No abstract

Although arsenic contamination of underground water in southern Taiwan is well known, few studies examine atmospheric arsenic deposition in this area, which might be the major source of such pollution to the soil, water, and even underground water. This research focused on the atmospheric arsenic concentration, dry and wet depositions, and the As distribution around Chiayi County, located in the south of Taiwan. Eight sampling sites are used, both upwind and downwind of an area with heavy industrial and human activities. All samples were collected by a PS-1 high volume sampler at each site, pretreated by a digestion process, and further analyzed with an ICP-MS. The results show that the arsenic deposition flux ranged from 65.0 to 473 μg/m 2 -month in Chiayi County. This deposition flux has no significant seasonal variation, based on the multiple trend results obtained from pooling the dry and wet deposition data. The average dry deposition flux of As ranged from 34 to 161 μg/m 2 -month during the sampling year, and had the opposite trend to the wind speed. Additionally, the correlations between atmospheric arsenic concentration and PM levels were significant, supported by the low p-value (< 0.01) at a 99% confidence level. Meanwhile, the highly linear correlation between As and PM concentrations was also evaluated. The amount of precipitation was statistically correlated to the wet deposition flux (11.3-414 μg/m 2 -month with a p-value = 2 × 10 -7 and r-value = 0.9306. Furthermore, the composition of the As mass concentrations in ambient air were dominated by As (V) in both fall (66.4%) and winter (68.9%). According to the GIS spatial analysis of the As concentration in the dry season, from October to March, the As contribution of local emissions were not significant. Consequently, this study indicates that the atmospheric As around Chiayi County might be sourced from the upwind northern area, and mainly deposited through wet scavenging.

Algae-based biodiesel is considered a promising alternative energy; therefore, the treatment of microalgae residues would be necessary. Anaerobic processes can be used for treating oil-extracted microalgae residues (OMR) and at the same time for recovering bioenergy. In this study, anaerobic batch experiments were conducted to evaluate the potential of recovering bioenergy, in the forms of butanol, H2, or CH4, from pretreated OMR. Using pretreated OMR as the only substrate, a butanol yield of 0.086 g/g-carbohydrate was obtained at carbohydrate of 40 g/L. With supplemented butyrate, a highest butanol yield of 0.192 g/g-carbohydrate was achieved at pretreated OMR containing 25 g/L of carbohydrate with 15 g/L of butyrate addition, attaining the highest energy yield of 3.92 kJ/g-OMR and energy generation rate of 0.65 kJ/g-OMR/d. CH4 production from pretreated OMR attained an energy yield of 8.83 kJ/g-OMR, but energy generation rate required further improvement. H2 production alone from pretreated OMR might not be attractive regarding energy yield, but it attained a superb energy generation rate of 0.68 kJ/g-OMR/d by combining H2 production from pretreated OMR and butanol production from pretreated OMR with supplementary butyrate from H2 fermentation supernatant. This study demonstrated an integrated system as an option for treating OMR and recovering bioenergy.