Polycyclic aromatic hydrocarbons in air on small spatial and temporal scales – I. Levels and variabilities

Polycyclic aromatic hydrocarbons (PAHs) were measured together with inorganic air pollutants at two urban sites and one rural background site in the Banja Luka area, Bosnia and Hercegovina, during 72 h in July 2008 using a high time resolution (5 samples per day) with the aim to study the spatial and temporal variabilities and to explore the significance of averaging effects inherent to 24 h-sampling. Measurement uncertainty was quantified on basis of three independent side-by-side samplers, deployed at one of the sites.PAH abundances in the urban and rural environments differed largely. Levels at the urban sites exceeded the levels at the rural site by >100%. The discrepancy was largely dominated by emission of 3–4 ring PAHs in the city, while 5–6 ring PAHs were more evenly distributed between city sites and the hill site. During the night a higher fraction of the semivolatile PAHs might have been stored in the soil or sorbed to surfaces. PAH patterns were undistinguishable across the three sites. However, concentrations of more particle-associated substances differed significantly between the urban sites than between one of the urban sites and the rural site (3σ uncertainty). Time-averaging (on a 24 h-basis) would have masked the significant inter-site differences of half of the substances which were found at different levels (on a 4 h-basis).     

Environmental monitoring of PCDD/Fs and metals in the vicinity of a cement plant after using sewage sludge as a secondary fuel

In 2005, the partial substitution (20%) of fossil fuel by sewage sludge was tested in a Spanish cement plant. In order to establish the environmental impact for the surroundings, in 2006, the levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and heavy metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sn, Tl, V, and Zn) were monitored in soil and vegetation samples collected near the cement plant. The temporal trends in the pollutant levels were studied by comparing the concentrations with those obtained in a previous survey (2003) in the same sampling sites. Very slight changes of the PCDD/F concentrations in both monitors were registered in the period 2003–2006 (0.17–0.15 and 0.94–1.10 ng I-TEQ kg⁻¹ dw in herbage and soil, respectively). In turn, there was a notable heterogeneity in the evolution of metal levels, which varied according to each particular element. Anyhow, the current levels of organic and inorganic pollutants are in the low part of the range in comparison with other zones impacted by cement plants, as well as industrial and urban areas worldwide. The human health risks derived from the exposure to PCDD/Fs and metals were also assessed. Although the cancer risks due to PCDD/Fs slightly increased, a reduction of the total carcinogenic risks, including metals, was noted. In conclusion, there were not observed impact changes for the environmental and the local population as a consequence of using sewage sludge as secondary fuel.     

Cost–benefit analysis of using sewage sludge as alternative fuel in a cement plant: a case study

Background, aim, and scope  To enforce the implementation of the Kyoto Protocol targets, a number of governmental/international institutions have launched emission trade schemes as an approach to specify CO₂ caps and to regulate the emission trade in recent years. These schemes have been basically applied for large industrial sectors, including energy producers and energy-intensive users. Among them, cement plants are included among the big greenhouse gas (GHG) emitters. The use of waste as secondary fuel in clinker kilns is currently an intensive practice worldwide. However, people living in the vicinity of cement plants, where alternative fuels are being used, are frequently concerned about the potential increase in health risks. In the present study, a cost–benefit analysis was applied after substituting classical fuel for sewage sludge as an alternative fuel in a clinker kiln in Catalonia, Spain. Materials and methods  The economical benefits resulting in the reduction of CO₂ emissions were compared with the changes in human health risks due to exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and carcinogenic metals (As, Cd, Co, and Cr) before and after using sewage sludge to generate 20% of the thermal energy needed for pyro-processing. The exposure to PCDD/Fs and metals through air inhalation, soil ingestion and dermal absorption was calculated according to the environmental levels in soil. The carcinogenic risks were assessed, and the associated cost for the population was estimated by considering the DG Environment’s recommended value for preventing a statistical fatality (VPF). In turn, the amount of CO₂ emitted was calculated, and the economical saving, according to the market prices, was evaluated. Results  The use of sewage sludge as a substitute of conventional energy meant a probability cancer decrease of 4.60 for metals and a cancer risk increase of 0.04 for PCDD/Fs. Overall, a net reduction of 4.56 cancers for one million people can be estimated. The associated economical evaluation due to the decreasing cancer for 60,000 people, the current population living near the cement plant, would be of 0.56 million euros (US$ 0.83 million). In turn, a reduction of 144,000 tons of CO₂ emitted between 2003 and 2006 was estimated. Considering a cost of 20 euros per ton of CO₂, the global saving would be 2.88 million euros (US$ 4.26 million). Discussion  After the partial substitution of the fuel, the current environmental exposure to metals and PCDD/Fs would even mean a potential decrease of health risks for the individuals living in the vicinity of the cement plant. The total benefit of using sewage sludge as an alternative fuel was calculated in 3.44 million euros (US$ 5.09 million). Environmental economics is becoming an interesting research field to convert environmental benefits (i.e., reduction of health risks, emission of pollutants, etc.) into economical value. Conclusions  The results show, that while the use of sewage sludge as secondary fuel is beneficial for the reduction in GHG emissions, no additional health risks for the population derived from PCDD/F and metal emissions are estimated. Recommendations and perspectives  Cost–benefit analysis seems to be a suitable tool to estimate the environmental damage and benefit associated to industrial processes. Therefore, this should become a generalized practice, mainly for those more impacting sectors such as power industries. On the other hand, the extension of the study could vastly be enlarged by taking into account other potentially emitted GHGs, such as CH₄ and N₂O, as well as other carcinogenic and non-carcinogenic micropollutants.     

