Effects of changes in land use structure on nitrogen input in the Pingzhai Reservoir watershed, a karst mountain region

Optimizing land use composition to control nitrogen input into water bodies is one way to address surface source pollution in karst mountain regions. In this study, changes in land use, N sources, and spatial and temporal changes of N migration in the Pingzhai Reservoir watershed were evaluated from 2015 to 2021, and the relationship between land use composition and N input was elucidated. N was the main pollution in the water of the watershed; NO₃^- was the dominant form of N, and it did not react during migration. N came from soil, livestock manure or domestic sewage, and atmospheric deposition. Isolating the fractionation effects of source nitrogen is crucial to improve the accuracy of nitrogen and oxygen isotope traceability in the Pingzhai Reservoir. From 2015 to 2021, the grassland area in the Pingzhai Reservoir increased by 5.52%, the woodland area increased by 2.01%, the water area increased by 1.44%, the cropland decreased by 5.8%, unused land decreased by 3.18%, and construction land remained unchanged. Policies and reservoir construction were the main drivers of changes in land-use type in the catchment. Changes in land use structure affected nitrogen input patterns, with unused land having a highly significant positive correlation with inputs of NH₃-N, NO₂^-, and TN, and construction land having a significant positive correlation with the input of NO₂^-. The inhibitory effect of forest and grassland on nitrogen input in the basin was offset by the promoting effect of cropland and construction land on nitrogen input, with unused land becoming a new focus area for nitrogen emissions due to a lack of environmental management. Modifying the area of different land use types in the watershed can effectively control nitrogen input to the watershed.

Isolation and identification of the endophytic fungus J2-3 and its disease-preventive and growth-promoting effects on cucumber

There are many problems that result from the use of a large number of chemical pesticides to control plant diseases, including pathogenic bacteria resistance, environmental contamination, and human health effects. Recently, endophytic fungi have become a significant source of bioactive fungicide products and an invaluable resource for excavating microbial pesticides. In this study, endophytic fungi with biocontrol potential were isolated and screened from Mikania micrantha leaves, stems, and roots. Fifty endophytic fungi were isolated and their antagonistic activity was studied in vitro using the confrontation culture method. The J2-3 strains from stems exhibit broad-spectrum and high activity. The strain's biological characteristics were determined by various culture conditions, and it was identified as Fusarium proliferatum by both morphological and ITS sequence analysis. Biological characteristics of the J2-3 strain were also tested. The optimum temperature for mycelium growth and sporulation was 25 °C and 30 °C, respectively. For mycelium growth, starch was the optimum carbon source, and peptone was the optimum nitrogen source for sucrose, mycelium growth, and sporulation. Mycelium growth was killed by a temperature of 60 °C, and sporulation was killed by a temperature of 55 °C. The light aided mycelium growth, and the light alternated between light and dark cycles for sporulation. Further, pot experiments were conducted to determine the antagonistic and viable effects of highly antagonistic strains on cucumber. The spore suspension's final control efficacy on cucumber wilt disease was up to 62.79% and it also promoted cucumber growth significantly. The results show that the entophytic fungus J2-3 from M. micrantha can protect cucumbers from wilt disease and promote growth.

Relationship between imidacloprid residues and control effect on cotton aphids in arid region

In this case, the dissipation and residues of imidacloprid as well as its control efficacy against aphids (Aphis gossypii Glover) in cotton cropping system were reported. After the final spray at the rates of 10.5-42.5 g a.i. ha^-1, the initial deposits were 0.59-2.25 mg kg^-1 with half-lives of 2.12-2.84 days on leaves and 0.06-0.21 mg kg^-1 with half-lives of 1.51-4.20 days in soil, respectively. The initial residues were significantly higher with longer persistence in the upper position of the leaf than in middle and lower positions. The different application dosages could induce a significant difference in the initial deposits, but not show consistent correlation with the dissipation rate. The repeated applications of imidacloprid could alter its residue levels and dissipation rates. The long-term residue concentrations of imidacloprid (60 days after the final application) reached to the nondetectable level in soil. Combined with the control efficacy results, it was considered that the recommended dose of imidacloprid on cotton could be used effectively and safe in this arid area from the view of crop protection and environmental contamination.

