Tectona grandis is a valuable timber species with heartwood that is used worldwide. Most of the previous studies on its heartwood and sapwood have focused on dominant or mean trees, while trees with different social status might show different vertical and horizontal distributions of heartwood and sapwood. Studies on their heartwood and sapwood properties could be conducive to increasing heartwood yield at stand level. In 31-year-old plantations of T. grandis in southwest Guangxi, China, the trees were divided into three groups including dominant, mean and suppressed trees. Stem analysis was conducted for sampled trees in each of these groups to explore the differences in the horizontal and vertical distribution of their heartwood and sapwood. The results indicated that the heartwood radius, heartwood and sapwood areas of T. grandis showed significant differences in horizontal and vertical directions among trees of different social status. Heartwood began to form when xylem radius was 2–3 cm, and the heartwood radius ratio tended to be stable when the xylem radius reached about 8 cm. Heartwood radius and area, sapwood area and section heartwood volume all decreased with increasing tree height. The ratios of heartwood radius and area were relatively stable for sections under 50% of tree height. The sapwood width did not vary largely in horizontal and vertical directions among the three social status tree groups, which mainly fluctuated in the range of 1–4 cm. The heartwood volume proportions for dominant, mean and suppressed trees were 60%, 55% and 51%, respectively. There was a significant exponential relationship between heartwood volume and diameter at breast height (DBH) regardless of social status. The model HV = 0.000011 × DBH^2.9787 (R² = 0.8601) could accurately estimate heartwood volume for all T. grandis with different social statuses at this age. These findings could provide evidence for stand management and high-quality and large-sized timber production of T. grandis.

Zr-modified materials have an adsorption affinity for phosphate ions, but because of the cost of carrier materials, they are difficult to apply on a large scale. Herein, coal gasification coarse slag (CGCS) was used as a carrier material and modified with Zr, and its dephosphorization performance was studied. A series of adsorbents with different CGCS/ZrOCl₂·8H₂O mass ratios were prepared, from which the adsorbent with a CGCS/ZrOCl₂·8H₂O mass ratio of 5 : 4 (denoted as CGCS-Zr4) was identified as the most promising for phosphate adsorption. The specific surface area of CGCS-Zr4 was much greater than that of raw CGCS (100.12 vs. 12.43 m² g⁻¹). CGCS-Zr4 showed good adsorption selectivity towards phosphate when competitive anions co-existed, and exhibited good reusability; the adsorption capacity in the fourth adsorption–desorption cycle remained above 11.98 mg g⁻¹. The adsorbent was also suitable for the continuous treatment of up to 830 and 743 bed volumes of synthesised and actual wastewater, respectively. The results of Fourier-transform infrared and X-ray photoelectron spectroscopy indicated that CGCS not only plays the role of a carrier, but also that Ca and Al in CGCS play an important role in phosphate adsorption. Compared with other carrier materials such as biochar and synthetic zeolite, CGCS has the advantages of a large stockpile, low cost, and easy availability. In addition, the preparation of CGCS-Zr4 is simpler and more energy-saving. Zr-modified CGCS is a promising dephosphorization material.