The purposes of this study are to investigate the sources, distributions, fluxes and phosphorus burial efficiency (PBE) of particulate phosphorus in the Gaoping (GP) coastal sea. The GP River carried about 3.14 ¡Ñ 104 ton yr-1 (1.03 ¡Ñ 109 mol yr-1) particulate P into the GP coastal sea. The total P flux was primarily determined by the river runoff during the May-yu (monsoon) and typhoon seasons. The river P was approximately consisted of 90.8% particulate inorganic-P (PIP), 7.4% particulate organic-P (POP), 1.5% dissolved inorganic-P (DIP) and 0.3% dissolved organic-P (DOP). The particulate-P existed mainly in 10-63 £gm particles. In the GP costal sea, particulate P in surface sediments was found to be 80-90% as PIP and 10-20% as POP. The highest distribution of PIP was located on the flanks of GP Canyon at the upper slope (200-600 m) region. This distribution may be caused by plumes of river sediments or turbidity currents overflowing the canyon. The sedimentation rates of sediments ranged from 0.032 to 1.62 g cm-2 yr-1 in the GP coastal sea and the highest rates were also located on both sides of the GP Canyon. The burial fluxes of total phosphorus (TP) ranged from 0.02 to 0.84 g cm-2 yr-1, consisted approximately by 88% PIP and 12% POP. The burial fluxes of this study area were generally similar to those in other continental margins (Bohai Sea, Yellow Sea, Mississippi Delta). The total depositions of sediment and TP were approximately 6.6 ¡Ñ 106 ton yr-1 and 4227 ton yr-1, respectively, in the study area. The burial TP was equivalent to 0.06% of deposited sediments. The buried TP can be proportionate approximately into 15% in the continental shelf (< 200 m), 69% in the continental slope (200-1000 m), and 16% in the slope basin (> 1000 m). The continental shelf (<200 m) region was apparently influenced by wave and tidal processes and prevented from sediment accumulation. The burial efficiency of TP (PBE) in the GP costal sea is estimated accordingly to PBE (%) = 100 ¡Ñ PBF / (PBF+JP), where PBF is the burial flux of TP and JP is the diffusion flux of TP from porewater. The PBE decreases with the depth of sampling location and the maximum PBE locates on the station of southern canyon (779-1), the station of northern canyon (791-L18) and the station within the canyon (732-38). The PBE(s) are similar to those found in the Nazar&#x00E9; Canyon, showing a high PBE in coastal and/or canyon regions. The budget model shows that the major sources of particulate-P are derived from the GP River and the net ecosystem production (NEP) from the euphotic zone of study area. The annual river load and NEP input to the study area are 1.03 ¡Ñ 109 mol P yr-1 and 1.5 ¡Ñ 108 mol P yr-1, respectively. However, annual TP accumulation in the GP costal sea is just 1.48 ¡Ñ 108 mol P yr-1, corresponding to 12.5% of river load and NEP input. In addition, about 80% of GP River loads do not deposit into GP sediments and may be exported out of the study area.

Environmental contamination issues related to phosphorus (P) in surface waters substantiates the need to identify minimally-sufficient P fertilization amounts for production of containerized nursery crops and better understand the effect of routine amendments (i.e., dolomite [DL] and micronutrient fertilizer [MF]) added to pine bark substrates on chemical fate of P fertilizer. Four studies were conducted to accomplish two overarching objectives: 1) determine the minimum P fertilization amount and corresponding pore-water P concentration needed to achieve maximal growth of common containerized nursery crops and 2) determine the effect of DL and MF amendments in pine bark on P retention during irrigation and P fractions in substrate pore-water. In a fertigation, greenhouse study, calculated lowest P-fertilizer concentration that sustained maximal growth in Hydrangea paniculata ‘Limelight’ (panicle hydrangea) and Rhododendron ‘Karen’ (azalea) was 4.7 and 2.9 mg·L⁻¹ , respectively, and shoot growth Ilex crenata ‘Helleri’ (holly) was the same when fertilized with 0.5 to 6.0 mg·L⁻¹ P. Porewater P concentrations corresponding with treatments that sustained maximal growth of panicle hydrangea, azalea and holly were as low as 0.6, 2.2 and 0.08 mg·L⁻¹ P, respectively. In a separate study, utilizing low-P controlled-release fertilizers (CRFs), shoot growth of Hydrangea macrophylla ‘P11HM-11’ (bigleaf hydrangea) produced in two ecoregions was maximal when fertilized with as little as 0.3 g CRF-P per 3.8-L container, a 50% P reduction from the industrystandard CRF. Holly required 0.2 or 0.4 g CRF-P depending on ecoregion. Mean pore-water P concentrations that corresponded with highest SDW were 0.8 and 1.2 mg·L⁻¹ for hydrangea and holly, respectively. When irrigating fallow pine bark columns containing CRF for 48 d, amending pine bark with DL and MF reduced orthophosphate-P (OP-P) leachate concentrations by ≈ 70%, most of which was retained within the substrate. In a greenhouse study, containerized Lagerstroemia ‘Natchez’ (crape myrtle) were grown for 91 d in pine bark containing CRF. In pine bark amended with DL and MF, pore-water OP-P and total P concentrations, measured approximately weekly, were reduced by, on average, 64% and 58%, respectively. Total dry weight values of plants grown with DL plus MF or MF-only were 40% higher than those grown with no amendments; however, tissue P amounts and relative P uptake efficiency were the same among plants in these three treatments. Therefore, sorption of OP-P by DL and MF reduced water-extractable OP-P but did not limit P uptake by plants. / Ph. D.