[Effects of Land Use Patterns on Soil Microplastic Pollution in the Luoshijiang Sub-watershed of Erhai Lake Basin].

Microplastic pollution in the soil environment has received extensive attention, but the effects of different land use patterns on the sub-watershed scale on soil microplastic pollution are poorly understood. The Luoshijiang sub-watershed in the north of Erhai Lake was selected as the research object, and the characteristics of microplastic pollution in farmland, riparian zone, grassland, and woodland soils were analyzed. The pollution risks of microplastics in the four types of soil were assessed using the polymer risk index method, and the effects of land use patterns on the distribution and risk of microplastic pollution were further explored. The results showed that:① The abundance of microplastics in the soil of the Luoshijiang sub-watershed ranged from 220 to 1 900 n·kg-1, and the average abundance was (711 ± 55) n·kg-1. The main polymer types were polyester (PES, 32.52%) and polyethylene terephthalate (PET, 21.95%). The particle size of microplastics was concentrated in the range of 0.5-2 mm (61.89%). Fiber was the main shape of microplastics (>75%), and the dominant color was transparent (58.50%). ② Land use patterns determined the abundance and pollution characteristics of soil microplastics in the Luoshijiang sub-watershed. A significantly higher abundance of microplastics was found in the soil of farmland[(885 ± 95) n·kg-1] and riparian zone[(837 ± 155) n·kg-1], which had stronger intensities of human activity, than that in woodland soil[(491 ± 53) n·kg-1] (P<0.05). Film and fragment microplastics mainly occurred in farmland soil, which also had the largest number of polymer types and the most abundant colors. ③ The risk index level of microplastics (Level Ⅲ) in the soil of farmland was higher than that of the other three land use patterns (Level Ⅰ). This research indicated that the higher the intensity of human activities of a sub-watershed was, the more complex the occurrence characteristics of soil microplastics, the richer the types of polymers, and the higher the potential pollution risks would be. Therefore, it is necessary to strengthen the control of soil microplastic pollution in farmland.

[Effects of Wastewater Treatment Processes on the Removal Efficiency of Microplastics Based on Meta-analysis].

Microplastics (MPs) are ubiquitous emerging pollutants that have been found in the marine, freshwater, air, and soil environments. Wastewater treatment plants (WWTPs) play an important role in releasing MPs to the environment. Therefore, understanding the occurrence, fate, and removal mechanism of MPs in WWTPs is of great importance towards microplastic control. In this review, the occurrence characteristics and removal rates of MPs in 78 WWTPs from 57 studies were discussed based on Meta-analysis. Specifically, the key aspects regarding MPs removal in WWTPs, such as wastewater treatment processes and MPs shapes, sizes, and polymer compositions were analyzed and compared. The results showed that:① the abundances of MPs in the influent and effluent were 1.56×10-2-3.14×104 n·L-1 and 1.70×10-3-3.09×102 n·L-1, respectively. The abundance of MPs in the sludge ranged from 1.80×10-1 to 9.38×103 n·g-1. ② The total removal rate (>90%) of MPs by WWTPs using oxidation ditch, biofilm, and conventional activated sludge treatment processes was higher than that using sequencing batch activated sludge, anaerobic-anoxic-aerobic, and anoxic-aerobic processes. ③ The removal rate of MPs in primary, secondary, and tertiary treatment process were 62.87%, 55.78%, and 58.45%, respectively. The combination process of "grid+ sedimentation tank+primary sedimentation tank" had the highest removal rate towards MPs in primary treatment processes, and the membrane bioreactor had the highest one beyond other secondary treatment processes. Filtration was the best process in tertiary treatment. ④ The film, foam, and fragment MPs were easier to remove (>90%) than fiber and spherical (<90%) MPs by WWTPs. The MPs with particle size larger than 0.5 mm were easier to remove than those with particle size smaller than 0.5 mm. The removal efficiencies of polyethylene (PE), polyethylene terephthalate (PET), and polypropylene (PP) MPs were higher than 80%.

Multi-scale analysis of the characteristics of the changing landscape of the typical mountainous region of Southwest China over the past 40 years.

CONTEXT: Yunnan Province is an important ecological security barrier in China. This study investigated the temporal and spatial changes to landscape ecology and is of great significance for guiding landscape protection and future socio-economic development. OBJECTIVES: To analyze the temporal and spatial changes of the landscape patterns at the county, river basin, and provincial levels, and clarify and describe the temporal and spatial differentiation characteristics of the landscape patterns in Yunnan Province. METHODS: Based on landscape ecology, GIS spatial analysis, and spatio-temporal change analysis, nine landscape pattern indices, and spatial autocorrelation for different years, were calculated. RESULTS: The landscape of Yunnan Province has evolved as a whole toward isolation. The indices of separation and fragmentation changed significantly from 2010 to 2015. From 2015 to 2018 the rate of fragmentation decreased. Fragmentation in the Nu Jiang and Irrawaddy River basins was less than in other basins. The landscape patterns of the Jinsha and Pearl River basins were relatively fragmented due to human activity, socioeconomic development, and utilization. The differences between the Lancang and Red River Basins were relatively small and at an intermediate level. CONCLUSIONS: Spatial autocorrelation analysis indicated that there are three areas with typical clusters, namely the Hengduan Mountains where the degree of fragmentation of the landscape was low, while landscape connectivity and aggregation were high. The subtropical region of Southern Yunnan displayed high landscape heterogeneity, a complex shape index, and high connectivity and sprawl. Central Yunnan exhibited a fragmented landscape with poor connectivity and aggregation. These three regions correspond with "the three screens and two belts" in the Main Functional Planning Area of Yunnan Province.

