Evaluating the effectiveness of routine water quality monitoring in Miyun reservoir based on geostatistical analysis.

This study used geographic information system techniques and geostatistics methods to evaluate the effectiveness of routine water quality monitoring in the western segment of the Miyun reservoir in Beijing. Methodologies as well as the sampling design are evaluated. The single-layer evaluation and three integrated evaluation methods including principal component analysis (PCA), ordinary kriging (OK)_Mean, and Mean_Layers were used to validate the effectiveness of evaluation methods, and the effectiveness of each sampling design was validated by comparing their errors. Results indicated that, while a single-layer evaluation only shows the trophic state of water at a specific level, an integrated evaluation synthetically analyzes and evaluates the trophic state of the entire water body. Furthermore, results of the integrated analysis show that a PCA method is more accurate and can represent the trophic state of the entire water body. The OK_Mean and Mean_Layers methods are only able to represent the mean level for trophic state of the entire water body but cannot reflect local trophic state and distribution details. Although methods used in the routine monitoring of Miyun reservoir have some similarities to the OK_Mean and Mean_Layers methods, their range of errors and uncertainty are greater because of a lack of detailed spatial continuous information. The analysis on the number of sampling points shows that, within a certain range of error, minor changes of sampling points will have no obvious impact on the monitoring results. For the routine monitoring of western Miyun reservoir, using only three to five sampling points for monitoring is inadequate. According to our analysis, it is more appropriate to use at least ten sampling points for monitoring these areas.

Use of satellite imagery to assess the trophic state of Miyun Reservoir, Beijing, China.

The objective of this research is to explore an appropriate way of monitoring and assessing water quality by satellite remote sensing techniques in the Miyun reservoir of Beijing, China. Two scene Thematic Mapper images in May and October of 2003 were acquired and simultaneous in situ measurements, sampling and analysis were conducted. Statistical analysis indicates that satellite-based normalized ratio vegetation index (NRVI) and in situ measured water chlorophyll a (Chl-a) concentration have very high correlation. Two linear regression models with high determination coefficients were constructed for NRVI and Chl-a of sample points. According to the modified trophic state index map, water quality in the western section of Miyun reservoir was consistently higher than in the eastern section during the two months tested. The trophic grade of the eastern reservoir remained mesotrophic with a tendency for eutrophication.

Intraoperative device closure of secundum atrial septal defect with a right anterior minithoracotomy in 100 patients.

OBJECTIVE: This study aims to report our experience using intraoperative device closure of secundum atrial septal defects and to evaluate the feasibility and clinical outcome of this technique. METHODS: One hundred patients with secundum atrial septal defects (mean age, 29 +/- 16 years; age range, 5-71 years; mean weight, 54 +/- 18 kg; weight range, 16-94 kg) underwent intraoperative device closure through a right minithoracotomy without cardiopulmonary bypass and fluoroscopy. A 2.5- to 3-cm parasternal or submammary incision was made in the right third or fourth intercostal space. Exposed with a miniretractor, a specially designed plastic sheath loaded with the device was inserted through the purse-string sutures placed on the right atrium. Under transesophageal echocardiographic guidance, it was advanced through the atrial septal defect into the left atrium, and the device was deployed in place. RESULTS: The procedure was successful in all patients, including 5 patients with double atrial septal defects. The maximum diameter of the atrial septal defect ranged from 5 to 37 mm (mean, 21 +/- 7 mm). There were 61 patients with an atrial septal defect diameter of more than 20 mm, 16 of them with a diameter of more than 30 mm. The mean size of implanted devices was 25 +/- 7 mm (range, 8-36 mm). Residual shunts were found in 9 (9%) patients immediately after the operation. The complete occlusion rate was 95% at discharge, 99% at the 3-month follow-up, and 100% at the 1-year follow-up. There were no other late complications during the follow-up period. CONCLUSIONS: Intraoperative device closure is a safe, cost-effective, cosmetic, and less-invasive operation of most secundum atrial septal defects. Follow-up results are encouraging. It can be considered an acceptable alternative to transcatheter closure or surgical repair.