except for Zn and Cu. Generally, the heavy metal concentrations in water samples obtained in May and in August were found to be in sequence of Fe>Zn>Pb>Cr>Cu>Mn>Co>Cd and Fe>Zn>Cu>Pb>Cr>Mn>Co>Cd, respectively. The gross-alpha and gross-beta activity concentration varies between 0.063 and 0.782, 0.021 and 0.816 Bq l(-1) in samples collected in May, and 0.009 and 0.037, 0.081 and 3.116 Bq l(-1) in samples collected in August.     

Gross alpha and beta radioactivity concentration in water, soil and sediment of the Bendimahi River and Van Lake (Turkey)

The concentrations of the natural radioactivity in water, soil and sediment samples collected from Bendimahi River which originates near the Tendürek Mountain (Van, Turkey), its tributaries and Van Lake (Turkey) were measured. The gross-alpha and gross-beta radioactivity concentrations were investigated in May and August in 2005. Determination of the gross-alpha and gross-beta radioactivity of river water, soil and sediment samples was obtained by using gas-flow proportional counter, PIC-MPC 9604-alpha/beta counter. In water samples, the obtained results show that in May; gross-alpha and gross-beta activity concentrations varied between 0.063-0.782 and 0.021-0.816 Bq l(-1) and in August the values were 0.009-0.037 and 0.081-3.116 Bq l(-1), respectively. The gross-alpha and gross-beta activity concentrations in soil samples ranged from 0.800 to 4.277 Bq g(-1) and 0.951 to 11.773 Bq g(-1) in May and 0.686 to 4.713 Bq g(-1) and 0.073 to 9.524 Bq g(-1) in August, respectively. Concentrations ranging from 0.782 to 4.596 Bq g(-1) and from 0.482 to 10.372 Bq g(-1) in May and from 0.580 to 5.824 Bq g(-1) and from 0.303 to 9.702 Bq g(-1) in August for gross-alpha and gross-beta radioactivity were observed in sediments, respectively.     

Partition of heavy metals in a tropical river system impacted by municipal waste

A research program was established to identify the governing factors for the partition coefficient (K _D ) of heavy metals between suspended particulate and dissolved phases in the Day River system a tropical, highly alluvial aquatic system, in Vietnam. The targeted river system, draining an urbanized–industrialized catchment where discharged wastewater is mostly untreated, could be separated into the least impacted, pristine area, and the most impacted, polluted area. Organic matter degradation was shown to govern the variation of parameters like total organic carbon, biochemical oxygen demand, chemical oxygen demand, nutrients, conductivity, or redox potential. Heavy metals in both dissolved and particulate phases were enriched in severely polluted area because of wastewater inflow that contains concentrated metals and intensification of metal influx from sediment. Results show log K _D in the order Mn?<?As?<?Zn?<?Hg?<?Ni?<?Cu?<?Cd?<?Co?<?Pb?<?Cr?<?Fe and As?<?Zn?<?Ni?<?Mn?<?Cr?<?Cu?<?Co?<?Fe in the polluted zone and the pristine zone, respectively. A decreasing tendency of partition coefficients of 11 heavy metals considered from the pristine to the impacted zones was observed. Three explanations for the difference are: (1) increase of solubility of most heavy metals in low redox potential, (2) competition for the binding sites with major and minor cations, and (3) complexation with dissolved organic matter concentrated in municipal waste impacted water. Apart from domestic waste impact, statistical analysis has contributed to identify the influence of climate condition and hydrological regime to the partition of heavy metals in the area.     

Concentrations of As, Be, Cr, Hg, Mn, and Ni in ambient air at four urban locations in Japan

The metal concentrations of As, Be, Cr, Hg, Mn, and Ni in ambient air were measured at four sites in Japan from October 1997 to March 2006. The mean metal concentration data measured from the four sites (K1, K2, M, and Y) are found on the order of Mn > Cr–Ni > As > Hg > Be. The concentrations of Mn with the highest mean value were fairly variable across four sites such as 45.9 ± 42.8 (K1), 25.6 ± 19.4 (K2), 22.5 ± 19.7 (M), and 25.4 ± 19.8 ng m^???3 (Y). In contrast, the concentrations of Be with the lowest mean value were less variable across four sites with means of 0.03 to 0.04 ng m^???3. Inspection of the seasonal patterns indicates the peak occurrence of most metals during spring, although relative dominance during winter is seen at the most polluted area (K1). Evaluation of long-term patterns indicates that the noticeably high values of metals in the early stage of study reduced gradually across the years, although the metal concentration levels in most areas were affected significantly by anthropogenic activities. However, efforts to control pollution levels seemed to gradually contribute to a decrease in metal concentration levels of all study sites through the years.     

