August 15 is the first National Ecological Day. In recent years, with the sustained efforts of ecological environment protection in China, more and more efforts have been made to crack down on illegal and criminal acts that damage the ecological environment.
Illegal sand mining seriously endangers the ecological environment, especially the illegal mining of sea sand, which not only infringes on national mineral resources, but also causes great damage to the marine environment, marine coastal resources, coastal topography, coastal vegetation, marine aquatic organisms and so on. However, how to scientifically assess the damage caused by illegal sand mining has always been a difficult point in handling relevant cases. In recent years, around such cases, the Academy of Forensic Science has been exploring working methods to "fix the damage" for the sea ecology.
In 2019, a ship collision accident occurred in the Yangtze River Estuary, one of which was loaded with about 8000 tons of sea sand, all of which were illegally collected. In order to prosecute smoothly, the procuratorial organ entrusted the Institute of Judicial Expertise to assess the damage value of biological resources caused by illegal sand mining.
"Where does the sea sand come from, what kind of ore resources does it contain, how much sand does it contain, and what are the scope and objects of environmental damage to the occupied sea area and adjacent sea area?"? This is one of the first pieces of evidence we tracked. Cheng Kuan, an assistant researcher at the Environmental Damage Forensic Research Department of the Academy of Forensic Science, said, "The composition of sea sand varies according to the place where it is formed, the geological environment of the sea area, the transportation process of sea sand and the aquatic environment, mainly including the highest content of quartz, potassium feldspar, plagioclase, amphibole, etc. Rock mineral debris;"; Shells, gastropods, coral fragments, foraminiferal shells and other biological debris, as well as zircon, tourmaline, magnetite and other heavy minerals.
She introduced that the illegal mining of sea sand caused a lot of damage:
to the marine environment, the suspended sediment produced in the process of illegal sand mining will affect the marine water quality environment; After the bottom sand is hollowed out, the silt layer covering and around it will collapse due to gravity, resulting in the burial and coverage of benthic species at the sand mining site, resulting in the loss of biological resources.
For topography and geomorphology, sand mining activities are easy to cause local landform collapse and affect hydrodynamic conditions, and sand pit sediment will form siltation after sand mining. Illegal sand mining is often disorderly and random, and sand pits are distributed in disorder. In the process of siltation, it will erode the nearby seabed and affect the topography of the sea area.
For the shoreline, illegal sand mining will cause sudden depression of the seabed along the direction of water flow, resulting in vortex water flow in the pit, which makes the slope of the sand pit more easily scoured, resulting in the continuous outward extension of the sand pit. When the location is close to the coast, it may affect the stability of the adjacent shoreline.
For the coastal vegetation, when the illegal sand mining site is close to the seaside mangrove, the generated suspended matter will form a silt layer in the mangrove and other growth areas, covering its aerial roots and affecting its growth; if the illegal sand mining site causes local submarine landform collapse, it may cause the mangrove to fall and be damaged due to landslides.
In addition, sand mining has changed the original habitat of aquatic organisms, affected the biological resources such as phytoplankton, fish and benthic organisms in the affected area of sand mining to a certain extent, and threatened the health and safety of aquatic ecosystems, thus leading to certain damage to aquatic ecosystem services.
"We use sonar mapping and other scientific and technological means to compare in detail the changes in seabed topography before and after sand mining; through the investigation of biodiversity, we understand the impact of sand mining on the changes in biological populations; through the analysis of mineral composition, particle size, heavy minerals and elements, and foraminifera of sea sand, we trace the source information of sea sand." Cheng Kuan said, "By combining all the physicochemical analysis results with the ecological model, the overall impact of illegal sand mining activities on the marine ecosystem can be comprehensively assessed."
Foraminifera is one of the characteristic indicators of marine sediments and marine environment.There are different species of foraminifera in different sea sands.The species of foraminifera in sea sand is an important basis for tracing the source of sea sand, and foraminifera observation is a common method for tracing the source of sea sand.
It is reported that the restoration of marine ecology is a long-term and complex process. When formulating the restoration plan, the judicial appraiser of environmental damage needs to set specific restoration objectives, including restoring specific biological communities and improving water quality, according to the specific conditions such as topography, damage degree of biological communities and changes in water quality. According to the objectives, specific restoration schemes should be formulated according to local conditions, following the inherent mechanism and succession law of natural ecosystems, with natural restoration as the main and artificial restoration as the supplement. Artificial restoration measures usually include restriction or prohibition of sand mining and artificial reconstruction of ecological environment.
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