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Resultados 1021-1030 de 4,042
The influence of wastewater discharge on water quality in Hawai'i: A comparative study for Lahaina and Kihei, Maui Texto completo
2016
Miller-Pierce, Mailea R. | Rhoads, Neil A.
In Maui, Hawai'i, wastewater reclamation facilities (WWRFs) dispose of partially treated effluent into injection wells connected to the nearshore environment. Hawai'i State Department of Health data from 2004–2015 were assessed for qualitative trends in nutrient, turbidity, and Chlorophyll a water quality (WQ) impairments for fourteen marine sites on Maui Island. We introduce a novel method, the Qualitative Impact Percentage (QIP), to facilitate a qualitative comparison of disparate factors contributing to WQ impairment. Sites near the Lahaina WWRF in West Maui, which was found in violation of the Clean Water Act in 2014, had fewer exceedances and lower geometric means compared to sites near the Kihei WWRF. Our results suggest that WQ impairments may be a greater concern in Kihei than previously acknowledged. This paper attempts to raise the awareness of policymakers and the public and to encourage further research assessing the effects of the Kihei WWRF on the marine environment.
Mostrar más [+] Menos [-]Spatial mismatch between pollutant emission and environmental quality in China — A case study of NOx Texto completo
2016
Li, Mingsheng | Ren, Xiaoxia | Zhou, Lei | Zhang, Fengying
Although pollutant emission is the main cause of environmental quality deterioration, regional environmental quality may not be consistent with pollutant emission volume. To investigate the relationship between environmental quality and pollutant emission in Chinese provinces, a spatial mismatch index model and a barycenter model were established. NOx emissions and NO2 concentrations for the period 2006–2012 were used to verify the models. Results showed that regional differences in emission intensity were found; total NOx emissions for the nine highest-emission provinces accounted for 61.7% of the national total. Spatial distributions of NO2 pollution remained stable. Areas below Grade II of the National Ambient Air Quality Standard (GB 3095-2012) were mainly in the eastern coastal region, especially the Yangtze River Delta, Pearl River Delta, and Beijing-Tianjin-Hebei area. Spatial mismatches could be found between NOx emission and NO2 concentration, with the spatial mismatch index ranging 29.6–32.7, while barycenter distance for these two variables ranged 45.4–138.5 km. Spatial mismatches between NOx emission and NO2 concentration have decreased gradually over time. Our findings enhance understanding of the link between environmental quality and pollutant emission and should be taken into account when establishing regional environmental goals.
Mostrar más [+] Menos [-]Assessment of pollutant mean concentrations in the Yangtze estuary based on MSN theory Texto completo
2016
Ren, Jing | Gao, Bing-Bo | Fan, Hai-Mei | Zhang, Zhi-Hong | Zhang, Yao | Wang, Jin-Feng
Reliable assessment of water quality is a critical issue for estuaries. Nutrient concentrations show significant spatial distinctions between areas under the influence of fresh-sea water interaction and anthropogenic effects. For this situation, given the limitations of general mean estimation approaches, a new method for surfaces with non-homogeneity (MSN) was applied to obtain optimized linear unbiased estimations of the mean nutrient concentrations in the study area in the Yangtze estuary from 2011 to 2013. Other mean estimation methods, including block Kriging (BK), simple random sampling (SS) and stratified sampling (ST) inference, were applied simultaneously for comparison. Their performance was evaluated by estimation error. The results show that MSN had the highest accuracy, while SS had the highest estimation error. ST and BK were intermediate in terms of their performance. Thus, MSN is an appropriate method that can be adopted to reduce the uncertainty of mean pollutant estimation in estuaries.
Mostrar más [+] Menos [-]Effect of high sedimentation rates on surface sediment dynamics and mangrove growth in the Porong River, Indonesia Texto completo
2016
Sidik, Frida | Neil, David H. | Lovelock, Catherine E.
Large quantities of mud from the LUSI (Lumpur Sidoarjo) volcano in northeastern Java have been channeled to the sea causing high rates of sediment delivery to the mouth of the Porong River, which has a cover of natural and planted mangroves. This study investigated how the high rates of sediment delivery affected vertical accretion, surface elevation change and the growth of Avicennia sp., the dominant mangrove species in the region. During our observations in 2010–2011 (4–5years after the initial volcanic eruption), very high rates of sedimentation in the forests at the mouth of the river gave rise to high vertical accretion of over 10cmy−1. The high sedimentation rates not only resulted in reduced growth of Avicennia sp. mangrove trees at the two study sites at the Porong River mouth, but also gave rise to high soil surface elevation gains.
