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Potentially toxic metals in farmland soil have recently become a significant environmental concern in China. In this study, the occurrence and distribution of eight (8) heavy metals (HMs) were investigated from 54 topsoil samples obtained across 18 provinces. Human health and ecological hazards associated with HMs were assessed through different risk characterization indices and their sources predicted. The statistically mean concentrations of HMs ranged from 0.08 to 70.05 mg kg−1, which were below the determined threshold values for agricultural lands according to the Chinese National Standard (GB 15618–2018). The respective ecological risk index ( E r i) of HMs revealed that they posed a lower risk ( E r i < 40) but their potential cumulative ecological risk (RI) was determined as a considerable risk (300 ≤ RI < 600). Spatial distribution and heterogeneities of HMs were found to be highly concentrated in the southern parts (e.g., Yunnan, Guangdong) of China, particularly for Arsenic (As), Zinc (Zn), and Chromium (Cr). PMF model was found capable of efficiently elucidating respective sources of HMs across the studied provinces as most were impacted by geological/pedogenic and anthropogenic activities (e.g., agricultural, industrial discharge fallouts). Probabilistic health risk assessment indicated that the non-carcinogenic risk (NCR) and total carcinogenic risk (TCR) of HMs in both adults and children were low and acceptable. [Display omitted] [ABSTRACT FROM AUTHOR]

Rare earth elements and yttrium (REY) in coal, fly ash as well as coal preparation products have attracted much attention due to the increasing demand worldwide. In this paper, the distribution of REY in different size and density fractions, their mode of occurrence, and the insight they provide on the sediment source region of the Reshuihe coal in southern China are studied. The results show that the physical separation method caused light-REY (LREY) to be enriched in the low-density and large-sized coal particles, whereas medium-REY (MREY) and heavy-REY (HREY) are enriched in small-sized and high-density fractions. In addition, LREY are more closely associated with organic matter, while MREY and HREY occur more often in aluminosilicate minerals. Moreover, the sediment source of the Reshuihe coal was mainly derived from the felsic–intermediate rocks at the top of the Emeishan basalt sequence. Further, REY in the feed coal are generally not enriched, though REY are enriched in density fractions of 1.4 kg/L. The combustion products of coal with a density of 1.4 kg/L obtained by gravity separation have a potential economic value as promising raw materials for REY. • LREY (MREY and HREY) are enriched in the larger (smaller) size fractions with low (high) density grades. • LREY are more closely associated with organic matter, while MREY and HREY tend to occur in aluminosilicate minerals. • The combustion products of coals with a density of 1.4 kg/L have a potential economic value. [ABSTRACT FROM AUTHOR]

Mengzi locates in the south 20 km away from the outlet of Nandong subsurface river, and has been suffering from water deficiency in recent years. It is necessary to find out the water resources underground according to the geological characteristics such as the positions and buried depths of the underground river to improve the civil and industrial environments. Due to the adverse factors such as topographic relief, bare rocks in karst terrains, the geophysical approaches, such as Controlled Source Audio Magnetotellurics and Seismic Refraction Tomography, were used to roughly identify faults and fracture zones by the geophysical features of low resistivity and low velocity, and then used the mise-a-la-masse method to judge which faults and fracture zones should be the potential channels of the subsurface river. Five anomalies were recognized along the profile of 2.4 km long and showed that the northeast river system has several branches. Drilling data have proved that the first borehole indicated a water bearing channel by a characteristics of rock core of river sands and gravels deposition, the second one encountered water-filled fracture zone with abundant water, and the third one exposed mud-filled fracture zone without sustainable water. The results from this case study show that the combination of Controlled Source Audio Magnetotellurics, Seismic Refraction Tomography and mise-a-la-Masse is one of the effective methods to detect water-filled channels or fracture zones in karst terrains. [ABSTRACT FROM AUTHOR]

