Safety concept and criteria for hazardous waste sites

The problem of waste disposal in Germany has been solved by using a combination of above-ground and underground disposal. Site selection criteria and precise criteria for the performance assessment of various types of waste disposal are available. In view of long-term safety of disposal, it is necessary to include geological and hydrogeological viewpoints in addition to purely engineering viewpoints.

In particular, the geotechnical site-specific safety assessment is described, as defined by the government in “Technical Regulations on Wastes” (TA-Abfall) in the section “Underground Disposal”. This safety assessment must cover the entire system comprising waste, cavern/mine and surrounding rock. For this purpose geo-mechanical models have to be developed.

According to the multi-barrier principle, the geological setting must be able to contribute significantly to isolation of the waste over longer periods. The assessment of the integrity of the geological barrier can only be performed by making calculations with validated geomechanical models.

Various engineering geological data are required for the selection of a site, for the design and construction of a repository, and for a safety analysis for the post-operational phase. These data can only be attained by the execution of a comprehensive site-specific geomechanical exploration and investigation program. The planning and design of an underground repository in rock salt layers are described, as an example for the various steps of this type of safety assessment.     

Mercury concentrations in environmental media at a hazardous solid waste landfill site and mercury emissions from the site

Mercury (Hg) concentrations in air, effluent water, landfill gas, leachate, groundwater, and soil at a hazardous solid waste landfill site in Korea were measured along with air–soil surface Hg exchange fluxes at the site. The concentrations and fluxes were considerably higher than have been found elsewhere in Korea. Gaseous Hg concentrations in the air peaked during the day, coinciding with Hg being released from the landfill surface. This suggests that air–soil exchange increased the Hg concentrations in the atmosphere. The air–soil exchange flux increased abruptly when solar radiation reached the soil surface. The Hg flux peaked about 3 h before the solar radiation peaked, possibly because reducible Hg was abundant at the soil surface. The Hg emission flux activation energy (E _a) was low, indicating that the Hg species present and Hg–soil binding were probably not as important (because of the high Hg content of the soil) as in previous studies. The methylmercury to total Hg ratios in the discharged effluent, groundwater, and leachate was clearly higher than typically found in coastal water and freshwater, suggesting bacteria caused active methylation to occur under the reducing conditions in the anaerobic landfill. The results suggested that considerable amounts of Hg are probably transported from the landfill to nearby environmental media and that this will continue if waste with a high Hg content continues to be added to the landfill without being pretreated.     

Travel times of seepage water through multilayered covering systems for hazardous waste sites

In a field experiment station near Frankfurt am Main, West Germany, a three-layer covering system was constructed in order to evaluate the amount of seepage water through clay barrier systems and their long-term effectiveness. The test area is equipped with two large-scale lysimeters, excess tubes for neutron-moisture and gamma-gamma-density measurements, tensiometers, surface runoff and drain discharge recorders as well as with meteorological instruments.The results of the three-year observation period give a complete impression of the infiltration and seepage processes within the different covering layers. With the help of hydrochemical and isotopical analyses as well as with tracer experiments the velocity of the soil water was determined. Three major waterpaths were found in the vadose zone of the vegetation support layer as well as in the saturated zone of the barrier layer. Very low velocities follow the matrix porosity of the soil. High velocities occur along preferential waterpaths which follow inhomogenities within the soil. Minor parts of the lysimeter outflow react directly to the precipitation inflow and therefore reveal, that unretarded flowpaths exist as well.These results lead to the conclusion that a heterogeneous flow is predominant in clay liners even under distinctive conditions. This has consequences on the applicability of hydraulic equations, as well as on the prediction of tightening effects of clay barriers.     

Locating hazardous waste treatment facilities and disposal sites in the State of Yucatan,Mexico

In this work, geographic information systems (GIS) and multi-criteria decision analysis (MCDA) were used in order to identify the appropriate location for hazardous waste (HW) treatment facilities and final disposal sites in the State of Yucatan, Mexico. For HW-treatment facilities, in addition to the distance to generators and treatment facilities, geographic conditions of the site, such as vegetation, soil type, accessibility, distance to urban or rural communities, and all the boundary elements as agricultural or livestock areas, were considered in GIS and MCDA. Final disposal was taken into account only for those HW that could not be avoided or treated. In order to find the most suitable areas, the Mexican Official Norm NOM-055-SEMARNAT-2003 criteria were observed too. It was found that the most suitable zones for HW-treatment facilities were at the centre of the State, whereas the most recommended areas for HW final disposal sites were at the south.     

