Landfill Leachate Plume Research Articles

In situ and laboratory studies on the fate of specific organic compounds in an anaerobic landfill leachate plume, 2. Fate of aromatic and chlorinated aliphatic compounds

The transformation of specific organic compounds was investigated by in situ and laboratory experiments in an anaerobic landfill leachate pollution plume at four different distances from the landfill. In a previous paper (Part 1, also published in this issue) we described the in situ microcosm and laboratory batch microcosm experiments performed focusing on redox conditions, microbiology and the fate of 7 phenolic compounds. In this paper we present the results on the fate of 8 aromatic compounds and 4 chlorinated aliphatic compounds. Nitrobenzene was transformed at all distances from the landfill in methanogenic, and Fe(III)-and NO 3 −-reducing conditions. Toluene was transformed slowly in one out of three in situ experiments at the distance of 250 m from the landfill in the Fe(III)-reducing part of the plume after a lag phase of ∼ 3 months. Benzene, o-xylene, p-dichlorobenzene, o-dichlorobenzene, naphthalene and biphenyl were not transformed at any of the investigated distances from the landfill, neither in in situ nor in laboratory experiments. In the methanogenic part of the aquifer 2 m from the landfill, 1,1,1-trichloroethane, tetrachloromethane and tetrachloroethene were transformed in in situ experiments while trichloroethene was not. Lag phase periods were up to 40 days for 1,1,1-trichloroethane and up to 100 days for tetrachloroethene. No or only short lag phases (< 10 days) were observed for tetrachloromethane. Tetrachloromethane was furthermore transformed at distances of up to 250 m from the landfill in Fe(III)-reducing conditions but not in NO 3 −-reducing conditions at 350 m from the landfill. Abiotic processes apparently contributed to the transformation of tetrachloromethane. A local variation in the transformation of the chlorinated aliphatic hydrocarbons was observed at 2 m from the landfill. In general, good accordance with respect to compound transformation was observed between in situ and laboratory experiments, but in a few cases more compounds were transformed in in situ experiments that in the corresponding laboratory experiments.

In situ and laboratory studies on the fate of specific organic compounds in an anaerobic landfill leachate plume, 1. Experimental conditions and fate of phenolic compounds

The transformation of specific organic compounds was investigated by in situ and laboratory experiments in an anaerobic landfill leachate pollution plume at four different distances from the landfill. This paper presents the experimental conditions in the in situ microcosm and laboratory batch microcosm experiments performed and the results on the fate of 7 phenolic compounds. Part 2 of this series of papers, also published in this issue, presents the results on the fate of 8 aromatic compounds and 4 chlorinated aliphatic compounds. The redox conditions in the plume were characterized as methanogenic, Fe(III)-reducing and NO 3 −-reducing by the redox sensitive species present in groundwater and sediment and by bioassays. With a few exceptions the aquifer redox conditions were maintained throughout the experiments as monitored by redox sensitive species present in groundwater during the experiments, by redox sensitive species present in the sediment after the experiments and by bioassays performed after the experiments. Transformation of nitrophenol was very fast close to the landfill in strongly reducing conditions, while transformation was slower in the more oxidized part of the plume. Lag phases for the nitrophenols were short (maximum 10 days). Phenol was only transformed in the more distant part of the plume in experiments where NO 3 −, Fe(III) and Mn(IV) reduction was dominant. Lag phases for phenol were either absent or lasted up to 2 months. Dichlorophenols were only transformed in experiments representing strongly reducing, presumably methanogenic, redox conditions close to the landfill after lag phases of up to 3 months. Transformation of o-cresol was not observed in any of the experiments throughout the plume. Generally, there was good accordance between the results obtained by in situ and laboratory experiments, both concerning redox conditions and the fate of the phenolic compounds. However, for phenol and 2,4-dichlorophenol, transformation was observed in some in situ experiments but not in the corresponding laboratory experiments. In some experiments, this coul be explained by differences in the redox conditions developing during the experiments. Nitrophenols were apparently transformed abiotically in the most reduced part of the plume, at 2 m from the landfill.

Evidence for microbial iron reduction in a landfill leachate-polluted aquifer (Vejen, Denmark).

Aquifer sediment samples obtained from the anaerobic part of a landfill leachate plume in Vejen, Denmark, were suspended in groundwater or in an artificial medium and incubated. The strictly anaerobic suspensions were tested for reduction of ferric iron [Fe(III)] oxides, which was measured as an increase in the concentration of dissolved Fe(II). Iron reduction did not occur when the medium was inoculated with inactive sediment and when the organisms in the inoculated medium were killed by formaldehyde, by chloroform, or by pasteurization, whereas the level of iron reduction was significant when living bacteria were present. Mixed cultures were obtained from the sediment samples, and differences in apparent iron reduction rates among the different cultures were maintained during several transfers. In addition, iron reduction was observed in unamended incubation mixtures containing whole sediment and groundwater. Synthetic amorphous Fe(III) oxides, as well as naturally occurring sediment-bound Fe(III) oxides, could be reduced by the cultures. Together, our results provide evidence that iron-reducing bacteria are present and microbial iron reduction occurs in the polluted aquifer sediments which we studied.