Monitoring and evaluating the control effect of dust suppressant on heavy metals based on ecological and health risks: a case study of Beijing

Dust suppressant is widely applied to control the road dust pollution, while the unified statement on its control effect has not been obtained. To fill this gap, an experiment was conducted at four typical sites in Beijing, where dust suppressant and water were sprayed at test and control sites, respectively. Samples were collected to analyze the concentrations of PM_2.5, PM₁₀, and heavy metals. With the application of potential ecological risk index and probabilistic health risk assessment, the ecological and health risks of heavy metals were obtained. Results showed that compared with control sites, the total concentrations of heavy metals in PM₁₀ and PM_2.5 at test sites decreased by 1555.40 and 784.95 ng/m³ in 14 days, with the suppression rate of 11.95% and 12.06%. Especially, the total ecological risks of heavy metals in PM₁₀ reduced from 165.77 to 143.64, with their ecological hazard level changed from medium to slight. The carcinogenic risks of PM_2.5 and PM₁₀ reduced by 0.60E-05 and 1.52E-06, respectively. As for the non-carcinogenic risks, there were a reduction of 5.78% and 12.28% for PM_2.5 and PM₁₀, respectively. Notably, the ecological risk of Pb was the highest; Cr and Zn contributed the most to carcinogenic and non-carcinogenic risk. Finally, to mitigate road dust pollution from an integration perspective, some preventive measures were proposed.

The fate and effect of chlorpyrifos and lambda-cyhalothrin in soybean (Glycine max L. Merril) field

Soybean pod borer (Leguminivora glycinivorella) is an important pest in soybean production, and chemical pesticides was major way for prevention. However, it is difficult to balance the efficiency and safety of pesticide application. In this paper, we evaluated safety and effectiveness of common insecticides (chlorpyrifos and lambda-cyhalothrin) on soybean from three aspects, including distribution, dissipation and control effect, around three major soybean production area (Anhui, Jilin and Shandong) in China. For chlorpyrifos, the initial deposition of each position (upper leaf, lower leaf, upper stem, lower stem, soybean and root) was determinated for 0.23 mg/kg to 70.7 mg/kg, and the half-lifes ranged from 1.96 days to 5.36 days. For lambda-cyhalothrin, the initial deposition of the position was determinated for 0.10 mg/kg to 2.54 mg/kg, and the half-lifes ranged from 2.45 days to 7.26 days. We found that the target insecticides were major deposition and faster degradation in upper stem and leaf. Through comparing the relationship between field control effect and residue, it can be suggested that 40% chlorpyrifos EC and 2.5% lambda-cyhalothrin WE should be sprayed at 600 g a.i./ha and 5.63 g a.i./ha for SPB prevention. This study enhanced our understanding of distribution, dissipation and relationship between residue and control effect. The results provided data support for guiding the precise and scientific application of chemical insecticides on soybean.

[Comparison of epidemic characteristics between SARS in 2003 and COVID-19 in 2020 in Guangzhou]

Objective: By analyzing the epidemic characteristics and related indicators of SARS and COVID-19, to explore the reasons for the similarities and differences of the two epidemics, so as to provide reference for epidemic prevention and control. Methods: The general situation, clinical classification, activity history, contact history, family members' contact and incidence of the two infectious diseases in Guangzhou were collected and used to analyze the time characteristics, occupational characteristics, age characteristics and other key indicators of the two diseases, including the number of cases, composition ratio (%), mean, median, crude mortality, etc. Results: A total of 1 072 cases of SARS were included in the study. Three hundred and fifty three were severe cases with the incidence of 30.13%. Forty three cases of death were reported with a mortality rate of 4.01%. The average age was 46 years old, and 26.31% of the cases were medical staff. The interval time between first report to continuous zero reports was 129 days. As to COVID-19, a total of 346 cases were included. 58 of which were severe cases with the incidence of 16.67%. One case of death was reported with a mortality rate of 0.29%. The average age was 38 years old, and no hospital infection among medical staff was reported. The interval time between first report to continuous zero reports was 35 days. Conclusions: The prevention and control strategies for COVID-19 were more effective compared to that of SARS, and the emergency response procedures were worth to be evaluated and summarized.

