Systematic approach to source-sink apportionment of copper in paddy fields: Experimental observation, dynamic modeling and prevention strategy.

The accumulation of heavy metals in paddy rice severely impacts the health of consumers and plants. In this study, a systematic approach to source-sink apportionment of copper in paddy fields was developed by considering all bioenvironmental interfaces. Experimental data from two experimental fields (namely Field A and Field B) in the first harvest period was collected. Then, mass-balance-based models with dynamic critical loads were established to evaluate the year of excess for copper. The results indicated that irrigation water contributed the highest portion (96.2-98.8%) of total copper inputs. Under the business-as-usual scenario, the soil copper concentration of Field A and Field B might exceed the Taiwanese national standard within 66 and 24 years, respectively. In addition, alternate wet-dry irrigation was found to be one of the total solutions to reducing copper accumulation in soils by 17-48%. It could also provide a significant reduction of water usage in paddy fields by ~25%, thereby increasing the resilience to extreme climate change events. Lastly, based on the field observations, three improvement strategies on sustaining soil quality towards better agricultural environment were proposed. The connection of copper accumulation in soils with dietary and ecological risks was also briefly illustrated.

Applying factor analyses of statistics to evaluate habitat biodiversity index in dry-season creeks.

The purpose of this study is to analyze the habitat factors (environmental variables) affecting dry-season creek fish, and evaluate habitat biodiversity index (HBI) in dry-season creeks. This research determined HBI formula by 133 study sites in the creek flows in seven rivers in Taiwan from 2007 to 2008. This research considered 10 habitat factors: water depth, width, length, pH, electrical conductivity, temperature, current velocity, rainfall, elevation, and substrate diversity. Using the principal component analysis (PCA), varimax rotated factor analysis (FA), and the simultaneous regression in product-exponential model (PEM), fish total numbers and HBI were formulated by these 10 habitat factors. Pearson's correlation coefficient matrix and three-factor loading plots reported that current flow velocity, rainfall, and elevation affected on fish numbers similarly; besides, water length (logarithmic) and width (logarithmic) had the positive and similar influences in fish numbers. Habitat evaluation levels were classified six groups, namely, excellent habitat, very good habitat, good habitat, fair habitat, poor habitat, and then very poor habitat. In brief, HBI was reasonable and calculated simply by 10 environmental variables of fish habitats. The results of this study can be applied extensively to evaluate the conditions of fish habitats in dry-season creeks for habitat recovery projects.