ABSTRACT
We demonstrate a narrow-linewidth, high side-mode suppression ratio (SMSR) semiconductor laser based on the external optical feedback injection locking technology of a femtosecond-apodized (Fs-apodized) fiber Bragg grating (FBG). A single frequency output is achieved by coupling and integrating a wide-gain quantum dot (QD) gain chip with a Fs-apodized FBG in a 1-µm band. We propose this low-cost and high-integration scheme for the preparation of a series of single-frequency seed sources in this wavelength range by characterizing the performance of 1030 nm and 1080 nm lasers. The lasers have a maximum SMSR of 66.3 dB and maximum output power of 134.6 mW. Additionally, the lasers have minimum Lorentzian linewidths that are measured to be 260.5 kHz; however, a minimum integral linewidth less than 180.4 kHz is observed by testing and analyzing the power spectra of the frequency noise values of the lasers.
ABSTRACT
Substrate type is an important factor affecting the quality of water deriving from rainfall onto extensively green roofed areas. Here, stabilized sludge was used as the main nutrient component of the substrate combined with biochar and a dual-substrate structure. Five green roof pilot facilities were constructed, and the effect of control measures on effluent quality was analyzed. The results showed that the stabilized sludge dosage was 3%, and the annual average mass concentrations of total nitrogen (TN) and nitrate nitrogen (NO3--N) were 3.27 mg·L-1 and 1.61 mg·L-1. The use of stabilized sludge as a nutrient component under real rainfall and temperature conditions in Shanghai did not cause significant leaching of TN and NO3--N. In order to further improve the quality of the effluent, biochar was used as an amendment measure. As a result, the concentrations of TN and NO3--N in the effluent were decreased to 2.16 mg·L-1 and 1.38 mg·L-1, respectively. Using an adsorption layer of pumice can alleviate the leaching of total phosphorus (TP) and chemical oxygen demand (COD). For the total nitrogen budget of each pilot facility, the retained TN was about 55% of the original TN after one year of operation. Thus, stabilized sludge could be used as a nutrient substrate to meet the long-term requirements of plants. In the substrate with biochar, the retained TN in the substrate and the NO3--N concentration in the effluent was decreased, which was related to the mineralization of organics during dry periods and the enhancement of denitrification during rainfall periods. Stabilized sludge was not a polluting source of N but was a source of P. Using biochar and a dual-substrate structure can effectively reduce the TN and COD load of the tested green roof facilities.
ABSTRACT
Phthalic acid esters (PAEs) are still widely applied in China, and their pollution characteristics in urban surface runoff are important to receiving water protection. To evaluate the pollution characteristics of PAEs in urban runoff, six priority PAEs in road and roof runoff were monitored in nine storm events from June to September 2017 in Shanghai, China, and related rainwater samples were collected simultaneously. The average ∑6PAEs in urban road and roof runoff were 170.64 µg·L-1 and 40.92 µg·L-1, respectively, much higher than the values reported in Europe and Australia. Di-2-ethylhexyl phthalate (DEHP) was the dominating pollutant in both road and roof runoff. Significance analyses indicated there was no significant difference for low molecular weight(LMW)PAEs concentrations between road and roof runoff, whereas high molecular weight (HMW) PAEs concentrations in road runoff were significantly higher than those in roof runoff and rainwater (P<0.01), which implied that traffic was an important factor contributing to PAEs pollution in urban runoff. The pollutograph of PAEs, total suspended solids (TSS), and chemical oxygen demand (COD) concentrations vs rainfall duration for road runoff showed the same trend, and the first flush effect of PAEs was generally apparent. The influencing factors of PAEs in urban runoff were investigated. EMCs of PAEs in roof runoff were negatively correlated with rainfall intensity and positively correlated with TSS. EMCs of PAEs in road runoff were negatively correlated with rainfall volume and intensity and positively correlated with antecedent dry period, TSS, and COD. PAEs in surface runoff were significantly correlated with particulate matter. According to the criteria of the National Standard of Surface Water Quality of China, DEHP and DBP have limiting values of 8 µg·L-1 and 3 µg·L-1, respectively. The ratios of DEHP concentrations in road and roof runoff to the limiting values are 32 and 7, respectively. DBP concentrations were higher than the limiting value in most rainfall events for road runoff but lower than those for roof runoff. Without reasonable management measures, urban runoff could contaminate receiving water, especially drinking water sources.