[Effects of the Application of Irrigation Water Containing Zn at the Key Growth Period on the Uptake and Transport of Cd in Rice].

In this study， a field experiment was conducted to examine the effects of the application of irrigation water containing Zn at the key growth period （booting stage and filling stage） on exchangeable Cd content in the soil， Cd concentration in pore water， and Cd uptake and transport in rice in a Cd-contaminated paddy field in Liuyang City， Hunan Province. The results indicated that： ① the application of irrigation water containing Zn during the key growth period could inhibit the releasing process of exchangeable Cd from the soil into pore water. Compared with that in the control， the content of exchangeable Cd in soil was slightly changed， but the concentration of Cd in soil pore water at the mature stage was significantly reduced by 16.7%-57.6%. ② The application of irrigation water containing Zn at the key growth period could significantly reduce the Cd content in various parts of rice. Cd contents in root， stem， and brown rice with the application of irrigation water containing 20 mg·L-1 Zn before the booting and the filling stage （BF1） were significantly decreased by 56.0%， 83.8%， and 85.2%， respectively. ③ Compared with the application of 100 mg·L-1 irrigation water containing Zn， the application of 20 mg·L-1 irrigation water containing Zn significantly reduced the uptake and transport of Cd in rice， and the translocation factor （TF） of Cd from rice roots to stems was also significantly reduced by 12.5%-56.3%， with the B1 and BF1 treatments reaching significant levels. These results suggested that the application of irrigation water containing Zn could significantly reduce the uptake and accumulation of Cd in rice， and the application of 20 mg·L-1 irrigation water containing Zn before the booting and filling stage could effectively realize the safe production of Cd-contaminated paddy fields.

A positive association between RDW and coronary heart disease in the rheumatoid arthritis population: A cross-sectional study from NHANES.

Previous research has indicated that higher red blood cell distribution width (RDW) increases the risk of coronary heart disease. However, no studies have established a link between RDW and coronary heart disease in the rheumatoid arthritis population. This research aims to explore the association between RDW and coronary heart disease among individuals with rheumatoid arthritis. We selected demographic data, laboratory data, lifestyle, and medical history from the National Health and Nutrition Examination Survey (NHANES), specifically including age, gender, poverty, RDW, race, BMI, diabetes, education, coronary heart disease, hypertension, cholesterol, smoking, and drinking. RDW and coronary heart disease were found to have a positive association in the rheumatoid arthritis population (OR = 1.145, 95%CI: 1.036-1.266, P = .0098), even after adjusting for factors such as age, gender, race, education level, smoking, and drinking. Subgroup analysis showed a stronger positive association, particularly in individuals aged 55-66 years, males, and the Hispanic White population with diabetes or hypercholesterolemia. There is a significant correlation between RDW and coronary heart disease among individuals with rheumatoid arthritis.

[Effects of Straw Removal Measure on Soil Cd Bioavailability and Rice Cd Accumulation].

A field experiment was conducted in a lightly Cd-contaminated rice field in Ningxiang City, Hunan Province, to study the effects of straw removal measures on the soil Cd bioavailability and rice Cd accumulation. The results showed that:① two consecutive seasons of straw removal measures (T1-T4 treatments) effectively increased soil pH by 0.04-0.58 units, reduced soil organic matter by 0.68%-25.87%, and reduced the Cd content of rhizosphere soil by 3.76%-12.78%. ② The proportions of Cd in the acid-extractable fraction and oxidizable fraction decreased, and the proportion of Cd in the residual fraction increased. Furthermore, straw removal measures significantly reduced the bioavailability of Cd in rhizosphere soil, and the Cd contents in TCLP, DTPA, and CaCl2 extracts all significantly decreased compared with those in CK. ③ The straw removal measure could significantly reduce the content of DOC and Cd in soil pore water; and the contents of Cd in soil pore water decreased by 4.54%-40.00% and 2.75%-67.34% under the straw removal measure (T1-T4) for two consecutive seasons, respectively, indicating that DOC was one of the key factors affecting the content of Cd in soil pore water. ④ Two consecutive straw removal measures (T1-T4) reduced the accumulation of Cd in different rice tissues, among which, under the treatment of all straw and root removal (T4), the Cd contents of brown rice in late rice planting in 2020 and early rice planting in 2021 decreased by 18.52% and 39.69%, respectively. Therefore, full or partial removal of straw in Cd-contaminated rice fields is a powerful measure to reduce the risk of exceeding Cd levels in brown rice.

Simultaneous alleviation of Cd availability in contaminated soil and accumulation in rice (Oryza sativa L.) by Fe-Mn oxide-modified biochar.

Fe-Mn oxide-modified biochar (BC-FM) was used to remediate Cd-contaminated soil and mitigate Cd accumulation in rice. The roles of Fe and Mn in soil Cd immobilization and in controlling Cd uptake by rice were investigated via X-ray photoelectron spectroscopy (XPS) characterization and chemical analysis. Fe and Mn loaded on BC-FM increased the removal efficiencies of CaCl2 extractable Cd in soil and Cd in pore water compared to those in only biochar (BC)-treated soil, with maximum removal rates at 67.9 % and 77.8 %, respectively. The XPS results indicated that the redox reactions of the Fe-Mn oxides on BC-FM surface affected Cd immobilization in the soil. The Fe (II/III) components on BC-FM were primarily converted to Fe3O4 in the soil system, which may form stable complexes with Cd2+ (Fe-O-Cd) during the entire rice growth period, and Cd may be bound to MnO or Mn2O3 in the form of CdMn2O4. The excellent adsorption performance of BC-FM enhanced by Fe-Mn oxides reduced the available Cd in the soil and stimulated Fe and Mn transport in rice, thereby inhibiting Cd accumulation in the aerial parts of rice. Cd concentrations in brown rice under BC-FM treatments reached the national safety standard (0.2 mg/kg, GB2762-2017). And BC-FM significantly increased the biomass of brown rice with a maximum rate of 26.8 %. These findings suggest that BC-FM could be used as an efficient material for Cd-contaminated soil remediation, and Fe-Mn plays important role in immobilizing Cd in soil and reducing Cd transport in rice.

