C. Paul Nathanail

Comparison of Batch Mode and Dynamic Physiologically Based Bioaccessibility Tests for PAHs in Soil Samples

A fed state in vitro methodology capable of use in commercial testing laboratories has been developed for measuring the human ingestion bioaccessibility of polyaromatic hydrocarbons (PAHs) in soil (Fed ORganic Estimation human Simulation Test- FOREhST). The protocol for measuring PAHs in the simulated gastro-intestinal fluids used methanolic KOH saponification followed by a combination of polymeric sorbent solid phase extraction and silica sorbent cartridges for sample cleanup and preconcentration. The analysis was carried out using high pressure liquid chromatography with fluorescence detection. The repeatability of the method, assessed by the measurement of the bioaccessibility of 6 PAHs (benz[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[ah]anthracene, and indeno[1,2,3-c,d]pyrene) in eleven gas works soils, was approximately 10% RSD. The method compared well with the results from an independent dynamic human simulation reactor comprising of the stomach, duodenal and colon compartments tested on the same soils. The measured bioaccessible fraction of the soils varied from 10-60% for soils containing 10-300 mg kg(-1) PAH (the sum of the six studied) with total organic carbon concentrations in the soils ranging from 1-13%. A multiple regression model showed that the PAH bioaccessible fraction could be explained using the PAH compound, the soil type and the total PAH to soil organic carbon content. The method described here has potential for site specific detailed quantitative risk assessment either to modify the risk estimation or to contribute to the risk evaluation.

Incorporating bioaccessibility in detailed quantitative human health risk assessments

Current English policy and practice allows, and in places encourages, site specific estimates of arsenic oral bioavailability to be used in detailed quantitative human health risk assessment. English land contamination legislation does not differentiate between natural and man made arsenic soil contamination. English planning guidance requires developers to demonstrate that new houses are fit for purpose, including ensuring that there are no unacceptable risks to human health from soil contaminants. Naturally occurring arsenic in soils at a new housing site in southwest England was demonstrated not to pose unacceptable risk to human health by site specific estimates of bioavailability and region specific estimates of soil to plant uptake factors. Independent lines of evidence were used to justify the arsenic exposure factors for oral bioavailability and soil to plant uptake. Using site specific assessment criteria based on tools and information that give a better estimate of the actual exposure avoided both unnecessary public concern and considerable local authority expenditure across the outcrop of such soils as part of their legal duties.

Mine spoil acts as a sink of carbon dioxide in Indian dry tropical environment.

Economically important mining operations have adverse environmental impacts: top soil, subsoil and overburden are relocated; resulting mine spoils constitute an unaesthetic landscape and biologically sterile or compromised habitat, and act as source of pollutants with respect to air dust, heavy metal contamination to soil and water bodies. Where such spoils are revegetated, however, they can act as a significant sink for atmospheric carbon dioxide (CO2) through combined plant succession and soil formation. Revegetation, drainage, reprofiling and proper long term management practices help recapture carbon, improve soil quality and restore the soil organic matter content. A survey along an age gradient of revegetated mine spoils of 19 years in Singrauli, India by the authors showed an accumulation of total C in total plant biomass, mine soil and soil microbial biomass by 44.5, 22.9 and 1.8 t/ha, respectively. There was an increase in total sequestered C by 712% in revegetated mine spoils after 19 years, which can be translated into annual C sequestration potential of 3.64 t Cha(-1) yr(-1). Carbon sequestered in revegetated mine spoil is equivalent to 253.96 tonnes/ha capture of atmospheric carbon dioxide (CO2). This indicates that mine spoil can act as a significant sink for atmospheric CO2. Annual C budget indicated 8.40 t Cha(-1) yr(-1) accumulation in which 2.14 t/ha was allocated to above ground biomass, 0.31 t/ha in belowground biomass, 2.88 t/ha in litter mass and 1.35 t/ha in mine soil. This shows that litter mass allocation is much important in the revegetated site. Decomposition of root and litter mass contributes C storage in the mine soil. Therefore, revegetation of mine soils is an important management option for mitigation of the negative impacts of mining and enhancing carbon sequestration in mine spoils.

