Land Contamination: Technical Guidance on Special Sites: Acid Tar ...

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4.5.1 Approach• Acid tars are chemically extremely complex with many thousands of individualchemicals, most of which (the asphaltenes) have been characterised to a very limitedextent. When deciding what to analyse for, it is important to have regard to theobjectives of the analysis that is to be undertaken. For example, if the immediatehazard posed to human health is the only hazard that needs to be assessed, thencharacterisation in terms of pH, volatile organic compounds and gas evolution(sulphur dioxide, hydrogen sulphide, methane) may be all that is required;• even very simple analysis can indicate the likely source of the acid tars e.g. BTX atrelatively high concentrations (% levels) will indicate that the acid tars originate frombenzole refining and that risks to groundwater may be higher than for other types ofacid tars due to the mobility and toxicity of BTX compounds;• very simple analysis can also reveal variability between different lagoons e.g. acidcontent can vary between 10 and 90 per cent, water content between 5 and 40 per centand organics content from 15 to 70 per cent;• a more sophisticated analytical approach may be needed in some cases. If anassessment is being made of risks to groundwater or surface water, greater emphasiswill need to be placed on characterising the organic component. In particular,characterising liquid tars and free oils present is likely to be important. This is likelyto include both analysis of samples of free phase hydrocarbons from within the lagoonbut also free phase and dissolved components in groundwater or surface water outsidethe lagoon. The heavy end asphaltenes (high molecular weight viscous tars) may be ofless interest in this context although this is subject to confirmation of thehydrogeological regime and the absence of preferential migration routes off-site suchas fissures, mine-workings etc;• if the purpose of the assessment is to evaluate potential remedial technologies, thencharacterising various layers within the lagoon will be important in assessing thepracticality of handling and achieving intimate mixing in any neutralisation or“dispersing by chemical reaction” (DCR) process. Chemical analysis will also beuseful in this context in assessing the degree of heterogeneity which any treatmentprocess will need to be able to address;• if the tars are to be characterised for waste disposal purposes, then the acceptancecriteria at landfill must be taken into account when developing the analytical schedule.4.5.2 Analytical techniquesAcid tars do pose specific analytical problems, as the highly sulphonated polar residues makechromatographic analysis difficult. Nesbit et al (1995) detail non-conventional analysis usedto characterise the nature of the organic material, including:• class separation by thin layer chromatography/flame ionisation detection to separatearomatic hydrocarbons, saturated hydrocarbons and tarry residues;R&D <strong>Technical</strong> Report P5-042/TR/04 26
• gas chromatography by simulating fractional distillation to produce a boiling pointdistribution curve (which can be compared to a series of relevant standards); and• thermogravimetric analysis (analyse percent weight loss as a function of temperature)to indicate the thermal behaviour of different waste materials.The first and third of these are low cost screening-type methods. The above analysis allowsthe major phases of contamination to be identified. In the particular study, the phases foundwere:• a free tar phase (high molecular weight asphaltenes and polar hydrocarbons plus somemid-distillate hydrocarbons);• a free-flowing oil mainly comprising mid-distillate saturated hydrocarbons (up to 85%of the cyclohexane extract was present in this form); and• an aqueous phase with very high sulphate concentrations (greater than 10% by weight)and very acidic (pH
Page 1 and 2: Land Conta
Page 3 and 4: CONTENTSFOREWORDiGLOSSARYii1. Intro
Page 5 and 6: FOREWORDPart IIA of the Environment
Page 7 and 8: CresolsCreosoteDCRDesorptionDesulph
Page 9 and 10: PVCRCRASelosafeSodium saltsSodium h
Page 11 and 12: 1. INTRODUCTION1.1 BackgroundThis r
Page 13 and 14: SECTION 2: INDUSTRIAL PROCESS/FACIL
Page 15 and 16: 1.5 Linkages Between the Gu
Page 17 and 18: 2.1.2 Overview of acid tar lagoon s
Page 19 and 20: Overall CommentsAcid tars can be of
Page 21 and 22: White Oil• Acid tar lagoons from
Page 23 and 24: Box 2.5 Scenario: Acid tar disposal
Page 25 and 26: 3. CHEMICAL AND PHYSICAL CHARACTERI
Page 27 and 28: Table 3.1 - General Physical Charac
Page 29 and 30: The chemicals listed in Table B.1,
Page 31 and 32: 4.2.3 Common mistakesIt is possible
Page 33 and 34: Geophysical methods, such as resist
Page 35: Investigation locations will need t
Page 39 and 40: 5.2.2 Water environmentThere is lit
Page 41 and 42: 5.3 Assessment of Investigation Dat
Page 43 and 44: 6. REMEDIATION ASPECTSKEY QUESTIONS
Page 45 and 46: 6.2.5 Solidification and stabilisat
Page 47 and 48: Box 6.1 Example of Remediation of A
Page 49 and 50: 6.3 Natural AttenuationNatural atte
Page 51 and 52: Table 6.1 - Remedial Options/Techni
Page 53 and 54: Table 6.2 - Remedial Options/Techni
Page 55 and 56: 6.4 ValidationThe principles of val
Page 57 and 58: • all personnel should follow a d
Page 59 and 60: Verschueren (1983) Handbook of Envi
Page 61 and 62: USEPA. Innovative Site Remediation

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