Comparison of chlorine and chlorine dioxide disinfection in drinking water: Evaluation of disinfection byproduct formation under equal disinfection efficiency.

Disinfection efficiency and disinfection byproduct (DBP) formation are two important aspects deserving careful consideration when evaluating different disinfection protocols. However, most of the previous studies on the selection of disinfection methods by comparing DBP formation were carried out under the same initial/residual dose and contact time of different disinfectants, and such a practice may cause overdose or underdose of a certain disinfectant, leading to the inaccurate evaluation of disinfection. In this study, a comprehensive and quantitative comparison of chlorine (Cl2) and chlorine dioxide (ClO2) disinfection was conducted with regard to their DBP formation under equal disinfection efficiency. The microbial inactivation models as well as the Cl2 and ClO2 demand models were developed. On such basis, the integral CT (ICT) values were determined and used as a bridge to connect disinfection efficiency and DBP formation. For 3-log10 and 4-log10 reductions of Pseudomonas aeruginosa, ClO2 had 1.5 and 5.8 times higher inactivation ability than Cl2, respectively. In the premise of equal disinfection efficiency (i.e., the ICT ratios of Cl2 to ClO2 = 1.5 and 5.8), the levels of total organic chlorine, total organic bromine, and total organic halogen formed in the Cl2 disinfection were significantly higher than those formed in the ClO2 disinfection. Among the 35 target aliphatic DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs) were the dominant species formed in both Cl2 and ClO2 disinfection. The total THM levels formed in Cl2 disinfection were 14.6 and 30.3 times higher than those in ClO2 disinfection, respectively. The total HAA levels formed in Cl2 disinfection were 3.5 and 5.4 times higher than those in ClO2 disinfection, respectively. Formation of the target 48 aromatic DBPs was much favored in Cl2 disinfection than that in ClO2 disinfection, and the formation levels was dominated by contact time. This study demonstrated that ClO2 had significant advantages over Cl2, especially at higher microorganism inactivation and lower DBP formation requirements.

A group of emerging heterocyclic nitrogenous disinfection byproducts: Formation and cytotoxicity of halopyridinols in drinking water.

Recently, a new group of halopyridinol disinfection byproducts (DBPs) was reported in drinking water. The in vivo developmental and acute toxicity assays have shown that they were more toxic than a few commonly known aliphatic DBPs such as bromoform and iodoacetic acid. However, many pyridinol DBPs with the same main structures but different halogen substitutions were still unknown due to complicated water quality conditions and various disinfection methods applied in drinking water treatment plants. Studies on their transformation mechanisms in drinking water disinfection were quite limited. In this study, comprehensive detection and identification of halopyridinols were conducted, and five new halopyridinols were first reported, including 2-chloro-3-pyridinol, 2,6-dichloro-3-pyridinol, 2-bromo-5-chloro-3-pyridinol, 2,4,6-trichloro-3-pyridinol and 2,5,6-trichloro-3-pyridinol. Formation conditions and mechanisms of the halopyridinols were explored, and results showed that chlorination promoted their formation compared with chloramination. Halopyridinols were intermediate DBPs that could undergo further transformation/degradation with increasing contact time, disinfectant dose, bromide concentration, and pH. The in vitro cytotoxicity of the halopyridinols was evaluated using human hepatocellular carcinoma cells. Results showed that the cytotoxicity of 3,5,6-trichloro-2-pyridinol was the highest (EC50 = 474.3 µM), which was 13.0 and 1.6 times higher than that of 2-bromo-3-pyridinol (EC50 = 6214.5 µM) and tribromomethane (EC50 = 753.6 µM), respectively.

Preliminary risk assessment of regional industrial enterprise sites based on big data.

