Non-controlled biogenic emissions to the atmosphere from Lazareto landfill, Tenerife, Canary Islands

GOAL, SCOPE AND BACKGROUND: [corrected] Historically, landfills have been the simplest form of eliminating urban solid waste with the minimum cost. They have been the most usual method for discarding solid waste. However, landfills are considered authentic biochemical reactors that introduce large amounts of contaminants into the environment in the form of gas and leachates. The dynamics of generation and the movement of gas in landfills depend on the input and output parameters, as well as on the structure of the landfill and the kind of waste. The input parameters include water introduced through natural or artificial processes, the characteristics of the urban solid waste, and the input of atmospheric air. The main output parameters for these biochemical reactors include the gases and the leachates that are potentially pollutants for the environment. Control systems are designed and installed to minimize the impact on the environment. However, these systems are not perfect and a significant amount of landfill gas could be released to the atmosphere through the surface in a diffuse form, also known as Non-controlled emission. In this paper, the results of the Non-controlled biogenic gas emissions from the Lazareto landfill in Tenerife, Canary Islands, are presented. The purpose of this study was to evaluate the concentration of CH4 and CO2 in the soil gas of the landfill cover, the CH4 and CO2 efflux from the surface of the landfill and, finally, to compare these parameters with other similar landfills. In this way, a better understanding of the process that controls biogenic gas emissions in landfills is expected. METHODS: A Non-controlled biogenic gas emission survey of 281 sampling sites was carried out during February and March, 2002. The sampling sites were selected in order to obtain a well-distributed sampling grid. Surface landfill CO2 efflux measurements were carried out at each sampling site on the surface landfill together with soil gas collection and ground temperatures at a depth of 30-40 cm.The CH4 efflux was computed from CO2 efflux and from the ratio CH4/CO2 in the soil gas. Soil gas samples were collected at a depth of 30-40 cm using a metallic probe and 20 cc hypodermic syringes, and later stored in evacuated 10 cc vacutainers for laboratory analysis of bulk composition. The gas sample was introduced in a vacutainer filled with deionized water and displacing the water until the vacutainer was filled with the gas sample in order to avoid air contamination from entering. The surface landfill temperature of the landfill was measured at a depth of 40 cm using a digital thermometer type OMEGA 871A. Landfill gases, CO2 and CH4, were analyzed within 24 hours using a double channel VARIAN micro-GC QUAD CP-2002P, with a 10 meter PORAPLOT-Q column, a TCD detector, and He as a carrier gas. The analysis temperature was 40 degrees C and the injection time was 10 msec. Surface landfill CO2 efflux measurements were performed using a portable NDIR spectrophotometer Licor-800 according to the accumulation chamber method (Chiodini et al. 1996). The data treatment, aimed at drawing the flux map and computing the total gas output, was based on the application of stochastic simulation algorithms provided by the GSLIB program (Deutsch and Journel 1998). RESULTS: Diffuse CH4 and CO2 efflux values range from negligible values up to 7,148 and 30,573 g m(-2) d(-1), respectively. The spatial distribution of the concentration and efflux of CO2, CH4 and soil temperature, show three areas of maximum activity in the landfill, suggesting a non-uniform pattern of diffuse degassing. This correlation between high emissions and concentration of CO2, CH4 and soil temperatures suggests that the areas of higher microbial activity and exothermic reactions are releasing CO2 and CH4 to the atmosphere from the landfill. Taking into consideration the spatial distribution of the CO2 and CH4 efflux values as well as the extension of the landfill, the Non-controlled emission of CO2 and CH4 to the atmosphere by the Lazareto's landfill are of 167 +/- 13.3 and 16 +/- 2.5 t d(-1), respectively. DISCUSSION: The patterns of gas flow within the landfill seem to be affected by boundary materials at the sides. The basalt layers have a low permeability and the gas flow in these areas is extensive. In this area, where a basalt layer does not exist, the flow gas diffuses toward the sea and the flux emissions at the landfill surface are lower. This behavior reflects the possible dissolution of gases into water and the deflection of gases towards the surface at the basalt boundary. The proximity to the sea, the installation of a palm tree garden and, as a result, the contribution of water coming from the watering of this garden has reactivated the system. The introduction of sea water into the landfill and the type of boundary could be defining the superficial gas discharges. CONCLUSIONS: Results from this study indicate that the spatial distribution of Non-controlled emission of CO2 and CH4 at the Lazareto's landfill shows a non-uniform pattern of diffuse degassing. The northeast, central and northwest areas of the Lazareto's landfill are the three areas of high emissions and concentration of CO2 and CH4, and high temperatures. The correlation between high emissions and the concentration of CO2, CH4, and the high temperatures suggest that the areas of higher microbial activity and exothermic reactions are releasing more CO2 and CH4 to the atmosphere from the landfill. A high concentration of CO2 is probably due to the presence of methanotrophic bacteria in the soil atmosphere of the landfill. Patterns of gas flow within the landfill seem to be affected by boundary materials (basalt layers) of low permeability, and side boundaries of the flux emissions at the surface are higher. At the sides of seawater and sediment boundaries, flux emissions at the landfill surface are lower. This behavior reflects a possible dissolution of gases into the water and the deflection of gases towards the surface at the basalt boundary. With this study, we can compare the data obtained in this landfill with other landfills and observe the different levels of emission. The proximity to the sea and the installation of the palm tree garden palms and, as a result, the contribution of water coming from the watering of this garden has reactivated the system. Many landfills worldwide located in similar settings could experience similar gas production processes. RECOMMENDATIONS AND PERSPECTIVES: The need for investigating and monitoring sea water and sediment quality in these landfills is advisable. Concentrations and fluxes of contaminants and their impact in the area should be assessed. With this study we can compare the data obtained in these landfills with other landfills and observe the different levels of emission.     

