Supported by Blackland GRASS Geographic Information System (GIS), the basic and special environmental databases of West Lake Watershed were established. The vulnerability map of ground water pollution was calculated and drawn by integrating GIS and DRASTIC model. Comparing to the present situation of land use, critical area of ground water pollution had been determined. The residential area accounted for 14.7% of the high susceptible area, and wastewater in the residential area should be piped and treated first.
Rare earth elements (REEs) and Si in five species of seaweed, ambient surface seawaters, and suspended solid particles in the seawaters were determined separately. Inductively coupled plasma mass spectrometry (ICP‐MS) was used for REEs and inductively coupled plasma emission spectrometry (ICP‐ES) was used for Si in order to evaluate REEs as a tracer in seaweeds and to understand the source of inorganic elements, especially Si, in seaweeds. Two different REE patterns, one similar to that of the seawater solution and another resembling that of suspended particles, were observed in seaweeds, and the variation of REE patterns seems to show a clear dependence on the abundance of Si. The REE pattern and Si concentration seem to vary depending on the division: green and red algae showed REE patterns similar to that of suspended particles, but brown algae showed patterns closer to that of seawater solutions and relatively lower Si concentration. The possibility of contamination from silicate particles on the surface of seaweeds was ruled out for several reasons. Silicate particles, not dissolved silicate, have been identified as the direct source of REEs and Si in plants ( Fu et al. 1998 ), and seaweeds are no exception. We have to consider that seaweeds can take up Si from suspended particles through their blade or branches. From the appearance of tetrad‐effect‐like variation of REEs, Si is assumed to enter a dissolved state just before the particles are taken up. From the results of a sonication experiment, REEs, once taken up as silicate particles, seem to be separated from Si in the thallus.
The carbon isotopic ratio for ecosystem respiration ( δ 13 C R ) is an important parameter in isotopic mass balance models for the global carbon budget. Recent studies in North American and European temperate forests showed that δ 13 C R was controlled by stomatal regulation of gas exchange and associated changes in photosynthetic carbon isotope discrimination. In this model, δ 13 C R depends on the vapor pressure deficit (vpd) and precipitation (i.e., plant water availability). We investigated the monthly and annual variation in δ 13 C R and its controlling factors in two cool‐temperate deciduous forests in the monsoon climate area of Japan. The Keeling plot approach was used to evaluate variation in δ 13 C R . Overall, δ 13 C R varied from −24.1‰ to −29.7‰ and was most negative in late summer and autumn. The amplitude of the variation was 2.0‰ to 2.2‰ within a forest. In 1996, which had unusually little precipitation (63% of normal precipitation), δ 13 C R was correlated with vpd measured 7 d before sampling and monthly precipitation, consistent with predictions based on the stomatal regulation model. In contrast, δ 13 C R in 1995 was insensitive to vpd and precipitation, but was significantly correlated with air temperature, suggesting temperature control associated with variabilities in the decomposition of labile and recalcitrant pools of soil carbon and in the availability of recent photosynthate‐derived carbon for respiration. Variation in heterotrophic respiration rather than photosynthetic discrimination appeared to be the dominant factor governing δ 13 C R in our forests at near‐normal levels of precipitation. The results of our study can be used to better constrain future model estimates using δ 13 C R and ecosystem‐level discrimination in a temperate forest in the Asian monsoon region.
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