均衡的植物养分有助于增强茶树抵御真菌的能力从而减少杀虫剂的使用

人们正加大努力以求最大限度地降低杀虫剂的使用,这些杀虫剂是控制茶树和其它作物的病虫害的基本手段 .在中国,由于土壤常常缺少碳酸钾,所以适量使用这种养料有助于减少对杀虫剂的需要 .已经证实,在土壤中加入钾后,茶树感染真菌病的比率下降 .     

Evaluating Controlling Factors to Ali/(Ca + Mg) Molar Ratio in Acidic Soil Water, Southern and Southwestern China: Multivariate Approach

Al_i/(Ca + Mg) molar ratio in soil water has been used as an indicator to the effects of acid deposition on terrestrial ecosystems. However, the main factors controlling this ratio have not been well documented in southern and southwestern China. In this study, we presented the variation in inorganic aluminum (Al_i) and Al_i/(Ca + Mg) molar ratio in different sites and soil horizons based on two to three years monitoring data, and evaluated the main factors controlling Al_i/(Ca + Mg) molar ratio using principle component analysis (PCA) and partial least square (PLS) regression. Monitoring data showed although Al_i/(Ca + Mg) molar ratios in most soil water were lower than assumed critical 1.0, higher molar ratios were found in some soil water at TSP and LXH site. Besides acid loading, both soil properties and soil water chemistry affected the value of Al_i/(Ca + Mg) molar ratio in soil water. Partial least square (PLS) indicated that they had different relative importance in different soil horizons. In A-horizon, soil aluminum saturation (AlS) had higher influence on Al_i/(Ca + Mg) molar ratio than soil water chemistry did; higher soil aluminum saturation (AlS) led to higher Al_i/(Ca + Mg) molar ratio in soil water. In the deeper horizons (i.e., B₁-, B₂- and BC-horizon), inorganic aluminum (Al_i) in soil water had more and more important role in regulating Al_i/(Ca + Mg) molar ratio. On regional scale, soil aluminum saturation (AlS) as well as cation exchange capacity (CEC) was the dominant factor controlling Al_i/(Ca + Mg) molar ratio. This should be paid enough attention on when making regional acid rain control policy in China.     

Identification of soil contamination hotspots with veterinary antibiotics using heavy metal concentrations and leaching data—a field study in China

In regions with high livestock densities, the usage of antibiotics and metals for veterinary purposes or as growth promoters poses a risk in manured soils. We investigated to which degree the concentrations and depth distributions of Cu, Zn, Cr and As could be used as a tracer to discover contaminations with sulfonamides, tetracyclines and fluoroquinolones. Besides, we estimated the potential vertical translocation of antibiotics and compared the results to measured data. In the peri-urban region of Beijing, China, soil was sampled from agricultural fields and a dry riverbed contaminated by organic waste disposal. The antibiotic concentrations reached 110 μg kg^?1 sulfamethazine, 111 μg kg^?1 chlortetracycline and 62 μg kg^?1 enrofloxacin in the topsoil of agricultural fields. Intriguingly, total concentrations of Cu, Zn, Cr and As were smaller than 65, 130, 36 and 10 mg kg^?1 in surface soil, respectively, therewith fulfilling Chinese quality standards. Correlations between sulfamethazine concentrations and Cu or Zn suggest that in regions with high manure applications, one might use the frequently existing monitoring data for metals to identify potential pollution hotspots for antibiotics in topsoils. In the subsoils, we found sulfamethazine down to ≥2 m depth on agricultural sites and down to ≥4 m depth in the riverbed. As no translocation of metals was observed, subsoil antibiotic contamination could not be predicted from metal data. Nevertheless, sulfonamide stocks in the subsoil could be estimated with an accuracy of 35–200 % from fertilisation data and potential leaching rates. While this may not be sufficient for precise prediction of antibiotic exposure, it may very well be useful for the pre-identification of risk hotspots for subsequent in-depth assessment studies.     

EcoEffect for outdoor environments; the process of tool development

Numerous evaluation tools for the built environment have been developed in recent decades only some however integrate the outdoor environment. In EcoEffect, a Swedish assessment system, the outdoor environment is one of five areas covered. The purpose of this article is to describe and discuss various issues that evolved during the testing and developing phase of the EcoEffect Outdoor tool. The tool is designed to cover all important health risks to people in an outdoor environment, to show the relationship between circumstances in the outdoor environment and the levels specified in Swedish legislation and to enable a speedy and accurate assessment of the outdoor environment on a property. The work has been carried out in cooperation with experts, residents and representatives of the construction and property sectors. The tool has been tested on existing properties, discussed in focus groups, and has been subject to theoretical development. The results have provided a basis for changing both the EcoEffect Outdoors tool and the framework of the EcoEffect system. Important conclusions here include the notion that a clear account should be given of the fundamental values of the tool, that environmental impact should be reported in the same way throughout the whole assessment process and that the tool has to adhere to both scientific and practical validity to be useful for the building sector.     