Geochemical evaluation of suitability of sites for hazardous waste disposal: a case study of recent and old waste-disposal sites in Calabar Municipality, SE Nigeria

 Two waste-disposal sites (old and new) in Calabar Municipality, SE Nigeria were evaluated to assess their suitability as landfill sites and their impact on the groundwater. The field investigation included surface geological/hydrogeological and geochemical studies. Leachate and groundwater were sampled and analysed for 3 months (April, May and June, 1997) for geochemical characterisation. The results indicate that the two waste-disposal sites in the Calabar Municipality do not meet the requirements as landfill sites. Physico-chemical analyses for temperature, pH, conductivity, dissolved oxygen, biological oxygen demand after 5 days of incubation (BOD₅), sulphate, nitrates, nitrite, trace and major elements in the leachate known to impact human health and the environment, indicate high levels of pollution. The values for groundwater in the vicinity of the disposal sites were found to be within the World Health Organisation (WHO) permissible limit. Received: 29 March 1999 · Accepted: 3 January 2000     

Tracing leachates at waste sites using geophysical and geochemical modelling

Tracing leachates at landfills is usually carried out using either geophysical methods or chemical analyses of groundwater. There are often problems with fingerprinting pollution sources or clarifying the spreading pattern due to a wide variety of possibilities giving similar anomalies. The aims of the project were to evaluate the advantages of combining results from multigeophysical modelling and statistical/chemical modelling in order to identify pollution sources and the spreading pattern and to test a new technique for chemical fingerprinting. The project was carried out at a landfill in central Sweden using geophysical measurements and modelling of CVES, GPR and VLF as well as chemical modelling using M3 (multivariate mixing and mass balance calculations). The results indicate that by combining geophysical modelling and chemical calculations, the possibilities of fingerprinting the origin of pollution as well as delineating the spreading pattern are significantly increased.     

Selection of hazardous waste dumpsites based on parameters effecting soil adsorption capacity – a case study

A careful selection of waste dumpsites, particularly hazardous ones, is very important for sustainable water resources management. Several laboratory experiments were carried out on the field samples to study adsorption capacity using p-dichlorobenzene (a solvent used in various industrial processes) as the test contaminant. The effect of parameters such as organic matter, clay, and iron and aluminium oxides, which are known to influence the soil adsorption capacity, are studied in the present work. Several soil samples from the Patancheru Industrial Area (Hyderabad, India) were collected and characterized. Only three soils, which had a comparatively high percentage of organic matter, clay, iron and aluminium oxide contents were used for the adsorption studies. The results clearly indicated a decrease in the adsorption capacity of the soils by as much as 75% when organic matter was removed. The other parameters such as clay and iron and aluminium oxides also play an important role in adsorption (57 and 39.8% reduction respectively). It was observed that out of the selected factors organic matter in the soils has the maximum effect regarding the adsorption of p-dichlorobenzene. Since the selected soils contain comparatively more organic matter, clay and iron and aluminium oxides in the selected industrial area, these can be used as sites for dumping hazardous waste, which can be further treated by methods like bioremediation.     

How to speak for aquifers and people at the same time: Environmental justice and counter-network formation at a hazardous waste site

A common source of conflict at hazardous waste sites in the US Environmental Protection Agency’s Superfund program is the accuracy of scientific investigations and representations produced to inform cleanup decisions. Liable firms often produce these technical representations themselves, and communities surrounding sites frequently argue that such “voluntary” investigations are compromised by conflicts of interest. In order to challenge the representations of powerful firms, locally situated actors often develop trans-local connections with expertise and equipment concentrated at distant centers of calculation. Although some interpret the spatial politics of such connecting in terms of “jumping scales,” another important spatial dimension of this network construction is differential positioning. In a conflict over groundwater models at the St. Regis Superfund Site in Minnesota, the counter-network that emerged to challenge the owner’s representations of the site positioned some actors as “outsiders” and others as “insiders.” This differential positioning enabled the counter-network to balance the need to demonstrate the reliability and impartiality of its claims with the requirement to maintain its accountability to local public interests. I argue that these requirements result from the prevalent view of the science-policy interface, which assumes a rigid separation between science and politics. Nonetheless, the conflict over groundwater at St. Regis reveals how at the science-policy interface, speaking for things and speaking for people are thoroughly entangled.     