Effects of public health interventions on industrial emissions and ambient air in Cartagena, Spain

Background, aim, and scope

Ten years of public health interventions on industrial emissions to clean air were monitored for the Mediterranean city of Cartagena. During the 1960s, a number of large chemical and non-ferrous metallurgical factories were established that significantly deteriorated the city’s air quality. By the 1970s, the average annual air concentration of sulfur dioxide (SO₂) ranged from 200 to 300 µg/m³ (standard conditions units). In 1979, the Spanish government implemented an industrial intervention plan to improve the performance of factories and industrial air pollution surveillance. Unplanned urban development led to residential housing being located adjacent to three major factories. Factory A produced lead, factory B processed zinc from ore concentrates, and factory C produced sulfuric acid and phosphates. This, in combination with the particular abrupt topography and frequent atmospheric thermal inversions, resulted in the worsening of air quality and heightening concern for public health. In 1990, the City Council authorized the immediate intervention at these factories to reduce or shut down production if ambient levels of SO₂ or total suspended particles (TSP) exceeded a time-emission threshold in pre-established meteorological contexts. The aim of this research was to assess the appropriateness and effectiveness of the intervention plan implemented from 1992 to 2001 to abate industrial air pollution.

Materials and methods

The maximum daily 1-h ambient air level of SO₂, NO₂, and TSP pollutants was selected from one of the three urban automatic stations, designed to monitor ambient air quality around industrial emissions sources. The day on which an intervention took place to reduce and/or interrupt industrial production by factory and pollutant was defined as a control day, and the day after an intervention as a post-control day. To assess the short-term intervention effect on air quality, an ecological time series design was applied, using regression analysis in generalized additive models, focusing on day-to-day variations of ambient air pollutants levels. Two indicators were estimated: (a) appropriateness, the ratio between mean levels of the pollutant for control days versus the other days, and (b) effectiveness, the ratio between mean levels of the pollutant for post-control days versus the other days. Ratios in regression analyses were adjusted for trend, seasonality, temperature, humidity and atmospheric pressure, calendar day, and special events as well as the other pollutants.

Results

A total of 702 control days were made on the factories’ industrial production during the 10-year period. Fifteen reductions and five shutdown control days took place at factory A for ambient air SO₂. At factory B, more controls were carried out for the SO₂ pollutant in the years 1992–1993 and 1997. At factory C, the control days for SO₂ decreased from 59 reductions and 14 shutdowns to a minimum from 1995 onwards, whereas the controls on TSP were more frequent, reaching a maximum of 99 reductions and 47 shutdowns in the last year. SO₂ ambient air mean levels ranged from 456 to 699 µg/m³ among factories on reduction control days and between 624 and 1,010 µg/m³ on shutdown days. The TSP ambient air mean levels were 428 and 506 µg/m³ on reduction and shutdown days, respectively. For all types of control days and factories, a mean ratio of 104% (95% confidence interval [CI] 88 to 121) in SO₂ levels was obtained and a mean ratio of 67% (95% CI 59 to 75) in TSP levels. Post-control days at all factories showed a mean ratio of ?16% (95% CI ?7 to ?24) in SO₂ levels and a mean ratio of ?13% (95% CI ?7 to ?19) in TSP levels.

