Average Concentrations Of TN Research Articles

Multivariate Analysis of Interactions Between Phytoplankton Biomass and Environmental Variables in Taihu Lake, China

Phytoplankton variation in large shallow eutrophic lakes is characterized by high spatial and temporal heterogenity. Understanding the pattern of phytoplankton variation and the relationships between it and environmental variables can contribute to eutrophic lakes management. In this study Taihu Lake, one of the largest eutrophic fresh water lake in China, was taken as study area. The water body of Taihu Lake was divided into five regions viz. Wuli bay (WB), Meilian Bay (MB), West Taihu Lake (WTL), Main Body of Taihu Lake (MBTL) and East Taihu Lake (ETL). Concentrations of chlorophyll-a and the related environmental variables were determined in each region in the period 2000-2003. Factor analysis and multivariate analysis were applied to evaluate the interactions between phytoplankton variation and environmental variables. Results showed that the highest average concentrations of TN, TP and Chl-a were observed in WB, followed in a descending order by MB and WTL, and the lowest concentrations of TN, TP and Chl-a were observed in MBTL and ETL. Chl-a and TP concentrations in most regions (except ETL) declined during the study period. It suggested that to some extent the lake was recovering from eutrophication. However, persistent ascending of TN and NH(4)-N in all five regions indicated the deteriorating of water quality in the study period. Results of multivariate showed that the relationships between phytoplankton biomass and environmental variables varied among regions. TP illustrated itself a controlling role on phytoplankton in WB, MB, WTL and MBTL according to the significant positive relations to phytoplankton biomass in these regions. Nitrogen could be identified as a limiting factor to phytoplankton biomass in ETL in view of the positive correlations between TN and phytoplankton and between NH(4)-N and phytoplankton. Spatial variation of interactions between phytoplankton and environmental parameters suggested proper eutrophication control measures were needed to restore ecological system in each region of Taihu Lake.

Improvement of existing nightsoil treatment plant for nitrogen removal

This study was performed to increase the treatment efficiency and to reduce operation and maintenance costs of the existing nightsoil treatment plant. The existing nightsoil plant was not established by the nitrogen removal process, and was operated ineffectively with deterioration of treatment efficiency rate, and according to the demand of many operators, the expenses of operation and maintenance have become excessive. Modified plant has been changed through two steps. The first step, liquid decayed tank using closed oxidation ditch is operated to increase retention time only for nitrification. The second step, modified liquid decayed tank including anoxic tank is operated, it has an excellent nitrogen removal rate. In first step, when HRT was increased from 10 days to 13 days in liquid decayed tank including aeration tank using closed oxidation ditch, TN concentration of effluent appeared below 51 mg/L less than discharge limit, 60 mg/L. In second step, when anoxic tank and oxic tank were installed, HRT has been increased to 13 days and 26 days, respectively. Then average TN concentration of effluent was detected less than 13 mg/L for over one year. The simple process modified the existing two processes resulted in the reduction of costs for operation and maintenance in the personnel, chemical, and filter change sphere.

Evaluation of the impact of paddy fields on stream water nitrogen concentration in Central Hokkaido

We investigated the impact of paddy fields on stream water N concentration in the Sorachi and Kamikawa districts in central Hokkaido, Japan. Water sampling was carried out at the post-fertilization (PF), crop growing (CG), and post-harvest (PH) stages of paddy cropping (hereafter referred to as ‘seasons’) in 2001. The proportion of the land use types in drainage basins was obtained from topographic maps. The results of land use analysis showed that the proportion of paddy fields tended to increase when the proportion of arable lands including upland fields and grass lands but excluding paddy fields, hereafter referred to as ‘upland’ increased in Sorachi, but decreased in Kamikawa. Linear regression analysis indicated that the TN and NO3 −-N concentrations in stream water were significantly correlated with the proportion of upland in the drainage basins in all seasons. However, the TN concentration showed a significant correlation with paddy fields only during the paddy growing seasons (PF and CG seasons) but not during the PIE season. The NO3 −-N concentration was no correlated with the proportion of paddy fields in all seasons, while the Org-N concentration showed a highly positive correlation with the proportion of paddy fields during the paddy growing seasons. Multiple regression analysis showed that the average TN concentration was significantly correlated with a combination of proportion of paddy fields, upland, and urban areas in Sorachi (r 2 = 0.84, p < 0.001) and with a combination of proportion of paddy fields and upland in Kamikawa (r 2 = 0.28, p < 0.05). The values of the partial regression coefficients or impact factors were much lower for paddy fields than those for upland in Kamikawa and Sorachi, respectively. It is concluded that although the distribution pattern of paddy fields and upland in the drainage basins was different in the two districts, the impact of paddy fields on N pollution in stream water was much lower than that of upland in both districts.

The Annual Fluctuation of Chlorophyll-a and the Algal Growth Potential Test in West Lake, Hangzhou

通过1999年1- 12月对杭州西湖主要湖区叶绿素a含量及水质理化指标的逐月测定,分析了西湖主要湖区叶绿素a含量周年动态变化特征及各种环境生态因子对叶绿素a的影响,并对湖水进行了藻类增长潜力试验.研究结果表明,西湖主要湖区叶绿素a含量总体保持在同一水平,年变化在41.16- 191.26mg/m³之间,年均值为99.98mg/m³.叶绿素a含量有明显的季节变化特征,夏季和初秋为高峰,冬季最低.水体总磷浓度与叶绿素a年周期动态变化一致,叶绿素a含量的季节变化与水温变化呈显著正相关.西湖为典型的蓝藻型湖泊,总氮年均值为2.08mg/L,总磷年均值为0.121mg/L,N:P大于17,水体中磷对藻类增长的促进作用比氮更为明显;The annual fluctuation of chlo rophyll-a concent rations and some chemical indicators were measured in the main areas of West Lake, Hangzhou during January-December 1999.The algal grow th potential test in water from West Lake were made.The relations between the chlo rophylla concent rations and various ecolog ical factors were discussed.The experimental results are as follows.The concent rations of chlorophyll-a in main Lake-areas appear in the same level.The range was 41.16-191.26mg/m³ and the annual average concent ration was 99.98mg/m³.The concentrations of chlo rophyll-a showed marked seasonal variation the highest in summer and early autumn and the low est in winter.The concent ration of chlorophyll-a has close relation with water temperature and TP.The West Lake is a typical Cyanophyta-pat tern lake in which the annual average concent rations of TN and TP were 2.08mg/L and 0.121mg/L respect ively.The ratio of TN to TP is more than 17 in West Lake, indicating TP's domination in the stimulation of algal growth.