Subsurface geology of Louisiana hazardous waste landfills: A case study

Many hazardous waste sites in the south Louisiana Gulf Coast have been emplaced in sediments of Plio-Pleistocene to Recent age. Because of the fining upward nature of these regressive-transgressive fluvial-deltaic sequences and the purported confining capabilities of the shallow clay layers within them, this area would seem to be ideal for the location of surface waste landfills. However, detailed geologic mapping at a site in southeastern Louisiana documents how the three-dimensional distribution of sediment types and early diagenetic features, both of which were ultimately controlled by depositional history, can increase effective vertical permeability of finegrained sequences. Many bodies of sand that appear to be isolated in standard geotechnical cross sections can be shown to be part of spatially complex three-dimensional distributary networks, with fine-grained sediments representing overbank and backswamp deposits. Some clay layers are actually a composite of thinner clay beds, each subjected to subaerial exposure and the development of secondary porosity related to soil formation. There has been documented leakage of wastes down through the clays, and a recent study indicates that the effective vertical hydraulic conductivity of the clay layers exceeds 10^–5 cm s^–1, or from one to four orders of magnitude higher than values measured on samples from cores of the same sediment. An understanding of the depositional framework, facies architecture, and diagenetic history of geologic materials underlying waste disposal sites in Louisiana is required for rational development of monitoring and remediation plans.     

Investigation of mercury levels in soil around a municipal solid waste incinerator in Shenzhen,China

Within the management hierarchy of municipal solid waste (MSW), incineration with energy recovery is a desired and viable option often used in densely populated and economically developed cities. The gaseous and particulate mercury (Hg) emitted from MSW incinerators may accumulate in the soil entering via dry and wet deposition. To investigate the soil Hg level and estimate the effects of the local meteorological and topographical characteristics (e.g., winds and terrain) on the soil Hg distribution, two layers of soil samples around an MSW incinerator in Shenzhen, China were collected and analyzed. Results showed that the Hg levels ranged from 0.012 to 0.136 mg kg⁻¹ and from 0.013 to 0.100 mg kg⁻¹ in the surface and subsurface soils, respectively. Long-term exposure of the soil to atmospheric Hg from the MSW incinerator dominates the spatial pattern of soil Hg. The wind frequency directly affected Hg distribution but not decisively. Interestingly, the variations of Hg level with downwind distance away from the stack were highly consistent with the terrain profile (r ²: 0.412–0.748). The effects of winds and terrain on soil Hg distribution and their mechanisms are discussed and general Hg dispersion patterns for transport on terrain are further proposed.     

Geological and geophysical study of salt diapirs for hazardous waste disposal

Solving the problem of waste is one of the central tasks of environmental protection. It is becoming increasingly difficult to find suitable sites that are acceptable to the public. Salt and salt formations have relevant properties to be utilizing as a repository for each kind of waste. The favourable properties of salt make rock salt highly suitable as a host rock, in particular for non-radioactive and radioactive wastes. Tehran and suburb as an industrial state require a waste reservoir. The Great Kavir (the largest salt desert in Iran) with more than 50 diapirs has surrounded the eastern and southern part of Tehran Province. The Qom and Garmsar basins are the nearest salt diapirs to Tehran province, and there are suitable repository for waste disposal. Great Kavir diapirs have been investigated as a case study based on surface and subsurface studies for its suitability to host a repository for various types of waste. The procedure should be based on field work for surface investigation and also include geophysical studies for subsurface investigations. This research work is presented in regard to site selection in the Central Iran Salt Basins for deposition of only certain types of waste. Results of this study will indicate if the Central Iran Salt Basins are appropriate place to deposit industrial wastes in the deep bedded salt.     

Spatial modelling of hazardous elements at waste dumps using geostatistical approach: a case study Sarcheshmeh copper mine,Iran

Mining activities and resulting wastes can be considered as one of the most important sources of hazardous elements in the environment. Knowledge of the spatial distribution of toxic elements in waste dump systems is necessary to assess environmental hazard and strategy. To achieve this goal, this paper investigates spatial distribution of toxic elements using statistical and geostatistical analysis. A total of 58 soil samples were collected, and the amount of As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb and Zn was then determined at “Sarcheshmeh” copper mine waste dumps. In order to evaluate the presence of multivariate outliers, Mahalanobis distance technique (D ²) was applied and the multivariate outlier samples were removed. This resulted in an increase in correlation coefficient. To reduce dimension of data set, principal component analysis was applied and four principal components were determined which indicate 83.463% of the total variance of data set. Estimated PCs together with the toxic elements maps based on the ordinary kriging display aggregation of toxic elements in some parts, and validity of predictions was evaluated using the leave-one-out cross-validation method. The regression coefficients of estimated and observed values presented the reliability of the kriging estimates. Sequential Gaussian simulation method was applied for principal components due to similar results of estimated principal components and toxic elements. The results of simulation maps are almost identical to estimated outcomes.     