An accurate and inexpensive preliminary risk assessment of industrial enterprise sites at a regional scale is critical for environmental management. In this study, we propose a novel framework for the preliminary risk assessment of industrial enterprise sites in the Yangtze River Delta, which is one of the fastest economic development and most prominent contaminated regions in China. Based on source-pathway-receptors, this framework integrated text and spatial analyses and machine learning, and its feasibility was validated with 8848 positive and negative samples with a calibration and validation set ratio of 8:2. The results indicated that the random forest performed well for risk assessment; and its accuracy, precision, recall, and F1 scores in the calibration set were all 1.0, and the four indicators for the validation set ranged from 0.97 to 0.98, which was better than that for the other models (e.g., logistic regression, support vector machine, and convolutional neural network). The preliminary risk ranking of industrial enterprise sites by the random forest showed that high risks (probabilities) were mainly distributed in Shanghai, southern Jiangsu, and northeastern Zhejiang from 2000 to 2015. The relative importance of the site industrial, production, and geographical features in the random forest was 69%, 22%, and 9%, respectively. Our study highlights that we could quickly and effectively establish a priority (or ranking) list of industrial enterprise sites that require further investigations, using the proposed framework, and identify potentially contaminated sites.

Animal models of male subfertility targeted on LanCL1-regulated spermatogenic redox homeostasis.

Oxidative stress in spermatozoa is a major contributor to male subfertility, which makes it an informed choice to generate animal models of male subfertility with targeted modifications of the antioxidant systems. However, the critical male germ cell-specific antioxidant mechanisms have not been well defined yet. Here we identify LanCL1 as a major male germ cell-specific antioxidant gene, reduced expression of which is related to human male infertility. Mice deficient in LanCL1 display spermatozoal oxidative damage and impaired male fertility. Histopathological studies reveal that LanCL1-mediated antioxidant response is required for mouse testicular homeostasis, from the initiation of spermatogenesis to the maintenance of viability and functionality of male germ cells. Conversely, a mouse model expressing LanCL1 transgene is protected against high-fat-diet/obesity-induced oxidative damage and subfertility. We further show that germ cell-expressed LanCL1, in response to spermatogenic reactive oxygen species, is regulated by transcription factor specific protein 1 (SP1) during spermatogenesis. This study demonstrates a critical role for the SP1-LanCL1 axis in regulating testicular homeostasis and male fertility mediated by redox balance, and provides evidence that LanCL1 genetically modified mice have attractive applications as animal models of male subfertility.

Identification and risk prediction of potentially contaminated sites in the Yangtze River Delta.

Identification and risk prediction of potentially contaminated sites (PCS) are crucial for the management of contaminated sites. However, the identification and risk prediction methods of PCS are lacking at a regional scale. Here, we established the fuzzy matching algorithm based on the site's name for identifying PCS in the Yangtze River Delta (YRD) from 2000 to 2020. The results showed that PCS in the YRD increased by over ten times, from 336 in 2000 to 4191 in 2020. Socio-economic and physical geography drive the growth of PCS and its spatiotemporal distribution, while the former has a more significant impact than the latter. We also presented a risk probability zoning strategy based on the source-pathway-receptor model, and proposed the patch-generating land-use simulation model to predict the risk probability of PCS in 2030. The results of risk probability zoning from 2000 to 2020 indicated that the local government of the YRD has started to pay attention to PCS management and risk control while developing social and economic. The results of risk prediction demonstrated that the proportion of low-risk probability pixels is 96.1% in 2030. Therefore, the planned indicator in the Action Plan on contaminated sites established by the State Council of China can be achieved in the YRD. Our experience in identifying and predicting PCS can inform how the local government worldwide manages PCS and tackles future challenges of achieving the ambition of site pollution control.

Response characteristics of root to moisture change at seedling stage of Kengyilia hirsuta.

