Optimal design of surface CO2 observation network to constrain China's land carbon sink.

Accurate estimate of the size of land carbon sink is essential for guiding climate mitigation actions to fulfill China's net-zero ambitions before 2060. The atmospheric inversion is an effective approach to provide spatially explicit estimate of surface CO2 fluxes that are optimally consistent with atmospheric CO2 measurements. But atmospheric inversion of China's land carbon sink has enormous uncertainties, with one major source arising from the poor coverage of CO2 observation stations. Here we use a regional atmospheric inversion framework to design an observation network that could minimize uncertainties in inverted estimate of China's land carbon sink. Compared with the large spread of inverted sink (∼1PgCa-1) from state-of-the-art inversions using existing CO2 observations, the uncertainty is constrained within 0.3PgCa-1 when a total of 30 stations were deployed, and is further reduced to approximately 0.2PgCa-1 when 60 stations were deployed. The proposed stations are mostly distributed over areas with high biosphere productivity during the growing season, such as Southeast China, Northeast China, North China, and the Tibetan Plateau. Moreover, the proposed stations can cover areas where existing satellites have limited coverage due to cloud shadowing in the monsoon season or over complex topography. Such ground-based observation network will be a critical component in the future integrated observing system for monitoring China's land carbon fluxes.

Assessment of HCHO in Beijing during 2009 to 2020 using satellite observation and numerical model: Spatial characteristic and impact factor.

Formaldehyde (HCHO) is an air pollutant that has a detrimental effect on human health and atmospheric environment. Until now, satellite observation has been increasingly a valuable source for monitoring the unconventional atmospheric pollutants due to the limited availability of ground-based HCHO data. Here, we used Ozone Monitoring Instrument (OMI) and the weather research and forecasting with chemistry (WRF-Chem) model to synergistically analyze the spatiotemporal variations of tropospheric HCHO in Beijing during 2009-2020, and the response of O3 to HCHO and NO2 in hotspots. We also discuss the multiple factors influencing the variation of HCHO and identify potential source area. The results indicated that HCHO column concentration is higher in eastern Beijing, and peaking in 2018 (16.68 × 1015 mol/cm2). O3 shows a good response to HCHO, with higher HCHO and NO2 photolysis leading to O3 increase in summer. In winter, decreasing HCHO and increasing NO2 inhibits the formation of O3. Transportation emissions contributed the most to HCHO, followed by the industrial sector, while residential sources have long-term effects. Isoprene produced by plants is one of the main sources of HCHO, whereas meteorological conditions can affect production efficiency. Biomass burning contributes less. Moreover, HCHO in Beijing is affected by the combined effects of local emission and external transport, and Hebei is the potential source area. This study reveals HCHO has a great accumulation potential in cities and highlights the dominant role of anthropogenic emissions, but also need to consider the influence of natural factors and regional transport.

Comparative mitogenomic analysis of mirid bugs (Hemiptera: Miridae) and evaluation of potential DNA barcoding markers.

The family Miridae is one of the most species-rich families of insects. To better understand the diversity and evolution of mirids, we determined the mitogenome of Lygus pratenszs and re-sequenced the mitogenomes of four mirids (i.e., Apolygus lucorum, Adelphocoris suturalis, Ade. fasciaticollis and Ade. lineolatus). We performed a comparative analysis for 15 mitogenomic sequences representing 11 species of five genera within Miridae and evaluated the potential of these mitochondrial genes as molecular markers. Our results showed that the general mitogenomic features (gene content, gene arrangement, base composition and codon usage) were well conserved among these mirids. Four protein-coding genes (PCGs) (cox1, cox3, nad1 and nad3) had no length variability, where nad5 showed the largest size variation; no intraspecific length variation was found in PCGs. Two PCGs (nad4 and nad5) showed relatively high substitution rates at the nucleotide and amino acid levels, where cox1 had the lowest substitution rate. The Ka/Ks values for all PCGs were far lower than 1 (<0.59), but the Ka/Ks values of cox1-barcode sequences were always larger than 1 (1.34 -15.20), indicating that the 658 bp sequences of cox1 may be not the appropriate marker due to positive selection or selection relaxation. Phylogenetic analyses based on two concatenated mitogenomic datasets consistently supported the relationship of Nesidiocoris + (Trigonotylus + (Adelphocoris + (Apolygus + Lygus))), as revealed by nad4, nad5, rrnL and the combined 22 transfer RNA genes (tRNAs), respectively. Taken sequence length, substitution rate and phylogenetic signal together, the individual genes (nad4, nad5 and rrnL) and the combined 22 tRNAs could been used as potential molecular markers for Miridae at various taxonomic levels. Our results suggest that it is essential to evaluate and select suitable markers for different taxa groups when performing phylogenetic, population genetic and species identification studies.

