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The accident occurring at the Fukushima Daiichi nuclear power plant on March 11, 2011 resulted in leakage of a large amount of radionuclides, contaminating farmlands, including rice field, in Fukushima and its neighboring prefectures. Potential contamination of the rice growing these areas by the radionuclides has thus attracted public attention. The objective of this paper is to analyze rice contamination in this region and its remediation. Literature review showed that the radionuclide that was most potential to contaminate the rice is the radioactive cesium. Among all available methods to detect radioactive cesium in rice grain, belt conveyor testers is quicker in measurement but is less accurate, while germanium semiconductor detectors is more accurate but is tedious. Rice contamination by cesium accumulation is modulated by a multitude of factors, one of which is fertilization. For example, potassium fertilizer (potassium chloride is more effective than potassium metasilicate) can reduce the absorption of the radioactive cesium in rice, while nitrogen fertilizer works in the opposite. The movement and transfer of radioactive cesium in soil was affected by its concentration, potassium content, immobilization of the cesium by soil, and the thickness of the topsoil. Apart from these, rice cultivars also affect cesium accumulation. Different methods for ameliorating rice contamination by radionuclides had been developed and tested. In paddy fields, rice contamination by cesium can be reduced by amending the soil or planting. The radioactive cesium is sportive to soil and cyanobacteria can be used to facilitate the exfoliation of top soil. Also, rice is a shallow-rooted plant and deep ploughing could bury the contaminated topsoil beyond the reach of roots so as to reduce its uptake by rice. Secondary contamination can be avoided by controlling fertilization and irrigation, and the transformation of the radioactive cesium from soil to rice can be inhibited by amending the soil with schwertmannite, zeolite and vermiculite, or by controlling fertilizer application rate and the secondary contamination. Implementation of above mitigating methods over the past few years reduced the radioactive cesium content in rice in Fukushima Prefecture to 25 Bq/kg in 2014 (the radiation level set by the Food Sanitation Act of Japan in 2012 was 100 Bq/kg). This paper has implications for constructing a database for mitigating and remediating crop contamination by radionuclides which is also relevant to food production in China. [ABSTRACT FROM AUTHOR]

Underground brine of Qinghai Saline Lake, which contains many kinds of mineral deposits such as potash, magnesium, sodium, and lithium, is a kind of important raw material for chemical products such as salt, potash fertilizer, and lithium carbonate. The pumps are easily prone to be out of order due to the fact they must keep running around the clock in a complicated climate environment around the saline lake mining sites. However, traditional monitoring for the chemical brine pump in Qinghai Saline Lake is a manual monitoring technology with high cost, non-real time, inflexibility and high energy consumption. This paper proposed a remote monitoring system based on the wireless sensor network (WSN) for the brine well in the production of potash. It consists of 2 units: one is real-time monitoring unit based on WSN with ZigBee protocol and CC2530 wireless sensor SoC, and the other unit is remote management information system (RMIS) of brine well based on a PHP (Hypertext Preprocessor) software platform. The real-time monitoring unit based on WSN is responsible for acquiring and transmitting the data, which consists of a number of sensor or router nodes and a network coordinator, and is deployed at the site of the brine well mining. Meanwhile, the RMIS serves as the management system for end-users, which has 4 functions: 1) Managing static information of the brine well; 2) Maintaining the database for the data acquired by the WSN; 3) Providing functions to automatically control the speed of brine pump according to real-time operating state data of the brine pump or shut down the brine pump when the monitoring indicators exceed the threshold; 4) And generating a list of mining brine failure reports of mining equipment. The system is evaluated by testing the power consumption of sensor nodes first. The experimental results showed that the package loss ratio (PLR) of the nodes gradually decreased with the increase of the transmission power. However, the battery consumption increased with the increase of the transmission power. The transmission power was configured as 1 dBm which could prolong the lifetime of sensor nodes to 13.5 months. And then the PLR and RSSI (received signal strength indicator) of sensor nodes were tested in different distance and transmitting power, respectively. In the case of the same transmission power, the PLR and RSSI had the opposite change trend with the change of distance: The PLR increased and the RSSI decreased with the increase of the distance. The effective transmission distance of the nodes was 30 m when they were placed on the ground and their PLR was less than 3.6%. Last, the RSSI was also tested within 24 h, to analyze the influence of the field deployment environment on the link quality. The experimental results showed the RSSI was relatively better during the daytime (5:40-19:20) which ranged from -80 to -56 dBm. And during the night (00:00-5:40 and 21:30-24:00), the RSSI had a significant drop (around -85 and -95 dBm, respectively). And the system test under the potash production environment proves that monitoring data can accurately reflect the operating status of the pump and the brine level. [ABSTRACT FROM AUTHOR]