Efficacy of the Bartha-K61 vaccine and a gE-/gI-/TK- prototype vaccine against variant porcine pseudorabies virus (vPRV) in piglets with sublethal challenge of vPRV.

Pseudorabies has caused huge economic losses in China's pig industry and recurred on many large pig farms since late 2011. The disease is caused by highly pathogenic, antigenic variant pseudorabies virus (vPRV) strains. Therefore, the prevention and control of this recurrence of pseudorabies in China has been given priority. In a previous study, we showed that a suitable dose [1 × 106.3 50% tissue culture infectious dose (TCID50) per animal] of commercial Bartha-K61 vaccine protects growing pigs against lethal challenge by the emerging vPRV strain XJ5. In this study, different doses of the Bartha-K61 vaccine and our newly developed rPRV-gI-/gE-/TK- prototype vaccine derived from the vPRV strain XJ5 were used to evaluate immune protection against sublethal challenge by the vPRV strain XJ5. Pigs vaccinated with high doses of the Bartha-K61 vaccine or rPRV-gI-/gE-/TK- prototype vaccine showed no differences in their humoral immune responses, clinical symptoms, body weight gains, viral shedding, or gross and histological lesions after sublethal challenge by the vPRV strain XJ5. Therefore, we concluded that the Bartha-K61 vaccine at a dose of 1 × 105 TCID50 per animal protects pigs against sublethal challenge by the vPRV strain XJ5 and performs equally well as the same dose of the rPRV-gI-/gE-/TK- vaccine, whereas lower doses of the Bartha-K61 vaccine alone do not protect pigs from this challenge. These findings provide useful information for vaccination interventions and the ultimate eradication of pseudorabies caused by vPRV strains emerging in China.

Retrospective survey and phylogenetic analysis of porcine circovirus type 3 in Jiangsu province, China, 2008 to 2017.

Porcine circovirus type 3 (PCV3) is a novel porcine circovirus recently identified in pigs associated with porcine dermatitis nephropathy syndrome, reproductive failure and multi-systemic inflammation. This study aimed to identify PCV3 in clinical samples from pigs collected between 2008 and 2017 in Jiangsu province, China. A total of 272 pig tissue samples from 141 pig farms in Jiangsu province were examined and analyzed. Forty of the 272 (14.7%) samples tested were positive for PCV3, while 28/40 (70%) of the PCV3-positive samples were co-infected with PCV2. Among them, 18, 1, 14 and 7 of the PCV3-positive samples were identified in 2013, 2014, 2015 and 2017, respectively. The complete genome sequences from four of the PCV3s contained 2,000 nucleotides, and shared 98.6% to 99.6% nucleotide sequence identity with the PCV3 isolates available in GenBank. Our results indicate that a large outbreak of PCV3 occurred in Jiangsu province pig herds in 2013, after which a fairly stable infection rate was recorded. It is imperative, therefore, to gain a better understanding of the pathogenicity of PCV3 and control its further dissemination in this region.

Evaluation of the Efficacy and Cross-Protective Immunity of Live-Attenuated Chimeric PCV1-2b Vaccine Against PCV2b and PCV2d Subtype Challenge in Pigs.

