A case study of long-term CCA preservative leaching from treated hardwood poles in a humid tropical condition

Chromated copper arsenate (CCA)-treated Malaysian hardwoods have long been used as utility poles, posts, construction piles and motorway fencing in soil contact exposed to the threats of decay fungi and termites. Despite global concerns citing predominantly temperate conditions of long-term leaching of CCA toxic heavy metals from wood into surrounding soils and groundwater since the 1990’s, the preservative leaching severity in the tropics has been far less appreciated due to dearth of work in this area. In 2013 (after 30 years exposure), levels of total copper, chromium and arsenic within 20 treated hardwood poles of Sarawak and in soils surrounding these poles, installed in 1980 and 1981 at a plot located in Timber Research and Technical Training Centre, Kuching, Sarawak, Malaysia, were sampled. The ground is waterlogged after heavy rainfall. It is shown that there is insignificant variations of CCA salt retention in wood between 1300 cm above ground and 0-20 cm below ground (P<0.05). Nevertheless levels of these elements are significantly (P<0.05) elevated in soils surrounding, especially up to 25 mm away from, the poles than at distant sampling points (150 – 300 mm) from poles as well as at sites well away from the poles containing very low levels (<6 – 13.4 ppm) of such heavy metals. Metal levels were also highest at the soil surface directly in contact with the poles (0 – 50 mm soil depth position) and decreased with remaining 2 soil depth positions 150 – 200 mm and 300 – 350 mm. Mean extractable arsenic levels ranged from 14.5 to 100.1 ppm, chromium levels from 23.3 to 148.3 ppm and copper from 21.8 to 104.7 ppm. Results, rather than indicating relatively higher CCA leaching, concurred with that reported temperate experience and showed that soil closest to the treated poles are most contaminated, albeit slightly, after 30 years of in-ground exposure

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe