Ground-Based Atmospheric CO_(2),CH_(4),and CO Column Measurements at Golmud in the Qinghai-Tibetan Plateau and Comparisons with TROPOMI/S5P Satellite Observations

Measurements of carbon dioxide(CO_(2)),methane(CH_(4)),and carbon monoxide(CO)are of great importance in the Qinghai-Tibetan region,as it is the highest and largest plateau in the world affecting global weather and climate systems.In this study,for the first time,we present CO_(2),CH_(4),and CO column measurements carried out by a Bruker EM27/SUN Fourier-transform infrared spectrometer(FTIR)at Golmud(36.42°E,94.91°N,2808 m)in August 2021.The mean and standard deviation of the column-average dry-air mixing ratio of CO_(2),CH_(4),and CO(XCO_(2),XCH_(4),and XCO)are 409.3±0.4 ppm,1905.5±19.4 ppb,and 103.1±7.7 ppb,respectively.The differences between the FTIR co-located TROPOMI/S5P satellite measurements at Golmud are 0.68±0.64%(13.1±12.2 ppb)for XCH_(4) and 9.81±3.48%(–10.7±3.8 ppb)for XCO,which are within their retrieval uncertainties.High correlations for both XCH_(4) and XCO are observed between the FTIR and S5P satellite measurements.Using the FLEXPART model and satellite measurements,we find that enhanced CH_(4) and CO columns in Golmud are affected by anthropogenic emissions transported from North India.This study provides an insight into the variations of the CO_(2),CH_(4),and CO columns in the Qinghai-Tibetan Plateau.

Fast and Accurate Simulation of Canopy Reflectance under Wavelength-Dependent Optical Properties Using a Semi-Empirical 3D Radiative Transfer Model

Generating canopy-reflectance datasets using radiative transfer models under various leaf and optical property combinations is important for remote sensing retrieval of vegetation parameters.Onedimensional radiative transfer models have been frequently used.However,three-dimensional(3D)models usually require detailed 3D information that is difficult to obtain and long model execution time,limiting their use in remote sensing applications.This study aims to address these limitations for practical use of 3D models,proposing a semi-empirical speed-up method for canopy-reflectance simulation based on a LargE-Scale remote sensing data and image Simulation model(LESS),called Semi-LESS.The speed-up method is coupled with 3D LESS to describe the dependency of canopy reflectance on the wavelength,leaf,soil,and branch optical properties for a scene with fixed 3D structures and observation/illumination configurations,allowing fast generating accurate reflectance images under various wavelength-dependent optical parameters.The precomputed dataset stores simulated multispectral coefficient images under few predefined soil,branch,and leaf optical properties for each RAdiation transfer Model Intercomparison-V scene,which can then be used alone to compute reflectance images on the fly without the participation of LESS.Semi-LESS has been validated with full 3D radiative-transfer-simulated images,showing very high accuracy(root mean square error<0.0003).The generation of images using Semi-LESS is much more efficient than full LESS simulations with an acceleration of more than 320 times.This study is a step further to promote 3D radiative transfer models in practical remote sensing applications such as vegetation parameter inversions.

A smart strategy for controlling disinfection byproducts by reversing the sequence of activated carbon adsorption and chlorine disinfection

Chlorine disinfection is a vital treatment process to inactivate pathogens, but it also generates numerous halogenated disinfection byproducts (DBPs) via reactions with halides and natural organic matter (NOM)[1]. Epidemiological studies have shown that consumption of chlorinated drinking water with halogenated DBPs is related to increased spontaneous abortions, stillbirth,

Effects of ultrasonication on the DBP formation and toxicity during chlorination of saline wastewater effluents

Chlorine disinfection of saline wastewater effluents rich in bromide and iodide forms relatively toxic brominated and iodinated disinfection byproducts(DBPs). Ultrasonication is a relatively new water treatment technology, and it is less sensitive to suspended solids in wastewaters. In this study, we examined the effects of ultrasonication(in terms of reactor type and combination mode with chlorination) on the DBP formation and toxicity in chlorinated primary and secondary saline wastewater effluents. Compared with the chlorinated wastewater effluent samples without ultrasonication, ultrasonic horn pretreatment of the wastewater effluent samples reduced the total organic halogen(TOX) levels in chlorination by ~30%, but ultrasonic bath pretreatment of the wastewater samples did not significantly change the TOX levels in chlorination, which might be attributed to the higher energy utilization and decomposition extent of organic DBP precursors in the ultrasonic horn reactor. Moreover, the TOX levels in the chlorinated samples with ultrasonic horn pretreatment(USH–chlorination), simultaneous treatment(chlorination + USH) and subsequent treatment(chlorination–USH) were also significantly reduced, with the maximum TOX reductions occurring in the samples with ultrasonic horn pretreatment. A toxicity index was calculated by weighting and summing the levels of total organic chlorine, total organic bromine and total organic iodine in each treated sample. The calculated toxicity index values of the chlorinated wastewater effluent samples followed a descending rank order of “chlorination” > “chlorination + USH” > “chlorination–USH” > “USH–chlorination”, with the lowest toxicity occurring in the samples with ultrasonic horn pretreatment. Then, a developmental toxicity bioassay was conducted for each treated sample. The measured toxicity index values of the chlorinated wastewater samples followed the same descending rank order.