Porcine circovirus type 2 (PCV2) commercial vaccines are either inactivated PCV2 isolates or subunit vaccine based on the Cap protein of PCV2. Currently, no live-attenuated vaccines are yet available. Although the predominant circulating subtype worldwide is PCV2b, the emerging PCV2d subtype is also increasingly associated with PCV disease. In this study, piglets were inoculated with a live-attenuated chimeric PCV1-2b vaccine before challenged with PCV2b and PCV2d isolates. Thirty-two piglets were randomly divided into seven groups: negative (sham-vaccinated, sham-challenged), VAC+PCV2b (PCV1-2b vaccinated, PCV2b-challenged), VAC+PCV2d (PCV1-2b vaccinated, PCV2d-challenged), CHAL+PCV2b (sham-vaccinated, PCV2b-challenged), CHAL+PCV2d (sham-vaccinated, PCV2d-challenged), CV+PCV2b (commercial-vaccinated, PCV2b-challenged), and CV+PCV2d (commercial-vaccinated, PCV2d-challenged). The results showed that vaccinated challenged groups demonstrated high levels of anti-PCV2 antibody and reduced PCV2b and PCV2d loads both in serum and nasal swabs compared with the challenge-only groups. PCV2 DNA was detected in the superficial inguinal lymph nodes of only one pig in each of the VAC+PCV2b and VAC+PCV2d groups (group mean values, 101.81 and 101.77 genomic copies/g, respectively), which was significantly lower than those in CHAL+PCV2b and CHAL+PCV2d animals (group mean values, 1011.65 and 1010.60 genomic copies/g, respectively; P < 0.01). In addition, PCV2 DNA in each of the VAC+PCV2b and VAC+PCV2d groups was significantly lower than those in CV+PCV2b and CV+PCV2d animals (group mean values, 108.47 and 108.34 genomic copies/g, respectively; P < 0.01), indicating that the live-attenuated PCV1-2b vaccine was more effective than commercial vaccine. The live-attenuated PCV1-2b vaccine was effective in reducing PCV2b/PCV2d viremia, shedding, and tissue viral loads in vaccinated challenged pigs compared with challenge-only piglets, indicating that the PCV1-2b prototype vaccine is a good candidate for a live-attenuated vaccine against both PCV2b and PCV2d subtypes. And we first revealed that the live-attenuated PCV1-2b vaccine could protect piglets from challenge with either PCV2b or PCV2d equivalently.

Application of Biotic Ligand Model in Predicting Copper Acute Toxicity to Carp (Cyprinidae).

Three representative species of Cyprinidae fishes (Aristichthys nobilis, Ctenopharyngodon idellus, and Cyprinus carpio), which are abundant in Chinese surface waters, were studied to determine their sensitivity to copper (Cu) in acute exposures. We first performed acute toxicity tests to determine the Cu LC50 value for each species in water with varying characteristics. The biotic ligand model (BLM) was then calibrated using the toxicity data for these species together with binding properties specific to Cu. The BLM calibration involved the calculation of the level of Cu accumulation in the gills that resulted in 50% lethality (i.e., LA50). The LA50 values for A. nobilis, C. idellus and C. carpio were 5.16, 11.60 and 9.00 nmol g-1. The model calibrated to these data was improved by adjusting the Cu-proton exchange constant (pK CuHA-A) and dissolved organic carbon (DOC) to values of 1.84 and 4.67E-3 mol g-1, respectively. The calibrated Cu-BLM was validated for these three common fish species by comparing predicted and observed LC50 values, which were in agreement to within a factor of 2. The results of this study provide an important contribution to ecological risk assessment and establishment of water quality criteria for Cu in China.

[Simplification of biotic ligand model and evaluation of predicted results].

The prediction accuracy of LC50 on four species (Fathead minnow, D. magna, D. pulex, Rainbow trout) was 0. 075, 0. 52, 0.96 and 0.29 respectively as determined by their onserved values of LC50 in surface water. Predicted results indicated that the correlation between forecast error and LA50 was exponential. The accuracy of Fathead minnow and Rainbow trout became 0.59 and 0.42 after adjusting LA50. The correlation between hardness and LA50 showed that the prediction effectiveness of BLM was poor in soft water. In addition, four important parameters (DOC, pH values, the concentration of HCO3-, temperature) were selected to build the multiple linear relationship with LC50 by applying 500 groups of random uniform water quality parameter in BLM. Biotic ligand model was effectively simplified.

[Predicting copper toxicity to Hypophthalmichthys molitrix and Ctenopharyngodon idellus based on biotic ligand model].

A series of 96 h copper acute toxicity experiments were conducted with Ctenopharyngodon idellus and Hypophthalmichthys molitrix under different concentrations of DOC [ρ(DOC) 0.05, 0.5, 1, 2, 4 mg · L(-1)]. Higher DOC resulted in a reduction of toxicity, which was in line with the concepts of the biotic ligand model (BLM). It was concluded that the mean absolute deviation (MAD) of LC50 with Ctenopharyngodon idellus and Hypophthalmichthys molitrix was 591.2, 157.14 µg · L(-1) and 728.18, 91.24 µg x L(-1), respectively, by the prediction of copper BLM developed for Fathead minnow and Rainbow trout. Based on speciation analysis of biotic ligand model, it was shown that LA50 values of Ctenopharyngodon idellus and Hypophthalmichthys molitrix were 10.960 and 3.978 nmol · g(-1), respectively. Then the MAD values became 280.52 and 92.25 µg · L(-1) for Ctenopharyngodon idellus and Hypophthalmichthys molitrix using the normalized LA50. Finally by searching toxicity data in literature, the MAD values on Ctenopharyngodon idellus and Hypophthalmichthys molitrix were 252.37 and 50.26 µg · L(-1), successively. This result verified that the toxicity prediction based on biotic ligand model was practical.