Sustainability and Remediation

Sustainable remediation has come to exist as a popular term used to describe contaminated site management that is demonstrably sustainable, i.e. where some form of sustainability appraisal has been used in decision making to identify the “most sustainable” approach for any particular management intervention required. The “most sustainable” approach is one that, in the view of the stakeholders involved in making or considering management decisions, has the optimal balance of effects and benefits across the three elements of sustainability: environment, economy and society. This chapter describes how the Brundtland Report concept of sustainable development can be linked with contaminated site remediation practice, both how sustainability can be assessed and used as a tool in decision making; and also how sustainability thinking is creating new contaminated site remediation approaches, for example, marrying concepts of Risk Management and renewable energy production. The chapter discusses the individual “indicators” or metrics that contribute to an understanding of sustainability, the tools available for combining these into a sustainability appraisal, and the types of boundary conditions that need to be considered in setting the scope of sustainability appraisal. The chapter also discusses the linkage of “sustainability” with “Risk Management”, the importance of engaging stakeholders in sustainability appraisal, and an emerging set of international initiatives in the field. Finally it presents a series of sustainable remediation case studies (technologies and decision making tools) and a view of the possible future for “sustainable remediation”.

Effects of drying and comminution type on the quantification of Polycyclic Aromatic Hydrocarbons (PAH) in a homogenised gasworks soil and the implications for human health risk assessment.

This research investigates the effect of nine physical treatment types comprising a serial combination of three drying (air, freeze and oven) and two comminution (milling and sieving) methods on the quantification of PAH in a soil sample from a former gasworks. Results show that treatment type has a significant effect on PAH concentration (p⩽0.05). Naphthalene, 1-methylnaphthalene and 2-methylnaphthalene concentrations were significantly higher for air drying and freeze drying treatments than for oven drying. It is suggested that naphthalene and similarly volatile PAH losses were greater for oven drying due to the application of fanned warm air which is thought to cause volatilisation. Analytical precision was significantly improved for milled samples compared with sieved samples. The reason milling results in greater precision is assigned to the improved solvent extraction efficiency when natural grain size is altered due to crushing. The analytical data were compared to residential generic assessment criteria (GAC) used for risk-based land management. It was shown that the naphthalene GAC was lower than all freeze drying and air drying concentrations but was within the oven drying concentration range, illustrating that a false negative could be concluded during risk evaluation is oven dried data were used. Overall, it is recommended that air drying or freeze drying is a better choice than oven drying if the quantification of low molecular weight PAH forms an important objective of sample characterisation for risk-based land management, otherwise freeze drying and milling is recommended.

Sustainable Brownfield Regeneration

Sustainable Brownfield regeneration involves making abandoned, underused, derelict and, only occasionally contaminated, land fit for a new long-term use in order to bring long-lasting life back to the land and the community it lies within. Brownfields sites have been affected by former uses of the site or surrounding land; are derelict or underused; are mainly in fully or partly developed urban areas; may have real or perceived contamination problems; and require intervention to bring them back to beneficial use. While Brownfields do not have to be contaminated, contaminated sites are the focus of this book so it is important to point out that risk based contaminated land management is an essential prerequisite to ensuring efficient deployment of resources to deliver land that is fit for use. Vision and strong leadership are needed to build up and maintain momentum during the long time for remediation, reclamation and redevelopment and before regeneration can begin. Brownfields occur throughout the world and, while local definitions of Brownfield may vary, there is growing consensus on the opportunity they offer and great benefit on sharing experiences of and good practice in their regeneration. Specialist Brownfield regeneration process managers are needed to help deliver more successful projects. Suitable enabling policy and facilitating public sector finance usually lag behind the structural change that causes Brownfields yet must respond quickly if regions are to survive and deliver the stability and opportunity their citizens have come to expect.

