Contamination of heavy metals and metalloids in biomass and waste fuels: Comparative characterisation and trend estimation.

The use of contaminated biomass and waste fuels is essential for waste management, waste to energy (WtE) and mitigating carbon emissions. The contamination of heavy metals and metalloids is specially concerned by environmental regulation and waste to energy processes. In this study, comparative characterisation is performed for three typical contaminated biomass and waste fuels. i.e. recycled woods, combustible municipal solid waste, and industrial and commercial wastes. The contamination characteristics are further analysed using statistical methods (e.g. significance, correlation, profile, and principal component analyses) to identify specific contamination features, relations among the contaminants and potential contamination sources. Contamination trend is estimated based on the continuously monitoring fuel qualities, the driving forces for regulating and reduction of the contaminations, and potential changes in major contamination sources. The comparative characterisation combined with statistical analyses provides a better way to understand the contamination mechanisms. The approach can also relate the fuel contamination with the contamination sources and their changes for trend estimation. Generally, the toxic heavy metals and metalloids are expected to be significantly reduced due to stricter regulations, but there is no general trend for the reduction of other metals and metalloids because of the complicated changes in contamination sources and waste recycling streams in the near future.

Private and Non-Private Disc Herniation Patients: Do they Differ?

OBJECTIVES: In the 2006 yearly report from the Swedish National Register for Lumbar Spine Surgery it was claimed that international studies show obvious differences between private and non-private patients with regard to results from back surgery. Therefore our aim was to reveal such possible differences by comparing the two categories of patients at a private clinic. MATERIAL AND METHODS: The material comprises 1184 patients operated on for lumbar disc herniation during the period of 1987 to 2007. Basic pre-operative data were obtained from the medical records and follow-up was performed by a questionnaire around 5 years post-operatively. RESULTS: Small but statistically significant differences between private and non-private patients were seen pre-operatively regarding the proportions of a/ men and women in the samples, b/ those with physically demanding jobs, c/ those on sick leave and d/ those with lumbar pain. Over the years the admitted private patients had a decreasing mean duration of symptoms which was not seen in the non-private patients. No apparent differences (n.s.) were seen between the two categories of patients pre-operatively regarding age, presence and level of leg pain or the proportion who smoked. Post-operative improvement in leg and lumbar pain was very similar in private and non-private patients as was satisfaction with the results and the proportion of patients returning to work. CONCLUSION: Despite small pre-operative differences concerning some variables and a significant difference in symptom duration between private and non-private disc herniation patients, the final clinical results were very similar.