Response mechanism of Chlamydomonas reinhardtii to nanoscale bismuth oxyiodide (nano-BiOI): Integrating analysis of mineral nutrient metabolism and metabolomics

Nanoscale bismuth oxyiodide (nano-BiOI) is widely studied and applied in environmental applications and biomedical fields, with the consequence that it may be deposited into aquatic environments. However, the impact of nano-BiOI on aquatic ecosystems, especially freshwater microalga, remains limited. Herein, the nano-BiOI was synthesized and its response mechanism towards microalga Chlamydomonas reinhardtii was evaluated. Results showed that a low concentration of nano-BiOI (5 mg/L) could stimulate algal growth at the early stage of stress. With the increase in concentration, the growth rate of algal cells was inhibited and showed a dose effect. Intracellular reactive oxygen species (ROS) were significantly induced and accompanied by enhanced lipid peroxidation, decreased nonspecific esterase activity, and significantly upregulated glutathione S-transferase activity (GST) activity. Mineral nutrient metabolism analysis showed that nano-BiOI significantly interfered with the mineral nutrients of the algae. Non-targeted metabolomics identified 35 different metabolites (DEMs, 22 upregulated, and 13 downregulated) under 100 mg/L BiOI stress. Metabolic pathway analysis demonstrated that a high concentration of nano-BiOI significantly induced metabolic pathways related to amino acid biosynthesis, lipid biosynthesis, and glutathione biosynthesis, and significantly inhibited the sterol biosynthesis pathway. This finding will contribute to understanding the toxicological mechanisms of nano-BiOI on C. reinhardtii.     

Potential influence of overwintering benthic algae on water quality

Overwintering benthic algae not only directly impact drinking water safety, but also affect the algae recruitment in warm spring seasons. Thus, understanding the characteristics of overwintering benthic algae can provide scientific references for formulating preventative strategies of reasonable water resource. However, they have received less attention. In this study, the spatiotemporal variation of benthic algae and their harmful secondary metabolites were studied from autumn to summer in Qingcaosha Reservoir. Benthic algae (picophytobenthos accounting for 55.42%) had a high biomass during overwintering, and the groups of overwintering benthic algae included pico-Cyanobacteria, pico-Cryptomonas, pico-Chlorophyta, pico-Diatoms, Cyanobacteria, Chlorophyta, Cryptomonas and Diatoms, which were consistent with the planktonic algae species in warm seasons. In oligotrophic or mesotrophic water bodies, micronutrients of iron and manganese were key nutrient factors influencing the biomass of benthic algae. Furthermore, picophytobenthos were important potential contributors of harmful secondary metabolites. The content of microcystins, anatoxin-a, geosmin and 2-methylisoborneol in sediment were 15.75 µg/kg·FW, 48.16 µg/kg·FW, 3.91 ng/kg·FW, and 11.76 ng/kg·FW during winter, which had potential to be released into water bodies to impact water quality. These findings indicate that water quality monitoring programs need to consider sediment in winter as a potential source of toxins and preventative measures to prevent excessive proliferation of algae should be implemented in winter.     

Sex-dependent obesogenic effect of tetracycline on Drosophila melanogaster deteriorated by dysrhythmia

Antibiotics have been identified as obesogens contributing to the prevalence of obesity. Moreover, their environmental toxicity shows sex dependence, which might also explain the sex-dependent obesity observed. Yet, the direct evidence for such a connection and the underlying mechanisms remain to be explored. In this study, the effects of tetracycline, which is a representative antibiotic found in both environmental and food samples, on Drosophila melanogaster were studied with consideration of both sex and circadian rhythms (represented by the eclosion rhythm). Results showed that in morning-eclosed adults, tetracycline significantly stimulated the body weight of females (AM females) at 0.1, 1.0, 10.0 and 100.0 µg/L, while tetracycline only stimulated the body weight of males (AM males) at 1.0 µg/L. In the afternoon-eclosed adults, tetracycline significantly stimulated the body weight of females (PM females) at 0.1, 1.0 and 100.0 µg/L, while it showed more significant stimulation in males (PM males) at all concentrations. Notably, the stimulation levels were the greatest in PM males among all the adults. The results showed the clear sex dependence of the obesogenic effects, which was diminished by dysrhythmia. Further biochemical assays and clustering analysis suggested that the sex- and rhythm-dependent obesogenic effects resulted from the bias toward lipogenesis against lipolysis. Moreover, they were closely related to the preference for the energy storage forms of lactate and glucose and also to the presence of excessive insulin, with the involvement of glucolipid metabolism. Such relationships indicated potential bridges between the obesogenic effects of pollutants and other diseases, e.g., cancer and diabetes.     