Speciation of Fe(II) and Fe(III) in Contaminated Aquifer Sediments Using Chemical Extraction Techniques

The iron mineralogy of aquifer sediments was described by chemical extraction techniques. Single-step extractions including 1 M CaCl 2 , NaAc, oxalate, dithionite, Ti(III)-EDTA, 0.5 M HCl, 5 M HCl, hot 6 M HCl, and a sequential extraction by HI and Cr II HCl were tested on standard iron minerals and nine aquifer sediments from different redox environments sampled in a landfill leachate plume. Ion-exchangeable Fe(II) is easily quantified by anaerobic CaCl 2 extraction. A rapid indication of the redox status of a sediment sample can be achieved by a 0.5 M HCl extraction. This extraction gives an indication of the content of amorphous Fe(III) and reduced Fe(II) species such as FeS and FeCO 3 , though the fractions are not quantified

Detection of Contaminant Plumes by Borehole Geophysical Logging

AbstractTwo borehole geophysical methods—electromagnetic induction and natural gamma radiation logs—were used to vertically delineate landfill leachate plumes in a glacial aquifer. Geophysical logs of monitoring wells near two land‐fills in a glacial aquifer in west‐central Vermont show that borehole geophysical methods can aid in interpretation of geologic logs and placement of monitoring well screens to sample landfill leachate plumes.Zones of high electrical conductance were delineated from the electromagnetic log in wells near two landfills. Some of these zones were found to correlate with silt and clay units on the basis of drilling and gamma logs. Monitoring wells were screened specifically in zones of high electrical conductivity that did not correlate to a silt or clay unit. Zones of high electrical conductivity that did not correlate to a silt or clay unit were caused by the presence of ground water with a high specific conductance, generally from 1000 to 2370 μS/cm (microsiemens per centimeter at 25 degrees Celsius). Ambient ground water in the study area has a specific conductance of approximately 200 to 400 μS/cm. Landfill leachate plumes were found to be approximately 5 to 20 feet thick and to be near the water table surface.

The organic geochemistry of a sanitary landfill leachate plume

Leachate from the North Bay municipal landfill has contaminated an unconfined, sandy aquifer throughout the 700 m flow system from the site to a discharge zone at a creek. The major organic contaminants identified are aromatic hydrocarbons, especially substituted benzenes. The high groundwater velocity of about 75 m yr −1 and the low organic sorption properties of the sand have permitted non-transformed contaminants to spread throughout the total flow system. There is considerable temporal and spatial variability in groundwater chemistry. Most of the aqueous organic carbon has a nominal molecular weight of <2000 and the general decrease in the mass of this fraction relative to Cl indicates it is being mineralized significantly during transport. IR spectra indicate a general trend of increased aromaticity and decreased OH content of organic matter along the flow system. The aqueous organic matter has a significant apparent complexing capacity and so it is somewhat surprising that toxic metal concentrations in leachate-impacted groundwaters are low. In the leachate plume, this complexing capacity is taken up by major cations and H + and to a far lesser extent by toxic metals such as Pb, Cd or Zn. Dispersion is clearly responsible for considerable decrease in contaminant concentration along the flow system. Biotransformation under strictly anaerobic conditions has probably caused 1,1,1-trichloroethane and trichloroethylene to be restricted to the immediate vicinity of the landfill. A simple method of comparing the concentrations of pairs of organics at points along the flow system provides relative transformation rates for pairs of organics even with variable inputs from the landfill and dispersive dilution. Relative to ethylbenzene, o-xylene is rapidly lost from this system. O-xylene may be less persistent than m- or p-xylene; a result unexpected from previous studies of these dimethylbenzenes. In the initial, strictly anarobic segment of the flow system 1,2,4-trimethylbenzene and 1,4-dichlorobenzene are equally persistent, but in the final, less anaerobic segment, the former appears to be degraded more rapidly than the latter. Contaminant distributions in aquifers reflect the results of a number of processes integrated in a complex manner and so are difficult to interpret in terms of specific processes. However, they do provide evidence for what processes are most significant in real groundwater systems and they will also provide critical tests of how well laboratory-derived information relates to real groundwater contamination situations.

Occurrence and distribution of organic chemicals in two landfill leachate plumes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOccurrence and distribution of organic chemicals in two landfill leachate plumesMartin. Reinhard, James F. Barker, and Naomi L. GoodmanCite this: Environ. Sci. Technol. 1984, 18, 12, 953–961Publication Date (Print):December 1, 1984Publication History Published online1 May 2002Published inissue 1 December 1984https://doi.org/10.1021/es00130a011RIGHTS & PERMISSIONSArticle Views602Altmetric-Citations178LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Assessing hazardous waste problems

Relatively inexpensive methods for delineating subsurface features near hazardous waste sites are needed. During the past 10 years the extensive development of remote-sensing geophysical equipment including field methods, analytical techniques, and associated computer processing, has greatly improved the ability to characterize hazardous waste sites. The use of seismic refraction and resistivity to investigate a subsurface geologic structure is illustrated. A second example is offered using ground-penetrating, electromagnetic induction, and magnetic surveys to locate and estimate the amount of buried wastes. Resistivity surveys have been conducted to map a landfill leachate plume. Electromagnetic induction has aided in the choice of locations of monitoring wells that were used to map another contaminant plume. While in the past most geophysical methods for plume detection have been applied to inorganic contaminants, such as chlorides and sulfates, in groundwater, attention is now being turned to the detection of organics. 8 figures, 1 table.