ig_con">Table 1. Data statistics of annual emission of pollutants.
As, Cd and Pb. According to surface water quality standards (GB3838-2002), the evaluation criterion in Table 2 was applied to calculate the equal standard pollution load of each pollution source and its ratio.
On the basis of formula (1), (2) and Table 2, the calculation results are given in Table 3, that the equal standard pollution load of each pollutant were in descending order of ammonia nitrogen (49.62%), TP (29.94%), COD (14.71%), oil (5.19%) and heavy metals (Cd, As, Pb) (0.54%). This shows that the main pollution source in the Dongjiang Lake is agricultural non-point source, which account for 87.74%, and the main pollutants were ammonia nitrogen, TP, COD, whose equivalent pollution load represent 94.27% of the total load. According to the perennial monitoring data, the water quality of Dongjiang Lake is generally good to reach even more than the national II class standard in China. However, some sectional monitoring data show an increase in nutrient quality of local waters, with water quality mainly controlled by heavy metals Cd and TN, TP, and part of regions in middle nutrient levels  .
4. Multi-Sources Catastrophic Chain and Its Control in Regional Water Environment
4.1. Multi-Sources Catastrophic Chain Model of Regional Water Environment
Water pollution of Dongjiang Lake is mainly due to human’s manufacture and life. According to disaster chain theory, the regional water environment in Dongjiang Lake is hazard inducing environment, the various pollutants are the hazard factors, and the final output morphology of disaster is both at the expense of the physical health of people, animals and plants in the lake area. Therefore, from the perspective of disaster chain, water environment pollution in the Dongjiang Lake generally belongs to multisource disaster implication chain caused by human activities, with characteristics of branches and trunk basin disaster chain  . Then we can construct the schematic diagram (Figure 3) of disaster chain of water environment pollution in the Dongjiang Lake.
According to Figure 2, there are i sub-chains of water pollution disaster induced by six kind of pollution sources. All these sub-chains can be divided into two types: direct and indirect disaster chain of water environment pollution. During the chain effect of disaster, assuming that there are k disaster
Table 2. Evaluation criterion of pollutants.
Table 3. The equivalent load of mainly pollutants in the Dongjiang Lake basin.
Figure 3. Disaster chain of water environment pollution of Dongjiang Lake.
reacts with disaster D(i), who leads to a sub-chain, on the action of the external environment, and the relationship when disaster D(i(j)) reacts with D(i) is at time t. So it can be inferred that there has the following effect relationship between the response status, the internal structural relationship and external behavior of disaster D(i) and disaster D(i) based on system theory:
Obviously, disaster (water environment pollution caused by pollutants) is a responsive behavior on the coupling effect of external (artificial) numerous environment (pollution sources production environment) factors. Formula 4 to 6 show that only when mutual effect relations established between the water environment pollution disasters, will it perform the burst of hazardous effects and aggregation of matter, energy and information. Also it could be argued that there exist discontinuity and concealment between coupling relationship and the convergence of water environment disaster. Moreover, because the external environment on the coupling process of multi-source disasters caused by pollution sources (this can be considered as a carrier of heavy metal migration process or branches watershed environment), with uncertainty and ambiguity on this coupling relation, water environment disasters chain shows the protracted nature and latency.
4.2. Chain-Cutting Disaster Mitigation from Gestation Source of Water Pollution
Chain-cutting disaster mitigation from gestation source refers to that damaging efforts is too weak to form a destruction on the early formation of the disaster chain, namely embryonic stage, and the energy is also on the initial stages of gathering or coupling. Chain-cutting disaster mitigation is the most efficient for cutting catastrophe during a long evolution process  . To control the water environment disaster chain in the Dongjiang Lake with chain-network structure of branches basin, the all-direction control for gestation source conditions is needed, namely the source management, monitoring and technical disposal of the 6 major pollution sources.
1) Water transportation, tourism and fishery pollution control. As for the direct discharge of pollutants, water transportation and tourism should perfect laws and regulations, strengthen supervision and management, such as the prohibition of solid pollutants into water, the recycling of residual or waste oil, the discharge standard must be met before exhausting oily wastewater, and the timely salvage of charged oil stain. In Fishery, project of cage culture reduction and making a living on land has achieved great results.
