ABSTRACT
Soil zinc (Zn) plays a crucial role in plant growth, but excessive accumulation in the environment may lead to air, water and soil pollution. It is affected by various chemical, environmental and spatial factors. Therefore, it is important to identify the factors influencing Zn content in the landscape. The main motivation for this study is to determine the suitability of a generalized additive model (GAM) to describe change in soil Zn content due to influencing factors. A total of 1497 soil nutrient samples were collected in Fangshan District, Beijing, China. Organic matter (OM), available phosphorus (AP), available potassium (AK), alkali-hydrolyzed nitrogen (AHN) and slowly available potassium (SAK) are considered. The relationship between Zn, nutrients and geographic location (latitude & longitude) is investigated using the GAM. More precisely, the Akaike information criterion (AIC) is used to select influencing factors on Zn content and cross-validated to avoid overfitting of the multivariate model. The results show that Zn content reaches its maximum at latitude 39.8°N and longitude 115.9°E. Zinc content increases as AP increases to 150 mg/kg. When OM content is greater than 90 g/kg, Zinc content decreases with an increase in OM content. Factors that affected Zn content, in descending order of significance derived from deviance explained and adjustment coefficient of determination (Adj.R2) were AP, latitude, AHN, AK and OM. Moreover, the interactions between latitude and longitude, AHN and AP, OM and AK have significant impact on Zn.
ABSTRACT
OBJECTIVE: Pre-competition sports training can have varying effects on an athlete's immune function, including causing reduced resistance. The aim of this study was to explore effects of pre-competition training on some biochemical indices and immunologic functions in top-level volleyball athletes to determine whether training should be modified for optimal health. METHODS: Biochemical indices (Hb, BUN, CK, LDH) and immunologic function (IgA, IgG, IgM, CD3(+), CD4(+), CD8(+)) were detected by semiautomatic biochemistry analyzer, light scattering photometer, or flow cytometry in sera from 24 top-level volleyball athletes and compared before and after pre-competition training. RESULTS: After training, the levels of Hb, IgA, IgG, IgM, and CD4(+) and the CD4(+)/CD8(+) ratio decreased significantly, while BUN, CK, LDH, and CD8(+) increased significantly (P < 0.05). Further, the decrease in Hb levels in female athletes was more significant than that in male athletes (P < 0.05). CONCLUSIONS: These results indicate that pre-competition training affects biochemical indices and immunologic function in this group of athletes. Additionally, more dramatic changes in Hb in female athletes may indicate a need for adapted training loads and rest periods for females.