Discussion

Interventions on industrial production based on the urban SO₂ and TSP ambient air levels were justified by the high concentrations detected. The best assessment of the interventions’ effectiveness would have been to utilize the ambient air pollutant concentration readings from the entire time of the production shutdowns or reductions; however, the daily hourly maximum turned out to be a useful indicator because of meteorological factors influencing the diurnal concentration profile. A substantial number of interventions were carried out from 1 to 3 am, when vehicular traffic was minimum. On the other hand, atmospheric stability undergoes diurnal cycling in the autumn–winter period due to thermal inversion, which reaches maximum levels around daybreak. Therefore, this increases the ambient air levels and justified the interventions carried out at daybreak in spite of the traffic influence.

Conclusions

All the interventions for SO₂ and TSP were carried out when the measured ambient air levels of pollutants were exceeded, which shows the appropriateness of the intervention program. This excess was greater when intervening on SO₂ than on the TSP levels. For both ambient air levels of SO₂ and TSP, significant drops in air pollution were achieved from all three factories following activity reductions. The production shutdown controls were very effective, because they returned excess levels, higher than in the reduction controls, to everyday mean values.

Recommendations and perspectives

The Cartagena City observational system of intermittent control has proven to effectively reduce industrial emissions’ impact on ambient air quality. This experienced model approach could serve well in highly polluted industrial settings. From a public health perspective, studies are needed to assess that the industrial interventions to control air pollution were related to healthier human populations. Legislation was needed to allow the public administration to take direct actions upon the polluting industries.     

Exposure to heavy metals and PCDD/Fs by the population living in the vicinity of a hazardous waste landfill in Catalonia, Spain: Health risk assessment

Most fly ashes produced in municipal waste incinerators of Catalonia (Spain) are deposited in a hazardous waste landfill (HWL) placed in Castellolí (Barcelona). This facility means a concern for the population living nearby. In response to this, we performed a probabilistic study focused on assessing human health risks derived from environmental exposure to heavy metals and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) around the HWL. Concentrations of various metals and PCDD/Fs were determined in soil and air samples collected at the HWL, and in 4 locations around it. Health risks were evaluated according to the distance from the sampling locations to the HWL (near and far-sites). In general terms, metal and PCCD/F levels were relatively low in air and soil samples. However, concentrations of PCDD/Fs, as well as those of some metals, were found to be relatively higher in the HWL and Castellolí (the nearest village) samples than in those collected far away, resulting in a slight increase of exposure to those pollutants. Anyhow, the current concentrations of metals and PCDD/Fs suggest that it is highly unlikely that there are any additional non-carcinogenic and carcinogenic risks for the population living near the HWL.     

Cell size dependence of additive versus synergetic effects of UV radiation and PAHs on oceanic phytoplankton

Polycyclic Aromatic Hydrocarbons’ (PAHs) toxicity is enhanced by the presence of ultraviolet radiation (UVR), which levels have arisen due to the thinning of the ozone layer. In this study, PAHs’ phototoxicity for natural marine phytoplankton was tested. Different concentrations of a mixture of 16 PAHs were added to natural phytoplankton communities from the Mediterranean Sea, Atlantic, Arctic and Southern Oceans and exposed to natural sunlight received in situ, including treatments where the UVR bands were removed. PAHs’ toxicity was observed for all the phytoplankton groups studied in all the waters and treatments tested, but only for the pico-sized group a synergetic effect of the mixture and UVR was observed (p = 0.009). When comparing phototoxicity in phytoplankton from oligotrophic and eutrophic waters, synergy was only observed at the oligotrophic communities (p = 0.02) where pico-sized phytoplankton dominated. The degree of sensitivity was related to the trophic degree, decreasing as Chlorophyll a concentration increased.     