2) Agricultural and domestic pollution control. Actually, the transformation process between agricultural practices and non-point source pollution is relatively complicated, so we do not have much successful experiences for the control and prevention of agricultural nonpoint source pollution on the international currently, which shows the arduousness and protracted nature of its governance. In the long term, technological progress and institutional innovation is still fundamental way to solve the nonpoint source pollution  .
Besides policy system, the domestic pollution control also requires technical means, mainly including the construction of domestic sewage treatment plants; the centralized treatment of living garbage from surrounding area; the implementation of rural households toilets amelioration, improving stoves and biogas utilization project; the establishment of the ecological model village project with the New Rural Construction in China.
3) Control of industrial pollution and heavy metals. The heavy metal pollution of Dongjiang Lake mainly comes from the mining, processing and smelting industry, which is the key to control pollutions from the source and upstream of industry. At the beginning of this century, in order to protect the Dongjiang Lake, Chenzhou government has promoted a shift in the mode of economic development. Through the integration of resources, coalmines were reduced from 576 to 270, and metal mines from 177 to 128 in Chenzhou area. As shown in Figure 4, on the surrounding of the Dongjiang Lake basin, six main ore districts, including Nanmuxia tungsten ore district, Qingyao town tungsten ore district, Qingjiang lead-zinc mining area, Dongping gold field, Chukou tungsten ore district, and Lianping tungsten ore district had been closed by the year 2008.
Essentially, the cut off emissions of pollutant from the head stream achieved the primary chain-cutting disaster mitigation from gestation source measures. At the same time, the ecological restoration and environment management of mining area around the Dongjiang Lake were carried out, which can be regarded as the secondary chain-cutting disaster mitigation from gestation source of pollution (heavy metals) resistance control, as you can see in Figure 5. The technologies are mainly as follows.
Firstly, land rehabilitation of breeding and growing specialized plants, such as Alnus cremastogyne Burk, Quercus virginiana, Rhus chinensis, K. striata, vetch and so on, are the most economic and effective approach to control the removal of heavy metals Pb, Zn, Cu in environment. It plays an inactivation of the heavy metals in polluted soil based on combined effect of the target species and chemical scavenger.
Figure 4. Main ore districts distribution around Dongjiang Lake.
Figure 5. Chain-cutting measures of heavy metal control.
Secondly, for ecological treatment and intercept of soil and water pollution, permeable reactive barrier (PRB) and ecological gully were built in the right place.
Thirdly, resource utilization of soil contained heavy metals, tailings, waste rock and waste residue was studied, including producing cement with lead-zinc tailings, environmental friendly cementation materials with tailings and waste residue in non-ferrous smelting.
Fourthly, by hazard identification, risk assessment, testing and monitoring on industrial sites such as tailings dam and open pit slopes, disasters avoid heavy rainfall and take control of heavy metals removal effectively.
This paper developed the research of disaster chain to regional water environment security research, and discussed the connotation of regional environment disaster chain. Under the background of water pollution in the Dongjiang Lake, this paper carried out the definition and evaluation of pollution disaster resources in regional water environment of the Dongjiang Lake and analyzed the major sources of water pollution in the lake. Combining disaster chain theory, the disaster chain model of regional water environment pollution in the Dongjiang Lake is constructed, and the Dongjiang Lake water pollution generally belongs to the multisource disaster implication chain caused by human activities, which possess features of branches and trunk basin disaster chain with incubation period in a long term. In this paper, we also proposed primary and secondary chain-cutting disaster mitigation from gestation source thought on regional water environment governance, with emphasis on technology of ecological restoration and heavy metal control in mining area.
This work is supported by the Natural Science Foundation of China (Grant No. 51204205) and the National Science and Technology Support Program of China in the 12th Five-Year Plan (Grant No. 2012BAC09B02).
Cite this paper
FengGao,RonglanXiao, (2015) Multisource Disaster Chain and Control in Regional Water Environment of the Dongjiang Lake in China. Journal of Water Resource and Protection,07,1174-1182. doi: 10.4236/jwarp.2015.715096