Mostrar más [+] Menos [-]Recommendations for calibration factors for a photo-reference method for aerosol black carbon concentrations Texto completo
2016
Lalchandani, Vipul | Tripathi, Sachida N. | Graham, Eric A. | Ramanathan, Nithya | Schauer, James J. | Gupta, Tarun
Large measurement networks of Black Carbon (BC) aerosol are important for understanding its impacts on climate and health. PM2.5 filter samples were collected at three urban US locations and one India urban location and were analyzed for Elemental Carbon (EC) and Organic Carbon (OC) concentrations using thermo-optical analysis (TO) following the IMPROVE protocol for US samples and NIOSH protocol for India samples. Site and season-specific calibrations of an inexpensive photo-reference (PR) method were created with TO EC measurements of the US filter samples whereas method-specific calibration was prepared using India filter samples. Piece-wise calibration based on filter loading was also explored. Calibrations were applied across different sites, seasons and methods to determine Root Mean Square Error (RMSE) and average absolute error in each calibration by comparing with reference EC measurements. This paper investigates various calibrations of PR method to improve the agreement between PR method and TO EC measurements. Difference in BC estimated error remained within ±10% among three urban US site-specific calibrations, which suggests that site-specific calibrations are not necessary. Season based calibrations were found to perform best (least RMSE/Mean EC), when applied to same season test samples but resulted in large errors of up to 60% RMSE/Mean EC when applied to different seasons, thus warranting the use of season-specific calibrations of the PR method. RMSE relative to mean EC was 50% when calibration prepared from US samples (IMPROVE protocol) was used to test India samples (NIOSH protocol). However, method-specific calibration prepared from India samples reduced the error to 24%, showing the large dependency of PR method on reference BC measurement method. Calibration based on filter loading reduced the RMSE slightly for both US urban and India samples and indicated that filters with loadings higher than 20 μg cm−2 are not suitable for estimating BC by PR method.
Mostrar más [+] Menos [-]Modelling PUF passive air samplers: Temperature dependence of polyurethane foam – Air partitioning of PAHs and their O-, N-, and S-derivatives computed by COSMO-RS Texto completo
2016
Parnis, J Mark | Mackay, Donald | Harner, Tom
The response of polyether-type polyurethane foam (PUF) passive samplers used to estimate the gaseous concentration of organic chemicals has been modelled using the COSMO-RS methodology. Experimental data for equilibrium partitioning ratios were used to evaluate several different oligomers as surrogates for polyurethane foam over a temperature range of 15–95 °C. Models were built with varying mole ratios of mono- or di-isocyanates and ether-based linkers derived from glycerol, ethylene oxide, propylene oxide, styrene and oligomers of ethylene oxide. Several models were found to have comparable root-mean-square (RMS) error, and COSMO-RS results were generally consistent with the empirical data. A PUF model consisting of a 1:1 condensed pair of 2,4-toluene-diisocyanide and glycerol was found to have minimal RMS error for both aromatic organic molecules and a large set of organic molecules studied between 15 and 95 °C. This model was applied to a series of simple and heteroatom-substituted polycyclic aromatics, for which the temperature dependence of air-polymer partitioning was predicted between −5 and 40 °C. Log K(PUF-Air) is found to decrease by 1.5–2.5 log units over this range, reflecting the increased volatility of the compounds with temperature, demonstrating the need for accurate exposure temperatures for partitioning involving air. The model results support the application of the passive samplers for monitoring and research studies of polycyclic aromatic compounds (PACs) in air. The approach also illustrates an efficient strategy of selective acquisition of experimental data for COSMO-RS validation, coupled by theoretical prediction of a much larger number of chemicals at various temperatures.
