The bioremediation potential of bacteria indigenous to soils of the Yellow River Delta in China was evaluated as a treatment option for soil remediation. Petroleum hydrocarbon degraders were isolated from contaminated soil samples from the Yellow River Delta. Four microbial communities and eight isolates were obtained. The optimal temperature, salinity, pH, and the ratios of C, N, and P (C:N:P) for the maximum biodegradation of diesel oil, crude oil, n-alkanes, and polyaromatic hydrocarbons by indigenous bacteria were determined, and the kinetics changes in microbial communities were monitored. In general, the mixed microbial consortia demonstrated wider catabolic versatility and faster overall rate of hydrocarbon degradation than individual isolates. Our experimental results demonstrated the feasibility of biodegradation of petroleum hydrocarbon by indigenous bacteria for soil remediation in the Yellow River Delta.
WANG Zhen-YuGAO Dong-MeiLI Feng-MinZHAO JianXIN Yuan-ZhengS. SIMKINSXING Bao-Shan
A series of pot experiments with Alternanthera philoxeroides,Typha latifolia,Sagittaria sagittifolia and Phragmites communis were conducted to assess the phosphorus depletion effect in the rhizosphere.The ratio of root to shoot,root morphology,phosphorus uptake efficiency and phosphorus utilization efficiency were analyzed.An obvious variation in phosphorus concentrations between the rhizosphere soil and non-rhizosphere soil was observed.The water-soluble P contents in the rhizosphere soil of A.philoxeroides,T.latifolia,S.sagittifolia and P.communis were reduced by 81%,42%,18%and 16%,respectively,compared with that in the non-rhizosphere soil.A.philoxeroides had the highest phosphorus uptake efficiency(1.32 mg/m),while T.latifolia achieved the effective phosphorus depletion by the strong rooting system and the high phosphorus uptake efficiency(0.52 mg/m).T.latifolia not only used phosphorus to produce biomass economically,but also adjusted carbon allocation to the roots to explore the soil for more available phosphorus.A.philoxeroides and T.latifolia were more effective in depleting phosphorus in the rhizosphere than S.sagittifolia and P.communis.
Zhenyu WANGShengfang WENBaoshan XINGDongmei GAOFengmin LI
Five different sites with a soluble salt gradient of 3.0-17.7 g kg^-1 dry soil from the coast to the inland were selected, and the microbial population size, activity and diversity in the rhizospheres of five common plant species and the adjacent bulk soils （non-rhizosphere） were compared in a degraded wetland of the Yellow River Delta, Shandong Province, China to study the effects of soil environment （salinity, seasonality, depth, and rhizosphere） on microbial communities and the wetland＇s ecological function, thus providing basic data for the bioremediation of degraded wetlands. There was a significant negative linear relationship between the salinity and the total number of microorganisms, overall microbial activity, or culturable microbial diversity. Salinity adversely affected the microbial community, and higher salinity levels resulted in smaller and less active microbial communities. Seasonal changes were observed in microbial activity but did not occur in the size and diversity. The microbial size, activity and diversity decreased with increasing soil depth. The size, activity and diversity of culturable microorganisms increased in the rhizospheres. All rhizospheres had positive effects on the microbial communities, and common seepweed had the highest rhizosphere effect. Three halophilic bacteria （Pseudomonas mendocina, Burkholderia glumae, and Acinetobacter johnsonii） were separated through BIOLOG identification, and common seepweed could be recommended for bioremediation of degraded wetlands in the Yellow River Delta.
WANG Zhen-YuXIN Yuan-ZhengGAO Dong-MeiLI Feng-MinJ. MORGANXING Bao-Shan
