Wood plastic composites (WPCs) have been gaining market share in the exterior materials such as decking because of their good water and decay resisting properties. However, the problem of weathering properties, such as discoloration and chalking (formation of fine powder on the surface of WPCs) that often occur during the long term outdoor use, still remains to be solved. In this study, WPCs specimens with various wood contents were manufactured and half of them were subjected to sanding treatment to form a wood-like appearance. They were then exposed to outdoor weathering for 6 months to examine the effects of sanding process and wood content on the extent of discoloration and chalking of WPCs. It was shown that discolorations of sanded WPCs were greater than that of unsanded ones throughout the exposure. The discoloration behavior of WPCs with more than 30% of wood contents was clearly different from that with 20% of wood content. The amount of chalking products for sanded WPCs was higher than that for the unsanded ones, and the degree of chalking increased as wood contents increased. Possible causes of these behaviors were discussed and a surface degradation model of WPCs in outdoor exposure were proposed.

View full abstract

The utilization of cellulose nanofiber (CNF) has potential as one of the promising ideas to revitalize the hilly and mountainous areas in Japan. To clarify the problems and improvements related to CNFs derived from domestic timbers, a market trend survey was performed. Many respondents pointed out high prices of CNFs, the establishment of technology for dispersing, characteristic evaluation, the stabilization of quality, and confirming the safety of CNFs as problems and challenges. The survey results also suggested the importance of a business promotion system for improving productivity and obtaining a stable supply of inexpensive CNFs by scaling up through commercialization. Regarding user benefits of using "CNFs derived from domestic timbers produced in the hilly and mountainous areas", some respondents agreed with the view that the use of CNFs is environmentally conscious and the attitude of natural origin contributes to the improvement of corporate images. For future efforts of CNFs derived from domestic timbers, it is important to communicate to the manufacturer and consumers specific and value-added information such as environmentally conscious resources using sustainable forest resources.

View full abstract

We calculated mean annual solute concentrations in rainwater and streamwater between 2001 and 2014 at the Kahoku experimental watershed no. 3 and considered the inter-annual trend. Mean annual non-sea salt Ca²⁺ and Ca²⁺ concentration in rainwater peaked in 2006 and 2007. Other elements in rainwater showed no trend. Mean annual dissolved inorganic nitrogen input through rainwater was 8.9 kg ha⁻¹ y⁻¹, about 60% of which was in the NH₄⁺-N form. Mean annual non-sea salt SO₄²⁻ input was 34.0 kg ha⁻¹ y⁻¹, which was about 90% of the total SO₄²⁻ input. Mean annual K⁺ concentration in streamwater tended to increase gradually over the 15 years of observation. Other elements in streamwater showed no trend. We conducted quality control of the data and evaluated the completeness of the data using the quality assurance/quality control program of the Acid Deposition Monitoring Network in East Asia (EANET). Each year’s completeness of the data was generally high (more than 80%) in both rainwater and streamwater.

View full abstract