• There is no standard for the ratio of SS:SA of the i n situ nylon bag technique(ISNBT) for the evaluation of ruminant feed and there are varying approaches used in China and around the world. • Increasing the ratio of sample size to nylon bag area (SS:SA) lowered the effective dry matter degradability of rye straw at SS:SA ratios of 29.17 and 37.5 mg/cm2. There was a trend for higher effective degradability (ED) at the lower SS:SA ratios for soybean meal crude protein. • These results show that with a standard nylon bag with external dimensions of 6 × 10 cm, increasing the amount of sample, thus raising the ratio of sample size to bag surface area (SS:SA ratio) reduces feed degradation. • Our recommendation is to operate at a SS:SA ratio of about 25 mg/cm2 for concentrate feed and a lower ratio (20 mg/cm2) for roughage. We thought that our work can accelerate the development of the standard of ISNBT. The in situ nylon bag technique (ISNBT) is traditional and necessary for the evaluation of ruminant feed, but there are exists some disunity operation schemes. Therefor, we select one way that varying SS:SA to determine the effects of it on feed degradation in the rumen. Eight Yunnan semi-fine wool sheep fitted with permanent ruminal cannul as were used and the nylon bags containing different sample size with fixed surface area. The results demonstrated that increasing the ratio of sample size to nylon bag area (SS:SA) lowered the effective dry matter (DM) degradability of rye straw. There was no difference in degradability with SS:SA ratios of 12.5 and 20.85 mg/cm2 but DM degradability was reduced (P < 0.05) at SS:SA ratios of 29.17 and 37.5 mg/cm2. At these higher SS:SA ratios DM degradability was also reduced (P < 0.05), at incubation durations of less than 36 h. A similar picture was obtained for rye straw crude protein (CP) degradability, although the effects of sample size and incubation time were less marked. In the case of the concentrated feedstuff, soybean meal, ruminal degradation was almost complete at 36 h and there was a trend for higher effective degradability (ED) at the lower SS:SA ratios. These results show that with a standard nylon bag with external dimensions of 6 × 10 cm, increasing the amount of sample, thus raising the ratio of sample size to bag surface area (SS:SA ratio) reduces feed degradation. It is recommended that sample size influenced feed degradation in the nylon bag technique and a sample weight of 2.5 g (SS:SA about 20 mg/cm2) should be used for evaluation of roughage and 3 g (SS:SA about 25 mg/cm2) for evaluation of concentrated diets for sheep using this technique. [ABSTRACT FROM AUTHOR]

• Two kinds of magnetite are identified at porphyry-related deposits in the Zhongdian region. • Some magnetite grains had undergone dissolution-reprecipitation processes. • The compositions of magnetite are affected by temperature, oxygen fugacity and hydrothermal alteration. The Zhongdian region in northwestern Yunnan (SW China) hosts a number of important porphyry and skarn deposits. In this study, we integrate petrographic observations, SEM-EDS elemental mapping, EPMA and LA-ICP-MS geochemical analyses on magnetite from several key deposits in the region. Magnetite grains from the Pulang porphyry Cu-Au, Lannitang porphyry Au-Cu, Langdu Cu skarn, Disuga porphyry, and andesite of Tumugou Formation were analyzed to unravel the magnetite formation mechanism, and the relative oxygen fugacity of the porphyry/skarn ore-related hydrothermal fluids in this region. Two types of magnetites (Magnetite I and II) have been identified. Magnetite I is commonly distributed in the chlorite and/or sericite alteration zone(s). Magnetite I grains are characterized by being textually inhomogeneous. The Magnetite I core (with local ilmenite exsolution lamellae) is Ti-Cr rich, indicative of a dominantly igneous origin. The Magnetite I core and its surrounding primary igneous minerals (biotite, amphibole and plagioclase) underwent late alteration. Magnetite I grains are characterized by core-rim texture, sharp core-rim contact, and irregular grain boundaries. These textural features indicate that Magnetite I may have undergone dissolution-reprecipitation processes, during which the Magnetite I core was chemically purified via losing Ti and gaining Fe. Magnetite II (in potassic and sericite alteration zones) is textually homogeneous with relatively low contents of Ti, Mg, Al, V, Ni, and Mn. We suggest that Magnetite II was formed by hydrothermal alteration. Compared to Magnetite II grains from the Pulang and Langdu deposits, those from the Lannitang deposit have lower Mn and V but higher Sn contents, indicative of higher oxygen fugacity of the hydrothermal fluids. We propose that binary plots such as Ti vs. Sc, V vs. Sn and Ga vs. Sn can distinguish the different origins of magnetites. From an exploration perspective, Magnetite II from the altered Disuga porphyries has similar texture and composition to its counterpart from the potassic-altered Pulang porphyries. This, together with the presence of Cu-sulfide inclusions in the Disuga Magnetite I, suggests significant mineralization potential in these porphyries. [ABSTRACT FROM AUTHOR]