The first mitochondrial genome for the subfamily Podopinae (Hemiptera: Pentatomidae) and its phylogenetic implications.

Here, we determined the complete mitogenome of Graphosoma rubrolineata, as the first representative for the subfamily Podopinae. This mitogenome is 15,633 bp long and contains 37 typical mitochondrial genes. The genome size, gene arrangement, A + T content, codon usage and secondary structures of 22 tRNAs of the G. rubrolineata mitogenome were similar to that of other sequenced pentatomoids. This mitogenome exhibited a reverse nucleotide strand bias, i.e. positive GC-skew (0.021) and negative AT-skew (-0.086). Phylogenetic analyses based on mitogenomic data strongly supported the monophyly of each of the five superfamilies within Pentatomomorpha and recognized a phylogeny of (Aradoidea + (Pentatomoidea + (Lygaeoidea + (Pyrrhocoroidea + Coreoidea)))). However, G. rubrolineata clustered with three Pentatominae species, suggesting that Pentatominae probably was not monophyletic, or Podopinae may not be a valid taxonomic group. The mitogenome sequence of G. rubrolineata could contribute for better understanding of population genetics and evolution of this insect pest.

In vitro and in silico investigations of the binary-mixture toxicity of phthalate esters and cadmium (II) to Vibrio qinghaiensis sp.-Q67.

Phthalate esters (PAEs) are widely used as plasticizers and have become one of the emerging contaminants with an increasing public concern. The residues of PAEs frequently co-exist with heavy metals such as cadmium (Cd) in waters; however, their joint ecotoxicity remains largely unknown. We herein investigated the single and joint toxicity of commonly used PAEs and Cd using freshwater luminescent bacteria Vibrio qinghaiensis sp.-Q67. The median effective concentration (EC50) of benzyl butyl phthalate (BBP), dibutyl phthalate (DBP), diethyl phthalate (DEP), dimethyl phthalate (DMP), diisooctyl phthalate (DIOP) and di-n-octyl phthalate (DOP) were determined to be in the range from 134.4mg/L to as high as 1000mg/L, indicating very weak toxicity to Vibrio qinghaiensis sp.-Q67. The toxicity of single PAEs showed a significant linear relationship with Log Kow, indicating the dependence of the elevated toxicity on the increasing hydrophilicity. The toxicity of binary mixture of PAEs was further evaluated in silico using the independent action (IA) model and concentration addition (CA) model. DMP-DEP, DEP-DBP or DMP-DBP exhibited antagonistic effects with the toxic unit value higher than 1.2. The CA and IA models poorly predicted the joint toxicity of DMP-DEP, DEP-DBP or DMP-DBP. The joint toxicity of the binary mixtures of DMP, DEP or DBP with Cd was simple additive as predicted by the CA and IA models. Our results indicated the potentially higher risk of PAEs in the presence of Cd, emphasizing the importance of determining the impact of their joint effects on aquatic organisms. The integrated in vitro and in silico methods employed in this study will be beneficial to study the joint toxicity and better assess the aquatic ecological risk of PAEs.