Research On The Effect Of Captured CO₂Leakage On Crops, Grass And Soil Environment

With the trend of global CO2concertration climbing, Carbon Dioxide Capture and Storage (CCS), as a significant approach with huge potential for the mitigation of global climate change, will be a key technology for reducing CO2emission in the future. However, the captured and stored CO2underground has the risk of leaking which will bring serious threats to the agro-ecology system and produce an indirect effect on the security of grain crops, grass and the whole soil environment. Thus, it is significative to scheme an experimental platform for the observation of the effects of CO2leakage on agro-ecology system and set an accurate threshold of grain crop and grass to different CO2leakage scenarios, and finally accumulate relevant technologies about the counter measures, mitigation measures and environment modification measures of ecological system to cope with CO2leakage, for the practical operation of CCS and the fulfillment of the obligations that our China has to undertake.Two experimental platforms fitting for field and plotting agoricultural experiments of leaked CO2effects on crops and grass respectively were constructed in the research, which consisted of a CO2gas supply equipmentsystem, a CO2leakage controlling equipment system and a monitoring equipment system for the survey of crops and grass physiological indicators, consequently providing a feasible access to the study of the leaked CO2effects on crops and the whole soil environment. Different tolerances of four kinds of crops/grass after necessary estimating were put forward and the results of the effects of CO2leakage on field Spring Wheat, plotting Spring Maize, Zea Mexicana and Trifolium were following:1、In the field Sping Wheat experiment, the leakage of CO2at a rate of25kg·d-1from1.5m underground exerted a negative influence on the growth and development of the crops with a distribution of0.5m*0.5m around the CO2leaking point, meanwhile the growth of Spring Wheat was blocked-up and the yield decreased.0.5m～1m outside the CO2leaking point was a transitional zone which showed a minor effect on the Spring Wheat while the Spring Wheat lm outside the CO2leaking point were not affected by the leaked CO2.2、The effect of the CO2leakage at a rate of25kg·d-1from1.5m underground on the soil environment extended beyond0.5m*0.5m outside the CO2leaking point and the soil at deeper layers bore a heavier influence of the leaked CO2than the shallower soil. The CO2leakage caused more serious influence on the Spring Wheat and the soil near the CO2leaking point, while the temperature, moisture and pH of the soil were not changed significantly, simultaneously the soil organic matters and the total nitrogen showed a slightly change.3、The CO2leakage generated negative effects on the growth and development of Zea Mexicana and Trifolium, as the growth rate of plant height and the underground biomass and belowground biomass decreased with smaller leaf area and the roots became shorter with abundant fine roots and fibrous roots in the shallow soil layer. The photosynthesis turned weak and the yield of both kinds of pasture grass reduced obviously. The moisture content of the pasture grass fell notably and there was no apparent change rule in the variation of the grass nutrition content including crude protein, crude fibre, ash, and crude fat. The orgnic matters, total nitrogen and pH of soil showed little change. The most distinguishing pressure to survive the CO2leakage of the grass appeared after the first clipping of the grass.4、The CO2leakage also produced negative effects on the growth and development of Spring Maize, in adittion, with the increase of CO2leakage, the negative effect became heavier, and the range of soil pH fluctuation turned larger, while there was no trend towards acidification of the soil and the soil organic matters barely changed, at the same time, the soil total nitrogen showed a trend of decreasing at first and accelerating later. The O2concentration declined rapidly following the CO2concentration going up. As to the soil bacteria, the richness and diversity of the bacteria community declined gradually and there was a trend of simplification of the bacteria community5、It was endurable for Spring Maize, Zea Mexicana and Trifolium to tolerate the CO2leakage of500g·m-2·d-1，however, the crops had to face a death threat when the amount of CO2leakage was above1000g·m-2·d-1.It was concluded that Spring Maize displayed a stronger tolerance to CO2leakage than Zea Mexicana and Trifolium after the comparison of these three kinds of crops and grass.6、There were similar changes of the plants’ physiological indicators that the total biamoss of the crops and grass reduced, the length of the roots became shorter and more fine roots and fibrous roots appreared in the shallow soil layer among several kinds of crops and grass under different CO2leakage scenarios. Consequently, it was predicated that the effects mechanism of the CO2leakage on crops and grass lies in that the increased CO2concerntration restained the root respiration and changed the growth and shape of roots, which made the crops and grass unable to absorb sufficient nutrition and water to support the whole plant, thus the plants senesced and died.