Deposition rates on smooth surfaces and coagulation of aerosol particles inside a test chamber

Because aerosol particle deposition is an important factor in indoor air quality, many empirical and theoretical studies have attempted to understand the process. In this study, we estimated the deposition rate of aerosol particles on smooth aluminum surfaces inside a test chamber. We investigated the influence of turbulent intensity due to ventilation and fan operation. We also investigated two important processes in particle deposition: turbophoresis, which is significant for micron particles, and coagulation, which is relevant to ultrafine particles (UFP diameter <0.1 μm) at high particle concentrations. Our analysis included semi-empirical estimates of the deposition rates that were compared to available deposition models and verified with simulations of an aerosol dynamics model. In agreement with previous studies, this study found that induced turbulent intensity greatly enhanced deposition rates of fine particles (FP diameter <1 μm). The deposition rate of FP was proportional to the ventilation rate, and it increased monotonically with fan speed. With our setup, turbophoresis was very important for coarse particles larger than 5 μm. The coagulation of aerosol particles was insignificant when the particle concentration was less than 10⁴ cm^?3 during fan operation. The model simulation results verified that the aerosol dynamics module incorporated in our Multi-Compartment and Size-Resolved Indoor Aerosol Model (MC-SIAM) was valid. The behavior of aerosol particles inside our chamber was similar to that found in real-life conditions with the same ventilation rates (0.018–0.39 h^?1) and similar air mixing modes. Therefore, our findings provide insight into indoor particle behavior.     

Temperature and salinity: two climate change stressors affecting early development of the New Zealand sea urchin Evechinus chloroticus

Temperature and salinity are important environmental factors affecting the normal functioning of marine animals, particularly animals such as sea urchins living in shallow waters and tide pools. Here, we evaluated the effect of different combinations of temperature and salinity on early embryos of the endemic New Zealand sea urchin Evechinus chloroticus. Animals were collected at Matheson’s Bay (36º18′17′′S; 174º47′51′′E) in north-eastern New Zealand in February 2013. Embryos were exposed to five salinities (29, 31, 34, 35 and 37 ppt) and two temperatures (18 and 21 °C) during the first 24 h of development. Low salinity (29 ppt) affected all parameters (fertilization, development rate, gastrulation and normal development), with ca. 50 % of embryos surviving at 29 ppt, whereas seawater temperature only affected development rate and gastrulation. An increase in temperature from 18 to 21 °C minimized the negative effect of low salinity (≤31 ppt) on development rate and gastrulation of E. chloroticus. Overall, the results of this study suggest that early embryos of E. chloroticus have developmental plasticity to withstand reductions in salinity up to 29 ppt; however, it is still unknown whether the surviving embryos will be able to complete larval development at low salinities, particularly whether the embryos and larvae are carried into extreme environments such as estuaries where salinity is even lower. Multistressor studies are very important for climate change research as multiple environmental factors will act together in the wild, having major consequences for development and recruitment of marine invertebrates.     

Milk ejection solicitations and non-nutritive nursings: an honest signaling system of need in domestic pigs?