Mostrar más [+] Menos [-]Characteristics of aerosols over Beijing and Kanpur derived from the AERONET dataset Texto completo
2016
Chen, Hao | Cheng, Tianhai | Gu, Xingfa | Li, Zhengqiang | Wu, Yu
Beijing and Kanpur are two cities identified as high aerosol optical thickness (AOT) and complex composition of aerosols in Asian monsoon regions. Detail knowledge of key aerosol types in these two countries would be helpful for clarifying the mechanisms of aerosol radiative forcing and improving the accuracy of satellite remote sensing in these two countries. This study examines the characteristics of aerosol types over Beijing and Kanpur derived from a 12-year dataset from Aerosol Robotic Network (AERONET) stations and compares them via cluster analysis of optical and microphysical properties. Aerosols in Beijing are more complex than in Kanpur. Four fine-size dominated aerosol types (including two types of moderately absorbing aerosols, one highly absorbing aerosol type and one non-absorbing aerosol type) and one coarse-size dominated aerosol type are identified over Beijing. In Kanpur, two fine-sized dominated aerosol types (one high absorbing aerosol type and one non-absorbing aerosol type) and one coarse-sized dominated aerosol type are obtained. Compared to Beijing, the average SSAs of non-absorbing and high-absorbing aerosols are lower for the four wavelengths (440 nm, 676 nm, 869 nm, 1020 nm) in Kanpur. High absorbing aerosols usually occur in the months December to February (DJF) for both sites. The proportion in Kanpur (14%) is about twice that in Beijing (7%). Non-absorbing aerosols are usually observed in the months June to August (JJA) for both sites. Their proportion in Kanpur (31%) is ∼3 times larger than that in Beijing (11%). Coarse aerosols are frequently observed in the months March to May (MAM) for both sites. Their proportion in Kanpur (54%) is two times larger than in Beijing (21%).
Mostrar más [+] Menos [-]Effect of historical contamination in the fish community structure of a recovering temperate coastal lagoon Texto completo
2016
García-Seoane, Eva | Coelho, João Pedro | Mieiro, Cláudia | Dolbeth, Marina | Ereira, Tiago | Rebelo, José Eduardo | Pereira, Eduarda
This study aimed to assess the impact of trace element concentrations in fish assemblages of a recovering coastal lagoon. Fish, water and sediment were sampled in winter and summer in the Ria de Aveiro (Portugal). Multivariate analyses were used to examine the relationship between fish assemblages and environmental variables (physical-chemical parameters, contaminants and sediment grain size). In winter, fish density and biomass were mainly affected by the water turbidity, while Li concentration in the water column was found to be significant for fish biomass. During summer, a significant relationship was found between fish density and temperature, Hg, Li and Zn concentration in the sediment. These contaminants were mainly associated with the historically contaminated area, were Liza spp. and Dicentrarchus labrax appeared as dominant species. Environmental variables were not significant for fish biomass. The historical contamination in the Ria de Aveiro still seems to exert some influence on fish community structure.
Mostrar más [+] Menos [-]Occurrence and distribution of antifouling biocide Irgarol-1051 in coral reef ecosystems, Zanzibar Texto completo
2016
Sheikh, Mohammed A. | Juma, Fatma S. | Staehr, Peter | Dahl, Karsten | Rashid, Rashid J. | Mohammed, Mohammed S. | Ussi, Ali M. | Ali, Hassan R.
2-methythiol-4-tert-butylamino-6-cyclopropylamino-s-triazine (Irgarol-1051) has been widely used as effective alternative antifouling paint in marine structures including ships. However, it has been causing deleterious effects to marine organisms including reef building corals. The main objective of this study was to establish baseline levels of Irgarol-1051 around coral reefs and nearby ecosystems along coastline of Zanzibar Island. The levels of Irgarol-1051 ranged from 1.35ng/L around coral reefs to 15.44ng/L around harbor with average concentration of 4.11 (mean)±0.57 (SD) ng/L. This is below Environmental Risk Limit of 24ng/L as proposed by Dutch Authorities which suggests that the contamination is not alarming especially for coral reef ecosystem health. The main possible sources of the contamination are from shipping activities. This paper provides important baseline information of Irgarol-1051 around the coral reef ecosystems within the Western Indian Ocean (WIO) region and may be useful for formulation of marine conservation strategies and policies.
Mostrar más [+] Menos [-]The status and management of the lionfish, Pterois sp. in Trinidad and Tobago Texto completo
2016
Alemu I., Jahson B.
Trinidad and Tobago was the last Caribbean island to be invaded by the lionfish and since its invasion in 2012 they have spread to most coral reef and hard bottom environments. Standard reef fish surveys were used to assess lionfish population densities and size distributions from 2013–2015. Total lengths ranged between 6.2–40.4cm and 2.2–950g in weight. The length-weight relationship was described by W=0.0002L2.5654. Fish densities were highest in the northeast Tobago at 326lionfish/ha and the lowest in the southwest Tobago at 10.5lionfish/ha. In order to curtail the spread of this invasive species, a culling programme was initiated at selected reefs to regularly remove lionfish at monthly intervals. On the selected reefs 26–30% reduction in mean lionfish biomass and 25–27% reduction in abundance was noted compared to control sites (p<0.05).
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