Adsorption Characteristics and Mechanisms of Fe-Mn Oxide Modified Biochar for Pb(II) in Wastewater.

This study prepared iron-manganese oxide-modified biochar (FM-BC) by impregnating rice straw biochar (BC) with a mixed solution of ferric nitrate and potassium permanganate. The effects of pH, FM-BC dosage, interference of coexisting ions, adsorption time, incipient Pb(II) concentration, and temperature on the adsorption of Pb(II) by FM-BC were investigated. Moreover, the Pb(II) adsorption mechanism of FM-BC was analyzed using a series of characterization techniques. The results showed that the Fe-Mn oxide composite modification significantly promoted the physical and chemical functions of the biochar surface and the adsorption capacity of Pb(II). The specific surface area of FM-BC was 18.20 times larger than that of BC, and the maximum Pb(II) adsorption capacity reached 165.88 mg/g. Adsorption kinetic tests showed that the adsorption of Pb(II) by FM-BC was based on the pseudo-second-order kinetic model, which indicated that the adsorption process was mainly governed by chemical adsorption. The isothermal adsorption of Pb(II) by FM-BC conformed to the Langmuir model, indicating that the adsorption process was spontaneous and endothermic. Characterization analyses (Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy) showed that the adsorption mechanism of Pb(II) by FM-BC was mainly via electrostatic adsorption, chemical precipitation, complexation, ion exchange, and the transformation of Mn2O3 into MnO2. Therefore, FM-BC is a promising adsorbent for Pb(II) removal from wastewater.

[Effects of Phosphorus Sufficiency and Deficiency on Cadmium Uptake and Transportation by Rice].

Phosphorus (P) is an essential nutrient element for crop growth. The effects of P surplus or deficit on Cd absorption and transport in rice in Cd-polluted farmland is not clear. The effects of P deficiency and P sufficiency on Cd uptake, transport, and accumulation in rice under Cd stress were investigated by applying different levels of phosphorus (NaH2PO4) in a hydroponic experiment. The results showed that:① with the increase in ρ(P) (1.5-48.0 mg·L-1), the biomass in all parts of the rice plants had no obvious change, and the contents of photosynthetic pigment (chlorophyll a, chlorophyll b, and carotenoid) firstly ascended and then descended; high concentrations of P inhibited the synthesis of photosynthetic pigments. ② Under Cd stress, when the P was deficient (1.5-6.0 mg·L-1) or sufficient (12.0-48.0 mg·L-1), the Cd content in different parts of the rice increased with the increase in P addition level, and the maximum increase in Cd content in brown rice was 132.1% and 191.2%, respectively. ③ The P/Cd of brown rice showed a piecewise decreasing rule under P deficiency and P sufficiency, and the Cd content in brown rice was significantly negatively correlated with P/Cd (P<0.01). These results indicated that elevating phosphorus concentration when rice was under both the conditions of P deficiency and P sufficiency could promote the uptake and transport of Cd by rice roots under Cd stress, thus increasing the accumulation of Cd in aboveground parts and the risk of excessive Cd in rice.

Enhancing Cd(II) adsorption on rice straw biochar by modification of iron and manganese oxides.

Metal oxide-modified biochar showed excellent adsorption performance in wastewater treatment. Iron nitrate and potassium permanganate were oxidative modifiers through which oxygen-containing groups and iron-manganese oxides could be introduced into biochar. In this study, iron-manganese (Fe-Mn) oxide-modified biochar (BC-FM) was synthesized using rice straw biochar, and the adsorption process, removal effect, and the mechanism of cadmium (Cd) adsorption on BC-FM in wastewater treatment were explored through batch adsorption experiments and characterization (SEM, BET, FTIR, XRD, and XPS). Adsorption kinetics showed that the maximum adsorption capacity of BC-FM for Cd(II) was 120.77 mg/g at 298 K, which was approximately 1.5-10 times the amount of adsorption capacity for Cd(II) by potassium-modified or manganese-modified biochar as mentioned in the literature. The Cd(II) adsorption of BC-FM was well fit by the pseudo-second-order adsorption and Langmuir models, and it was a spontaneous and endothermic process. Adsorption was mainly controlled via a chemical adsorption mechanism. Moreover, BC-FM could maintain a Cd removal rate of approximately 50% even when reused three times. Cd(II) capture by BC-FM was facilitated by coprecipitation, surface complexation, electrostatic attraction, and cation-π interaction. Additionally, the loaded Fe-Mn oxides also played an important role in the removal of Cd(II) by redox reaction and ion exchange in BC-FM. The results suggested that BC-FM could be used as an efficient adsorbent for treating Cd-contaminated wastewater.