Kengyilia hirsuta is an important pioneer plant distributed on the desertified grassland of the Qinghai-Tibet Plateau. It has strong adaptability to alpine desert habitats, so it can be used as a sand-fixing plant on sandy alpine land. To study the response mechanisms of root morphological and physiological characteristics of K. hirsuta to sandy soil moisture, 10%, 25% and 40% moisture levels were set up through potted weighing water control method. The biomass, root-shoot ratio, root architecture parameters, and biochemical parameters malondialdehyde, free proline, soluble protein, indole-3-acetic acid, abscisic acid, cytokinin, gibberellin, relative conductivity and antioxidant enzyme activities were measured in the trefoil stage, and the response mechanisms of roots at different moisture levels were analyzed. The results showed that with the increase of soil moisture, root morphological indexes such as root biomass, total root length, total root volume and total root surface increased, while the root topological index decreased continuously. The malondialdehyde content, relative conductivity, superoxide dismutase activity, peroxidase activity, catalase activity, free proline content, soluble protein content, abscisic acid content and cytokinin content at the 25% and 40% moisture levels were significantly decreased compared with the 10% level (P< 0.05). Thus, the root growth of K. hirsuta was restricted by the 10% moisture level, but supported by the 25% and 40% moisture levels. An artificial neural network revealed that total root length, total root surface area, root link average length, relative conductivity, soluble protein, free proline and moisture level were the key factors affecting root development. These research results could contribute to future agricultural sustainability.

Effect of carriers' sex on meiotic segregation patterns and chromosome stability of reciprocal translocations.

RESEARCH QUESTION: Does the sex of reciprocal translocation carriers affect meiotic segregation patterns and stability of non-translocated chromosomes during meiosis? DESIGN: A total of 790 couples who underwent preimplantation genetic testing for reciprocal translocations by using the single nucleotide polymorphism (SNP) array platform between October 2016 and December 2019 were included. Among them, 294 couples had their euploid embryos distinguished between normal euploidies and balanced translocation carriers. RESULTS: Female translocation carriers had a significantly lower incidence of alternate segregation pattern than male carriers (43.26% versus 47.98%, P = 0.001), but a higher incidence of 3:1 segregation pattern (6.70% versus 4.29%, P < 0.001). Stratified analysis showed only female translocation carriers with acrocentric chromosome (Acr-ch) involved had a lower incidence of alternate segregation pattern and a higher incidence of 3:1 segregation pattern compared with male carriers (41.63% versus 47.73%, P = 0.012; 9.32% versus 5.03%, P = 0.001). In 2233 embryos of 294 couples with identification of normal and balanced embryos, no significant differences were found in the paternal-origin aneuploidy rate (5.61% versus 5.82%, P = 0.861) and the maternal-origin aneuploidy rate (12.82% versus 12.08%, P = 0.673) in both male and female carriers. After excluding segmental aneuploidies, no differences were found between male and female carriers in both paternal-origin aneuploidy rate (2.14% versus 1.75%, P = 0.594) and maternal-origin aneuploidy rate (11.75% versus 11.06%, P = 0.683). CONCLUSION: The sex of the translocation carriers affected meiotic segregation patterns with no effect on the stability of non-translocated chromosomes during meiosis.

Non-thermal plasma oxidation of Cu(II)-EDTA and simultaneous Cu(II) elimination by chemical precipitation.

Cu2+ readily complexes with ethylenediaminetetraacetic acid (EDTA) to form a heavy metal complex (Cu-EDTA) that is typical in the effluents from mining and electroplating industries. It was difficult for the classical alkaline precipitation method to eliminate the heavy metal complex due to the strong bonding ability between Cu(II) and EDTA. Cu(II) release and removal performance after Cu-EDTA decomplexation in a non-thermal plasma oxidation system was carried out in this study. The removal process was characterized by chemical oxygen demand, total organic carbon, atomic force microscopy, and electroconductivity analysis. The toxicity effect of the treated Cu-EDTA solution was also tested by photobacterium bioassay. The experimental results showed that 80.2% of Cu was released and removed within 60 min of the non-thermal plasma treatment/alkaline precipitation. Relatively higher energy input, lower Cu-EDTA concentration, and acidic conditions were necessary to obtain greater Cu release and removal performance, and there existed an appropriate air flow rate for high-efficient Cu release and removal. O2-, OH, 1O2, and O3 were the main active substances leading to Cu2+ release. Its residual toxicity to P.phosphoreum sp.-T3 was significantly reduced after treatment.