Urbanization and weather dynamics co-dominated the spatial-temporal variation in pCO2 and CO2 fluxes in small montanic rivers draining diverse landscapes.

Rivers have been widely reported as important CO2 emitters to the atmosphere. Rapid urbanization has a profound impact on the carbon biogeochemical cycle of rivers, leading to enhanced riverine CO2 evasions. However, it is still unclear whether the spatial-temporal patterns of CO2 emissions in the rivers draining diverse landscapes dominated by urbanization were stable, especially in mountainous areas. This study carried out a two-year investigation of water environmental hydrochemistry in three small mountainous rivers draining urban, suburban and rural landscapes in southwestern China, and CO2 partial pressure (pCO2) and fluxes (fCO2) in surface water were measured using headspace equilibrium method and classical thin boundary layer model. The average pCO2 and fCO2 in the highly urbanized river were of 4783.6 µatm and 700.0 mmol m-2 d-1, conspicuously higher than those in the rural river (1525.9 µatm and 123.2 mmol m-2 d-1), and the suburban river presented a moderate level (3114.2 µatm and 261.2 mmol m-2 d-1). It provided even clearer evidence that watershed urbanization could remarkably enhance riverine CO2 emissions. More importantly, the three rivers presented different longitudinal variations in pCO2, implying diversified spatial patterns of riverine CO2 emissions as a result of urbanization. The urban land can explain 49.6-69.1% of the total spatial variation in pCO2 at the reach scale, indicating that urban land distribution indirectly dominated the longitudinal pattern of riverine pCO2 and fCO2. pCO2 and fCO2 in the three rivers showed similar temporal variability with higher warm-rainy seasons and lower dry seasons, which are significantly controlled by weather dynamics, including monthly temperature and precipitation, but seem to be impervious to watershed urbanization. High temperature-stimulated microorganisms metabolism and riched-CO2 runoff input lead much higher pCO2 in warm-rainy seasons. However, it showed more sensitivity of pCO2 to monthly weather dynamics in urbanized rivers than that in rural rivers, and warm-rainy seasons showed hot moments of CO2 evasion for urban rivers. TOC, DOC, TN, pH and DO were the main controls on pCO2 in the urban and suburban rivers, while only pH and DO were connected with pCO2 in the rural rivers. This indicated differential controls and regulatory processes of pCO2 in the rivers draining diverse landscapes. Furthermore, it suggested that pCO2 calculated by the pH-total alkalinity method would obviously overestimate pCO2 in urban polluted rivers due to the inevitable influence of non-carbonate alkalinity, and thus, a relatively conservative headspace method should be recommended. We highlighted that urbanization and weather dynamics co-dominated the multiformity and uncertainty in spatial-temporal patterns of riverine CO2 evasions, which should be considered when modeling CO2 dynamics in urbanized rivers.

Methane and nitrous oxide concentrations and fluxes from heavily polluted urban streams: Comprehensive influence of pollution and restoration.

Streams draining urban areas are usually regarded as hotspots of methane (CH4) and nitrous oxide (N2O) emissions. However, little is known about the coupling effects of watershed pollution and restoration on CH4 and N2O emission dynamics in heavily polluted urban streams. This study investigated the CH4 and N2O concentrations and fluxes in six streams that used to be heavily polluted but have undergone different watershed restorations in Southwest China, to explore the comprehensive influences of pollution and restoration. CH4 and N2O concentrations in the six urban streams ranged from 0.12 to 21.32 µmol L-1 and from 0.03 to 2.27 µmol L-1, respectively. The calculated diffusive fluxes of CH4 and N2O were averaged of 7.65 ± 9.20 mmol m-2 d-1 and 0.73 ± 0.83 mmol m-2 d-1, much higher than those in most previous reports. The heavily polluted streams with non-restoration had 7.2 and 7.8 times CH4 and N2O concentrations higher than those in the fully restored streams, respectively. Particularly, CH4 and N2O fluxes in the fully restored streams were 90% less likely than those found in the unrestored ones. This result highlighted that heavily polluted urban streams with high pollution loadings were indeed hotspots of CH4 and N2O emissions throughout the year, while comprehensive restoration can effectively weaken their emission intensity. Sewage interception and nutrient removal, especially N loadings reduction, were effective measures for regulating the dynamics of CH4 and N2O emissions from the heavily polluted streams. Based on global and regional integration, it further elucidated that increasing environment investments could significantly improve water quality and mitigate CH4 and N2O emissions in polluted urban streams. Overall, our study emphasized that although urbanization could inevitably strengthen riverine CH4 and N2O emissions, effective eco-restoration can mitigate the crisis of riverine greenhouse gas emissions.

[Role of prostate stem cell antigen in human pancreatic carcinoma: a tissue microarray-based study].

OBJECTIVE: To investigate the expression of prostate stem cell antigen (PSCA) in human pancreatic carcinoma and explore its role in the oncogenesis of pancreatic cancer. METHODS: A pancreatic carcinoma tissue microarray was constructed, which contained 10 normal adult pancreas tissues, 12 chronic pancreatitis tissues and 78 pancreatic carcinomas. Immunohistochemistry was employed to detect the expression of PSCA, and the relation between PSCA expression and the clinicopathological factors of pancreatic carcinoma was analyzed. RESULTS: The positivity rate of PSCA in pancreatic carcinoma was 79.5% (62/78), and PSCA staining was more intense in the malignant cells than in the benign cells (chi2=15.81, P<0.005) and chronic pancreatitis tissues (chi2=11.33, P<0.005). No obvious association was found between PSCA expression and the other variables of pancreatic carcinoma (including gender, age at surgery, tumor grade, and TNM stages). CONCLUSION: The expression of PSCA can be related to the development of pancreatic cancer, but not to the clinicopathological factors of the tumor.