Assessing pollutions of soil and plant by municipal waste dump

Research is few in the literature regarding the investigation and assessment of pollutions of soil and plant by municipal waste dumps. Based upon previous work in seven waste dumping sites (nonsanitary landfills) in Beijing, Shanghai and Shijiazhuang, this study expounds the investigation and assessment method and report major pollutants. Using relative background values, this study assesses soil pollution degree in the seven dumping sites. Preliminary conclusions are: (1) pollution degrees are moderate or heavy; (2) pollution distance by domestic waste that is dumped on a plane ground is 85 m; (3) the horizontal transport distance of pollutants might be up to 120 m if waste leachates are directly connected with water in saturated soils; (4) vertical transport depth is about 3 m in unsaturated silty clayey soils. Furthermore, using relative background values and hygiene standards of food and vegetable this study assesses the pollutions of different parts of reed, sorghum, watermelon and sweet-melon. It is found: (1) in comparison with the relative background values in a large distance to the waste dumping sites, domestic wastes have polluted the roots and stems of reed and sorghum, whereas fine coal ash has polluted the leaves, rattans and fruits of watermelon and sweet-melon; (2) domestic wastes and fine coal ash have heavily polluted the edible parts of sorghum, water melon and sweet-melon. As, Hg, Pb and F have far exceeded standard values, e.g., Hg has exceeded the standard value by up to 650–1,700 times and Cd by 120–275 times, and the comprehensive pollution index is up to 192.9–369.7; (3) the polluted sorghum, watermelon and sweet-melon are inedible.     

Simulation on forecast and control for groundwater contamination of hazardous waste landfill

The groundwater flow and solute transport models were established by Visual Modflow, which was used to forecast the transport process of Cr⁶⁺ in groundwater and simulate the effects of three control measures of contaminants transport after percolation solution leakage happened in the impermeable layer of the landfill. The results showed that the contamination plume of Cr⁶⁺ would reach the pool’s boundary in 10 years, and the distance of contamination transport was 1,450 m. However, the contamination plume will not be obviously expanded between 10 and 20 years. While the ground was covered by hardened concrete, the contamination plume would not reach the pool’s boundary in 20 years. When the leakage-proof barrier was set in the bottom of an unconfined aquifer, the concentration of Cr⁶⁺ was higher than that of the leakage-proof barrier unset, but the result was opposite when setting the leakage-proof barrier in the bottom of confined aquifer. The range of the contamination plume was effectively controlled by setting drainage ditches in which water discharge was 2,298.05 m³ d^?1, which produced monitoring wells which are not contaminated in 20 years. In sum, combining ground hardening with drainage ditches could produce the best effect in controlling contaminants diffusion, and meanwhile, the drainage ditches daily discharge was reduced to 1,710.19 m³ d^?1.     

Chemical and environmental compatibility of red mud liners for hazardous waste containment

Red mud residue from alumina production has been proposed as an alternative liner material. The chemical and environmental compatibility of red mud upon exposure to representative organic (methanol, heptane, TCE, and acetic acid) and inorganic liquids (CaCl₂ and seawater) was studied. Chemical compatibility assays comprised Atterberg limits and sedimentation and hydraulic conductivity tests for red mud interacted with the chemical liquids, whereas the environmental compatibility was assessed through the leaching of metals from red mud as permeated with the liquids. Methanol greatly reduced the plasticity at concentrations ≥80 % by volume, but it did not increase the hydraulic conductivity of compacted red mud. High concentrations (≥60 % v/v) of acetic acid reduced the plasticity and enhanced the sedimentation of red mud. Conversely, acetic acid concentrations ≤40 % caused dispersion, but damaged the hydraulic properties and structure of red mud. The percolation of a pH 2 acetic acid solution did not adversely affect the hydraulic performance of the red mud liner. Neither diluted heptane nor TCE affected the red mud. However, pure organics suppressed the plasticity and induced aggregation of red mud, suggesting a great detrimental effect on red mud liners. The red mud exhibited great resistance to attack by inorganic salt solutions. Some concerning leaching of metals (primarily Al and Cr) occurred as water, acetic acid, and CaCl₂ solutions percolated through red mud, but effluent metals concentration quickly dropped to permissible levels. In general, red mud exhibited a high resistance against chemical attack; nevertheless, exposure to low-dielectric-constant organic chemicals should be avoided.     

