The purpose of this paper is to determine the concentrations of dissolved heavy metals namely mercury (Hg), lead (Pb), cadmium (Cd), and copper (Cu) and to investigate the relationships between nutrients (nitrate-nitrogen and phosphate) and dissolved heavy metals. For this purpose, the concentrations of dissolved heavy metals were measured through 51 voyages form 1984 to 2006 in the Yangtze river estuary and its adjacent sea. Results analysis showed that dissolved heavy metals were not the main pollutants in the Yangtze river estuary, and the main source of heavy metal contamination was industrial wastewater from terrestrial pollution during the past 20 years. Heavy metal values showed significant abundance in the south branch of the Yangtze River estuary and Hangzhou Bay. In addition, Pb showed negative correlation with nutrients, while the positive correlations between Hg, Cd, and nutrients were shown. The obtained molar ratios, DeltaCd/DeltaN = 1.68 x 10(-5) and DeltaCd/DeltaP = 1.66 x 10(-4), are close to those in plankton, showing the biogeochemical behavior and process of dissolved cadmium.

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Drought has become an important natural disaster, affecting the development of Inner Mongolia, as an important animal husbandry region in China. In this study, the characteristics and trends of the Inner Mongolia drought are thoroughly analysed by calculating the standardised precipitation evapotranspiration index (SPEI) at different time scales, based on monthly precipitation and temperature data from 40 national meteorological stations in Inner Mongolia from 1958 to 2019. Subsequently, the area drought intensity (ADI), which is a comprehensive evaluation indicator for evaluating drought intensity within the region, is proposed, taking into account the effects of the persistent drought on drought intensity. The results show that drought has increased during this period, with a remarkable increase in the frequency and the area of drought. The areas with stronger drought intensity are mainly located in the west, north central, and the western area of the east. Since 2000, March to October are identified as drought-prone months and April is characterised as the month with the highest frequency of drought. The inflection points of SPEI and climate conditions both appeared in 1990s and it is speculated that the increase in drought may have been caused by excessive temperature rise. The frequency, coverage area, and continuous duration of drought have increased greatly after climate mutation in this region. According to the changes in the spatial distribution of the ADI and frequency of drought occurrence, the drought-stricken areas shifted from the southeast to the northwest after climate mutations. The findings from this study provide a theoretical basis for the drought management of Inner Mongolia.

The rational allocation of water resources in the basin/region can be better assisted and performed using a suitable water resources allocation model. Rule-based and optimization-based simulation methods are utilized to solve medium-and long-term water resources allocation problems. Since rule-based allocation methods requires more experience from expert practice than optimization-based allocation methods, it may not be utilized by users that lack experience. Although the optimal solution can be obtained via the optimization-based allocation method, the highly skilled expert experience is not taken into account. To overcome this deficiency and employ the advantages of both rule-based and optimization-based simulation methods, this paper proposes the optimal allocation model of water resources where the highly skilled expert experience has been considered therein. The "prospect theory" is employed to analyze highly skilled expert behavior when decision-making events occur. The cumulative prospect theory value is employed to express the highly skilled expert experience. Then, the various elements of the cumulative prospect theory value can be taken as the variables or parameters in the allocation model. Moreover, the optimal water allocation model developed by the general algebraic modeling system (GAMS) has been improved by adding the decision reversal control point and defining the inverse objective function and other constraints. The case study was carried out in the Wuyur River Basin, northeast of China, and shows that the expert experience considered as the decision maker's preference can be expressed in the improved optimal allocation model. Accordingly, the improved allocation model will contribute to improving the rationality of decision-making results and helping decision-makers better address the problem of water shortage.2 of 17 establish a water resources allocation and management decision-making tool. Abolpour et al. [7] adopted an adaptive neuro-fuzzy reinforcement learning method to enhance the accuracy of optimized parameters in the water resources allocation model. Prasad et al. [8] proposed a linear programming method for finding the optimal irrigation-planning model by considering various growth stages of crops in the water resources allocation. An inaccurate two-stage water allocation model was utilized by Li et al. [9] to simulate the irrigation water requirements of multiple crops in the large-scale areas. Dai and Li [10] constructed a multi-stage irrigation water allocation model for different season water allocation policies. An inaccurate multi-stage stochastic optimization model was proposed by Li and Guo [11] to solve the mesoscale agricultural water resources planning problem. Recently, the rational allocation of water resources has been devoted to solving many difficulties encountered in practice. Kralisch et al. [12] proposed a neural network method to solve the allocation problem between urban living water and agricultural water. Wang et al. [13] proposed a water rights allocation m...

It is of great significance to study the characteristics and change trends of drought in Xinjiang to provide a basis for implementing local strategies. Based on monthly precipitation and temperature data from 95 meteorological stations in Xinjiang, from 1960 to 2018, the Standardized Precipitation Evapotranspiration Index (SPEI) was calculated, and the characteristics and trends of drought in Xinjiang were analysed, in details. Furthermore, a comprehensive evaluation index, i.e., Regional Drought Severity (RDS), was proposed to analyse the effects of duration of the drought and the extent of the drought affected area. The results from our study suggested: (1) In consideration of global warming, droughts in Xinjiang have intensified during the past 59 years, and the frequency and range of droughts have increased significantly; (2) During the plant growing season, spring, summer, and autumn, a drying trend was observed, while, a wetting trend was identified for winter season; (3) The drought-prone months shifted from January and December to March-November in the 1970s, and April was identified as a month with the highest frequency of droughts; (4) The meteorological change occurred a period near 1997. It can be speculated that the intensified droughts can be triggered by the excessive temperature rise, through comparing the changes in SPEI and the Standardized Precipitation Index (SPI), before and after the meteorological change; (5) After the meteorological change, the frequency of droughts with different levels had significantly increased, in addition, the drought-prone areas shifted from the north-west to the south-east. The results from this research provide important support for drought management in Xinjiang, also offer scientific basis for the formulation of relevant policies on agricultural and animal husbandry production.Water 2020, 12, 741 2 of 20 areas also began to expand to the humid and sub-humid areas in the south and east of China, and this trend is likely to continue in future [7].The main types of drought are meteorological, agricultural, and hydrological droughts. In a broad definition, these droughts occur in a certain order, with meteorological drought occurring first, and then affecting the other two types of drought [2]. Among the various types of drought, the performance of meteorological drought is the most direct and clear [8]. Moreover, hydrological and agricultural droughts have more influencing factors and are more susceptible to human activities. Drought indexes are the basis for reflecting drought situations, and each drought index has its own characteristics, advantages, and disadvantages. In consideration of global warming, the indexes considering potential evapotranspiration (PET) may be more suitable for the study of drought. For one drought event, the results of different drought indexes may vary, due to using different calculation methods. Currently, the Standardized Precipitation Index (SPI) [9,10], the Standardized Precipitation Evapotranspiration Index (SPEI) [11][12][13][14]...