In domestic pigs, about 20% of nursing episodes end without milk transfer (non-nutritive nursings, NNNs). The function of NNNs has not been satisfactorily explained yet. Here, we suggest that NNNs may be a part of an honest signaling system that enables the sow to provide more frequent nutritive nursings (NNs) to those litters that can prove their need through exceptionally frequent milk ejection solicitations. We further propose that the system is kept stable through the accelerating costs attached to the solicitation in the form of NNNs. Based on this hypothesis, we predicted that (P1) with an increasing number of all nursings (ALL = NNNs + NNs) the number of NNs should increase and that (P2) with an increasing number of ALL the proportion of NNNs should increase. We tested P1 and P2 using a meta-analysis applied to data from eight studies that recorded the number of NNs and NNNs in domestic pigs. We confirmed both P1 (NNs increasing with ALL) and P2 (proportion of NNNs increasing with ALL). In combination, these results show a steeply accelerating cost of each additional nutritive nursing that piglets instigate. This cost sets limits to the piglets' ability to solicit higher maternal investment through more frequent nursing solicitations.     

Influence of cadmium on the growth of Agrocybe perfecta and two Pleurotus spp and translocation from polluted substrate and soil to fruitbodies

The presence of Cd in substrate (wheat straw) strongly depressed the growth and mineralization of substrate by Agrocybe perfecta. Pleurolus ostreatoroseus was only slightly depressed and Pleurotus sp. CCB 068 increased degradation by the two highest Cd concentration. Mineralization rate of fungal substrate were increased by indigenous soil flora. However increase in Cd concentrations added to the soil depressed mineralisation of organic matter. Cadmium also affected the fruitbody yield and only Pleurotus sp. was able to fructify in high Cd concentrations. Translocation and accumulation of Cd in fruitbodies increased with the increase of Cd concentrations in substrate.     

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.     

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).     

The Rengen Grassland experiment: bryophytes biomass and element concentrations after 65 years of fertilizer application

The Rengen Grassland Experiment in Germany, established in 1941, consists of the following fertilizer treatments applied under a two cut management: control, Ca, CaN, CaNP, CaNP-KCl, and CaNP-K₂SO₄. The aim of this study was (1) to identify effects of fertilizer application on biomass and species composition of bryophytes and (2) to investigate the impact of fertilizer application on macro- (N, P, K, Ca, Mg), micro- (Cu, Fe, Mn, Zn), and toxic (As, Cd, Cr, Pb, Ni) element concentrations in bryophyte biomass. In June 2006, Rhytidiadelphus squarrosus was the only bryophyte species recorded in the control. In treatment Ca, R. squarrosus was the dominant bryophyte species whereas Brachythecium rutabulum occurred sporadically only in a single plot of that treatment. The latter was the only bryophyte species collected in CaN, CaNP, CaNP-KCl, and CaNP-K₂SO₄ treatments. Dry matter accumulation of bryophytes was highest in the control (180 g m^???2) followed by Ca (46 g m^???2), CaNP (25 g m^???2), CaNP-KCl (15 g m^???2), CaNP-K₂SO₄ (9 g m^???2), and CaN (2 g m^???2) treatments. A negative correlation between biomass production of bryophytes and dry matter production of vascular plants was revealed up to a threshold value of 400 g m^???2. Above this limit, biomass production of bryophytes remained obviously unaffected by further increase in biomass production of vascular plants. A significant effect of treatment on As, Cd, Cr, Fe, Mn, Ni, Pb, P, Ca, Mg, K, and N concentrations was revealed. Concentrations of these elements were a function of amount of elements supplied with fertilizers. Bryophytes seem to be promising bio-indicators not only for airborne deposition of toxic element but also for fertilizer introduced as well.     

Assessment of bioavailable fraction of POPS in surface water bodies in Johannesburg City,South Africa,using passive samplers: an initial assessment

In this study, the semipermeable membrane device (SPMD) passive samplers were used to determine freely dissolved concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in selected water bodies situated in and around Johannesburg City, South Africa. The devices were deployed for 14 days at each sampling site in spring and summer of 2011. Time weighted average (TWA) concentrations of the water-borne contaminants were calculated from the amounts of analytes accumulated in the passive samplers. In the area of interest, concentrations of analytes in water ranged from 33.5 to 126.8 ng l^?1 for PAHs, from 20.9 to 120.9 pg l^?1 for PCBs and from 0.2 to 36.9 ng l^?1 for OCPs. Chlorinated pesticides were mainly composed of hexachlorocyclohexanes (HCHs) (0.15–36.9 ng l^?1) and dichlorodiphenyltrichloromethane (DDT) with its metabolites (0.03–0.55 ng l^?1). By applying diagnostic ratios of certain PAHs, identification of possible sources of the contaminants in the various sampling sites was performed. These ratios were generally inclined towards pyrogenic sources of pollution by PAHs in all study sites except in the Centurion River (CR), Centurion Lake (CL) and Airport River (AUP) that indicated petrogenic origins. This study highlights further need to map up the temporal and spatial variations of these POPs using passive samplers.