Search

Sloping farmland is an important cultivated land resource and erosion source. Cultivated-layer quality directly affects the soil productivity and erosion resistance of sloping farmland. We aim to select the most effective soil property index to construct a minimum data set (MDS) and use two methods (the weighted additive cultivated-layer quality index (CLQIW) and Nemoro cultivated-layer quality index (CLQIN)) to accurately evaluate the cultivated-layer quality of sloping farmland in purple hilly areas. The total data set (TDS) of 12 soil indexes was screened by principal component analysis (PCA) and correlation analysis, and a MDS was constructed to assess the CLQIW and CLQIN. The results showed that (1) the cultivated-layer soil quality of the MDS comprises cultivated-layer thickness, soil bulk density, saturated hydraulic conductivity, sand, clay, shear strength and soil organic matter. The MDS can accurately reflect the effective soil information (RW2=0.7524, RN2=0.8059) and can replace the TDS in cultivated-layer evaluation. (2) CLQIN-MDS has a higher Ef and lower ER than CLQIW-MDS does, so CLQIN-MDS is better for evaluating the cultivated-layer quality of purple soil of sloping farmland. (3) For the two evaluation methods, the quality classifications of the two small watersheds have similar trends, with most plots in grades II~III (approximately 90%). (4) The main obstacles of the two small watersheds are poor nutrients and low soil shear strength, which can be reasonably controlled by subsoiling combined with biochar. These results can facilitate the construction of reasonable cultivated-layers and improvements in the cultivated-layer soil quality of sloping farmland.

Blooms of some pico/nanophytoplankton have occurred frequently along the Qinhuangdao coast since 2009, and it is necessary to identify the critical environmental factors inducing them. In this study, variations in the physical and nutrient characteristics of the seawater were analyzed following the development of local blooms in 2013. The local environmental characteristics were also compared with those of the Changjiang River estuary, China, and the Long Island estuaries in the USA, which are also prone to blooms of special algal species. In Qinhuangdao the local water temperature varied seasonally and rose above 15°C in 2013 early summer, coincident with the water discoloration. The salinity was more than 28 with a variation range of

Mao, X.; Kuang, C.; Gu, J.; Kolditz, O.; Chen, K.; Zhang, J.; Zhang, W., and Zhang, Y., 2017. Analysis of chlorophyll-a correlation to determine nutrient limitations in the coastal waters of the Bohai Sea, China. The coastal water of Qinhuangdao, a famous resort located in the NW of the Bohai Sea, China, suffered algal bloom for a consecutive 3 years by 2011, causing great economic loss. Based on measurements at 46 sampling points in the study's coastal area in May, August, and October 2011, the seasonal and spatial characteristics of the chemical indicators and chlorophyll-a (Chl-a) were analyzed. The chemical indicators for pH, chemical oxygen demand (COD), and reactive silicate (SiO3-Si) showed higher concentrations in the summer than in the spring and fall, whereas the nutrients of reactive phosphate (PO4-P) and dissolved inorganic nitrogen (DIN) presented complex seasonal characteristics under the combined influence of abundant nutrients from rivers and nutrient consumption by large algal bl...

The assessment of cultivated-layer soil quality (CLSQ) is important for improving crop growth capacity and is the premise for taking effective remedial measures. The cultivated-layer soil quality index (CLSQI) is a significant tool for evaluating CLSQ. This study aims to select the most effective indicators to construct a minimum data set (MDS) for soil in erosion-impacted hilly areas with purple soil in China and to analyse the association between CLSQ and the erosional environment. Taking the erosion of purple soil of sloping farmland in China as the focus of this study, different combinations of scoring methods, indicators, and data set methods were compared. In this study, the MDS is constructed by principal component analysis (PCA) in conjunction with the norm value, and the accuracy of the MDS is verified by the Nash effective coefficient. Furthermore, the nonlinear scoring (NLS) method is used to normalize the indicator data and then assess the CLSQ of soils with different degrees of erosion using the CLSQI. The results showed the following. 1) The soil indicators significantly varied under the different erosion degrees: the soil productivity showed a decreasing trend with increasing erosion, while the soil anti-erosion ability and tillage performance showed increasing trends with increasing erosion. 2) For the study area, the generated MDS included saturated hydraulic conductivity, bulk density, shear strength, penetration resistance and available phosphorus. 3) The CLSQI-NLS evaluation method was most suitable for this research topic, and combined with the MDS indicators, it could be used to accurately evaluate the CLSQ. 4) As the erosion degree intensified, the CLSQI showed an obvious decreasing trend, and the CLSQI under soil erosion of 20 cm (S-20, 0.393) was significantly lower than that under other erosion degrees, indicating that soil erosion gradually reduced the CLSQ. After the cultivated-layer soil was eroded and the subsoil was converted to cultivated-layer soil, the soil quality obviously decreased. The indexing approach used in this study provides a practical and time- and cost-effective method for the quantitative evaluation of CLSQ for erosion-prone soil in hilly areas with purple soil worldwide.

In this study, we investigated the environmental impacts of scallop culture on two coastal estuaries adjacent the Bohai Sea including developing a quantitative PCR assay to assess the abundance of the bacterial pathogens Escherichia coli and Vibrio parahaemolyticus. Scallop culture resulted in a significant reduction of nitrogen, Chlorophyll a, and phosphorous levels in seawater during summer. The abundance of bacteria including V. parahaemolyticus varied significantly across estuaries and breeding seasons and was influenced by nitrate as well as nutrient ratios (Si/DIN, N/P). Bacterioplankton diversity varied across the two estuaries and seasons, and was dominated by Proteobacteria, Cyanobacteria, Actinobacteria, Bacteroidetes. Overall, this study suggests a significant influence of scallop culture on the ecology of adjacent estuaries and offers a sensitive tool for monitoring scallop contamination.

Sources of pollution discharges and water quality samples at 27 stations in 2006 in the coastal waters of Hebei Province, western Bohai Sea, have been analyzed in this study. Pollutant loads from industrial sewages have shown stronger impact on the water environment than those from the general sewages. Analysis indicates that pollution of COD is mainly resulted from land-based point pollutant sources. For phosphate concentration, non-point source pollution from coastal ocean (fishing and harbor areas) plays an important role. To assess the water quality conditions, Organic Pollution Index and Eutrophication Index have been used to quantify the level of water pollution and eutrophication conditions. Results show that pollution was much heavier in the dry season than flood season in 2006. Based on COD and phosphate concentrations, results show that waters near Shahe River, Douhe River, Yanghe River, and Luanhe River were heavily polluted. Water quality in the Qinhuangdao area was better than those in the Tangshan and Cangzhou areas.