最佳三维拟合直线

通过借助旋转矩阵的三维坐标变换，很容易将空间观测到的一序列点直线串起来，通过两次序列变换可给出中线的位置和方向，以及作为该线垂直支距的残差，然后通过逆变换产生直线在原坐标系中的坐标。本文包括一数字例子。     

Amelioration of marine farming impact on the benthic environment using artificial reefs as biofilters

An in situ monitoring of the sediment characteristics and macrobenthic communities was undertaken at a marine fish culture site in subtropical waters of Hong Kong before and after the deployment of biofilters which were made of cement concrete artificial reef (AR) structures. According to the distance to the boundary of the fish cages, 6 points were selected as sampling stations: 2 at the fish cages, 2 near the boundary of the fish culture area, and 2 reference sites further away from the culture area. Bimonthly sediment samples were collected for analysis of silt-clay fraction (SCF), moisture content (MC), total organic carbon (TOC), total Kjeldahl nitrogen (TKN) and total phosphorus (TP). The macrobenthos (>0.5mm) present in the sediment were sorted, identified and enumerated. TOC, TKN and TP levels at the fish cage stations were consistently higher than those at the reference stations over the 1-year pre-AR and 2-year post-AR deployment monitoring period. The diversity of macrofauna was significantly reduced at the fish cage stations relative to the reference sites. The intermediary stations near the fish culture area showed a transitional state of disturbance. Over the 2-year post-AR deployment period, TOC, TKN and TP showed a decreasing trend at the fish cage and intermediary stations. More diverse macrofaunal communities were recorded at the fish cage stations, with species diversity H'increasing from 0-1 at the beginning of the AR deployment to H'>2 at the end of the study. The present results demonstrated that artificial reefs can improve the benthic abiotic environment and biotic conditions beneath fish rafts which are deteriorated due to farming activities.     

Potential use of mangroves as constructed wetland for municipal sewage treatment in Futian, Shenzhen, China

A pilot-scale mangrove wetland was constructed in Futian, Shenzhen for municipal sewage treatment. Three identical belts (length: 33m, width: 3m, depth: 0.5m) were filled with stone (bottom), gravel and mangrove sand (surface). Seedlings of two native mangrove species (Kandelia candel, Aegiceras corniculatum) and one exotic species (Sonneratia caseolaris) were transplanted to the belts with one species for each belt. The hydraulic loading was 5m(3)d(-1) and hydraulic retention time 3d. High levels of removal of COD, BOD(5), TN, TP and NH(3)-N were obtained. The treatment efficiency of S. caseolaris and A. corniculatum was higher than that of K. candel. Faster plant growth was obtained for S. caseolaris. The substrate in the S. caseolaris belt also showed higher enzyme activities including dehydrogenase, cellulase, phosphatase, urease and beta-glucosidase. The removal rates of organic matter and nutrients were positively correlated with plant growth. The results indicated that mangroves could be used in a constructed wetland for municipal sewage treatment, providing post-treatment to remove coliforms was also included.     

Radionuclide monitoring in molluscs inhabiting intertidal region near a nuclear installation, Gulf of Mannar, India

Protection of non-human biota from ionizing contaminants, especially in the vicinity of nuclear installations is a very important aspect for nuclear engineers and ecologists. In this view, a baseline data on the activity concentration of (210)Po and (210)Pb were quantified in different tissues of molluscs inhabiting the intertidal region along the coast of Kudankulam. The activity concentration was noticed higher in the organs associated with digestion and metabolism. Filter feeding bivalve molluscs registered the maximum activity of (210)Po in their whole body compared to grazing gastropods. (210)Po:(210)Pb ratio was calculated to be greater than unity in most of the analysed tissues. The ecological sensitivity of molluscs to the radiation exposure and the safeness of the environment was analysed by calculating the external and internal dose rate. The hazard quotient for molluscs was lesser than the global bench mark dose rate of 10 μGyh(-1).     

Differences in leaf construction cost between alien and native mangrove species in Futian, Shenzhen, China: implications for invasiveness of alien species

Construction cost (CC) is a quantifiable measure of energy demand for biomass production, and low CC is hypothesized to give an alien plant growth advantages and increase its potential to be an invader. Comparison of leaf CC and growth traits between alien and native mangroves in Shenzhen Futian Nature Reserve showed CC per unit mass (CC_mass), carbon concentration and gross and ash-free caloric values of alien mangroves were significantly lower than those of native species, while the height and chest circumference were just the opposite. Alien species Sonneratia apetala had the lowest CC_mass while Sonneratia caseolaris had the lowest CC_area, and were 8.99% and 32.17% lower than those of native species, respectively. Conversely, specific leaf area (SLA) of these two Sonneratia species was significantly higher than native species. Lower CC and higher SLA make the two Sonneratia species grow and spread faster than other mangroves and enhance their invasive potential.     

Respiration rate and swimming activity of larvae of two sub-tidal nassariid gastropods under reduced oxygen levels: implications for their distributions in Hong Kong waters

The effects of hypoxia on the larvae of two sub-tidal nassariid gastropods, Nassarius siquijorensis and N. conoidalis were compared so as to understand how the species-specific tolerance to hypoxia might have resulted in changes in the abundance and distribution of these two species in the hypoxic Tolo Harbour, Hong Kong, since the 1980s. Respiration rates of N. siquijorensis and N. conoidalis larvae were reduced at 4.5 mg O2 l(-1), or below, as compared with the normoxic control. Significant reduction in swimming velocity was also observed for 10-day old larvae which were exposed to <2.0 mg O2 l(-1) for N. siquijorensis and <1.0 mg O2 l(-1) for N. conoidalis. The 48 h LC50 values of N. siquijorensis and N. conoidalis larvae were 0.7 and 1.7 mg O2 l(-1), respectively. The results suggested that N. siquijorensis are more tolerant to hypoxia than N. conoidalis.     

Impact of hypoxia on the structure and function of benthic epifauna in Tolo Harbour, Hong Kong

In Tolo Harbour, Hong Kong, where hypoxia occurs periodically, a large amount of benthic epifauna was found to be absent in the summer but become abundant again in the winter. This observation may indicate that some species are sensitive in detecting low dissolved oxygen (DO) levels and are able to escape from the harbour to more oxygenated, open waters when conditions deteriorate and return when DO levels are improved. Analysis of biological traits of these animals showed that 58% of the categories showed significant differences between the community structure in summer and winter. The significant biological traits of the few species, which remained in the harbour under the summer's hypoxic conditions suggested adaptation rather than opportunism to the low DO levels. Our data also showed that trawling can increase DO at the bottom and may benefit the less sensitive species that remained in the habitat during the summer.     

勘查深部矿的地电化学方法实际应用的一些情况

对于以分析土壤中多种赋存形式元素为基础的勘查深部矿的地球化学方法已引起全球范围兴趣的增加。基于十余年之经验，作者在这里讨论了这些方法各种地电化学变型的优势及不足之处。