[Measurement of dissolved organic nitrogen with nanofiltration pretreatment and its distribution characteristics in landscape water].

In this study, we present a nanofiltration (NF90, NF270) pretreatment to increase the precision of dissolved organic nitrogen (DON) measurements in water samples. The variations of DON measurements with and without NF pretreatment were investigated. And the effects on the removal of dissolved inorganic nitrogen (DIN) by NF90 and NF270 were compared. As shown in the results, the average removal rates reached 30.7%, 55.9% of NH4(+)-N, 50.0%, 73.1% of NO3(-) -N and 42.9%, 72.0% of NO2(-)-N for NF90 and NF270 pretreatment, respectively. NF270 was obviously more effective to remove the DIN species. Concentrations of DON measured using traditional methods varied from 0.09 to 0.46 mg x L(-1), with negative concentration (-0.08 mg x L(-1)) at site 2 and the DIN/TDN ratio ranged from 85.3% to 105%; while the concentrations of DON measurements varied from 0.03 to 0.58 mg x L(-1), and the DIN/TDN ratio ranged from 76.1% to 90.6% for NF90 pretreatment and varied from 0.10 to 0.59 mg x L(-1), and the DIN/TDN ratio ranged from 47.5% to 84.5% for NF270 pretreatment. The results indicated that nanofiltration pretreatment could effectively remove the DIN species, decrease the standard deviation of DON measurements and increase the precision of DON measurements. The distribution of DON in water samples of Beijing Olympic Forest Park was investigated. The results showed that there was seasonal variation in the concentrations of DON in landscape water from the Olympic Forest Park. And there was significant difference between the north and south part. The DON concentrations were less than 0.2 mg x L(-1) in November, March and May and higher in July in the north part, while the DON concentrations were lower in May and higher in November and March in the south part, ranging from 0.40-0.65 mg x L(-1).

[Characteristics of organic phosphorus fractions in different trophic sediments of lakes, China].

In this study, the characteristics of organic phosphorus fractions in sediments of seven lakes with different drainage basin feature, ecological structure, and polluted levels from different regions were investigated, and the relationships between organic phosphorus (Po), inorganic phosphorus (Pi) and bioavailable characters were also discussed. The difference of the related content of Po in different sediments indicated the discrepancy of phosphorus sources and biogeochemical cycles in different lakes. Organic matter (OM) was significantly correlated with Po (R2 = 0.80, p < 0.01), and except for Lake Qilu, OM was significantly correlated with labile Po, moderately labile Po and nonlabile Po in all studied sediments (R2 were 0.85, 0.52, 0.80 respectively, p < 0.01). The moderately labile Po and nonlabile Po were the main fraction of Po in all studied lakes, and the relative contributions to total Po were 15.12%-66.73% and 27.99%-77.72%, respectively. The mean proportion of labile Po was 6.1% in studied sediments. The rank order of Po fractions was residual Po > HCl-Po > fulvic acid-Po > humic acid-Po > NaHCO3-Po with mean relative proportion 8.3:3.1:2.2:1.8:1.0. Labile Po was significantly correlated with total phosphorus (TP), Pi , Po, NaHCO3-Pi and NaOH-Pi . Furthermore, Labile Po was also significantly correlated with T), Po and NaOH-Pi in all studied sediments, which suggested that labile Po was transformed into bioavailable phosphorus and the nonlabile Po may become a potential source of available phosphorus, although it was considered as highly resistant fraction.

[Rapid determination of chemical components in interstitial water of lake sediments using near-infrared spectroscopy].

The near infrared reflectance spectra (NIRS) of interstitial water samples of lake sediments in Chaohu lake were determined by near-infrared reflectance spectrometry. The respective near NIRS calibration models for predicting total nitrogen (TN), total organic carbon (TOC), phosphorus ( PO3(3-)), ammonia nitrogen(NH3-N) and silicate (SiO3-) were built using partial least squares (PLS) algorithm with two spectral pretreatment tools including, wavelet compression combining orthogonal signal correction (OSC) and orthogonal signal correction (OSC) combining wavelet compression. The correlation coefficients between measured values and predicted values in calibration set for TN, NH3-N, PO3(3-), TOC and SiO3(3-) were 0.975, 0.989, 0.937, 0.862 and 0.888, respectively. RMSEC (root mean square error of the calibration) for TN, NH3-N, PO3(3-), TOC and SiO3- were 0.353, 0.238, 0.031 3, 2.005 and 2.674 mg x L(-1), respectively. The correlation coefficients between measured values and predicted values in validation set for TN, NH3-N, PO3(3-), TOC and SiO3- were 0.912, 0.918, 0.773, 0.337 and 0. 856, respectively. RMSEP(root mean square error of the prediction)for TN, NH3-N, PO3(3-), TOC and SiO3- were 1.424, 0.945, 0.081, 7.866 and 4.273 mg x L(-1), respectively.

[Rapid determination of nutrient components in lake sediments using near infrared spectroscopy].

The lake sediments record important environmental evolution information of lake in recent 100 years. However, a rapid and precise combination analytical method measuring nutrient components in lake sediments can not be established. The near infrared reflectance spectra (NIRS) of sediment coring samples were determined by near-infrared reflectance spectrometry. The respective near NIRS calibration models for predicting total carbon (TC), total nitrogen (TN), total organic carbon (TOC) and total phosphorus (TP) were built first in China using partial least squares (PLS) algorithm with six spectral pretreatment tools including first-order derivate, wavelet denoise, orthogonal signal correction (OSC), wavelet denoise combining orthogonal signal correction (OSC), first-order derivate combining orthogonal signal correction (OSC), and orthogonal signal correction (OSC) combining wavelet compression. The results showed that although NIR all calibration models can not well predict TOC, the first-order derivate combining OSC spectral calibration model had a good prediction for TC and TN, and for TP OSC spectral calibration model was good. The correlation coefficients between measuring values and predicted values in validation set for TC, TN and TP were 0.76, 0.87 and 0.81, respectively. RMSEP (Root mean square error of the prediction) for TC, TN and TP were 0.13%, 0.0082% and 0.012%, respectively. The study has an important significance of driving the domestic researches on spectroscopy characteristic of lake sediments and establishment of rapid analytical technique determining nutrient components of lake sediments.