The National Health Interview Survey (NHIS) is a multipurpose household survey of the U.S. civilian non-institutionalized population conducted annually since 1957. From 1986 to 1994, over 450,000 U.S. workers, age 18 years and older, participated in a probability sampling of the entire non-institutionalized U.S. population; variables collected included a range of measures of acute and chronic disability. The objective of the present study was to assess predictors of health status, and acute and chronic disability for farmers and pesticide applicators (pesticide-exposed workers) compared to all other U.S. workers using the 1986-1994 NHIS. After adjustment for sample weights and design effects using SUDAAN, several measures of acute and chronic disability and health status were modeled with multiple logistic regression. Farmers (n = 9576) were significantly older compared to all other U.S. workers (n = 453,219) and pesticide applicators (n = 180). Farmers and pesticide applicators had a higher proportion of males, whites, and Hispanics and were less educated. After adjusting for age, gender, race-ethnicity, and education, compared to all other workers, farmers were significantly less likely to report acute and chronic disability and health conditions, while pesticide applicators were more likely to report chronic disability, health conditions, and poor health. Given the cross-sectional nature of the data and the significant job demands of farming, both leading to a relative healthy worker effect, the present results indicate that at any point in time, farmers report less acute and chronic disability, compared to other U.S. workers, whereas pesticide applicators report similar or poorer health. 相似文献
该文以甲苯为焦油模型化合物,利用生物质焦炭诱导其转化合成气,探讨加热方式和通入CO2对甲苯转化的影响。结果表明:同等工况下,微波加热(microwave heating,MH)下甲苯转化率高于常规加热(electrical heating,EH),甲苯转化率最大差值为15.58%。通入CO2可促进甲苯转化,MH和EH下分别在CO2流量为80和40 m L/min达到最高转化率93.73%和82.13%。引入CO2可调控甲苯定向制备合成气,且对生物质焦炭造成碳损耗。损耗碳可转化合成气,且CO2通入量越高,其贡献越大。MH下合成气最大产率为173.66 m L/min,为裂解反应的5.68倍。甲苯裂解率持续降至49.0%,之后趋于稳定。甲苯重整转化率维持较高水平,140 min后开始减弱,同时合成气收率平缓降低。该文研究结果对高效利用焦油和减排CO2有借鉴意义。 相似文献
以皖北平原典型农业生产大县亳州市蒙城县为代表,运用统计学、地统计学方法和GIS技术研究了其农田耕作层(0~20 cm)土壤有机碳(SOC)含量的空间分布及其影响因子。结果表明:研究区SOC含量为10.41±2.52 g kg-1,近30年来提高了55.61%,SOC变异系数为24%,属于中等变异程度。SOC含量在空间分布上表现为东北部、中部和西南部含量高,由西北向东南先逐渐增加后逐渐降低,变异程度较高。整个县域范围内SOC空间变异的主要影响因素为土壤机械组成(粉粒和砂粒含量),其次为秸秆还田。 相似文献
Soil nutrients, elemental stoichiometry, and their associated environmental control play important roles in nutrient cycling. The objectives of this study were (1) to investigate soil nutrients and elemental stoichiometry, especially potassium and its associative elemental stoichiometry with other nutrients under different land uses in terrestrial ecosystems; (2) to discuss the impacts of climate factors, soil texture, and soil physicochemical properties; and (3) to identify the key factors on soil nutrient levels and elemental stoichiometry.
Materials and methods
Soil data, including pH, bulk density (BD), cation exchange capacity (CEC), volumetric water content (VMC), clay, silt and sand contents, total carbon (TC), nitrogen (TN), phosphorous (TP) and potassium (TK), available nitrogen (AN), phosphorus (AP), potassium (AK), and soil organic matter (SOM) under different land-use types, were collected, and their elemental stoichiometry ratios were calculated. Climate data including temperature, precipitation, relative humidity, wind speed, and evapotranspiration were collected. The least significant difference test and one-way analysis of variance were applied to investigate the variability of soil nutrients and elemental stoichiometry among land-use types; the ordinary least squares method and the general linear model were used to illustrate the correlations between soil nutrients, elemental stoichiometry, and soil properties or climate factors and to identify the key influencing factors.
Results and discussion
Woodlands had the highest SOM, TN, AN, and AK contents, followed by grasslands, croplands, and shrublands, while the TP and TK contents only varied slightly among land-use types. SOM, TN, AN, N/P, and N/K were strongly negatively correlated to soil pH (p <?0.05) and were strongly positively correlated to soil CEC (p <?0.05). For soil texture, only C/N was moderately negatively correlated to silt content but moderately positively correlated to sand content (p <?0.05). For climate factors, SOM, TN, AN, N/P, and N/K were significantly negatively correlated to evapotranspiration and temperature (p <?0.05), and the correlations were usually moderate. Soil pH explained most of the total variation in soil nutrients, and climate factors explained 5.64–28.16% of soil nutrients and elemental stoichiometry (except for AP (0.0%) and TK (68.35%)).
Conclusions
The results suggest that climate factors and soil properties both affect soil nutrients and elemental stoichiometry, and soil properties generally contribute more than climate factors to soil nutrient levels. The findings will help to improve our knowledge of nutrient flux responses to climate change while also assisting in developing management measures related to soil nutrients under conditions of climate change.