纳米BiOBr对羊角月牙藻的毒性效应

纳米BiOBr(n-BiOBr)是具有广泛应用前景的高活性光催化材料,由于n-BiOBr能在可见光区响应,一旦进入水环境将会造成严重的水生态安全隐患.为探究n-BiOBr对藻类的毒性效应及机理,以羊角月牙藻(Pseudokirchneriella subcapitata)为受试生物,研究n-BiOBr对羊角月牙藻生长状况、光合色素、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)及脂质过氧化物丙二醛(MDA)的影响.结果表明,n-BiOBr对羊角月牙藻的生长有抑制作用,72 h半数效应浓度(EC_(50))为7.407 mg·L~(-1). n-BiOBr处理藻细胞72 h后,藻细胞的叶绿素总量及叶绿素a/b值随着n-BiOBr浓度的升高而降低,呈现一定的浓度-效应关系.随着n-BiOBr浓度增加,MDA、SOD和CAT活性呈现"升高-降低"的趋势.本研究可为纳米材料的科学、有效、无害化应用和管理提供理论依据.     

Transformation of erythromycin during secondary effluent soil aquifer recharging: Removal contribution and degradation path

Erythromycin (ERY), a widely used antibiotic, has recently been detected in municipal secondary effluents and poses serious threats to human health during wastewater reusing. In this study, the removal, fate, and degradation pathway of ERY in secondary effluent during soil aquifer treatment was evaluated via laboratory-scale SAT tests. Up to a 92.9% reduction of ERY in synthetic secondary effluent was observed in 1.0 m depth column system, which decreased to 64.7% when recharged with wastewater treatment plant secondary effluent. XRD-fractionation results demonstrated that the transphilic acid and hydrophobic acid fractions in secondary effluent compete for the adsorption sites of the packed soil and lead to a declined ERY removal. Moreover, aerobic biodegradation was the predominant role for ERY removal, contributing more than 60% reduction of ERY when recharged with synthetic secondary effluent. Destruction of 14-member macrocyclic lactone ring and breakdown of two cyclic sugars (l-cladinose and d-desosamine) were main removal pathways for ERY degradation, and produced six new intermediates.     

Spatial and temporal distribution of Mo in the overlying water of a reservoir downstream from mining area

This study aimed to evaluate the spatial and temporal variations of molybdenum (Mo) in the downstream water body of a Mo mine during three hydrologic periods (wet, dry and medium seasons). The physical properties in Luhun Reservoir reflected seasonal variations in different hydrological periods. The redox potential (ORP) and dissolved oxygen (DO) increased in the dry season. The concomitant decrease in temperature (T), conductivity (COND) and total dissolved solids (TDS) were lowest in the wet season. The pH value did not change significantly during the three hydrologic periods. The distribution of Mo in the dry season was high in upstream and low in downstream areas, which was significantly different from that of the wet and medium seasons. The total Mo concentration in wet (150.1 µg/L) and medium season (148.2 µg/L) was higher than that in the dry season, but the TDS (288.3 mg/L) and the percentage dissolved Mo (81.3%) in overlying water was lowest in the wet season. There was no significant relationship between the dissolved Mo and the total Mo with TDS. In the dry season, the mean total Mo concentration was 116.3 µg/L, which was higher than the standard limit value (70 µg/L) for drinking water (US EPA-United States Environmental Protection Agency recommended value 40 µg/L). Non-point source pollution is the main characteristic of mining area pollution, which was closely related to rainfall. Thus, the Luhun Reservoir contains substantial Mo pollution, which was a significant concern given that it is used as a source of drinking and irrigation water.     

Distribution of mercury and methylmercury in river water and sediment of typical manganese mining area

Manganese (Mn) ores contain substantial concentrations of mercury (Hg), and mining and smelting of Mn ores can bring Hg into the surrounding aquatic environment through atmospheric deposition, leaching of electrolytic Mn residue and Mn gangue dump. However, limited is known that how these processes influence the environmental behaviors of Hg in waterbody. Therefore, the seasonal distribution and existing form of Hg in water and sediment in one Mn ore area in Xiushan County, Chongqing were investigated. Our results showed that the mean Hg and methylmercury (MeHg) concentrations in water (n=35) were 5.8 ± 4.6 ng/L and 0.22 ± 0.14 ng/L, respectively. The mean Hg concentrations in retained riverbed and fluvial bank sediment (n=35) were 0.74 ± 0.26 mg/kg and 0.63 ± 0.27 mg/kg, respectively (the mean MeHg concentrations were 0.64 ± 0.40 µg/kg and 0.51 ± 0.30 µg/kg, respectively). It indicated that the mining and smelting of Mn ores were the main sources of anthropogenic Hg, and Mn may inhibit Hg methylation in rivers in Mn ore areas. Mercury in the bound to iron/ Mn (Fe/Mn) oxides of low crystallinity fraction (Hg-OX) accounted for 4.01% and 5.25% of the total Hg concentrations in the retained riverbed and fluvial bank sediment, respectively. The amount of Hg bound to Fe/Mn oxides in sediment increased significantly due to the manganese mining activities in the investigated area. Therefore, it could be hypothesized that high Hg concentrations in river sediment in Mn mining areas are closely related to high Mn concentration in sediment.