Derivation of a site-specific assessment criterion for benzo[a]pyrene in red shale at a former coking works.

A former coking works in England is being remediated to enable its redevelopment. We have developed site specific human health risk assessment criteria (SSAC) for benzo[a]pyrene (BaP) based on detailed characterisation of red shale proposed for reuse in an area allocated for residential development. Samples of red shale were analysed using the Colon-enhanced Physiologically Based Extraction Test (CEPBET) to estimate the bioaccessibility of BaP. The results indicate that between 5% and 28% of the red shale BaP is bioaccessible. A cautious value of 50% was used in calculating an SSAC. The CLEA human health assessment model was used to calculate the SSAC and any changes to the default input parameters have been discussed and justified. Based on the fact that BaP appears to be a point-of-contact, rather than a systemic, carcinogen in animal studies, individual assessment criteria were estimated for the oral, inhalation and dermal routes of entry in-line with current UK guidance. An overall SSAC of 2.5 mg/kg for BaP in red shale for the residential with home-grown produce land use was then derived as the lowest of the three route-specific assessment criteria. This value is specific to both the site and the material being assessed. The approach adopted however can be applied on other sites and for other materials to inform detailed quantitative risk assessments.

The use and misuse of CLR 7 acceptance tests for assessment of risks to human health from contaminated land

Generic and detailed quantitative assessments of the risks posed to human health from land contamination involve the comparison of representative contaminant concentrations against relevant generic or site-specific assessment criteria respectively. Technical guidance on statistical tests to determine whether contaminant concentrations exceed relevant assessment criteria fails to recognize the effects of sample clustering and heterogeneity in ground conditions on the validity of the test results. Reference to the conceptual model should be made to determine the likely level of contamination to which the critical receptor may be exposed within an averaging area.

Letter to the Editor on “Precipitation Forecasting Using Wavelet-Genetic Programming and Wavelet-Neuro-Fuzzy Conjunction Models” by Ozgur Kisi & Jalal Shiri [Water Resources Management 25 (2011) 3135–3152]

We write in response to “Precipitation Forecasting Using Wavelet-Genetic Programming and Wavelet-Neuro-Fuzzy Conjunction Models” (Kisi and Shiri 2011). Gene Expression Programming (GEP: Ferreira 2001) and Adaptive Neuro-Fuzzy Inference System (ANFIS: Jang 1993; Jang and Sun 1995) solutions were compared and contrasted using a common methodology: an extended version of that employed by Partal and Kisi (2007). Kisi and Shiri (2011) combined precipitation records and an integrated wavelet-based series according to lag. We comment below on issues regarding their GEP precipitation forecasting solution for the rain gauge station at Izmir:

A typology of different development and testing options for symbolic regression modelling of measured and calculated datasets

Data-driven modelling is used to develop two alternative types of predictive environmental model: a simulator, a model of a real-world process developed from either a conceptual understanding of physical relations and/or using measured records, and an emulator, an imitator of some other model developed on predicted outputs calculated by that source model. A simple four-way typology called Emulation Simulation Typology (EST) is proposed that distinguishes between (i) model type and (ii) different uses of model development period and model test period datasets. To address the question of to what extent simulator and emulator solutions might be considered interchangeable i.e. provide similar levels of output accuracy when tested on data different from that used in their development, a pair of counterpart pan evaporation models was created using symbolic regression. Each model type delivered similar levels of predictive skill to that other of published solutions. Input-output sensitivity analysis of the two different model types likewise confirmed two very similar underlying response functions. This study demonstrates that the type and quality of data on which a model is tested, has a greater influence on model accuracy assessment, than the type and quality of data on which a model is developed, providing that the development record is sufficiently representative of the conceptual underpinnings of the system being examined. Thus, previously reported substantial disparities occurring in goodness-of-fit statistics for pan evaporation models are most likely explained by the use of either measured or calculated data to test particular models, where lower scores do not necessarily represent major deficiencies in the solution itself.