[Schistosomiasis control effect in Mianyang City in ten years after Wenchuan earthquake]

OBJECTIVE

To evaluate the effect of schistosomiasis control in Mianyang City in ten years after Wenchuan earth-quake, so as to provide the experiences for schistosomiasis control post-disaster.

METHODS

The data of implementation of schistosomiasis control work in ten years after the Wenchuan earthquake were collected and analyzed for the epidemic situation of schistosomiasis in Mianyang City. Meanwhile, the awareness situation on schistosomiasis control of villagers and students was investigated by questionnaires in 2008 and 2015.

RESULTS

All of the 6 counties (cities, districts) with schistosomiasis endemic in Mianyang City were hit by the earthquake disaster. After the disaster, the measurements including the conventional schistosomiasis control measures, the control of exogenous infection sources, the control of Oncomelania hupensis snails, and health education were carried out. The relevant departments of schistosomiasis control were cooperated to implement the prevention and control measures. The schistosomiasis prevalence of population and the snail condition rose in the year of the earthquake, but then declined year by year. In 2015, the awareness rates of schistosomiasis control of both villagers and the students were significantly improved compared with those in 2008.

CONCLUSIONS

The measures of schistosomiasis control after the earthquake disaster are effective in Mianyang City, and the goal to prevent major plague after the earthquake is achieved.

[Effect of comprehensive schistosomiasis control strategy with focus on cattle and sheep removal in Junshan District, Yueyang City]

Objective To evaluate the effect of comprehensive schistosomiasis control measures with focus on total removal of cattle and sheep in Junshan District, Yueyang City. Methods The retrospective review and field survey were implemented in the pilot villages in Junshan District. The data of Schistosoma japonicum infection status of human, cattle, sheep and Oncomelania hupensis snails, and density of snails were gathered and modeled in the period of 2006 to 2016. Results The prevalence of schistosome infection in residents in the pilot villages decreased from 3.44% in 2006 to 0.59% in 2012 (F = 14.501, P = 0.013). After removal of all the cattle and sheep in 2013, the prevalence of schistosome infection in the residents decreased to zero in 2016 (F = 14.148, P = 0.033). The density of living snails decreased from 0.883 3/0.1 m² in 2006 to 0.308 8/0.1 m² in 2012 (F = 76.250, P = 0.005). Conclusion The comprehensive schistosomiasis control strategy with focus on cattle and sheep removal is remarkably effective.

[Retrospective analysis of schistosomiasis elimination history in Jingxi City, Guangxi Zhuang Autonomous Region]

OBJECTIVE

To understand the schistosomiasis epidemic and control history in Jingxi City, so as to provide the evidence for improving the future work.

METHODS

The data of schistosomiasis prevention and control work were collected and analyzed comprehensively in Jingxi City from 1956-2015.

RESULTS

From 1956, the schistosomiasis prevention and control work carried out, and in 1985, Jingxi City reached the standard of schistosomiasis transmission interrupted and no local schistosome infected residents and livestock were found for 36 years. In May 2016, the city reached the national standard of Schistosomiasis Elimination Assessment Review. The cumulative number of schistosomiasis detection of residents was 348 801 person-times, and 10 434 schistosomiasis patients were found. The cumulative number of schistosomiasis detection of cattle was 20 674 head-times, and 590 schistosome infected cattle were found. The cumulative schistosomiasis treatment number of residents was 18739 person-times, and 512 cattle were treated. The cumulative detection area with Oncomelania hupensis was 65 213.25 hm², and 353.80 hm² area with O. hupensis snails was found.

CONCLUSIONS

Jingxi City has reached the standard of schistosomiasis elimination, but there is still recurrence of O. hupensis snails, and the imported infection source exists. Therefore, we should strengthen the monitoring of floating population.