Guánica Bay, located in southwestern Puerto Rico, has suffered oil spills and other pollution discharges since the 1960s. Previous research showed elevated concentrations of polychlorinated biphenyls (PCBs) in coral reef and sediment. This research examined PCB concentrations in sediment and fish. Sediment and fish sampling in the bay was facilitated by community members. This study identified the second highest reported PCB level (129,300 ng/g) in sediment in the USA. Fish samples also showed elevated concentrations (1623 to 3768 ng/g), which were higher than the thresholds of safe levels of PCBs in fish for human consumption. The alarmingly high concentration of PCBs calls for proactive community engagement to bring awareness about contamination of the bay and more extensive sampling to test for the concentration of PCBs in seafood and the people of Guánica. This study also underscores the value of the involvement of local communities during sampling design aimed at identifying hot spots of contaminants. 相似文献
Measurements of carbonyls and C2–C6 non-methane hydrocarbons (NMHCs) were made in ambient air at a rural site at the summit of Whiteface Mountain (WFM) in New York State. Alkanes dominated in the samples, with ethane and propane making up about 55% of the total on a carbon-atom basis. Ethane, the longest-lived of the NMHCs, showed a mixing ratio in the range of 0.86–2.1 ppbv. Photochemical ageing analysis indicated an anthropogenic influence on the NMHC levels. The photochemical reactivity of the hydrocarbons, calculated in terms of propylene-equivalent concentration, was dominated by alkenes (propene and ethene), which accounted for 74% of the total NMHC sum. Air mass back-trajectories have been used to investigate the origin of the observed NMHCs and carbonyls. Higher concentrations were found when air masses arrived from the midwestern US corridor. Acetone was the most abundant species, comprising from 31% to 53% of the total detected carbonyls, followed by MEK (15–53%), HCHO (7–39%), and CH3CHO (7–19%). Average concentrations were determined to be 1.61 ppbv for CH3C(O)CH3, 1.40 ppbv for MEK, 1.16 ppbv for HCHO, and 0.49 ppbv for CH3CHO. The variations in carbonyl concentrations were observed to follow patterns similar to variations in O3 concentrations, typical of secondary products. Correlations and statistical analysis of the carbonyls and NMHCs were performed, and showed that most of the compounds derived from mixing and photochemical transformation of long-range transported pollutants from the major source areas. Ranking of the carbonyls with respect to removal of the OH radical showed HCHO to be the most important species, followed by CH3CHO, MEK, and CH3C(O)CH3. 相似文献
This study investigated the characteristics of iron corrosion scales in pipes at tube well, overhead tank, and consumers’ end in older untreated water distribution system in Peshawar city, Pakistan. Effect of water quality conditions on corrosion scales and that of scales on drinking water quality in such systems was also assessed by undertaking a comparison with new piped distribution systems. The scales were analyzed for chemical composition and morphology using X-ray diffraction (XRD), inductively coupled plasma (ICP), and a scanning electron microscope (SEM), while water quality was examined for physicochemical and biological characteristics. The main crystalline phases of corrosion scales were goethite, magnetite, siderite, and quartz. From tube well to consumers’ end, goethite increased from 36 up to 48%, quartz declined from 22 to 15%, while magnetite fluctuated and siderite disappeared. Elemental composition of scales showed the deposition of Zn, Al, Mn, Cr, Pb, Cu, As, and Cd with Zn (13.9 g/kg) and Al (3.6 g/kg) in highest proportion. The SEM analysis illustrated the presence of microbial communities indicating the formation of biofilms in the corrosion scales. The significant difference (P <?0.05) in levels of dissolved oxygen (DO), Cl?, SiO44?, electrical conductivity (EC), SO42?, NO3?, alkalinity, hardness, and trace metals between old (DS-O) and new piped systems indicated their role in corrosion scale formation/destabilization and the effect of scale dissolution on water quality. In DS-O, EC, Cu, and Mn were significantly higher (P?<?0.05), whereas turbidity, EC, DO, and SiO44? significantly increased from source to consumers’ end implying a higher dissolution of scales and lowered corrosion rates in DS-O to utilize SiO44? and DO for iron oxidation.
This article applies a stated preference choice model to assess trade-offs that residents of two squatter settlements in Dhaka,
Bangladesh might consider if they were given choices for relocation to flood-free areas. The respondents were asked to choose
repeatedly from a set of choice cards, which displayed different configurations of financial incentives for relocation, such
as free or inexpensive land, loans or nonrepayable grants, and provisions for temporary or permanent employment opportunities.
The survey results indicated that despite extensive experience with flood problems, many residents of Mirpur and Vasantek
found that certain configurations of economic incentives were not attractive enough for them to relocate to flood-free areas.
At the same time, they would prefer a reduction in the risk of flooding at their current location. The economic incentives
that would best assist in increasing voluntary relocation of residents from their current locations included free land, nonrepayable
grants (Taka 20,000), and long-term employment opportunities. Further, differences in geographic location (i.e., Mirpur vs.
Vasantek), income levels, and membership in neighborhood communities were linked with the tendency of residents to stay at
their current location. 相似文献