Anthropogenic NOx emissions alter the intrinsic water-use efficiency (WUEi) for Quercus cerris stands under Mediterranean climate conditions

We investigated the effect of N deposition (Ndep) on intrinsic water-use efficiency (WUE_i), the ratio of photosynthesis (A) to stomatal conductance (g_s), for two Quercus cerris stands at different distances to an oil refinery in Southern Italy. We used δ¹³C in tree rings for assessing changes in WUE_i; while the influence of climate and NO_x emission was explored through δ¹⁸O and δ¹⁵N, respectively. Differences in WUE_i between the two sites were significant, with trees exposed to different degrees of NO_x emissions showing an abrupt increase with the onset of pollution. Assuming similar g_s at the two sites, as inferred through δ¹⁸O, the higher N availability at the polluted site caused the shift of the A/g_s ratio in favour of A. Overall, our result suggests that an increase of Ndep may enhance tree WUE under a scenario of reduction of precipitation predicted for Mediterranean area.     

Exposure assessment at a PCDD/F contaminated site in Sweden—field measurements of exposure media and blood serum analysis

Background, aim, and scope  

The main pathway for human exposure to the highly toxic polychlorinated-p-dioxins and polychlorinated furans [polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs)] is via dietary intake. Other exposure pathways may, however, be important in close proximity to point sources, such as wood preservation sites, where PCDD/F contaminated chlorophenols (CP) were previously used. In this study, a heavily PCDD/F contaminated CP saw mill site in Sweden was investigated. Human exposure through a broad spectrum of exposure pathways was assessed. Such studies are in demand since the question whether contaminated sites represent a current or future risk can only be answered by detailed site-specific risk assessments.     

Dynamics of atmospheric nitrogen deposition in a temperate calcareous forest soil

In temperate forest ecosystems, soil acts as a major sink for atmospheric N deposition. A (15)N labeling experiment in a hardwood forest on calcareous fluvisol was performed to study the processes involved. Low amounts of ammonium ((15)NH(4)(+)) or nitrate ((15)NO(3)(-)) were added to small plots. Soil samples were taken after periods ranging from 1 h to 1 yr. After 1 d, the litter layer retained approximately 28% of the (15)NH(4)(+) tracer and 19% of (15)NO(3)(-). The major fraction of deposited N went through the litter layer to reach the soil within the first hours following the tracer application. During the first day, a decrease in extractable (15)N in the soil was observed ((15)NH(4)(+): 50 to 5%; (15)NO(3)(-): 60 to 12%). During the same time, the amount of microbial (15)N remained almost constant and the (15)N immobilized in the soil (i.e., total (15)N recovered in the bulk soil minus extractable (15)N minus microbial (15)N) also decreased. Such results can therefore be understood as a net loss of (15)N from the soil. Such N loss is probably explained by NO(3)(-) leaching, which is enhanced by the well-developed soil structure. We presume that the N immobilization mainly occurs as an incorporation of deposited N into the soil organic matter. One year after the (15)N addition, recovery rates were similar and approximately three-quarters of the deposited N was recovered in the soil. We conclude that the processes relevant for the fate of atmospherically deposited N take place rapidly and that N recycling within the microbes-plants-soil organic matter (SOM) system prevents further losses in the long term.     

Past changes in Arctic terrestrial ecosystems, climate and UV radiation

At the last glacial maximum, vast ice sheets covered many continental areas. The beds of some shallow seas were exposed thereby connecting previously separated landmasses. Although some areas were ice-free and supported a flora and fauna, mean annual temperatures were 10-13 degrees C colder than during the Holocene. Within a few millennia of the glacial maximum, deglaciation started, characterized by a series of climatic fluctuations between about 18,000 and 11,400 years ago. Following the general thermal maximum in the Holocene, there has been a modest overall cooling trend, superimposed upon which have been a series of millennial and centennial fluctuations in climate such as the "Little Ice Age spanning approximately the late 13th to early 19th centuries. Throughout the climatic fluctuations of the last 150,000 years, Arctic ecosystems and biota have been close to their minimum extent within the most recent 10,000 years. They suffered loss of diversity as a result of extinctions during the most recent large-magnitude rapid global warming at the end of the last glacial stage. Consequently, Arctic ecosystems and biota such as large vertebrates are already under pressure and are particularly vulnerable to current and projected future global warming. Evidence from the past indicates that the treeline will very probably advance, perhaps rapidly, into tundra areas, as it did during the early Holocene, reducing the extent of tundra and increasing the risk of species extinction. Species will very probably extend their ranges northwards, displacing Arctic species as in the past. However, unlike the early Holocene, when lower relative sea level allowed a belt of tundra to persist around at least some parts of the Arctic basin when treelines advanced to the present coast, sea level is very likely to rise in future, further restricting the area of tundra and other treeless Arctic ecosystems. The negative response of current Arctic ecosystems to global climatic conditions that are apparently without precedent during the Pleistocene is likely to be considerable, particularly as their exposure to co-occurring environmental changes (such as enhanced levels of UV-B, deposition of nitrogen compounds from the atmosphere, heavy metal and acidic pollution, radioactive contamination, increased habitat fragmentation) is also without precedent.