Evaluation of the Mesoscale Meteorological Model (MM5)-Community Multi-Scale Air Quality Model (CMAQ) performance in hindcast and forecast of ground-level ozone

This paper presents the first attempt to apply the Mesoscale Meteorological Model (MM5)-Community Multi-Scale Air Quality Model (CMAQ) model system to simulate ground-level ozone (O3) over the continental Southeast Asia (CSEA) region for both hindcast and forecast purposes. Hindcast simulation was done over the CSEA domain for two historical O3 episodes, January 26-29, 2004 (January episode, northeast monsoon) and March 24-26, 2004 (March episode, southwest monsoon). Experimental forecast was done for next-day hourly O3 during January 2006 over the central part of Thailand (CENTHAI). Available data from 20 ambient monitoring stations in Thailand and 3 stations in Ho Chi Minh City, Vietnam, were used for the episode analysis and for the model performance evaluation. The year 2000 anthropogenic emission inventory prepared by the Center for Global and Regional Environmental Research at the University of Iowa was projected to the simulation year on the basis of the regional average economic growth rate. Hourly emission in urban areas was prepared using ambient carbon monoxide concentration as a surrogate for the emission intensity. Biogenic emissions were estimated based on data from the Global Emissions Inventory Activity. Hindcast simulations (CSEA) were performed with 0.5 degree x 0.5 degree resolution, whereas forecast simulations (CENTHAI) were done with 0.1 degree x 0.1 degree hourly emission input data. MM5-CMAQ model system performance during the selected episodes satisfactorily met U.S. Environmental Protection Agency criteria for O3 for most simulated days. The experiment forecast for next-day hourly O3 in January 2006 yielded promising results. Modeled plumes of ozone in both hindcast and forecast cases agreed with the main wind fields and extended over considerable downwind distances from large urban areas.     

A long-term performance test on an autotrophic denitrification column for application as a permeable reactive barrier

The long-term performance of a sulfur-based reactive barrier system was evaluated using autotrophic denitrification in a large-scale column. A bacterial consortium, containing autotrophic denitrifiers attached on sulfur particles, serving as an electron donor, was able to transform 60mgNL(-1) of nitrate into dinitrogen. In the absence of phosphate, the consortium was unable to remove nitrate, but after the addition of phosphate, nitrate removal was readily evident. Once the column operation had stabilized, seepage velocities of 1.0x10(-3) and 0.5x10(-3)cms(-1), corresponding to hydraulic residence times of 24 and 48h, respectively, did not affect the nitrate removal efficiency, as determined by the nitrate concentration in the effluent. However, data on the nitrate, nitrite and sulfate distribution along the column indicated differential transformation patterns with column depths. Based on the dinitrogen concentration in the total gas collected, the denitrification efficiency of the tested column was estimated to be more than 95%. After 500d operation, the hydrodynamic characteristics of the column slightly changed, but these changes did not inhibit the nitrate removal efficiency. Data from a bacterial community analysis obtained from four parts of the column demonstrated the selective a spatial distribution of predominant species depending on available electron acceptors or donors.     

Hazardous industrial waste management in Vietnam: current status and future direction

This article concentrates on the existing situation of hazardous industrial waste management in Vietnam. To realize the importance of the development of a Vietnam national strategy based on the reduce, reuse, recycle (3R) concept to the year 2020, the author summarizes the practice of recycling activities of hazardous industrial waste and discusses the challenges arising from increases in the quantity and types of waste and the level of hazard of the waste generated considering that the technical infrastructure for handling and managing the waste is inadequate and the legal system on environmental protection is lacking. In order to improve the existing situation of hazardous industrial waste management, the Vietnamese Government recently has played an increasing role in promoting regional and international cooperation on environmental protection through ratifying the international conventions on the environment including the Basel Convention on the Control of Trans-boundary Movements of Hazardous Waste and their Disposal and the International Labor Organization Convention on Safety in the Use of Chemicals at Work and by adhering to the concept of the material-cycle society. These steps are key opportunities for applying the principles of 3R to the recovery of value from hazardous waste in the future.