Measuring and modeling atmospheric particles and particle bound mercury Hg(p) at five characteristic-sampling sites

The main purpose of this study was to monitor ambient air particles and particulate-bound mercury Hg(p) in total suspended particulates (TSP) concentration, dry deposition at five characteristic-sampling sites. In addition, the calculated/measured dry deposition flux ratios of ambient air particles and particulate-bound mercury Hg(p) using three dry deposition models during the years of 2009–2010 were also studied. The results showed that the order of seasonal variations for mean particulate-bound mercury Hg(p) concentrations in TSP at Bei-shi (suburban/coastal), Chang-hua (downtown) and He-mei (residential) were all shown as spring > fall, winter > summer, respectively. However, the order of seasonal variations mean particulate-bound mercury Hg(p) concentrations in TSP that occurred at Gao-mei (wetland) were shown as spring > fall > winter > summer, respectively. Finally, the results of this study also indicated that using the Noll and Fang model exhibited batten prediction results for ambient air particles and particulate-bound mercury Hg(p) dry deposition when compared with the other depositions models at any of the characteristic-sampling sites for this study.     

A comparison of winter mercury accumulation at forested and no-canopy sites measured with different snow sampling techniques

Atmospheric mercury (Hg) is delivered to ecosystems via rain, snow, cloud/fog, and dry deposition. The importance of snow, especially snow that has passed through the forest canopy (throughfall), in delivering Hg to terrestrial ecosystems has received little attention in the literature. The snowpack is a dynamic system that links atmospheric deposition and ecosystem cycling through deposition and emission of deposited Hg. To examine the magnitude of Hg delivery via snowfall, and to illuminate processes affecting Hg flux to catchments during winter (cold season), Hg in snow in no-canopy areas and under forest canopies measured with four collection methods were compared: (1) Hg in wet precipitation as measured by the Mercury Deposition Network (MDN) for the site in Acadia National Park, Maine, USA, (2) event throughfall (collected after snowfall cessation for accumulations of >8 cm), (3) season-long throughfall collected using the same apparatus for event sampling but deployed for the entire cold season, and (4) snowpack sampling. Estimates (mean ± SE) of Hg deposition using these methods during the 91-day cold season in 2004–2005 at conifer sites showed that season-long throughfall Hg flux (1.80 μg/m²) < snowpack Hg (2.38 ± 0.68 μg/m²) < event throughfall flux (5.63 ± 0.38 μg/m²). Mercury deposition at the MDN site (0.91 μg/m²) was similar to that measured at other no-canopy sites in the area using the other methods, but was 3.4 times less than was measured under conifer canopies using the event sampling regime. This indicates that snow accumulated under the forest canopy received Hg from the overstory or exhibited less re-emission of Hg deposited in snow relative to open areas. The soil surface of field-scale plots were sprayed with a natural rain water sample that contained an Hg tracer (²⁰²Hg) just prior to the first snowfall to explore whether some snowpack Hg might be explained from soil emissions. The appearance of the ²⁰²Hg tracer in the snowpack (0–64% of the total Hg mass in the snowpack) suggests that movement of Hg from the soil into the snowpack is possible. However, as with any tracer study the ²⁰²Hg tracer may not precisely represent the reactivity and mobility of natural Hg in soils.     

Long-term behaviour and mineralogical reactions in hazardous waste landfills: a comparison of observation and geochemical modelling

 Drill cores from a Bavarian hazardous waste landfill were investigated for their mineralogical composition. Because of the formation of many new minerals, geochemical equilibrium calculations were performed to find the most stable state of the waste body. A comparison of mineralogical observations and geochemical modelling was undertaken. The remaining solubilities of the newly formed secondary mineral assemblages were calculated. Newly formed minerals were shown using electron microscopy. Received: 26 November 1999 · Accepted: 15 May 2000     

Identification of hazardous waste landfill site: a case study from Zanjan province, Iran

The study of landfill sites is one of the most important studies in landfill engineering, and the landfill site selection involves combination of engineering, science, and politics. This paper describes a comprehensive hazardous waste landfill site selection methodology with the combined utilization of geographic information system and multiple criteria analysis methods, as applied to the Zanjan province in Iran. The six main data categories that were used are geological/engineering geological, geomorphological, hydrological/hydrogeological, climatological, pedological, and social/economical criteria, which included 31 input layers in total. A suitability map for hazardous waste landfilling was prepared for study area with five classes from most suitable to completely unsuitable. Finally, out of the three sites, one site was selected which was chosen by the local authorities. Our work offers a comprehensive methodology and provides essential support for decision-makers in the assessment of hazardous waste management problems in Zanjan province in I.R. Iran and other developing cities in other countries.