[Relationship Between Diversity of Aquatic Plant Communities and Water Environmental Factors in Lhalu Wetland].

Plant diversity plays an important role in the integrity and stability of wetland ecosystems. Lhalu Wetland is the highest wetland in the world and is the largest urban natural swamp in China. It plays an important role in ecological balance, increasing air humidity, improving the urban climate, and purifying the water environment in Lhasa. The changes in plant diversity in different areas of the Lhalu Wetland and its relationship with water environmental factors were analyzed via field investigation, field monitoring, and indoor analysis. Results showed that 18 species of aquatic plants were found in the Lhalu Wetland. The Margalef species richness index was in the order M (Middle west) > W (West) > E (East) > N (North) > S (South). Index of species richness ranked of W (11), M (11) > N (8) > E (7) > S (6). Index of ShannonWiener followed that of M (1.9) > W (1.89) > S (1.63) > E (1.26) > N(1.18). Index of Simpson ranked of N (0.44) > E (0.34) > M (0.24) > S (0.21) > W (0.18). The order of Pielou index was that of S (0.91) > M(0.79) > W(0.78) > E(0.65) > N(0.56). Redundancy analysis showed that the diversity of aquatic plants in the Lhalu Wetland was affected by dissolved oxygen, pH, water temperature, total nitrogen, and turbidity. The dominant species in the Lhalu Wetland are CeratopHyllum demersum L., Hippuris vulgaris, Polygonum hydropiper, Softstem bulrush, Acorus calamus, and Juncus effusus, which show a trend of non-pollution-resistant species succession to pollution-resistant species.

[Effect of Biochar on Root Morphological Characteristics of Wetland Plants and Purification Capacity of Constructed Wetland].

A constructed wetland with Acorus calamus L. was built. Straw biochar, reed biochar, and sawdust biochar was added into the constructed wetland individually to study the effect of different biochars on the root morphology, dissolved oxygen, and purification ability of the constructed wetland. The results show that the total root length, total projection area, total volume, total surface area, root number, branch number, and root dry weight of Acorus calamus L. significantly increased when all three kinds of biochar were added into the constructed wetland (P<0.05). Similarly, adding the biochars into the constructed wetland also significantly increased dissolved oxygen content in the wetland (P<0.05). Addition of sawdust biochar into the constructed wetland increased the root length, projection area, surface area, total volume, number of root tips, number of branches, and root dry weight of Acorus calamus L. by 96.1%, 106.2%, 185.6%, 172.5%, 75.3%, 121.6%, and 84.9%, respectively. After adding biochars into the constructed wetland, the root morphology of Acorus calamus L. and dissolved oxygen content was significantly correlated with removal rate of TN, TP, and COD, respectively. Addition of sawdust biochar into the constructed wetland significantly increased the removal rates of total nitrogen, total phosphorus, and COD when the hydraulic load was 0.022 m3·(m2·d)-1 (P<0.05). These results suggested that the addition of sawdust biochar to the constructed wetland increased the root growth of Acorus calamus L. and enhanced dissolved oxygen content, resulting in purification capacity of the constructed wetland.

[Effect of different substrates on photosynthetic characteristics of Iris pseudacorus L. and the capacity of purify wastewater].

The effect of the different substrates on the photosynthetic characteristics, transpiration rate and SPAD value, and capacity of purify wastewater was investigated by pot experiment, based on five ordinary substrates (soil, sand, mixture of soil and sand, mixture of sand and organic matter, and mixture sand, soil and organic matter). Results showed that the photosynthetic characteristics and transpiration rate of Iris pseudacorus L. were influenced by different substrates. The order of the photosynthetic and transpiration rate of Iris pseudacorus L. in soil was high, and that of Iris pseudacorus L. in sand was the lowest. The value of photosynthetic characteristics and transpiration rate of Iris pseudacorus L. in soil were 11.67 micromol x (m2 x s)(-1) and 9.18 mmol x (m2 x s) (-1) respectively, and that of Iris pseudacorus L. in sand were 8.38 micromol x (m2 x s)(-1) and 4.55 mmol x (m2 x s)(-1), respectively. The photosynthetic characteristics and transpiration rate of Iris pseudacorus L. were significantly correlated with the removal rate of permanganate index, NH4(+) -N and NO3(-) -N (p < 0.05). The SPAD value of Iris pseudacorus L. was also influenced by substrates, and SPAD value of Iris pseudacorus L. in soil was high (58.92), followed by mixture soil, sand and organic matter, that of Iris pseudacorus L. in sand was the lowest (51.14). The significant correlation between the SPAD value of Iris pseudacorus L. and the photosynthetic characteristics, transpiration rate, NH(+) -N was also found (p < 0.05). The SPAD vale of Iris pseudacorus L. in different substrates was different, which was used to monitored operation condition of the removal rate of nitrogen in constructed wetland.

[Biological responses of maize seedlings to single and combined stress of cadmium and phenanthrene].

Maize (Zea mays L.) pot-culture experiments were conducted in this study for exploring the biological responses of maize seedlings to single and joint stress of Cadmium (Cd) and phenanthrene. The results showed that single-Cd treatment with Cd concentration ranging from 0 to 50 mg/kg had no significant influences on the above-ground biomass, root biomass, and the soluble protein of maize seedlings; with the increase of Cd concentrations, the maize leaf SOD activities appeared as an increasing-decreasing trend, while the POD, CAT, APX activities increased persistently. The APX is very sensitive to Cd stress, which increased 38% than control treatment at lower Cd treatment (1 mg/kg). The accumulation of O2-* is one of the main cause of single-Cd toxicity. Under the Cd-phenanthren combined stress, the SOD activity increased at lower Cd concentration (1 mg/kg) , which can reached to 1.66 times of control treatment, and decreased when Cd concentration becomes high. The SOD activity is a sensitive index in response to the Cd-phenanthren combined pollution. Unlike SOD activity, the activities of POD, CAT and APX were obviously induced by combined pollution of Cd and phenanthren; but these enzyme activities decreased when compared with the single-Cd stress, which suggested that the combined toxicity of Cd and phenanthrene is stronger than the single-Cd stress. And the accumulation of O2-* and *OH is one of the main cause of Cd-phenanthrene combined toxicity.

Changes in enzymes activity, substrate utilization pattern and diversity of soil microbial communities under cadmium pollution.

Heavy metal pollution has received increasing attention in recent years mainly because of the public awareness of environmental issues. In this study we have evaluated the effect of cadmium (Cd) on enzymes activity, substrate utilization pattern and diversity of microbial communities in soil spiked with 0, 20, 40, 60, 80, and 100 mg/kg Cd, during 60 d of incubation at 25 degrees C. Enzyme activities determined at 0, 15, 30, 45, and 60 d after heavy metal application (DAA) showed marked declines for various Cd treatments, and up to 60 DAA, 100 mg/kg Cd resulted in 50.1%, 47.4%, and 39.8% decreases in soil urease, acid phosphatase and dehydrogenase activities, respectively to control. At 60 DAA, substrate utilization pattern of soil microbial communities determined by inoculating Biolog ECO plates indicated that Cd addition had markedly inhibited the functional activity of soil microbial communities and multivariate analysis of sole carbon source utilization showed significantly different utilization patterns for 80 and 100 mg/kg Cd treatments. The structural diversity of soil microbial communities assessed by PCR-DGGE method at 60 DAA, illustrated that DGGE patterns in soil simplified with increasing Cd concentration, and clustering of DGGE profiles for various Cd treatments revealed that they had more than 50% difference with that of control.