Long-term environmental monitoring of persistent organic pollutants and metals in a chemical/petrochemical area: human health risks

Organic pollutants such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs) and polycyclic aromatic hydrocarbons (PAHs), as well as some metals are periodically monitored in soil and vegetation samples collected in Tarragona County (Spain). We here report the temporal trends of the concentrations of the above pollutants between the initial survey (2002) and that recently (2009) performed. The area under evaluation was divided into 4 sections (chemical, petrochemical, urban/residential and unpolluted). In general terms, urban soils presented the highest concentrations of PCDD/Fs, PCNs and PAHs, confirming that traffic is a very important emission source of these pollutants. In addition, substantially higher levels of PAHs and some metals were found in vegetation samples from the petrochemical complex. The assessment of health risks of these contaminants indicated that the current concentrations of micropollutants did not mean additional non-carcinogenic or cancer risks for the population living in the zone.     

Microbial communities to mitigate contamination of PAHs in soil—possibilities and challenges: a review

Background, aim, and scope  

Although highly diverse and specialized prokaryotic and eukaryotic microbial communities in soil degrade polycyclic aromatic hydrocarbons (PAHs), most of these are removed slowly. This review will discuss the biotechnological possibilities to increase the microbial dissipation of PAHs from soil as well as the main biological and biotechnological challenges.     

Impact of nonaqueous phase liquid (NAPL) source zone architecture on mass removal mechanisms in strongly layered heterogeneous porous media during soil vapor extraction

An existing multiphase flow simulator was modified in order to determine the effects of four mechanisms on NAPL mass removal in a strongly layered heterogeneous vadose zone during soil vapor extraction (SVE): a) NAPL flow, b) diffusion and dispersion from low permeability zones, c) slow desorption from sediment grains, and d) rate-limited dissolution of trapped NAPL. The impacts of water and NAPL saturation distribution, NAPL-type (i.e., free, residual, or trapped) distribution, and spatial heterogeneity of the permeability field on these mechanisms were evaluated. Two different initial source zone architectures (one with and one without trapped NAPL) were considered and these architectures were used to evaluate seven different SVE scenarios. For all runs, slow diffusion from low permeability zones that gas flow bypassed was a dominant factor for diminished SVE effectiveness at later times. This effect was more significant at high water saturation due to the decrease of gas-phase relative permeability. Transverse dispersion contributed to fast NAPL mass removal from the low permeability layer in both source zone architectures, but longitudinal dispersion did not affect overall mass removal time. Both slow desorption from sediment grains and rate-limited mass transfer from trapped NAPL only marginally affected removal times. However, mass transfer from trapped NAPL did affect mass removal at later time, as well as the NAPL distribution. NAPL flow from low to high permeability zones contributed to faster mass removal from the low permeability layer, and this effect increased when water infiltration was eliminated. These simulations indicate that if trapped NAPL exists in heterogeneous porous media, mass transfer can be improved by delivering gas directly to zones with trapped NAPL and by lowering the water content, which increases the gas relative permeability and changes trapped NAPL to free NAPL.     

Solid waste management in Bogotá: the role of recycling associations as investigated through SWOT analysis

In emerging economies, recycling provides an opportunity for cities to increase the lifespan of sanitary landfills, to reduce the costs of solid waste management, to decrease environmental problems from waste treatment by reincorporating waste into the productive cycle and to protect and develop the livelihoods of citizens who work as informal waste pickers. However, few studies have analysed the possibilities of and strategies for integrating the formal and informal sectors in solid waste management for the benefit of both. This integration is the key, especially in developing countries, to understanding how the recycling population can develop a business despite their social and economic limitations. The aim of this study was to perform a strength, weakness, opportunity and threat (SWOT) analysis of three recycling associations in Bogotá with the aim of examining and understanding the recycling situation from the perspective of members of the informal sector in their transition to becoming authorised waste providers. This issue has rarely been studied in the context of developing countries. The data used in the analysis are derived from multiple sources, including a literature review, Bogota’s recycling database, focus group meetings, governmental reports, national laws and regulations and interviews with key stakeholders. The results of this study show that as the primary stakeholders, the formal and informal waste management sectors can identify the internal and external conditions of recycling in Bogotá. Several strategies were designed based on the SWOT analysis. The participation of recycling associations is important in the design and application of waste policy, the consolidation of recycling through an effective business model, promotional programmes for social inclusion and the development of new transformation processes and technologies to valorise recycling materials. In conclusion, recycling associations can become authorised waste providers through a profitable business that increases recycling rates to create a productive process from waste during the generation of new materials and to decrease environmental problems while improving the welfare and living conditions of recyclers. These findings are important for Bogotá to advance and promote recycling as a key strategy for integrated sustainable waste management in the city.