Dynamic characteristics of net anthropogenic phosphorus input to the upper Yangtze River Basin from 1989 to 2019: Focus on the phosphate ore rich area in China.

Phosphorus (P), a non-renewable essential resource, faces heavy exploitation and contributes to eutrophication in aquatic environments. Assessing P input is vital for a healthier P cycle in the Upper Yangtze River (UYR), a phosphate ore rich basin, where P mining and P chemical enterprises have prominent pollution problems. This study modified the net anthropogenic phosphorus input (NAPI) model to include ore mining P input (Pore). We analyzed the evolutionary characteristics of P input in five sub-basins of UYR from 1989 to 2019 using prefecture-level data, and assessed the uncertainty of the data. NAPI in all sub-basins exhibited an upward and then downward trend during 1989-2019, with the inflection point occurring in 2015 or 2016, showing a net increase of about 1.1 times (568-1162 kg P km-2 yr-1) in the whole UYR basin. Among the components of NAPI, P fertilizer inputs (Pfer) and food/non-food and feed P inputs (Pf/nf&feed) contributed comparably, though the growth rate of Pfer was most notable basin-wide. Pore proportion increased significantly (about 3-fold), with a peak of 20%, especially in Wujiang sub-basin. The multi-year (1989-2019) average NAPI in UYR rose sequentially from west to east, with hotspot areas mainly concentrated in the Sichuan-Chongqing urban agglomeration and cities of Hubei province. The regional P input closely related to the population density and the level of agricultural development, certainly the phosphate mining was also unignorable. This study emphasizes that based on current status of NAPI development in UYR, targeted management for different regions should focus on improving agricultural P use efficiency and rational exploitation of P mineral resources.

Streptomyces rock phosphate ore biomining evaluation in vitro.

The process of extracting metals from rock phosphate ore (RPO) by using microorganisms to convert them into soluble compounds is called biomining. Phosphorus is one of the elements proposed to be extracted from RPO. To understand the role of Streptomyces phospholyticus, 12 isolates of Streptomyces were isolated from RPO, their ability to grow on specific phosphate solubilization medium e.g., National Botanical Research Institute's phosphate growth agar (NBRIP) was studied, and the best strain with a 3 cm clear zone was selected. Its ability to grow at increasing RPO concentrations from 0.01 to 1 kgl-1 was investigated. This strain showed good growth, with extracellular red pigmentation for all concentrations, but no clear zone. In the modified liquid NBRIP, however, the Streptomyces growth patterns of the two concentrations of 0.25 kg and 1 kgl-1 RPO showed growth of single spherical red colonies with rhizoids on the surface, the colonies somehow grew and became embedded in the fine RPO granules. This ability to grow can resist gamma irradiation with a dose of 32 KGy. Within 3 days of growth, acidic and alkaline phosphatase were 76.2 and 67.1 µg p-nitrophenol g-1 ml-1, respectively. The RPO analysis showed that the %P in the ore was 16.5% at the beginning of the experiment, and after Streptomyces biotreatment, this percentage decreased to 8.4%, with a decomposition rate of 50.7%. This study, to our knowledge, is the first to investigate the efficiency of Streptomyces in mining phosphate rock ore in the laboratory, even at high concentrations, and to examine the role of irradiation as a preservative in increasing this efficiency.

Recovery of uranium from phosphate ore in the Sheikh Habil-Iran mine: part I- multivariable optimization of leaching process using the response surface method.

In this research, the recovery of uranium from the phosphate ore of the Sheikh Habil-Iran mine using flotation/calcination-leaching processes has been investigated. A 75-150 µm phosphate ore particle size, sodium oleate as a collector with a concentration of 2,000 g/ton of rock, pH = 10, and 5 min flotation time were obtained as the optimum parameters of flotation using the reverse method, leading to phosphate ore with a grade of 180 ppm UO2, 36.1% P2O5, 7.22% SiO2, and CaO/P2O5 = 1.23. The optimum calcination parameters were selected as 100 µm phosphate ore particles size at D80, 900°C temperature, and 2 h heating time, which resulted in phosphate ore with a grade of 173 ppm UO2 and 31.9% P2O5. An L/S (liquid to solid ratio) = 5, 3 M sulfuric acid concentration, 80°C temperature, and 5 h leaching time were obtained as the optimum leaching parameters using the response surface methodological approach. The efficiency of uranium recovery from phosphate ore pre-treated by flotation and calcination methods was 84.2% and 75.2%, respectively. The results indicated that flotation has superiority over calcination as a pre-treatment method of phosphate ore in the Sheikh Habil-Iran mine.

Phosphate distribution and sources in the waters of Huangbai River, China: using oxygen isotope composition of phosphate as a tracer.

We investigated the distributions of phosphate (PO4-P) and used the oxygen isotope composition of phosphate (δ18OP) to quantify PO4-P sources in the waters of Huangbai River. According to the environmental characteristics of Huangbai River basin, the sampling stations in the Huangbai River were divided into three groups: sampling stations in the phosphate mining area, in the outcrop area of phosphate rock, and in the residential/agricultural area. The average PO4-P concentration was highest (2.34 ± 1.00 µmol/L) in the outcrop area of phosphate ore, intermediate in the residential/agricultural area (1.06 ± 1.21 µmol/L), and lowest in the phosphate mining area (0.58 ± 0.31 µmol/L). The δ18OP measured in the Huangbai River waters ranged from 6.0 to 20.9‰, with the highest average value in the outcrop area of phosphate rock (average: 14.6‰ ± 3.1‰). The majority of the measured δ18OP values in the Huangbai River deviated greatly from the expected equilibrium values, indicating that δ18OP in this area could be used to trace PO4-P sources. We used two end-member mixing models to quantify the contribution of PO4-P from different sources. In the phosphate mining area, the average fractions of PO4-P from phosphate ore and sewage were 49.5% ± 23.8% and 50.5% ± 23.8%, respectively. In the outcrop area of phosphate rock, the average fractions of PO4-P from phosphate ore and sewage were 60.1% ± 21.7% and 39.9% ± 21.7%, respectively. In the residential/agricultural area, the average fractions of PO4-P from fertilizer and sewage were 49.2% ± 23.2% and 50.8% ± 23.2%, respectively. These results indicate that phosphate mining activities was not an important source for PO4-P in the waters of Huangbai River. The natural weathering of phosphate rock, fertilization, and domestic sewage contributed more to the high PO4-P concentrations in the Huangbai River waters.