Geochemistry of Water and Suspended Particulate in the Lower Yangtze River: Implications for Geographic and Anthropogenic Effects

The lower Yangtze River undergoes intense anthropogenic activities and various natural progress compared to the upper-middle reaches. We explore the aqueous geochemistry of ions and elements of suspended particulate in order to recognize the effects of natural conditions and anthropogenic inputs on rivers. These results show that total dissolved solids of water in the lower Yangtze River are similar as those in the upper-middle reaches of mainstream, but higher in tributaries. The major elements of suspended particulate in high-flow regime (HFR) have approximate concentrations with those in low-flow regime (LFR). But remarkable high concentrations of trace elements in tributaries exhibit regardless of HFR or LFR. Multivariate statistics show the suspended particulate matter (SPM) of mainstream presents similar characteristics in flood season and diverse characteristics in dry season. While SPM of tributaries reveals different results. The majority of suspended matter originates from municipal and industrial discharge both in flood season and dry season, and a part from road runoff in flood season, showing an effect of hydrological regime. Mining activity induces remarkably high concentrations of metals regardless of HFR or LFR. Therefore, the geochemistry of SPM in the lower reach of Yangtze River are significantly affected by the anthropogenic input of different sources, which is different from the upper-middle Yangtze River.

Temporal variation of soil carbon stock and its controlling factors over the last two decades on the southern Song-nen Plain,Heilongjiang Province

Against the current background of global climate change, the study of variations in the soil carbon pool and its controlling factors may aid in the evaluation of soil＇s role in the mitigation or enhancement of greenhouse gas. This paper studies spatial and temporal variation in the soil carbon pool and their controlling factors in the southern Song-nen Plain in Heilongjiang Province, using soil data collected over two distinct periods by the Multi-purpose Regional Geochemical Survey in 2005-2007, and another soil survey conducted in 1982-1990. The study area is a carbon source of 1479 t/km2 and in the past 20 years, from the 1980s until 2005, the practical carbon emission from the soil was 0.12 Gt. Temperature, which has been found to be linearly correlated to soil organic carbon, is the domi- nant climatologic factor controlling soil organic carbon contents. Our study shows that in the relevant area and time period the potential loss of soil organic carbon caused by rising temperatures was 0.10 Gt, the potential soil carbon emission resulting from land-use change was 0.09 Gt, and the combined potential loss of soil carbon （0.19 Gt） caused by warming and land-use change is comparable to that of fossil fuel combustion （0.21 Gt）. Due to the time delay in soil carbon pool variation, there is still 0.07 Gt in the potential emission caused by warming and land-use change that will be gradually released in the future.

A study of soil organic carbon distribution and storage in the Northeast Plain of China

Employing the Unit Soil Carbon Amount （USCA） approach, soil carbon storage was calcu- lated across the Northeast Plain of China based on the Multi-purpose Regional Geochemical Survey conducted in 2004-2006 （MRGS）. The results indicated that the soil organic carbon （SOC） storage in topsoil （0-0.2 m）, subsoil （0-1 m） and deep soil （0-1.8 m） was 768.1 Mt, 2978.4 Mt and 3729.2 Mt with densities of 3327.8 t/km^2, 12,904.7 t/km^2 and 16,157.5 t/km^2, respectively. These values were consistent with national averages, whereas the soil carbon densities showed a clear increasing trend from the southern area of the Northeast Plain （Liaoning）, to the middle （Jilin） and the northern Plain （Heilongjiang） -- particularly in terms of topsoil carbon density, which increased from 2284.2, to 3436.7 and 3861.5 t/kin2, respectively. In comparison to carbon data obtained from the Second National Soil Survey in 1984--1986 （SNSS）, the topsoil SOC storage values from the MRGS were found to have decreased by 320.59 Mt （29.4%）, with an average annual decline of 16.0 Mt （1.73%） over the 20 years. In the southern, middle and northern areas of the plain, soil carbon densities decreased by 1060.6 t/km^2, 1646.4 t/kin2 and 1300.2 t/km^2, respectively, with an average value of 1389.0 t/km^2 for the whole plain. These findings indicate that the decrease in soil carbon density varied according to the different ecosystems and land-use types. Therefore, ratios of soil carbon density were calculated in order to study the carbon dynamic balance between ecosystems, and to further explore distribution characteristics, as well as the sequestration potential of SOC.

Solid-solution partitioning of arsenic(As) in the paddy soil profiles in Chengdu Plain,Southwest China

To predict the long-term behavior of arsenic （As） in soil profiles, the solid-solution partitioning of As was studied in four paddy soil profiles obtained from agricultural areas in Chengdu Plain, Southwest China. Paddy soil profile samples were collected and soil solution samples were extracted. Total As contents in soil solution and soil solid were analyzed, along with the soil solid phase properties. The As in soil solu- tion was significantly higher in the upper layer （0--20 cm） and had a definite tendency to decrease towards 40 cm regardless of the sampling locations. When the concentration of arsenic in soil solution decreased, its content in solid phase increased. Field-based partition coefficient （Kd） for As was determined by calculating the ratio of the amount of As in the soil solid phase to the As concentration in the soil solution. Kj values varied widely in vertical samples and correlated well with soil pH, total organic carbon （TOC） and total As. The results of this study would be useful for evaluating the accumulation trends of hrsenic in soil profiles and in improving the management of the agricultural soils.

