The role of plants in channel-dyke and field irrigation systems for domestic wastewater treatment in an integrated eco-engineering system

Eight kinds of plants were tested in channel-dyke and field irrigation systems. The removal rates of TP, phosphate, TN, ammonia, CODcr and BOD, in the channel-dyke system with napiergrass (Pennisetum purpurem Schumach, x Pennisetum alopecuroides (L.) Spreng American) were 83.2, 82.3, 76.3, 96.2, 73.5 and 85.8%, respectively. The field irrigation systems with rice I-yuanyou No.1(88-132) (Oryza sativa L.) and rice II- suakoko8 (Oryza glaberrima) had high efficiency for N removal; the removal rate were 84.7 and 84.3%, respectively. The mass balance data revealed that napiergrass, rice I and II were the most important nutrient sinks, assimilating more than 50% of TP and TN. Plant uptake of N and P as percentage of total removal from wastewater correlated with biomass yield of and planting mode. (C) 2000 Elsevier Science B.V. All rights reserved.

青藏高原高海拔地区C4植物的发现

通过对青藏高原地区27°42′～40°57′N,88°93′～103°24′E海拔2210～5050m范围内采集的植物进行碳同位素分析,发现其中2种藜科和6种禾本科植物是C4植物.11个地点的4种C4植物海拔超过了3800 m,其中6个地点的3种C4植物(白草Pennisetum centrasiaticum,云南野古草Arundinella yunnanensis和固沙草Orinus thoroldii)分布在海拔4000 m以上,最高可达4520 m.分析认为在大气低CO2分压背景下,强光照提供的充足能量使C4植物能忍耐更低的温度,以及青藏高原南部降雨集中于高温季节的有利条件,可能是C4植物生长在高海拔地区的重要原因.