The SMALL crossword on "ENVIRONMENTAL CHEMISTRY" @ doc brown's chemistry

FOR PRINTING OUT ONLY, answers found via KS3 chemistry link above
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Across:

4. An important liquid fossil fuel. (3)
5. This is happening to glaciers and arctic ice more with global warming. (4)
7. This sort of 'converter' changes carbon monoxide and nitrogen oxide into less harmful gases in a car exhaust (9)
9. Another phrase for the 'greenhouse effect' (6,7)
10. This can happen to those pretty colours on fabrics with too much sunlight, though modern dyes are usually more resistant. (4)
12. These don't like low pH rain running into rivers! (4)
13. Sums up the effects of too much traffic and power station emissions (3,9)
15. The state of metal objects, especially when dug up by archaeologists! (8)
16. What we need to do with soil that's to acid for good crop growth! but not the z variety! (10)
18. What would we do without this plant factory process doing this in daylight! (14)
20. The condition of most stone after a long time. (9)
23. Most plants need this base to live on. (4)
24. In the upper atmosphere, this absorbs and protects us from harmful ultraviolet radiation (5,5)
25. The warming up effect for growing plants or environmental disaster! (10)
26. Nice to lie on in the sun, but a tanker spillage ruins it for quite a while! (5)
27. Useful structural materials but they so corrode without protection! (6)
28. Vital for life, requires purification treatment before domestic use. (5)

Down:

1. A solid fossil fuel, if only it wasn't so sooty! (4)
2. We all want to run one, whatever the costs involved! (3)
3. A sedimentary rock that readily weathers. (9)
6. A metal that doesn't corrode too badly or too fast, at least for a few years, and keeps the water in old pipes and out of chimney-roof joints. (4)
8. The name of the main gas formed on burning fossil fuels. (6,7)
10. This type of fuel causes a lot of pollution! (6)
11. It is used to treat over acidic soil. (4)
14. One of the 'fallout' effects of burning fossil fuels! (4,4)
17. Use sunblocker or this radiation causes skin cancer (11 or 5,6)
19. The compounds formed by burning things in air or oxygen. (6)
21. Possible increase in this effect of lack of rain in Africa from burning fossil fuels. (7)
22. It wears a bit better than limestone, nice statue Michaelangelo! (6)