Spatial analysis of land use change effect on soil organic carbon stocks in the eastern regions of China between 1980 and 2000

Spatial distributions of 0-20 cm soil carbon sources/sinks caused by land use changes from the year 1980 to 2000 in an area of 2.97 ~ 106 km2 in eastern China were investigated using a land use dataset from a recent soil geochemical survey. A map of soil carbon sourcesJsinks has been prepared based on a spatial analysis scheme with GIg. Spatial statistics showed that land use changes had caused 30.7 ＋ 13.64 Tg of surface soil organic carbon loss, which accounts for 0.33% of the total carbon storage of 9.22 Pg. The net effect of the carbon source was estimated to be ~ 71.49 Tg soil carbon decrease and ~ 40.80 Tg increase. Land use changes in Northeast China （NE） have the largest impact on soil organic carbon storage compared with other regions. Paddy fields, which were mainly transformed into dry farmland in NE, and constructed land in other regions, were the largest carbon sources among the land use types. Swamp land in NE was also another large soil carbon source when it was transformed into dry farmland or paddy fields. Dry farmland in the NE region formed the largest soil organic carbon sink, as some were trans- formed into paddy fields, forested land, and other land use types with high SOCD.

A Robust CRISPR/Cas9 System for Convenient, High-Efficiency Multiplex Genome Editing in Monocot and Dicot Plants

CRISPR/Cas9 genome targeting systems have been applied to a variety of species. However, most CRISPR/Cas9 systems reported for plants can only modify one or a few target sites. Here, we report a robust CRISPR/Cas9 vector system, utilizing a plant codon optimized Cas9 gene, for convenient and high- efficiency multiplex genome editing in monocot and dicot plants. We designed PCR-based procedures to rapidly generate multiple sgRNA expression cassettes, which can be assembled into the binary CRISPR/ Cas9 vectors in one round of cloning by Golden Gate ligation or Gibson Assembly. With this system, we edi- ted 46 target sites in rice with an average 85.4% rate of mutation, mostly in biallelic and homozygous status. We reasoned that about 16% of the homozygous mutations in rice were generated through the non-homol- ogous end-joining mechanism followed by homologous recombination-based repair. We also obtained uni- form biallelic, heterozygous, homozygous, and chimeric mutations in Arabidopsis T1 plants. The targeted mutations in both rice and Arabidopsis were heritable. We provide examples of loss-of-function gene mu- tations in To rice and T1Arabidopsis plants by simultaneous targeting of multiple （up to eight） members of a gene family, multiple genes in a biosynthetic pathway, or multiple sites in a single gene. This system has provided a versatile toolbox for studying functions of multiple genes and gene families in plants for basic research and genetic improvement.

Ecological risk assessment of Cd and other heavy metals in soil-rice system in the karst areas with high geochemical background of Guangxi,China

Karst areas are widely distributed in China,and the soil derived in these areas is enriched with trace elements and has the typical characteristics of high geochemical background.Therefore,soil ecological risk has gradually attracted extensive attention.In this study,1090 sets of rice grains and paired rhizosphere soils were collected as research objects from the outcropped karst areas of carbonate rocks in Guangxi,and the concentration characteristics and influencing factors of heavy metals,such as Cd and As,in rice grains and the corresponding soils were studied.According to the Chinese Soil Environmental Quality Standard(GB 15618-2018),the proportion of karstic soil samples in Guangxi with heavy metal(As,Cd,Cr,Cu,Hg,Ni,Pb and Zn)concentrations that exceed the standard risk screening values was generally greater than that of surface soils in China or non-karstic soils in Guangxi.Notably,Cd and As were the most prominently enriched heavy metals in soils.According to the Chinese Food Safety Standard(GB 2762-2017),Pb in rice grains from the studied area did not exceed the standard;the exceedance rates of Cr,Hg,and inorganic As were only about 1%;and the exceedance rate of Cd was 12.5%.Soil Cd concentration increased gradually whereas the concentration and exceedance rate of Cd in rice grains decreased gradually with the increase of soil pH.Specifically,the exceedance rate of Cd in rice grains was only 4%when soil pH>6.5.The results indicated that the risk screening values of Cd element in the Chinese Soil Environmental Quality Standard are not satisfactorily applicable to the ecological risk assessment of Cd in karstic soils.Therefore,the recommended threshold values for the safe utilization and risk control of Cd in karstic soils was proposed so as to provide a basis for soil environmental quality hierarchization,pollution risk control and land safety zoning of agricultural land in karst areas in China.

An effective strategy to establish a male sterility mutant mini-library by CRISPR/Cas9-mediated knockout of anther-specific genes in rice

Male sterility(MS),characterized by functional defects in male organs or gametes,is an important agronomic trait for hybrid seed production,especially for self-pollinated crops such as rice(Oryza sativa L)(Chen and Liu,2014).Spontaneous MS mutants are rare and difficult to maintain in nature,thus limiting basicresearch and breeding.Artificial mutants are typically generated by physical,chemical,or biological mutagenesis(Wei et al,2013).Recently developed genome editing systems such as CRISPR/Cas9 allow efficient and timesaving knockout of endogenous genes at specific sites(Smith et al,2000;Moscou and Bogdanove,2009;Gasiunas et al.,2012).